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Dnv   hull structure course
 

Dnv hull structure course

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    Dnv   hull structure course Dnv hull structure course Presentation Transcript

    • Hull Structure Course DNV 2005
    • How are the loads taken up by the structure? Consequence of a crack in this detail? Where is it likely to find cracks?
    • Hull Structure Course Objective: After completion of the course, the participants should have gained knowledge of basic hull strength and understanding of how to perform better hull inspections.
    • Hull Structure Course Purpose: To train technical personnel about the basics of hull structure. Target group is technical personnel within ship owner / manager organization in need of improved competence in structural matters, with special focus on Bulk Carriers and Oil Tankers.
    • Course breakdown: Day 1 • • • • Day 2 • • Day 3 • Day 4 • • Introduction Single beams & loads Structural connections Hull structure failure types Fore & aft ship Hull structural breakdown Oil Tanker Hull structural breakdown Bulk Carrier Fore & aft ship Hull structural breakdown Container Carrier
    • Agenda day 1 09.00-09.15 09.15-09.45 10.00-11.30 11.30-12.30 Welcome & Introduction Expectation & presentation of participants Beams + Buzz group Loads 12.30-13.15 Lunch 13.15-14.15 14.15-15.45 15.45-16.45 16.45-17.45 17.45-18.00 Structural connections Failure mode fatigue Buckling & Indent Corrosion Review questions
    • Agenda day 2 09.00 – 09.15 09.15 – 10.30 10.30 – 10.45 10.45 – 11.00 11.00 – 11.45 11.45 – 12.15 Answers to review questions Structural breakdown fore and aft ship Introduction to tank Coffee break Ship side & longitudinal bulkhead Webframes 12.15 – 13.00 Lunch 13.00 – 13.30 13.45 – 14.30 14.30 – 15.00 15.00 – 15.15 15.15 – 16.15 16.15 – 16.45 16.45 – 17.00 Case: Oil Tanker Part A Deck Bottom Coffee break Case: Oil Tanker Part B Transverse Bulkhead Review quiz
    • Agenda day 3 09.00 - 09.30 09.30 - 10.00 10.00 - 10.45 10.45 – 11.00 11.00 - 11.45 11.45 - 12.15 Answers to review questions Introduction to Bulk Side Coffee break Bottom Deck 12.15 - 13.00 Lunch 13.00 - 13.45 13.45 - 14.30 14.30 - 15.00 15.00 – 15.15 15.15 - 15.45 15.45 – 16.30 16.30 - 17.00 Case: Side hold no 1 Transverse Bulkhead Hopper tank & topside tank Coffee break Hatch coaming & covers Case: Ore Carrier Review Quiz and closing
    • Agenda day 4 09.00 - 09.30 09.30 - 10.30 10.30 - 11.00 11.00 – 11.15 11.15 – 12.15 Answers to review questions from day 1 Structural breakdown fore and aft ship Introduction – Container Carriers Coffee break Bottom and Ship Sides 12.15 - 13.00 Lunch 13.00 – 14.00 14.00 – 15.00 15.00 - 15.15 15.15 – 15.45 15.45 – 16.00 16.00 – 16.30 Hatch Covers, Deck & Hatch Coamings Case: Container Carriers Coffee Break Bulkheads Closing Review Quiz
    • Module 2: Basic Hull Strength Slide 1 Basic Hull Strength
    • Objectives Basic Hull Strength After completion of this module the participants should have gained: 1. Understanding of: The behaviour of simple beams with loads and corresponding shear forces and moments. The applicable local and global loads on the hull girder and the corresponding shear forces and bending moments. Slide 2
    • Simple beam properties Basic Hull Strength Bending moment Load A Compression Section A-A A Tension Shear force Bending: When a beam is loaded it will bend dependent on its stiffness and its end connections. A single load from above causes compression stress on the upper side and tension stress on the lower side of the beam. Shear area: The beam has to have a sufficient cross sectional area to take up the external load and transfer this towards the end supports. Slide 3
    • Simply supported beam - concentrated load L/2 ℓ Basic Hull Strength F Single beam with concentrated load, simply supported ends F/2 Shear Force F F/2 Q=F/2 Q=F/2 Bending Moment L/2 M=Q x ℓ Slide 4
    • Simply supported beam – distributed load Basic Hull Strength p Single beam with distributed load, simply supported ends pL/2 Shear Force L pL/2 Q=pL2 Q=pL/2 Bending Moment M=pL2/8 Slide 5
    • Beam with fixed ends - distributed load Basic Hull Strength No rotation! p Single beam with distributed load, fixed ends pL/2 Shear Force L pL/2 Q=pL/2 Q=pL/2 Bending Moment 2 M=pL /12 2 M=pL /24 Slide 6
    • Beam with spring supported ends Basic Hull Strength p Spring k k Spring Shear force and bending moment distribution varies with degree of end fixation (spring stiffness) Degree of end fixation = 0 Degree of end fixation = 1 Slide 7 Simply supported Fixed ends
    • End fixation Basic Hull Strength Structural clamping – spring support Symmetrical load – full fixation Slide 8
    • Beam – fixation at ends Basic Hull Strength • Load on structure is important with regard to fixation bottom longs connection to transverse bulkhead Symmetric load gives full fixation Non symmetry in loads gives less fixation or even forced rotation Slide 9 Empty Empty Loaded
    • Axial stress Basic Hull Strength Force Stress = Force Area Area σ = ε x E (Hook’s Law) ε : Relative elongation Youngs modulus E: (2,06E5 N/mm² - steel) Slide 10
    • Stress levels – elastic & inelastic region Elastic region: σ < σyield - A beam exposed to a stress level below the yield stress, will return to its original shape after the load is removed, Simple beam theory valid In-elastic region: σ σ fracture Yield = > σyield Inelastic region - A beam exposed to stresses above the yield stress will have a permanent deformation after removing the load (yielding, buckling, fractures) ε (elongation) Elastic region Slide 11 Basic Hull Strength σ=ε*E
    • High Tensile Steel (HTS) Basic Hull Strength Material grades NVA - NVE • Measure for ductility of material (prevent brittle fracture) • Material grade dependent on location of structure and thickness of plate. NVA NVB NVD NVE Slide 12 MS HT28 HT32 HT36 HT40
    • Bending stress - Simple beam with load A R1 F A A A R2 Area effective in transferring the bending of the beam n.a Section A-A Slide 13 Distribution of stress caused by bending Max stress at flanges. Zero stress at neutral axis: Basic Hull Strength
    • Shear stress - Simple beam with load A R1 F A A A R2 Distribution of the stress Area effective in transferring load to the supports Max shear stress at neutral axisis of profile: Section A-A Slide 14 Basic Hull Strength
    • Bending and shear stress flow A R1 A F Basic Hull Strength A A R2 Compression Bending stress is transferred in the Tension flanges, σ Shear stress is transferred in the web, τ Section A-A Slide 15
    • Beam stiffness and section modulus Basic Hull Strength As the axial stresses are transferred in the flange of a beam, it is the flange area that is governing a beam’s ‘bending stiffness’ Aflange y Bending Stress: b n.a l M σ= ZX y1 x Section modulus: Moment of Inertia: Ix Zx = y1 1 3 2 I x = bl + 2 A flange y1 12 The ‘Section Modulus’ is expressing the beam’s ability to withstand bending Slide 16
    • Shear stress & shear area Basic Hull Strength The load is carried in shear towards the supports by the web Shear force : n.a Slide 17 h As = h ⋅ t Shear stress: t Q Shear area : y Q τ= As x
    • Conventional profiles in ship structures Basic Hull Strength Flatbar (slabs) Easy with regard to production, flatbar stiffeners have poor buckling strength properties, low section modulus mostly applied in deck and upper part of side - long. bhd. Angle bar (rolled and welded) Angle bar will twist when exposed to lateral load due to nonsymmetric profile. This effect gives additional stress at supports due to skew bending. Angle bars are more prone to fatigue cracking than symmetrical profiles (Ref. sketch next page) Due to the skew bending, which gives a moment in the web-plate at welded connection to the plate, angle bars are also more critical with regard to grooving (necking) corrosion. Slide 18
    • Angle bar (rolled / built up) Basic Hull Strength An angle bar profile will twist when exposed to lateral loads due to asymmetric profile which gives additional stress at supports due to skew bending POSTFEM 5.6-02 MODEL: T1-1 DEF = 203 4: LINEAR ANALYSIS NODAL DISPLACE ALL MAX = 1.46 MIN = 0 SESAM 5 SEP 2 Side longs internal pressure Additional bending stress in web Z Y X Slide 19 1.39 1.32 1.25 1.18 1.11 1.04 .974 .905 .835 .766 .696 .626 .557 .487 .418 .348 .278 .209 .139 .696E-1
    • Conventional ship structure profiles Basic Hull Strength Bulb profile (single / double bulb) Bulb profiles are favourable with regard to coating application. Single bulb which is most common will (as for the L-profile) have some skew bending when exposed to lateral load. T- Profile The T-profile is symmetrical and will not be prone to skew bending. Favourable with regard to fatigue strength. The profile may have large section modulus. Some T-profiles on single skin VLCC’s have been found critical with regard to buckling due to a high and thin web-plate with a small flange on top. Slide 20
    • Hierarchy of hull structures Plate – Stiffener – Stringer / girder – Basic Hull Strength Panel – Stresses in a hull plate due to external sea pressure, are transferred further into the hull structure through the hierarchy of structures. Slide 21 Hull
    • Level 1: Plate - simple beam Basic Hull Strength Stiffener NO ROTATION Plating Water pressure A strip of plating considered as a beam with fixed ends and evenly distributed load Slide 22 PLATE AS A BEAM
    • Level 2 Longitudinal - simple beam Basic Hull Strength Longitudinal between two web frames Max shear and bending moment at supports (web frames) Symmetric load fwd and aft of web frames gives no rotation fixed ends Slide 23
    • Level 3 : Transverse web - simple beam Basic Hull Strength Beam with fixed ends and concentrated loads from the bottom longitudinals SF Slide 24 BM Max shear and bending moment towards ends (side & long bhd.)
    • Level 3 Longitudinal girder with transverse webframes Basic Hull Strength Longitudinal girder between two transverse bulkheads Max shear and bending moment towards transverse bulkheads Single beam with fixed ends and concentrated loads from the transverse web frames Max Shear and bending moment towards ends Slide 25
    • Beams, load transfer Basic Hull Strength Double bottom structure Loads taken up by the bottom plating are transferred through the hierarchy of structures into the hull Side girder Floor / transverse bottom girder Centre girder Stiffeners supported by floors Slide 26
    • Beams, load transfer Basic Hull Strength Longitudinal bulkhead Single skin structure Loads taken up by the bottom plating are transferred through the hierarcy of structures into the hull Transverse bottom girder /web frame Bottom longitudinals with plating Slide 27 CL girder
    • Damage experience • Level 1 Plate supported at stiffeners • Level 2 Stiffener supported at webframe • Level 3 Webframe supported at panel • Level 4 Panel – hull girder Consequences of damages level 1-4 above! Slide 28 Basic Hull Strength
    • Single beam VS Hull girder Basic Hull Strength A vessel’s hull has many of the same properties as a single beam. Hence simple beam theory may be applied when describing the nature of a vessels hull The term ‘Hull girder’ is used when thinking of the hull as a single beam Single beam Hull Slide 29
    • Hull girder bending Basic Hull Strength When a vessel’s hull is exposed to loading, it will bend similarly as a single beam Slide 30
    • Single beam VS Hull girder A A F A A Bending stress, σ Compression Tension Hull Girder Section A-A Shear stress, τ Deck and bottom acts as flanges in the ‘hull girder’, while ship sides and longitudinal bulkheads, act as the web Slide 31 Basic Hull Strength
    • Stress hierarchy in ship structure Local stress : Girder stresses: Hull girder stresses; Slide 32 Basic Hull Strength Plate / stiffener Webframes / Girders /Floors Deck & bottom / Side / long. Bhd.
    • Case Module 2: Loads Buzz Groups Basic Hull Strength • For a beam with fixed ends and evenly distributed load, i.e. from sea pressure, is it true that: – – – – Bending stresses are zero at one location Reaction forces are equal at both ends No rotation at ends Bending stresses are positive (tension) in one flange and negative (compression) in the other in the middle of the span – Shear stresses are highest in the middle of the span – Shear forces are carried by the web Slide 33
    • Case Module 2: Beams Buzz Groups Basic Hull Strength • Is it correct that the transverse girders are supported by the longitudinal stiffeners? • Are the longitudinals inside a tank structure for example bottom longitudinals between webframes normally fixed or simply supported? Slide 34
    • Summary: Beams • • • • • Basic Hull Strength BM and Shear force Stress axial / bending / shear Section modulus / Moment of inertia / Shear area Stress distribution Bending and shear BM and SF distribution depending on load and end fixation • Profile types and properties • Structural hierarchy plates-stiffeners-girder-panel Slide 35
    • Loads acting on a ship structure Slide 36 Basic Hull Strength
    • Loads acting on a ship structure 1. Internal loads: - Cargo - Ballast - Fuel - Flooding - Loading/unloading 2. External loads: - Sea - Ice - Wind Slide 37 Basic Hull Strength Anchor
    • Static and Dynamic loads Static local load: Basic Hull Strength The local load, internal and external due to cargo / ballast pressure Dynamic local load: External - dynamic wave loads, Internal - due to acceleration Static global loads: Global Bending Moment and Shear Force Wave loads: Dynamic Bending Moment and Shear Force Slide 38
    • Static and Dynamic loads Basic Hull Strength Total external local load acting on a vessel: Static Max at the bottom Dynamic Max around the waterline Note the relative size of static / dynamic pressure is not to scale! Slide 39
    • Sea Pressure – static and dynamic contribution Basic Hull Strength Plotted sea pressure curve is a sum of the static and dynamic contribution p (kN/m2) Constant in the midship area, increasing towards ends aft fwd Local sea pressure (example for a bottom longitudinal) Slide 40
    • Static and Dynamic loads Basic Hull Strength • Global dynamic vertical and horizontal wave bending moments give longitudinal dynamic stresses in deck, bottom and side Highest global dynamic loads for all longitudinal members in the midship area Slide 41
    • Loads on foreship Basic Hull Strength Bow Impact Pressure •Induced by waves, vessel speed, flare and waterline angle important factors •Dominant for ship sides in the bow at full draught Bottom Slamming Pressure •Induced by waves in shallow draft condition (ballast condition) •Dominant for flat bottom structure forward Slide 42
    • Loads on deck Slide 43 Green Seas Loading: • Dominant for hatch covers and fwd deck structure (incl. deck equipment, doors, openings etc) Basic Hull Strength
    • Weights and buoyancy Basic Hull Strength Weight distribution of cargo and fuel Steel weight, equipment and machinery Buoyancy Slide 44 Static Dynamic
    • Bulk Carrier typical load Static external sea pressure Dynamic external sea pressure Slide 45 Basic Hull Strength Static internal load from cargo Dynamic internal load from cargo
    • Net load on structure – ‘Ore hold’ Internal load - External load = Net load on double bottom Static and dynamic internal load from cargo Slide 46 Static and dynamic sea pressure Basic Hull Strength
    • Net load on structure - empty hold Net load from sea pressure Slide 47 Static and dynamic sea pressure Basic Hull Strength
    • Alternate loading condition Slide 48 Basic Hull Strength
    • Weights and buoyancy Basic Hull Strength Buoyancy and weights are not evenly distributed along a ships length… …hence, a global shear force and bending moment distribution is set up on the hull girder Slide 49
    • Hull girder still water bending moment and shear force Basic Hull Strength Slide 50 Example: SF and BM distribution for a double hull tanker in a fully loaded condition
    • Total BM acting on a vessel Basic Hull Strength Total hull girder bending moment MTotal = Mstill water + M wave Slide 51 Hogging Sagging BM limits Mtotal Mstill water Mwave
    • Case 2 Module 2 – Loads/Materials Basic Hull Strength • Where in the hull girder cross section of a hull girder are the local dynamic loads due to sea pressure highest? • Where along the hull girder are the dynamic sea pressure loads highest? • Where in the hull girder is the global dynamic bending moment highest? • Does a vessel in sagging condition experience compression or tension in deck? • A vessel in sagging condition experience flooding of a empty tank in midship. Will the hull girder bending moment increase or decrease? Slide 52
    • Summary: Loads • • • • • Slide 53 Static & dynamic Internal & external Load distribution Net load Longitudinal strength SF & BM Basic Hull Strength
    • Basic Hull Strength End of Module 2: Basic Hull Strength Slide 54
    • Module 3: Structural Connections Module 3: Structural Connections • Objectives of this Module: After completion of this module the participants should have gained: • • • Slide 1 Knowledge about connections between structural elements Understanding of the transfer of forces between structural elements and the relevant stress distributions Knowledge about how to improve the design of structural connections
    • Contents • • • • • Slide 2 Types of welds Connections of stiffeners Connections of girders/web frames Connections between panels Design details Module 3: Structural Connections
    • Module 3: Weld Types Structural Connections We will briefly touch upon the following types: • Fillet welds • Full penetration welds (Full pen) (Ref. Rules Pt.3 Ch.1 Sec.11) Slide 3
    • Module 3: Weld Types – Fillet welds Structural Connections Throat thickness Fillet welds: • The most common type Leg length Transferring shear forces (between profile and plate) • Building welded sections • Connections to other members • NDT by magnetic particle or dye penetrant Slide 4 Throat thicknessmeasure 3.5 mm = leg length 5.0 mm
    • Module 3: Weld Types – Full penetration Structural Connections Full penetration welds: • To be used where stress level normal to the weld is high t Gap <3 mm Throat thickness Root Face 2-4 mm for full penetration welds σ Slide 5 Transferring shear forces and forces normal to the weld • Connections to other members in highly stressed locations • NDT by ultrasonic, dye penetrant or magnetic particle
    • Module 3: Connections of stiffeners • What forces are to be transferred? L Shear Force Bending Moment Slide 6 Structural Connections
    • Load from stiffener to webframe How arethe How is the forces transferred from the stiffener to webframe Slide 7 Module 3: Structural Connections
    • Module 3: Connections of stiffeners Web fr. Slide 8 Stiffener Web fr. b) a) + + + c) d) Web fr. + Structural Connections
    • Module 3: Connections of stiffeners Structural Connections Effect of brackets on the max bending stress No or negative effect = Slide 9 =
    • Connections of stiffeners Web-plating Stiffener Slide 10 = Structural Connections Common crack locations in longitudinal Longitudinal = Module 3:
    • Static stress in stiffener on top Module 3: Structural Connections Stress distribution for different details ballast σx Slide 11 loaded σx
    • Connections of stiffeners Common crack locations Web-plating Stiffener Longitudinal = = Design improvement Slide 12 Module 3: Structural Connections
    • End-brackets on girders - forces Empty Wing Tank Structural Connections Full Centre Tank Net load Slide 13 Module 3: Net load
    • End-brackets on girders Module 3: Structural Connections Improved design Transverse welding of flange outside curved area a Increased stress at support bkts. i) i iii iii) iiib) High Stress Areas High Stress Areas Soft bkts. recommended High Stress Areas iv) ii) ii Slide 14 Flange attached and supported
    • Stringer connection to inner side Module 3: Structural Connections Repair Original Design Inner side Ship side Stringer Trv. Bhd. Crack Slide 15 Original thickness 16mm Insert 20 to 25 mm Bracket with thickness 20 to 25 mm
    • End-brackets on girders Module 3: Structural Connections Girder bracket Typical crack location Ref. iii b) previous fig. Slide 16
    • Module 3: Cross-Ties Full Centre Tank Empty Centre Tank Full Centre/Empty Wing at full draught = Max. Compression in Cross Tie Empty Centre/Full Wing at ballast draught = Max. Tension in Cross Tie Slide 17 Structural Connections Empty Full Wing Wing Tank Tank
    • Module 3: Knuckles Structural Connections helikopter Out of plane forces Deformation/low stiffness Slide 18
    • Knuckles Module 3: Structural Connections Support as close to the knuckle as possible Slide 19
    • Knuckles Module 3: Structural Connections Vertical Brackets Slide 20
    • Module 3: Knuckles Crack in shell plate at knuckle: New Brackets Slide 21 Structural Connections
    • Module 3: Knuckles Structural Connections Crack Locations Stress Concentrations In way of Webs Slide 22
    • Module 3: Knuckles Structural Connections Preferred design: • No misalignment in the connection. • No lugs or scallops Slide 23
    • Module 3: Intersecting Hull Elements Crossing Panel - No bracket Structural Connections Crossing Panel - With bracket Panel 2 Panel 1 Connecting area ~ (a+b) · t Connecting area ~ t · t b t t a Slide 24
    • Module 3: Intersecting Hull Elements Structural Connections TOP SIDE TANK NO. 7 ENGINE ROOM BULKHEAD DIESEL SUPPLY TANK Cracks ENGINE ROOM BULKHEAD CRACKS LONGITUDINAL WING TANK CRACKS STR BK TANK TOP BULKHEAD iv iii T. ENGINE ROOM BULKHEAD A EXISTING BRACKET TO BE REMOVED ADDITIONAL BRACKET NEW BRACKETS IN LINE WITH BOTTOM PLATE IN TOP SIDE TANK A ENGINE ROOM BULKHEAD SLANTING TANK TOP PLATING ENGINE ROOM BULKHEAD Slide 25 LONGITUDINAL BULKHEAD Section A-A A-A Reinforcements TO BE IN LINE
    • Notches, Drain/Lightening Holes i) Crack Common notch in way of weld Slide 26 Reduced risk of cracking Module 3: Structural Connections iii) Notch away from weld
    • Module 3: Summary module 3 • • • • • • • Slide 27 Welding Connection stiffener – girder Girder – panel Cross tie Knuckles Intersection of plates / panels Cut-outs and notches Structural Connections
    • Module 5 Hull Structural Breakdown Oil Tanker Bulk Carrier Container Ship Slide 1
    • Hull Structural Breakdown Oil Tanker – Bulk Carrier – Container Ship Objective of Module 5: After completion of this module the participants should have gained: • Understanding of hull structural design for Oil Tankers, Bulk Carriers and Container Ships through application of basic hull strength theory • Slide 2 Knowledge of typical structural damages and their consequences
    • Contents of Module 5 1. Fwd and aft structural parts 2. Oil Tankers – structures in cargo area 3. Bulk Carriers – structures in cargo area 4. Container Ship – structures in cargo area Slide 3
    • Fore ship Contents – Fwd and aft structural parts 1. Hull structure breakdown – fwd part of ship 2. Hull structure breakdown – aft part of ship 3. Slide 4 Case
    • Fore ship Structural functions of fore ship 1. Watertight integrity (local strength) - Resist external sea pressure / Bow impact / bottom slamming - Resist internal pressure from ballast 2. Web in hull girder (global strength) - Side plating act as the web in the hull girder beam Slide 5
    • Fore ship Structural build up fore ship Collision bhd. Chain locker Stringer decks Breast hook Side webframes Bulbous bow Slide 6
    • Fore ship Structural build up fore ship Vertical side frames Slide 7 Horizontal side longs
    • Fore ship Structural functions of fore ship • • Slide 8 • Shell side must withstand static and dynamic loads from external sea pressure. Bow impact and bottom slamming introduce additional loads Internal pressure from ballast
    • Fore ship Structural build up fore peak Horizontal stiffening Plate supported by side longs Side longs supported at webframes Webframes supported at stringer flats BM and SF distribution for a single beam with distributed load and fixed ends Slide 9
    • Fore ship Structural build up fore peak Horizontal stiffening Reduced efficiency due to flare angle Slide 10
    • Fore ship Structural build up fore peak Vertical stiffening Plate supported by side frames Side frames supported by stringer flats SF Slide 11 Bm
    • Fore ship Functions of fore peak global strength 2. Web in hull girder (global strength) • Ship side / longitudinal swash bulkhead carry global shear forces from net load in fore peak to the collision bhd. Side plating is acting as web in the hull girder beam Full draught with empty fore peak most critical Cont. Slide 12
    • Fore ship Functions of fore peak Global strength 2. Deck and Bottom in hull girder (global strength) - The global bending moments are always zero at fwd / aft end. - The longitudinal stresses in deck and bottom are moderate in fore structure - If large flare – wave induced compression stresses in deck may critical Slide 13
    • Fore ship Hull damages in fore ship Characteristic damages fore ship 1. 2. Buckling of stringers 3. Bow impact 4. Damages to the wave breaker 5. Slide 14 Corrosion – lost ship side fore peak Bottom slamming Fore ship specially prone to hull damages. Of top 10 damages on tankers are 6 of them in the fore ship!
    • Fore ship Lost shipside Oil Tanker 357 000 DWT built 1973 20 years Heavy local corrosion Experience feedback • Local heavy corrosion – increase stress level - reduced buckling strength • local buckling stiffener collapse – web frame buckling/collapse Slide 15 • Side longs double span – overload and collapse
    • Fore ship Lost shipside - Impact of function Oil Tanker 357 000 DWT built 1973 20 years • Shell side lost its watertight integrity • Lost buoyancy – increased fwd. draught – impact on longitudinal strength • Reduced shear carrying capacity for hull girder • Collision bhd. Exposed to dynamic sea loads Slide 16
    • Fore ship Slide 17 Buckling of stringer in fore peak tank Oil Tanker 302,419 DWT built 1992 Buckling of stringers in fore peak tank (after 1 year) Buckling in stringer no 1, 2 & 3 in fore peak tank. Stringer no 1 shown, other stringers similar buckling pattern
    • Fore ship Buckling of stringer in fore peak tank Oil Tanker 302,419 DWT built 1992 Buckling of stringers in fore peak tank (after 1 year) Stringer as beam Local web buckling due to lateral load axial stress in web Buckling of stringer due to high shear / compression stresses Experience feedback Slide 18
    • Fore ship Buckling of stringer Impact of function Oil Tanker 302,419 DWT built 1992 Buckling of stringers in fore peak tank (after 1 year) • Buckled / deformed stringers may develop cracks penetrating the shell – cause leak – impact on trim – draught • If stringers are significantly reduced in strength the webframes loose their support. • Side longitudinals loose their support at webframes. • Side longitudinals with excessive loads may collapse and ship side collapse – flooding of fore structure. Slide 19
    • Fore ship Bow Impact Damage Container ship 1 year A recent damage in 2001….. Occurred during the first year of operation Slide 20
    • Fore ship Slide 21 Bow Impact Damage Container ship 1 year
    • Fore ship Bow Impact Damage Container ship 1 year Bow impact: Peak pressure Important factors: Flare angle, α Waterline angle, β Height above waterline Vessel speed Roll and pitch α Sea Pressure: ”Evenly” distributed β Slide 22 h0
    • Fore ship Bow Impact Damage Container ship 1 year Local plate buckling Slide 23
    • Fore ship Bow Impact Damage Impact of function Container ship 1 year • Buckled plating may lead to leakage • Damages to longitudinals may reduce their load carrying capacity • Damages to stringers and webs could lead to reduced support of longitudinals which again may lead to ship side collapse and flooding. Slide 24
    • Fore ship Bottom slamming fore ship Bulk Carrier 220 000Dwt Built 1997 • Bottom plate set in • Bottom longs tripped ( L-profiles) • Webframes buckled between longs and access holes Slide 25
    • Fore ship Bottom slamming fore ship Plates set in and punctured Floors twisted and damaged Mostly for small ships in ballast condition Slide 26 Feeder L = 100 m
    • Fore ship Bottom slamming fore ship Feeder L = 100 m Parametres: T BF = Ballast draught forward. Increasing ballast draught B B = Breadth of flat bottom. “V” shape forward reduces slamming load. X = Distance from FP. Pitch component of relative velocity, and therefore slamming load, decreases with distance from FP decreases slamming load. Slamming Pressure Slide 27 Slamming Pressure
    • Fore ship Bottom slamming Impact of Function • Bottom longs tripped will not efficiently support plate – Bottom plate + longs will be set in – In plane buckling capacity significantly reduced • not critical in this area due to low vertical bending moment • Bottom floors buckled, webframes reduced their load carrying capacity • Loss of watertight integrity – flooding possible scenario – impact on trim - draught Slide 28
    • Aft ship Contents – Fwd and aft structural parts 1. Hull structure breakdown – fwd part of ship 2. Hull structure breakdown – aft part of ship 3. Slide 29 Case
    • Aft ship Structural build up aft ship Transom stern plate Engine room bulkhead Webframes Floors Slide 30
    • Aft ship Structural build up aft ship Engine room platform Side plate & longitudinals Webframe side Webframe deck Slide 31
    • Aft ship Structural build up aft peak tank Horizontal side longs Slide 32 Vertical side frames
    • Aft ship • • • Slide 33 Structural functions of aft ship Shell must withstand static and dynamic sea pressure, bottom slamming may introduce additional loads Internal pressure from ballast Dynamic impulses from the propeller Loads are taken up by the hull plating, stresses are transferred from plate to stiffener
    • Aft ship Functions of aft ship Web in hull girder (global strength) Ship side together with the longitudinal swash bulkheads are taking up global shear forces from net load on the hull girder in the aft end High shear forces fwd. of engine room full load conditions Global loads are acting on the hull girder beam Side plating is acting as web in the hull girder beam Cont. Slide 34
    • Aft ship Functions of Aft ship 2. Deck and Bottom in hull girder (global strength) - The global bending moments are always zero at fwd / aft end - The longitudinal stresses in deck and bottom are moderate in fore peak Slide 35
    • Aft ship Functions of Aft ship • Ensure adequate stiffness for: – Main engine support (double bottom engine room) – Steering gear support (steering gear flat / aft peak) – Rudder horn (aft peak structure) Slide 36
    • Aft ship Hull damages in aft ship Characteristic damages for the aft ship: 1. Buckling of engine room stringers 2. Stern Slamming 3. Cracks due to vibration 4. Cavitation damages to the rudder Slide 37
    • Aft ship Buckling Oil Tanker Built 1992 Buckling of stringers in engine room (after 1 year) Buckling of stringers aft in engine room 7100 / 11150 mm above baseline Buckling of side stringer 7700 mm above baseline in engine room (P/S) Slide 38
    • Aft ship Buckling External sea pressure Bending moment Bending + shear exceed the buckling capacity of the plate Slide 39
    • Aft ship Buckling Impact of function • Stiffeners may loose their support and areas may be overloaded • Collapse of panels and leakage may be a possible scenario Slide 40
    • Aft ship Stern Slamming Container Ship • Flat stern structure is prone to be high stern slamming impact load - the wider beam, the higher impact pressure and total load on the stern Slide 41
    • Aft ship Container Ship Stern Slamming Repaired connection area/ scallop Slide 42 Scallop and stiffener connection to outer shell longitudinals in ballast tanks in after body area were found fractured in several locations.
    • Aft ship Container Ship Stern Slamming F F Slide 43
    • Aft ship Stern Slamming Container Ship Impact of function • Side longitudinals may loose their support at web frames • Crack may penetrate the shell plating - loss of watertight integrity - flooding possible scenario Slide 44
    • Aft ship Cracks in aft peak tank due to vibrations Cracks in Trans. at Steering Gear Flat Supporting structure below oscillating machinery Passage doors in engine room area Slide 45 ibr V l ona ati s ack cr
    • Aft ship Cracks in aft peak tank due to vibrations Crack in weld between web frame and shell side Crack Repair; Crack caused by vibration of the web frame due to impulses from the propeller Crack start in scallop Slide 46 Additional intercostals to change natural frequency for side webs
    • Aft ship Vibration damages Impact of function • The supporting structure may get less effective • If the cracks are in the side shell frames or webs, this may lead to crack in the shell plate and thereby leakage. Slide 47
    • Aft ship Rudder Cavitation Typical repair; • Grind the affected area • Pre-heat Slide 48 • Re-weld Typical on Container Ship
    • Aft ship Rudder Cavitation Pressure distribution around typical rudder profile Pressure distribution (suction) Positive pressure Cavitation of rudder blade depend on: U = speed of ambient water Pressure distribution due to shape of profile Pressure distribution due to thickness of profile Slide 49 • • • • Shape of profile Thickness of profile Rudder angle Speed of water over profile
    • Aft ship Rudder Cavitation • Stainless steel shielding – Preferred solution welded with continuous weld in small pieces – not slot welds Slide 50
    • Aft ship Rudder Cavitation This is how it may end if the shielding is not welded properly Slide 51
    • Aft ship Rudder Cavitation Impact on function • Cracks may occur which could lead to reduced rudder support and maneuverability Slide 52
    • End of Module 5 Fore & aft ship Slide 53
    • Oil Tankers Oil Tankers - Hull Structure Slide 1 18.02.2005
    • Oil Tankers Contents – Oil tankers 1. Introduction 2. Hull structural breakdown – function of hull elements: • 3. Slide 2 Side, bottom, deck, transverse bulkhead, longitudinal bulkhead, web frames including relevant hull damages for all structural elements Case 18.02.2005
    • Oil Tankers Characteristics for Oil tankers Any proposals? - High number of tanks – good capability of survival - Low freeboard, green seas on deck - Pollution / public attention / fire explosion hazards - Fatigue - Liquid cargo – sloshing in wide tanks and stability aspect -Hull inspection environment - Fully utilizes BM limits hogging/sagging (double hull tankers) Slide 3 18.02.2005
    • Oil Tankers Size categories of tankers Oil Tankers Type ULCC VLCC Suezmax Aframax Panamax Products DWT 320,000+ 200 - 320,000 120 - 200,000 75 - 120,000 55 - 70,000 10 - 50,000 Source: INTERTANKO Slide 4 18.02.2005
    • Oil Tankers Size categories of tankers Panamax (55 - 75,000 dwt): • Max size tanker able to transit the Panama Canal • L(max): 274.3 m • B(max): 32.3 m • Typical vessel: 60,000 dwt, L=228,6m, B=32,2m, T=12,6m Age distribution Aframax (75 – 120,000 dwt): • AFRA= Average Freight Rate Assessment • Traditionally employed on a wide variety of short and medium-haul crude oil trades • Biggest tanker in US ports is 100,000 dwt • Typical vessel: 100,000 dwt, L=253,0m, B=44,2m, T=11,6m Source: INTERTANKO Slide 5 18.02.2005 Age distribution
    • Oil Tankers Size categories of tankers Suezmax (120 – 200,000 dwt): • Notation is soon to become redundant as the project of deepening the Suez Canal to 18,9m is completed • Typical vessel: 150,000 dwt, L=274,0m, B=50,0m, T=14,5m Age distribution VLCC (200 – 320,000 dwt): • Were prompted by the rapid growth in global oil consumption during the 60’s and the 1967 closing of the Suez canal • Today the most effective way of transporting large volumes of oil over relatively long distances • Typical vessel: 280,000 dwt, L=335,0m, B=57,0m, T=21,0m Source: INTERTANKO Slide 6 18.02.2005 Age distribution
    • Oil Tankers Size categories of tankers ULCC (320,000+ dwt): • Most ships of this type built in the mid to late 70’s • Ordered to take advantage of the economies of scale in a buoyant market • Less than 40 of these ships remaining • Rather inflexible, may enter very few ports • Typical vessel: 410,000 dwt, L=377,0m, B=68,0m, T=23,0m Source: INTERTANKO Slide 7 18.02.2005
    • Oil Tankers Single Skin Oil Tanker Ship data: L = 310m B = 56m D = 31,4m 284,497 DWT Slide 8 - Old design, build up to 1993 18.02.2005
    • Oil Tankers Single bottom with side ballast tanks Ship data: L = 236m B = 42m D = 19,2m 88,950 DWT - Built in the 80’s, considered as ‘single skin’ Slide 9 18.02.2005
    • Oil Tankers Double Hull – Two Longitudinal Bulkheads Ship data: L = 320m B = 58m D = 26,8m 298,731 DWT Slide 10 - Common VLCC design of today 18.02.2005
    • Oil Tankers Double Hull – CL Longitudinal Bulkhead Ship data: L = 264m B = 48m D = 23,2m 159,681 DWT Slide 11 - Common Aframax and Suezmax design of today 18.02.2005
    • Oil Tankers Double Hull – no CL bulkhead Ship data: L = 218m B = 32,2m D = 19,7m 63,765 DWT Slide 12 - Older design 18.02.2005
    • Oil Tankers Slide 13 Nomenclature for a typical double hull oil tanker 18.02.2005
    • Oil Tankers Structural breakdown of hull -A vessel’s hull can be divided into different hull structural elements - Each element has its own function contributing to the integrity of the hull - In order to assess the structure of an oil tanker, one needs to understand the function of each structural element Slide 14 18.02.2005
    • Oil Tankers Damages and repairs WWW.witherbys.com Slide 15 18.02.2005
    • Oil Tankers Function of hull elements Deck: Ship side: Webframes: Slide 16 18.02.2005 Longitudinal bulkhead: Bottom: Transverse bulkhead:
    • Oil Tankers Hull Structural Breakdown 2. Side Bottom 3. Deck 4. Transverse bulkhead Longitudinal bulkhead Web frames 1. 5. 6. Slide 17 18.02.2005
    • Oil Tankers End of Oil Tanker session Slide 18 18.02.2005
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Ship side Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Web frames 18.02.2005 1. Side
    • Oil Tankers Structural build up of ship side – single skin tanker Side plating with longitudinals Transverse bulkhead Cross ties Stringers Web frame Slide 2 18.02.2005 1. Side
    • Oil Tankers Structural build-up of a double hull ship side Side plating with longitudinals Inner side plating with longitudinals Stringers Web frame Slide 3 18.02.2005 1. Side
    • Oil Tankers Structural functions of ship side 1. Side Watertight integrity - Take up external sea loads and transfer these into the hull girder - Resist internal pressure from cargo and ballast Web in hull girder - Side plating act as the web in the hull girder beam Slide 4 18.02.2005
    • Oil Tankers Loads on the ship side - example 1. Side Fully loaded condition Ballast condition Water Line Net force Net force Water Line Slide 5 18.02.2005 Full wing tank Full centre tank
    • Oil Tankers Local function: Watertight integrity 1. Side External loads induces shear forces and bending moments in the side longitudinals as single beams (between each web frame) Side long.as a single beam between two web frames Slide 6 18.02.2005 BM and SF distribtion for a single beam with evenly distributed load and fixed ends
    • Oil Tankers Local function: Watertight integrity 1. Side -Side longs are supported at the web frames - Web frames are supported at the cross ties and at the deck and bottom Shear force Slide 7 18.02.2005 Part of web frame supported at two cross ties, shear max towards supports Bending moment
    • Oil Tankers Double hull ship side 1. Side • The structural functions of a double hull ship side is the same as for a single hull: As there are no cross ties, side web frame is supported at the deck and bottom High shear stress Slide 8 18.02.2005
    • Oil Tankers Global function: Web in hull girder 1. Global shear forces resulting from uneven distribution of cargo and buoyancy are taken up in the ship side plating Area effective in transferring shear force Slide 9 18.02.2005 Shear stress distribution resulting from global loads for midship section Side
    • Oil Tankers Stringers in a double side • Stringers contribute to the stiffness of the double hull ship side, which means: 1. Side 15mm 20mm 25mm 20mm High shear stress in stringer towards the Slide 10 18.02.2005 transverse bulkhead 15mm
    • Oil Tankers Characteristic damages for ship side: 1. Side 1. Cracks in side longitudinals at web frames 2. Cracks in cut-outs for longitudinals 3. Cracks in side longitudinals at transverse bulkheads 4. Indents of side shell and stiffeners Slide 11 18.02.2005
    • Oil Tankers Crack in side longitudinals Oil Tanker 285,690 DWT built 1990 Cracking in side longitudinal web frame connection (after 3 years) Side longitudinal flatbar connection to web frame Slide 12 18.02.2005 Crack in side longitudinal tripping bracket connection to web frame (various wing tanks) 1. Side
    • Oil Tankers Cause for cracking in side longitudinals 1. Side Dynamic loads (sea and cargo) are forcing the side longitudinal to flex in and out •High alternating bending stresses towards the end supports (web frames) •Highly stressed areas created around geometric ’hard points’ (bracket toes, scallops, flat bars) Slide 13 18.02.2005
    • Oil Tankers Stress concentration factors More Stress concentration factors ; • Kg : Gross Geometry (from FEM analysis) • Kw : Weld Geometry (typical 1,5) • Kn : Unsymmetrical Stiffeners (L& bulb-profiles) Slide 14 18.02.2005 1. Side
    • Oil Tankers Slide 15 Standard repair proposal longs / webframes 18.02.2005 1. Side
    • Oil Tankers Cracks in web frame cut outs Cr ac ks Slide 16 18.02.2005 1. Side Cracks around openings for side longitudinals in web frames
    • Oil Tankers Cause for cracking in cut outs for longitudinals 1. Side Sea loads induce shear stresses in the web frame High shear stresses around openings etc, where shear area is reduced Shear stress Shear stress Slide 17 18.02.2005
    • Oil Tankers Consequence of crack in web frame 1. Side How does this damage impact on the function of the web frame? Side longitudinals loose their support Re-distribution of shear stresses in web frame May lead to overloading of adacent structure Slide 18 18.02.2005
    • Oil Tankers Crack in side longitudinal at transverse bulkhead 1. Side longitudinal connections to transverse bulkheads Slide 19 18.02.2005 Cracks in side longitudinal connection to stringers at transverse bulkhead Side
    • Oil Tankers Why cracking at transverse bhd.? Ship side 1. Side Relative deflections occur between the ’rigid’ transverse bulkhead and the flexible web frame construction Sea pressure The relative deflection induces additional bending stresses at the end connection of side longitudinals to the transverse bulkhead. Also important at wash bulkheads. Slide 20 18.02.2005
    • Oil Tankers FEM plot of double hull oil tanker 1. Side Loading condition: External dynamic sea pressure at full draught Slide 21 18.02.2005 Relative deflection
    • Oil Tankers Suggestions? Consequence of damage 1. Side Cracks in side longitudinals: - leakage Slide 22 18.02.2005 oil leakage and pollution longitudinal may break off in worst case (a series of cracks in same area) could induce a larger fracture (loss of ship side)
    • Oil Tankers Indents of side shell with stiffeners 1. Side Mainly from contact damages: The terms ’indents’ and ’buckling’ should not be mixed up with each other, as the cause for these damages are different: -Indents: Mainly due to contact damages Slide 23 18.02.2005 -Buckling: Due to excessive in-plane stresses
    • Oil Tankers Slide 24 Consequense of indents 18.02.2005 1. Side
    • Oil Tankers Consequense of indents 1. Side Large area set in (plating and stiffeners) gives reduced buckling capacity Adjacent areas may then be overloaded Sharp indents may lead to cracks and possible leakage Slide 25 18.02.2005
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Bottom Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Web frames 18.02.2005 2. Bottom
    • Oil Tankers Structural functions of bottom 2. Bottom Watertight integrity • Resist external sea pressure • Resist internal pressure from cargo and ballast Flange in hull girder • Bottom plating and longitudinals act together as the lower flange in the hull girder beam Slide 2 18.02.2005
    • Oil Tankers Structural build up of bottom – single skin tanker Bilge Bottom plating w/longitudinals Keel plate Slide 3 18.02.2005 CL girder Web frame 2. Bottom
    • Oil Tankers Structural build-up of a double bottom structure Inner bottom plating (tank top) with longitudinals 2. Bottom Buttress Hopper plating with longitudinals Hopper web plating Outboard girder (margin girder) Slide 4 CL double bottom girder 18.02.2005 Bottom plating with longitudinals Transverse girder / floor
    • Oil Tankers Function: Watertight integrity 2. Bottom Fixation? External loads induce shear forces and bending moments in the bottom longitudinals, acting as single beams (between each web frame) Bottom longitudinal as a single beam between two web frames Slide 5 18.02.2005 Cont. BM and SF distribtion for a single beam with distributed load and fixed ends
    • Oil Tankers Function: Watertight integrity 2. Bottom Bottom plating with longitudinals are also acting as flange for the transverse web frame p L SF Transverse bottom girder/web frame is supported at the longitudinal bulkheads (max. shear force towards long. bhds.) Slide 6 18.02.2005 BM
    • Oil Tankers Bottom is supported by ship side and longitudinal bulkhead 2. Bottom Double span for double bottom without CL longitudinal bulkhead Shear stress in double bottom floor due to external sea pressure Slide 7 18.02.2005
    • Oil Tankers Function: Flange in hull girder 2. Bottom Global bending moment induces longitudinal stresses in the bottom plating and longitudinals σL σL Section A-A Slide 8 18.02.2005 Longitudinal stresses (+/-) are acting in the bottom plating and longitudinals due to bending of hull girder
    • Oil Tankers Double bottom structure 2. Bottom Load distribution in double bottom girder system Slide 9 18.02.2005
    • Oil Tankers Load response double bottom 2. Bottom Stresss flow shortest way to support Cont. Slide 10 18.02.2005
    • Oil Tankers Double bottom structure 2. Bottom The double bottom is a grillage structure built up by transverse girders/floors and longitudinal girders With few longitudinal girders, double bottom stresses resulting from the net load on the girder system are mainly transferred in the transverse direction Net load Shear force Shear fo Double bottom transverse girder (web frame) as a Slide 11 18.02.2005 single I-beam rce High shear stresses in floors & girders in way of transv. Bhd. And hopper tank
    • Oil Tankers Characteristic damages 2. Bottom 1. Bilge keel terminations – crack in hull plating 2. Fatigue cracking in bottom longitudinal connections to web frame and transverse bulkhead 3. Corrosion of bottom structures 4. Hopper knuckle – cracks Slide 12 18.02.2005
    • Oil Tankers Bilge keel cracking 2. Bottom Oil Tanker 285,690 DWT built 1990 Crack in hull plating i.w.o. bilge keel terminations Bilge keel Crack in hull plating in way of bilge keel toes Slide 13 18.02.2005
    • Oil Tankers Bilge keel cracking 2. Hot spot Bilge keel Longi Slide 14 18.02.2005 tudina l stres s Bottom
    • Oil Tankers Bilge keel cracking 2. Web frame/Bilge Bracket All measures in mm 125 Edges to be grinded smooth Ship side Pad plate 10-15mm Bilge Keel 200 Full pen. weld 1600 100 25 100 Slide 15 18.02.2005 Bottom
    • Oil Tankers Cracking in bottom longitudinals Bottom long. flat bar connection Similar16 Slide cracking in bottom longitudinals is also 18.02.2005 valid for double hull tankers 2. Bottom Bottom long. tripping bracket connection
    • Oil Tankers Cause for cracking in bottom longitudinals Bottom 2. Bottom longitudinals are subject to both: Web/ Trans bhd Web M M p 1. Local stress from lateral dynamic sea loading 2. Longitudinal stresses from hull girder bending Slide 17 18.02.2005
    • Oil Tankers Consequences of cracks in bottom longitudinals: 2. Bottom -Leakage of oil - Crack may propagate further into bottom plating and induce a larger transverse fracture Slide 18 18.02.2005
    • Oil Tankers Example: Cracks in inner bottom 2. Bottom Oil Tanker 95,371 DWT Crack in tank top plating at toes of transverse bulkhead buttress P/S Crack in toe of big brackets connecting transverse bulkhead and tank top plating (in various cargo tanks along ships length) Crack propagating through tank top plating (a few cases) Slide 19 18.02.2005 Crack in bracket toe
    • Oil Tankers Cracking in double bottom longitudinals 2. Bottom Cracks in flatbar connections for bottom and inner bottom longitudinals Slide 20 18.02.2005
    • Oil Tankers Cause for cracking in double bottom longitudinals 2. Bottom In a ballast condition there is a net overpressure in the double bottom ballast tank (full ballast tank and empty cargo tank) In a loaded condition there will be a negative net pressure on the double bottom (empty ballast tank, full draft and full cargo tank) This effect may cause yield stress in hot spots at flat bar connections Due to the dynamic +/- variation of stresses, low cycle fatigue may occur Slide 21 18.02.2005
    • Oil Tankers Illustration – double bottom flatbar connections 2. Bottom Tensile stresses in critical structural details The double bottom structure is exposed to large forces both in ballast and loaded condition Slide 22 18.02.2005
    • Oil Tankers Corrosion of bottom structures 2. Bottom Local corrosion (pitting): may occur all over the bottom plating, but area below and around bell-mouth is particularly exposed Pitting is also applicable for double hull tankers 23 Slide i.w.o. tank top plating 18.02.2005
    • Oil Tankers Corrosion of bottom structures 2. Bottom - Pittings and local corrosion may cause leakage, in general not any structural problem - General corrosion will reduce the bottom sectional area, which can lead to an increased stress level: 1. Higher risk for fatigue cracks in bottom longitudinals 2. Higher risk for buckling of plate fields in the bottom Longitudinal stress Force F σL = A Area Increased risk for fatigue cracking and buckling of bottom panels if general corrosion has developed over the cross section Slide 24 18.02.2005
    • Oil Tankers Slide 25 Cracking in hopper knuckle 18.02.2005 Crack in hopper knuckle at web frame connections 2. Bottom
    • Oil Tankers Cause for cracking in hopper knuckle 2. Bottom - Bending of double bottom due to external and internal dynamic loads induces membrane stresses in the inner bottom (flange in the double bottom transverse girder) σL Bending moment Bending stress in inner bottom plating Slide 26 18.02.2005 Bending stress in double bottom girder σL
    • Oil Tankers Cause for cracking in hopper knuckle 2. Bottom - Inner bottom membrane stresses are transferred into the hopper plating - The turn of the stress direction (inner bottom to hopper plating) results in an unbalanced stress component Resulting membrane stress in hopper plating Membrane stress from bending of transverse girder Un-balanced stress component - This effect together with the knuckle being a geometric ‘hard point’ at web frame connections, induce very high stresses in the knuckle point Slide 27 18.02.2005
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Deck Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Web frames 18.02.2005 3. Deck
    • Oil Tankers Structural functions of deck 3. Deck Flange in hull girder - Deck plating and longitudinals act as the upper flange in the hull girder beam Slide 2 18.02.2005
    • Oil Tankers Structural build up of deck – single skin tanker Deck plating w/longitudinals Transverse deck girder / Web frame Slide 3 18.02.2005 Deck CL girder 3. Deck
    • Oil Tankers Function: Flange in hull girder 3. Deck Hull girder bending moment induces longitudinal stresses in the deck plating and longitudinals Longitudinal stresses (+/-) are set up in the deck plating and longitudinals due to bending of hull girder σL Slide 4 18.02.2005 σ L
    • Oil Tankers Longitudinal stresses in deck 3. Longitudinal stresses from bending of hull girder is maximum at midship Midship area most susceptible to fatigue cracking and buckling Bending moment Slide 5 18.02.2005 Max Deck
    • Oil Tankers Characteristic damages 1. Cracks in deck longitudinals 2. Crack in deck plating 3. Corrosion of deckhead 4. Buckling of deck Slide 6 18.02.2005 3. Deck
    • Oil Tankers Cracking in deck longitudinals 3. Deck Deck longitudinal connection to web frames Deck longitudinal connection to transverse bulkhead Slide 7 18.02.2005
    • Oil Tankers Cracking in deck longitudinals Oil Tanker 135,000 DWT built 1991 Crack main deck plating Slide 8 Crack in underdeck support for hose handling crane (P/S, midship area) 18.02.2005 3. Deck
    • Cause for cracking in deck longitudinals Oil Tankers 3. The wave induced excitation of the hull girder leads to dynamic axial stress in the deck longitudinals + + _ _ The cyclic variation of axial stress may lead to fatigue cracks initiating at hot spots A loaded condition will normally induce compression stress in the deck (sagging) A ballast condition will normally induce tension stress in the deck (hogging) Slide 9 18.02.2005 Deck
    • Oil Tankers Cracks in deck longitudinals - May result in oil spill on deck - Corrosion is highly influencing the fatigue life of a detail - A crack could develop further in the deck plating (brittle fracture) Slide 10 18.02.2005 3. Deck
    • Oil Tankers Openings in deck 3. Deck σ Kg.Kw. σ σ Longitudinal stress-flow around manhole in deck Slide 11 18.02.2005 Increased stress level around openings in deck!
    • Oil Tankers Example: crack in scallop in deck longitudinal 3. Deck Oil Tanker 123,000 DWT built 2000 Crack main deck plating (after 3 years) Slide 12 Scallop in deck18.02.2005 longitudinal is close to access opening in deck. This will give an additional accumulated stress in the longitudinal, which is believed to be the cause for the damage.
    • Oil Tankers Crack in deck plating 3. Tanker for Oil 99328 DWT built 1996 Crack in deck plating Crack in deck plating at hose saddle support (midship area) Slide 13 18.02.2005 Deck
    • Oil Tankers Corrosion of deckhead The ullage space (deckhead) is an area susceptible to general corrosion Slide 14 18.02.2005 3. Deck
    • Oil Tankers Corrosion of deckhead 3. Deck A reduction of the deck transverse sectional area due to general corrosion will lead to an increased stress level in deck Higher stress σL Longitudinal stress level in deck Force F σL = A n.a. Area σL Longitudinal stress distribution Long. stress distribution (with reduced deck sectional area) Reduced sectional area in deck may lead to plate buckling Slide 15 18.02.2005
    • Oil Tankers Corrosion of deckhead 3. Deck Higher stress level in deck due to general corrosion σL Longitudinal stress Force F σL = A Area σL A reduction of the deck transverse sectional area due to general corrosion will lead may lead to buckling problems to an increased stress level in deck Slide 16 18.02.2005
    • Oil Tankers Corrosion of deckhead 3. Deck Flatbars have poor buckling capacity Slide 17 18.02.2005 L-profiles have good buckling capacity
    • Oil Tankers Buckling in deck Buckling in deck is most likely to occur in the midship region where the hull girder bending moment is at its maximum Buckling of a plate field (plating with stiffeners) Slide 18 18.02.2005 3. Deck
    • Oil Tankers Cause for buckling in deck 3. Deck Buckling in deck is a result of in plane compression forces in excess of the buckling capacity of the deck plate field Such a situation may occur if the transverse section of the deck is reduced due to general corrosion and the vessel is in a fully loaded (sagging) condition Buckling of complete plate field Slide 19 18.02.2005 The deck buckling may take the form of one plate between two deck longitudinals or in worst case a complete plate field (both deck plating with stiffeners)
    • Oil Tankers Corrosion of deckhead / buckling: 3. Deck - heavy corrosion of deck may lead to buckling - small buckles (plate between stiffeners) is a strong warning sign that longitudinal stresses are high - large buckles (plate field) may lead to loss of global strength and in worst case a total collapse of the hull girder Remember max 10% diminution of deck transverse sectional area! Slide 20 18.02.2005
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Transverse bulkhead Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Webframes 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Structural build up of transverse bulkhead Transverse bulkhead plating w/stiffeners Stringers Buttress Slide 2 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Structural functions 4. Transverse bulkhead Watertight integrity - Resist internal pressure from cargo and ballast (cargo boundary) - Safety against collapse if water ingress (boundary for flooding) Hull girder stiffness - Transverse bulkhead is an important contributor to the hull girder transverse stiffness Slide 3 18.02.2005
    • Oil Tankers Functions of transverse bulkhead The transverse bulkhead must withstand internal pressure loads from cargo and ballast The distribution of cargo and ballast introduces alternate loading on sections of the transverse bulkheads (single skin tanker) Typical fully loaded condition (single skin) Slide 4 18.02.2005 Typical ballast condition (single skin) 4. Transverse bulkhead
    • Oil Tankers Function: tank boundary 4. Transverse bulkhead Stringer Shear force Bending moment Slide 5 Stiffener 18.02.2005
    • Oil Tankers Function: tank boundary One sided loading on the transverse bulkhead introduces stresses in the transverse bulkhead as a panel Bulkhead will flex out and high stresses occur at end connections towards deck and bottom Slide 6 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Function: transverse stiffness 4. Transverse bulkhead Transverse bulkheads are an important contributor to the hull girder strength Sea pressure Sea pressure Transverse stiffness Slide 7 18.02.2005
    • Oil Tankers Characteristic damages 1. Stringer toes – cracking 2. Bottom longitudinal bracket connection to transverse bulkhead - cracks 3. Cracking of transverse bulkhead stiffeners connection to stringers Slide 8 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Cracking in stringer toe Cracks in stringer toes and heel Slide 9 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Slide 10 Cracking in stringer toe 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Cause for cracking in stringer toe Compression/tension stresses from one sided loading Full cargo tank Sea pressure Slide 11 Full cargo tank 18.02.2005 Very high alternating bending stresses in stringer toe 4. Transverse bulkhead
    • Oil Tankers Cracks in stringer 4. Transverse bulkhead Crack Stringer flange Longitudinal bulkhead Stringer web Slide 12 May cause contamination of ballast water and small oil spills 18.02.2005
    • Oil Tankers Cracks in bottom longitudinals 4. Transverse bulkhead 17. Cracks in toe of transverse bulkhead bracket ending at bottom longitudinals (wing tanks, midship area) Slide 13 18.02.2005
    • Oil Tankers Cause - cracks in bottom brackets 4. Transverse bulkhead Crack in bracket toe (hot spot) Slide 14 18.02.2005 One sided loading at the transverse bulkhead induce high local alternating bending stresses at the bracket toe
    • Oil Tankers Double btm at transverse bulkhead 4. Transverse bulkhead Similarily, one sided alternate loading at the transverse bulkhead also induces high stresses for a double bottom structure Modern designs have no longitudinal girders in double bottom giving large relative deflection Critical areas Slide 15 18.02.2005
    • Oil Tankers Crack in transverse bulkhead stiffeners connection to stringers Connection of stringer to transverse bulkhead with associated brackets Slide 16 18.02.2005 4. Transverse bulkhead
    • Oil Tankers Cause for cracking in transverse bulkhead stiffeners 4. Transverse bulkhead One sided internal loading from cargo and ballast sets up a shear stress distribution in the bulkhead stiffener Highly stressed areas are created around geometric ’hard points’ at stiffener end connections to the stringer -may cause ballast water contamination and possible oil spills Slide 17 18.02.2005
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Longitudinal bulkhead Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Web frames 18.02.2005 5. Longitudinal Bulkhead
    • Oil Tankers Structural build up of longitudinal bulkhead 5. Longitudinal bulkhead plating with stiffeners Web frame Slide 2 18.02.2005 Cross ties Longitudinal Bulkhead
    • Oil Tankers Structural functions of long.bhd 5. Longitudinal Bulkhead Watertight integrity - Resist internal pressure from cargo and ballast (cargo boundary) - Safety against collapse if water ingress (boundary for flooding) Web in hull girder - Contributes to hull girder longitudinal stiffness Slide 3 18.02.2005
    • Oil Tankers Function : Cargo boundary 5. Longitudinal Bulkhead Internal loads induce shear forces and bending moments in the longitudinal bulkhead longitudinal (between each web frame) Stresses are loaded onto the web frames and further into the hull girder structure Slide 4 18.02.2005
    • Oil Tankers Function: Web in hull girder 5. Longitudinal Bulkhead Longitudinal bulkhead together with ship side is taking up global shear forces from wave induced loads and weight/buoyancy distribution along the vessel length A R1 F A A R2 A Shear force distribution resulting from global loads for midship section Slide 5 18.02.2005 Section A-A SF
    • Oil Tankers Characteristic damages 5. Longitudinal Bulkhead 1. Cracks in bulkhead longitudinals connection to stringers at transverse bulkhead 2. Shear buckling of longitudinal bulkhead Slide 6 18.02.2005
    • Oil Tankers Crack in long.bhd longitudinals connection to stringers 5. Longitudinal Bulkhead Connection of longitudinal bulkhead longitudinals to stringers with associated brackets Slide 7 18.02.2005
    • Oil Tankers Cause for cracking in long.bhd at stringer connections 5. Longitudinal bulkhead is flexing depending on the loading condition (filling of tanks) Fully loaded condition Ballast condition High bending stresses towards the supports (transverse bulkheads) Slide 8 18.02.2005 Longitudinal Bulkhead
    • Oil Tankers Cause for cracking in long.bhd stringer connections Full ballast tank H ot sp ot May cause contamination of ballast water and small oil spills Slide 9 18.02.2005 5. Longitudinal Bulkhead
    • Oil Tankers Slide 10 Shear buckling of longitudinal bulkhead 18.02.2005 Shear buckling is most likely to occur in areas towards the transverse bulkheads, but may also occur in other areas depending on the thickness of the bulkhead plating 5. Longitudinal Bulkhead
    • Oil Tankers Shear buckling of longitudinal bulkhead SF maximum at transverse bulkheads Longitudinal shear force distribution – an example Slide 11 18.02.2005 5. Longitudinal Bulkhead
    • Oil Tankers Cause for shear buckling 5. Longitudinal Bulkhead Result of excessive shear stress in the bulkhead plating Corrosion increases possibility for shear buckling SF SF Shear buckling (middle and upper area of bulkhead most exposed due to corrosion risk and reduced original scantlings) Shear buckled panels will have a reduced shear strength, 18.02.2005 which may lead to an overload of adjacent areas Slide 12
    • Oil Tankers 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Web frames Side Bottom Deck Transverse bulkhead Longitudinal bulkhead Web frames 18.02.2005 6. Web frames
    • Oil Tankers Structural build up of web frame Web frame flange Web frames Cross tie Slide 2 18.02.2005 6. Web frames
    • Oil Tankers Function of web frames 6. Web frames - Web frames are supports for the longitudinal stiffeners - Web frames contributes to the hull girder transverse strength Slide 3 18.02.2005
    • Oil Tankers Function of web frame 6. Web frames • Web frames are supports for the longitudinals • Web frames take up local loads from the longitudinal stiffeners and transfer them further into the hull girder • Web frames keep the cross sections together and contribute to the transverse stiffness Slide 4 18.02.2005 Sea pressure Internal pressure
    • Oil Tankers Characteristic damages 6. Web frames 1. Corrosion / buckling of web frame 2. Corrosion / cracking of cross tie connection 3. Cracking of tripping bracket connection to web frame flange Slide 5 18.02.2005
    • Oil Tankers Shear buckling of web frame High shear stress SF SF Slide 6 18.02.2005 6. Web frames
    • Oil Tankers TYP. WEB SEC. (SHEAR STRESS) LC 2 Shear buckling may occur in areas where shear stress is high Slide 7 18.02.2005 6. Web frames
    • Oil Tankers Shear buckling of web frame: Corrosion of web frame increases the risk for shear buckling Corroded cut outs and openings in web frame are exposed to buckling, because of the reduced shear area (high τshear) Slide 8 18.02.2005 6. Web frames
    • Oil Tankers Corrosion of cross tie Weld connection of straight part of cross tie to the side and longitudinal bulkhead Slide 9 18.02.2005 6. Web frames
    • Oil Tankers Corrosion of cross tie 6. Web frames Cross ties are subject to both compression and tension stress depending on loading condition Corrosion Increased stress level Reduced Buckling capacity Cross tie collapse? Slide 10 18.02.2005 +/- Axial stress
    • Oil Tankers Crack in tripping bracket connection to web frame flange Weld connection of large curved flanges and tripping brackets on webframes Slide 11 18.02.2005 6. Web frames
    • Oil Tankers Cause for cracking in web frame flange 6. Web frames Cracks occur due to additional bending stresses from the presence of a tripping bracket in the curved part of the flange - If flange is exposed to tension, the flange will bend outwards - If exposed to compression, the flange will bend inwards Slide 12 18.02.2005 Deflection pattern of free flange
    • Oil Tankers Slide 13 FEM plot of cross tie with deflections 18.02.2005 6. Web frames
    • Oil Tankers Cracks in web frame 6. Web frames • • 18.02.2005 Increased loads on adjacent webframes • Slide 14 Webframe support for longidudinals – reduced support – excessive load on longitudinals May lead to loss of stiffened panel
    • Bulk Carriers Slide 1 Bulk Carriers - Hull Structure 18.02.2005
    • Bulk Contents – Bulk Carriers Carriers 1. Introduction to Bulk carrier hull structure 2. Hull structural breakdown – function of hull elements: • 3. Slide 2 Side, bottom, deck, transverse bulkhead, longitudinal bulkhead, web frames including relevant hull damages for all structural elements Case 18.02.2005
    • Bulk Carriers Characteristics for Bulk Carriers • • • • • • • • • • • Single skin / hopper & top-wing tanks Heavy cargoes Large net load on double bottom High shear stresses shell side Sensitive to leakage - total structural loss High loading rate Transverse strength Green seas Not much public attention (no vetting) Low survival capability when flooded High number of vessels lost Slide 3 18.02.2005
    • Bulk Carriers Bulk Carrier loading flexibility • Bulk Carrier HC/EA Reduced flexibility – Any hold empty at full draught • Bulk Carrier HC/E – hold 2,4,6 …. Empty – Given combination of holds empty at full draught • Bulk Carrier HC – Any hold empty at 80% of full draught • Bulk Carrier – Any hold empty at 60% of full draught Slide 4 18.02.2005
    • Bulk Carriers History • Built in 1954 - Cassiopeia • First bulk carrier with hopper tank – topside tank cross section Slide 5 18.02.2005
    • Bulk Carriers Bulk Carrier particulars 5 cargo holds 7 cargo holds 9 cargo holds Slide 6 18.02.2005
    • Bulk Carriers Slide 7 Nomenclature 18.02.2005
    • Bulk Carriers Slide 8 Nomenclature 18.02.2005
    • Bulk Carriers Structural breakdown of hull - A vessel’s hull can be divided into different hull structural elements - Each element has its function in the structure - In order to assess the structure of a Bulk Carrier you need to understand the function of the structural element you are looking at Slide 9 18.02.2005
    • Bulk Typical damages and repairs Carriers WWW.witherbys.com Slide 10 18.02.2005
    • Bulk Carriers Structural breakdown of Bulk Carrier 7. Hatch coaming & cover 3. 4. 1. 5. Topside tank Transverse bulkhead Side 6. Slide 11 Deck 2. Bottom 18.02.2005 Hopper tank
    • Bulk Hull Structural Breakdown Carriers 1. Side 2. Bottom 3. Deck 4. Transverse bulkhead 5. Hopper tank 6. Topside tank 7. Hatch cover & coaming Slide 12 18.02.2005
    • Bulk Carrier 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Ship side Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank 1. Side
    • Bulk Carrier Structural functions of ship side 1. 1. Watertight integrity (local strength) - Resist external sea pressure - Resist internal pressure from cargo and ballast 2. Web in hull girder (global strength) - Side plating act as the web in the hull girder beam Slide 2 Side
    • Bulk Carrier Structural build up of ship side 1. Upper bracket Side plating Side frames Lower bracket Slide 3 Side
    • Bulk Carrier Structural functions of ship side 1. Watertight integrity (local strength) Ship side must withstand static and dynamic loads from external sea pressure as well internal pressure from cargo and ballast Loads are taken up by the hull plating, stresses are transferred into the vertical side frames – further into the upper and lower bkt’s further into the topwing tank and hopper tank structure Slide 4 Side
    • Bulk Carrier Functions of ship side Watertight integrity (local strength) Lateral loads induces shear forces and bending moments in the vertical side frames. The side frame is a single beam supported at hopper / twt bkt’s Bm SF Slide 5 1. Side
    • Bulk Carrier Functions of ship side 1. Side Ore hold load response; Net load down cause rotation of hopper tank structure. additional moment in the mid-field and upper end SF Slide 6 Bm Bm
    • Bulk Carrier Functions of ship side 1. Side Bm Bm Empty hold load response; Net load up cause rotation of hopper tank structure. additional moment in the mid-field and lower end SF Slide 7
    • Bulk Carrier Functions of ship side 1. Side Web in hull girder (global strength) Ship side is taking up global shear forces resulting from the hull girder bending moment and weight/buoyancy distribution along the vessel length Global loads are acting on the hull girder beam Side plating is acting as web in hull girder beam Slide 8 Cont.
    • Bulk Carrier Function of ship side (longitudinal shear strength) Shear Distribution at a 0 Sagging Bending force Shear moment Shear force (t-m) Hogging cross section Slide 9 Cont.
    • Bulk Carrier Functions of ship side 1. Side Web in hull girder (global strength) - Global shear forces are distributed in the ship side plating Shear force distribution resulting from global loads for midship section Slide 10 Cont.
    • Bulk Carrier Hull damages in ship side 1. Two characteristic damages for ship side: 1. 2. Slide 11 Cracks in side frames at lower / upper bracket connection Corrosion of side frames and lower bkt. – detached bkt’s Side
    • Bulk Carrier Crack in side longitudinal web frame connection 1. Side Cracking in vertical side frame: Vertical side frame lower bkt. commection Slide 12
    • Bulk Carrier Cause for cracking in vertical side frames lower bkt. connections 1. 1b. 1a. The dynamic loads from the sea are taken up by the side plates supported by the vertical side frames and load is transferred to the upper and lower bkt’s. This gives peak of bending moment and shear in way of lower bkt. connection. 1a. 1b. Slide 13 The sniped termination of the bracket flange creates a local stress concentration, which may develop cracks from the toe of the bracket In this point a high bending stress in flange and a stress concentration due to weld (overlap) increase the risk for fatigue cracks. Side
    • Bulk Carrier Crack in side longitudinal web frame connection Possible consequence 1. Side • As these cracks develop, the lower end fixation of the side frame is reduced: – higher bending moment in the middle of the frame – some of the load will be carried by adjacent frames • Crack through stiffener: – beam simply supported lower end, profile may buckle at midfield • Side shell may crack. • Adjacent frames crack – panel collapse, possible water flooding. Slide 14
    • Bulk Carrier Corrosion of side frames and lower bkt. connection 1. Side frames and bkt’s are prone to corrosion, both general corrosion as well as grooving corrosion which may result in : • Fracture in plating/bracket toes • Fractured/detached frames • Local corrosion and grooving • General wastage. Slide 15 Side
    • Bulk Carrier Revised Minimum Thickness List Torig Hold 1: Aft end of Hold 1: Upper bracket web Frame web, middle and upper part Frame web, Lower part Lower bracket web Frame flange thickness, middle and upper part Frame flange thickness, lower part Lower bracket flange thickness Middle part of Hold 1: Upper bracket web Frame web, middle and upper part Frame web, Lower part Lower bracket web Frame flange thickness, middle and upper part Frame flange thickness, lower part Lower bracket flange thickness Forward end of Hold 1: Upper bracket web Frame web, middle and upper part Frame web, Lower part Lower bracket web Frame flange thickness, middle and upper part Frame flange thickness, lower part Lower bracket flange thickness Slide 16 T-min T-subst T-Coat 13,0 13,0 13,0 15,0 20,0 20,0 20,0 9,8 9,8 11,2 11,3 15,0 15,0 15,0 10,6 10,6 11,6 12,2 16,3 16,3 16,3 11,2 11,2 13,0 13,0 13,0 15,0 20,0 20,0 20,0 9,8 9,8 9,9 11,3 15,0 15,0 15,0 10,6 10,6 10,7 12,2 16,3 16,3 16,3 13,0 13,0 13,0 15,0 20,0 20,0 12,5 9,8 9,8 13,9 16,9 15,0 15,0 9,4 10,6 10,6 NB! NB! 16,3 16,3 10,2 11,2 12,7 N/A N/A N/A 11,2 11,2 11,2 12,7 Upper Bracket Middle and upper part of Frame Low er part of Frame N/A N/A N/A 11,2 11,2 N/A N/A N/A N/A N/A Low er Bracket
    • Bulk Carrier Corrosion of side frames and lower bkt. Connection – Consequences • General corrosion of side frames reduce the shear area and section modulus. – Bending moment stress level increases – Stiffeners may collapse in buckling • Local grooving of side frame support bkt’s – Shear area of profile web reduced – If angle bar specially critical • Detached lower side frames – Frames simply supported, increase BM – buckling – Side plate rupture top of hopper tank - flooding Slide 17 1. Side
    • Bulk Carrier Damage impact on function 1. Cracks in vertical side frame - may increase moment in field for frame - may increase loads on adjacent frames - may cause water ingress leakage - may develop to panel collapse - flooding – stability - strength (loss of ship) 2. Corrosion of side frames - As above Slide 18 1. Side
    • Bulk Carrier 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown Bottom Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank 2. Bottom
    • Bulk Carrier Structural functions of bottom 2. Bottom 1. Watertight integrity (local strength bottom / inner bottom) - Resist external sea pressure (bottom) - Resist internal pressure from cargo/ballast & fuel oil 2. Carry net load on double bottom girder structure - Inner bottom / bottom plate & stiffn. are girder flanges - double bottom floors / girders are webs in double bottom girders 2. Bottom flange in hull girder (global strength) - Bottom and inner bottom structure is the bottom flange in the hull girder Slide 2
    • Bulk Carrier Structural build up of bottom Longitudinal girders Floor Slide 3 Pipe tunnel 2. Bottom
    • Bulk Carrier Structural functions of bottom 2. Bottom 1. Watertight integrity (local strength) Bottom plate must withstand static and dynamic loads from external sea pressure as well internal pressure from ballast or fuel oil Inner bottom plate must withstand static and dynamic loads from cargo hold as well as static and dynamic pressure from ballast or fuel oil Cont. Slide 4
    • Bulk Carrier • Structural functions of bottom Stress distribution in a double bottom structure • Forces are taken up by the stiffest structure • • Slide 5 Middle of hold more stresses in transverse direction Towards bhd. – more stresse in longitudinal direction 2. Bottom
    • Bulk Carrier Functions of inner bottom (local 2. Bottom stiffener level) Cargo hold boundary (local strength) External loads induce shear forces and bending moments in the inner bottom longitudinals as single beams (between floors) BM and SF distribtion for a single beam with distributed load and fixed ends Cont. Slide 6
    • Bulk Carrier Load response double bottom 2. Bottom Stresss flow shortest way to support Cont. Slide 7
    • Bulk Carrier Double bottom girders load response 2. Bottom • girders & floors carry the net load to hopper tank and transverse bulkhead • floors carry most of the loads in middle of hold • longitudinal girders carry most of the load towards transverse bulkhead • length / width ratio is important for the distribution of loads between girders & floors • The stiffest elements are taking most of the load / stresses seek the shortest way to supports Slide 8
    • Bulk Carrier Functions of double bottom girder Net Load on double bottom Simple beam model Longitudinal girders represented by springs Slide 9 2. Bottom
    • Bulk Carrier Floors / girders- design 2. Bottom Long. Db. girder High Shear force – No cut-outs / increased thickness Floor Slide 10
    • Bulk Carrier 2. Functions of bottom Bottom 2. Bottom flange in hull girder (global strength) The bottom and inner bottom longs and longitudinal girders are carrying the vertical bending moments from still water and wave induced bending moments along the vessel length Slide 11 Global loads are acting on the hull girder beam Bottom structure is acting as web in hull girder beam Cont.
    • TM Bending moment Bulk Carrier Moment diagram Reduced global bending but high double bottom stresses Still water bending moment [intact] Max allowable bending moment [intact] Slide 12 2. Bottom
    • Bulk Carrier Highly stressed areas 2. Bottom Deck Tanktop + NA Inner bottom level Bottom Bottom Global bending Double bottom bending Bottom plate/longs middle of empty holds (compression ) Bottom plate in loaded holds (tension) Inner bottom plate middle of loaded holds (compression ) Slide 13
    • Bulk Carrier Hull damages bottom / inner bottom 2. Bottom Three characteristic damages for bottom are: 1. 2. Crack / Corrosion of floors – girders in ballast tanks 3. Slide 14 Cracks in inner bottom plate in way of knuckle to hopper tank Indents of inner bottom plate due to cargo handling
    • Bulk Carrier Cracks in way of hopper knuckle 2. • Heavy ballast condition – tension in inner bottom plate Fractures Slide 15 Bottom
    • Bulk Carrier Cracks in way of hopper knuckle Hopper plate Inner bottom plating Slide 16 2. Bottom
    • Bulk Carrier Cracks in way of hopper knuckle Impact on function 2. Bottom • Loss of watertight integrity – leak ballast – cargo • Cracks extending from one webframe to another severe impact on double bottom strength Slide 17
    • Bulk Carrier Fractures in connection of floors i.w.o. hopper Damage bottom Inner Fractures Repair A 2. Full penetration weld connection to the inner bottom and hopper plating A Double bottom floor Collar plate Hopper transverse web Edge chamfered for full penetration weld Side girder Reinforcement A View A-A Alternatively, may stop at longitudinals where fitted Transverse fractures in hopper web plating possibly extending into the hopper sloping plate Reinforcement B Inner bottom Slide 18 Floor or transverse web plating Fracture in the floor/web of the hopper transverse Intermediate brackets (i.e. between floors) Face plate of transverse web Inner bottom Scarfing brackets View B-B Bottom
    • Bulk Carrier Crack in floor 2. • Floor in way of high shear stress • Connection at bottom longitudinals Repair A Lug Damage Floor or transverse web frame Longitudinal Buckling and/or fracturing Fractures New plating of enhanced thickness Repair B Bottom shell plating, inner bottom plating, side shell plating or hopper sloping plate Slide 19 Fractures Full collar plate Bottom
    • Bulk Carrier Crack in floor impact on function 2. Bottom • Loss of support of longs – increased stresses at adjacent floors – longs • Large crack in floor – increased stresses in adjacent floors - girders Slide 20
    • Bulk Carrier Slide 21 Indents of inner bottom plate 2. Bottom
    • Bulk Carrier Indents of inner bottom plate 2. Impact on function • Difficult with discharge of cargo – cleaning • Severe indents – cracks – leak • Impact on buckling capacity of panel Slide 22 Bottom
    • Bulk Carrier Fracture in longitudinals at stool connection Damage Bottom Cause Stool Inner bottom longitudinal Fractures Bottom shell longitudinal Slide 23 2. Damage due to stress concentrations and large relative deflections (bulkhead stool - first floor) leading to accelerated fatigue in this region.
    • Bulk Carrier Fracture in longitudinals at stool connection 2. Bottom Repair Stool Too large brackets may cause further problems. Additional brackets with soft toes Where required the longitudinal to be cropped and part renewed Slide 24
    • Bulk Carrier Fracture in longitudinals at stool connection Damage Repair Stool Inner bottom Modified brackets with soft toes Bilge well Fracture Additional bracket with soft toes Fracture Slide 25 Where required the longitudinals to be cropped and part renewed 2. Bottom
    • Bulk Carrier 1. 2. 3. 4. 5. 6. 7. Slide 1 Hull Structural Breakdown - Deck Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank Hatch cover & coaming 3. Deck
    • Bulk Carrier Structural functions of deck 1. Watertight integrity (local strength) - Resist external sea pressure 2. Transverse strength of the hull girder 3. Upper flange in hull girder (global strength) Slide 2 3. Deck
    • Bulk Carrier Structural build up of deck • Main deck outside line of hatches • Deck between hatches • Longitudinal hatch coaming • Transverse hatch coaming • Deck webframe Slide 3 3. Deck
    • Bulk Carrier Structural functions of deck 1. Watertight integrity (local strength) Deck plate must withstand static and dynamic loads from green sea pressure as well as internal pressure from ballast tank Slide 4 3. Deck
    • Bulk Carrier • Slide 5 Structural functions of deck Stress distribution in deck 3. Deck
    • Bulk Carrier • Structural functions of deck Deck between hatches Flexing in transverse direcction Slide 6 3. Deck
    • Bulk Carrier Structural functions of deck 3. • The element contributing to transverse strength: – Deck plate and transverse stiffener between hatches – Hatch end girder – Upper stool tank Slide 7 Deck
    • Bulk Carrier 3. Functions of deck Deck 2. Upper flange in hull girder (global strength) The deck plating and longs outside line of hatches are carrying the vertical bending moments from still water and wave induced bending moments along the vessel length Global loads are acting on the hull girder beam Deck structure is acting as web in hull girder beam Cont. Slide 8
    • Bulk Carrier Hull damages deck 3. Deck Characteristic damages for deck are: 1. 2. Buckling of deck between hatches 3. Slide 9 Cracks in deck plate at end of longitudinal hatch coaming Crack in deck plate in way of hatch corner
    • Bulk Carrier Crack in deck plate at hatch coaming end 3. Deck • Longitudinal stresses are going into the side hatch coamings • At the toe of the bkt. There is a local stress concentration Possible consequences: - Water leak to cargo - Long crack – longitudinal strength problem Slide 10
    • Bulk Carrier Buckling of deck between hatches 3. • Ore carrier (250 000 DWT) Local buckling of deck plates and transverse stiffeners. • Deck plates and transv. Stiffn. buckled • Slide 11 Deck
    • Bulk Carrier Slide 12 Buckling of deck between hatches 3. Deck
    • Bulk Carrier Buckling of deck between hatches 3. • Buckling caused by excessive stresses in transverse direction deck between hatches 2 adjacent holds filled Slide 13 Deck
    • Bulk Carrier Buckling of deck between hatches 3. • Possible consequences of buckling of deck between hatches: - Ships transverse strength severely affected - Ships sides comes in - Hatch coamings deformed - Loss of weather tight integrity Slide 14 Deck
    • Bulk Carrier Hull Structural Breakdown Bulkhead 1. Side 2. Bottom 3. Deck 4. Transverse bulkhead 5. Hopper tank 6. Topside tank 7. Hatch cover & coaming Slide 1 4. Bhd.
    • Bulk Carrier Structural functions of bhd. 1. Cargo hold boundary (local strength) - Resist internal pressure from cargo / ballast - Resist water flooding 2. Transverse strength of the hull girder Slide 2 4. Bhd.
    • Bulk Carrier Structural build up of deck 4. Bhd. Corrugated bhd. Lower stool Upper stool Slide 3
    • Bulk Carrier Structural build up of deck 4. Bhd. Upper stool diaphragm Hatch coaming bkt Lower stool diaphragm Shedder plate Slide 4
    • Bulk Carrier Structural functions of bhd. 1. Cargo hold boundary (local strength) Transverse bhd. plate must withstand static and dynamic loads from bulk cargo and ballast The bulkhead must also withstand the water pressure from flooding of cargo hold without collapse Slide 5 4. Bhd.
    • Bulk Carrier Slide 6 4. Bhd.
    • Bulk Carrier Structural functions of bhd. 4. Bhd. Design load conditions • Water flooding • ” Light cargo ” full hold SF High stress lower / upper end & midfield Slide 7 Bm
    • Bulk Carrier Structural functions of bhd. flange Web Slide 8 4. Bhd.
    • Bulk Carrier Structural functions of bhd. Moment 4. Bhd. One sided load on bhd. Introduce a moment in lower stool. Size of moment incrase by narrow lower stool ( s – on sketch) High stress at intersection lower stool diaphrame and longitudinal girders s Slide 9 Narrow stool – high shear stress in diaphrames
    • Bulk Carrier Structural functions of bhd. 4. Bhd. • Transverse bhd. Supports the double bottom long. girders Moment on lower stool Empty hold Slide 10 Loaded hold
    • Bulk Carrier Structural functions of bhd. • Transverse bhd. Carry global shear from double bottom to ship side Net load from cargo Slide 11 4. Bhd.
    • Bulk Carrier Structural functions of bhd. • Upper and lower stool transverse strenght of hull Flexible part Slide 12 4. Bhd.
    • Bulk Carrier Hull damages transverse bulkhead 4. Bhd. Two characteristic damages for transverse bulkheads: 1. 2. Slide 13 Collapse of bulkhead due to corrosion in lower stool diaphrames. Shear buckling of corrugated bulkhead due to excessive corrosion
    • Bulk Carrier 4. Collapse of transverse bulkhead Capesize Bulk Carrier 9 holds – 20 years • Loaded with pellets alternate holds • Bhd. Hold 8/9 collapsed at bottom • Hatch coamings / covers pulled down • Inspection revealed heavy corrosion in lower stool • Void space – humidity – heating in double bottom below. Heavy corrosion Slide 14 Moment s Bhd.
    • Bulk Carrier Bulk Carrier loaded with pellets 1. 2. 3. Slide 15 4. Collapse of transverse bulkhead Bhd. LO W E DIA R STO PHR O AM L E Transverse bulkhead collapsed at connection between lower stool and tank-top Inspection revealed excessive corrosion at the lower end of the diaphrames in excess of 50%. Bulkhead collapsed due to insufficient shear area at connection to tank-top Casualty information SF Bm
    • Bulk Carrier Collapse of transverse bulkhead Impact on function • No boundary between cargo holds • Transverse strength of hull girder lost • Watertight integrity lost upper deck • To be repaired before leaving port Slide 16 4. Bhd.
    • Bulk Carrier Shear buckling transverse corrugated bulkhead 4. Bhd. Capesize bulkcarrier 7,5 years found with shear buckling on transverse corrugated bulkehad observed during routine inspection. Experience feedback 2 adjacent holds filled Buckling cause Slide 17
    • Bulk Carrier Shear buckling transverse corrugated bulkhead impact on function 4. Bhd. • Hatch end coaming will be deformed – impact on weather-tightness - flooding • Longitudinal girders in double bottom is getting less support at transverse bulkhead – more stresses in the floors. • Hopper tanks will rotate more – loads on side frames will increase • Vessels transverse strength will be severely affected. • Vessel may capsize! Slide 18
    • Bulk Carrier 1. 2. 3. 4. 5. 6. Slide 1 Hull Structural Breakdown – Hopper tank Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank 5. Hopper tank
    • Bulk Carrier Structural functions hopper tank 5. Hopper tank 1. Cargo hold boundary (local strength) - Resist internal pressure from cargo / ballast - Resist sea pressure on ship side 2. Give support for side structure and double bottom 3. Slide 2 Web in hull girder (global strength) - Side plating / hopper tank sloping plate are part of the web in the hull girder beam - Hopper tank bottom plate and lower part of side plate are part of the bottom flange in the hull girder
    • Bulk Carrier Structural build up hopper tank 5. Hopper tank Hopper tank sloping plate Hopper tank side plate Bilge plate Bottom side girder outboard Slide 3
    • Bulk Carrier Structural build up hopper tank 5. Hopper tank Hopper transverse web frame Vertical side frame supporting bkt. Slide 4
    • Bulk Carrier Structural functions of hopper tank Plate – Stiffener – Web frame – Panel – 5. Hopper tank Hull girder 1. Cargo hold boundary (local strength) Hopper tank sloping plate must withstand static and dynamic loads from bulk cargo and ballast 1. Watertight integrity (local strength) Bottom and side plate must withstand static and dynamic loads from external sea pressure and from internal ballast Slide 5 Cont.
    • Bulk Carrier Structural function Local loads 5. Hopper tank Design load conditions • Ballast pressure • Ore load Pressure due to cargo Pressure due to ballast Slide 6
    • Bulk Carrier Structural function Hopper tank Local loads 5. Hopper tank High stress at webframe connection & midfield BM and SF distribtion for a single beam with distributed load and fixed ends Slide 7 Similar for side longs and bottom longs
    • Bulk Carrier Structural function Hopper tank Local loads 5. Hopper tank Combined effect of pressure on ship side and on double bottom gives compression stresses in hopper plate Se Full load condition empty hold Sea pressure Slide 8 pre a ure ss
    • Bulk Carrier Structural function of webframe Local loads Hopper tank webframe 5. Concentrated loads from hopper longs SF Areas with high shear stress Slide 9 Hopper tank BM Back
    • Bulk Carrier Functions of hopper tank global loads Web in hull girder (global strength) Ship side, hopper tank and top-wing tanks is taking up global shear forces from wave induced loads and weight/buoyancy distribution along the vessel length Slide 10 5. Hopper tank Global loads are acting on the hull girder beam
    • Bulk Carrier Global function of hopper tank 5. Hopper tank Global shear force Shear flow distribution in hopper tank Slide 11 Note the shear force is distributed between hopper tank sloping plate and ship side
    • Bulk Carrier Global response of hopper tank High shear stress in hopper tank plate and outboard double bottom girder towards bulkheads NET LOAD ON DOUBLE BOTTOM GIRDER Slide 12 5. Hopper tank
    • Bulk Carrier Sea pressure Global response of hopper tank r hea ss S e str 5. Net load on double bottom Effect of side pressure and net load on double bottom gives torsion of hopper tank, specially in loaded ore hold Slide 13 Hopper tank
    • Bulk Carrier Hull damages Hopper tank 5. Hopper tank Characteristic damages for hopper tanks: 1. 2. Slide 14 Cracks in way of knuckle line between hopper tank sloping plate and inner bottom plate Crack in webframe in way of sloping plate lower long. Connection to webframe
    • Bulk Carrier Crack in webframe at hopper tank / inner bottom knuckle 5. Hopper tank Heavy ballast condition Net load down and out on shell side Stress concentration in way of scallop Slide 15
    • Bulk Carrier • • Repair method Close scallop by doubler plate, (reduce local stress concentration) Fit bracket in line with inner bottom (reduce effect of hard spot where inner bottom welded to webframe) Or: • Vertical brackets fwd. / aft of webframe (distribute the stresses in way of the webframe) Slide 16 5. Hopper tank
    • Bulk Carrier Crack in webframe at lower end sloping plate 5. Hopper tank Webframe cracked at scallop for longitudinal High Shear stress Slide 17
    • Bulk Carrier Crack in webframe impact on function 5. Hopper tank • Crack will reduce webframe strength • Hopper tank longitudinals will transfer more load to the adjacent webframes • Hopper tank longitudinal may loose its support – double span of stiffener • May develop cracks in adjacent webframes • May develop cracks in hopper tank plate – water flooding of cargo hold Slide 18
    • Bulk Carrier 1. 2. 3. 4. 5. 6. 7. Slide 1 Hull Structural Breakdown – topside tank Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank Hatch cover & coaming 6. Topside tank
    • Bulk Carrier Structural functions topside tank 6. Topside tank 1. Cargo hold boundary (local strength) - Resist internal pressure from cargo / ballast - Resist sea pressure on ship side 2. Give support for side structure and hatch coaming 3. Slide 2 Web in hull girder (global strength) - Side plating / top-wing tank sloping plat are part of the web in the hull girder beam - topside tanks upper part is part of the upper flange in the hull girder beam
    • Bulk Carrier Structural build up topside tank 6. Topside tank Deck plating & longs Topside tank, vertical strake Topside tank, sloping plate & longs Topside tank, side plate& longs Slide 3
    • Bulk Carrier Structural build up topside tank 6. Topside tank Topside tank transveres webframe, deck Topside tank transveres webframe, side Topside tank transveres webframe, sloping plate Vertical side frame supporting bkt’s, upper Slide 4
    • Bulk Carrier Structural functions of topside tank tank Plate – Stiffener – Web frame – Panel – 6. Topside tank Hull girder 1. Cargo hold boundary (local strength) topside tank sloping plate must withstand static and dynamic loads from bulk cargo and ballast 1. Watertight integrity (local strength) Deck and side plate must withstand static and dynamic loads from external sea pressure and from internal ballast Slide 5 Cont.
    • Bulk Carrier Structural function Local loads 6. Topside tank Design load conditions • Ballast pressure • Light bulk cargo / ballast Pressure due to ballast ( cargo) Slide 6 • Sea pressure
    • Bulk Carrier Structural function Hopper tank Local loads Topside tank lower side long. 6. Topside tank High stress at webframe connection & midfield BM and SF distribtion for a single beam with distributed load from external and sea-presure and fixed ends Cont. Slide 7
    • Bulk Carrier Structural function Hopper tank Local loads 6. Topside tank BM & SF upper end vertical side frame External sea pressure Distributed load on side frame Sea pressure on long + Load from vert. stiffener BM SF Back Resulting BM and SF Slide 8
    • Bulk Carrier Global strength function of topside tank, bending moment 6. Topside tank Flange in hull girder (global strength) Global loads are acting on the hull girder beam from cargo distribution and wave loads Upper part of ship side and sloping plate are important contributors to the top flange in the hull girder beam Cont. Slide 9
    • Bulk Carrier Global strength function of topside tank, shear Topside tank Global loads are acting on the hull girder beam Web in hull girder (global strength) Ship side, hopper tank and top-wing tanks is taking up global shear forces from wave induced loads and weight/buoyancy distribution along the vessel length Cont. Slide 10 6.
    • Bulk Carrier Global Strength topside tank 6. Topside tank Global shear force Shear flow distribution topside tank Slide 11 Note the shear force is distributed between hopper tank sloping plate and ship side
    • Bulk Carrier Strength topside tank 6. Topside tank Full load condition Ore hold FEM - PLOT Topside tank rotate up and out POSTFEM 5.6-02 SESAM 18 MAR 3 MODEL: T1-1 DEF = 100 2: LINEAR ANALYSIS GAUSS D-STRESS SIGMX SURFACE: 1 MAX = 85.8 MIN = -168 73.8 61.7 49.6 37.5 25.5 13.4 1.33 -10.7 -22.8 -34.9 -47 -59 -71.1 -83.2 -95.2 -107 -119 -131 -144 -156 Sea pressure Z X Y Cont. Slide 12 Net load on double bottom and side pressure rotate hopper tank as shown
    • Bulk Carrier Global response of topside tank High shear stress in topside tank sloping plate and ship side towards transverse bulkheads due to global shear stresses and torsion of topside tank Slide 13 6. Topside tank
    • Bulk Carrier Hull damages topside tank 6. Topside tank Characteristic damages for topside tanks: 1. 2. Crack in lower side long in topside tank 3. Slide 14 Buckling deformation due to overpressure of ballast tank Heavy corrosion topside tank webframe
    • Bulk Carrier 1. Overpressure of topside tank • Vessels with high ballast pump capacity, filled to overflow through air pipes, with possible excessive pressure in topside tank Typical location for overpressure buckling Slide 15 6. Topside tank
    • Bulk Carrier 1. Overpressure of topside tank impact on function 6. Topside tank • Deformed webframe has lost its strength and may not be able to support the side and sloping plate longs. – If longs are not efficiently supported at webframes they may be excessively loaded in the mid-field, and may buckle, however normally a local strength problem Slide 16
    • Bulk Carrier 2. Crack lower side long Fatigue crack through side long. Flange in way of weld to flatbar stiffener on top Slide 17 6. Topside tank Experience feedback
    • Bulk Carrier 2. Crack lower side long. impact on function S F B m 6. Topside tank • Crack impact on function – Crack through side long. may lead to penetration of shell side, and cause leak of water. • If side longs are cracked, the upper support for the vertical side frame is weakened • Less fixation at upper end of vertical side frame will give higher stresses in the field and in way of lower end. • The stresses in the vertical side frames may become excessive – could lead to collapse of side frame and water flooding. Slide 18
    • Bulk Carrier 3. Heavy corrosion in topside tank Vessel with vertical stiffener on ship side and sloping plate Poor buckling strength exposed to longitudinal compression stresses Calculation of allowable t-min values for side & sloping plate revealed marginal allowable reduction Slide 19 6. Topside tank
    • Bulk Carrier 4. Corrosion of webframes in topside tank Heavy local wastage of webframe in way of deck & side longs Slide 20 6. Topside tank
    • Bulk Carrier 4. Corrosion of webframes in topside tank consequence 6. Topside tank • Local corrosion of webframe may lead to deck longs lose their attachment to webframe – Span for deck longs two times design value, Local strength requirement increase by 4times (square of the stiffener span) – Buckling capacity significantly reduced May lead to global structural collapse ! Slide 21
    • Bulk Carrier 1. 2. 3. 4. 5. 6. 7. Slide 1 Hatch cover & coaming Side Bottom Deck Transverse bulkhead Hopper tank Topside-tank Hatch cover & coaming 7. Hatch cover & coaming
    • Bulk Carrier Structural functions of Hatch cover & coaming 7. Hatch cover & coaming 1. Watertight integrity (local strength) - Resist dynamic loads from green seas, horizontal & vertical pressure 2. Hatch coaming supports the hatch covers 3. Hatch end coaming contributes to transverse strength Slide 2
    • Bulk Carrier Structural build up of deck 7. • Longitudinal hatch coaming, web & flange • Hatch end coaming, web & flange • Hatch end bracket • Hatch side bracket Slide 3 Hatch cover & coaming
    • Bulk Carrier Structural functions Hatch cover & coamings 7. Hatch cover & coaming Plate – Stiffener – Web frame – Panel – Hull girder 1. Watertight integrity (local strength) Hatch cover & coaming plate must withstand dynamic loads from green sea pressure as well internal pressure from ballast in combined cargo / ballast hold. 2. Load on hatch covers (local strength) Hatch cover & coaming plate must withstand static and dynamic loads from deck cargo if this is allowed (containers / timber ). Slide 4 Cont.
    • Bulk Carrier Structural functions Hatch cover & coamings 7. Hatch cover & coaming High stress areas • Longitudinal global stresses • The longitudinal stresses in deck due to cargo distribution and wave loads will ”flow” into the longitudinal hatch coamings. The hatches in the midship region with full longitudinal stresses most exposed Slide 5
    • Bulk Carrier Structural functions Hatch cover & coamings • Slide 6 Transverse stresses 7. Hatch cover & coaming
    • Bulk Carrier Structural function local load hatch cover 7. Hatch cover & coaming l q Transv. girder q x l /2 Q = q x l /2 SF. BM. M = q x l2 / 8 Hatch cover with green seas load Slide 7 Transverse girder single beam with distributed load
    • Bulk Carrier Hull damages hatch cover/coaming 7. Hatch cover & coaming Characteristic damages for hatch cover & coaming are: 1. 2. Shedder plate 3. Slide 8 Crack in hatch coaming flange Corrosion on hatch covers
    • Bulk Carrier Crack in deck plate at hatch coaming end 7. Hatch cover & coaming Crack in hatch coaming flange amidships Note cut-outs for hatch cover hydraulic lifting jacks Local high stress concentration due to square cut-outs and reduced cross section area Slide 9
    • Bulk Carrier Crack in deck plate at 7. hatch coaming, consequence Hatch cover & coaming - Crack in coaming may cause water leakage – damage to cargo - Crack may propagate to main deck - Impact on longitudinal strength Slide 10
    • Bulk Carrier Slide 11 Corrosion of hatch covers 7. Hatch cover & coaming
    • Bulk Carrier Corrosion of hatch covers Impact on function 7. Hatch cover & coaming • Moisture in cargo – some dry bulk cargoes may become liquified (Ref. IMO code for safe practice for solid bulk cargoes BC code sec. 7 App. A) • Reduced thickness of stiffeners and girders may cause collapse of stiffener / girder • Possible flooding of cargo holds – impact on longitudinal strength and stability / trim Slide 12
    • Container Ships Slide 1 Container Ships - Hull Structure 18.02.2005
    • Container Contents – Container Ships Ships 1. Introduction to Container Ship hull structure 2. Hull structural breakdown – function of hull elements: • 3. Slide 2 Bottom, side, hatch, deck and hatch coaming and transverse bulkhead including relevant hull damages for all structural elements Case 18.02.2005
    • Container Ship related characteristics Ships Feeder • • • • • • • • Slide 3 Open Top Double Hull Flexible hull girder – torsion Critical hull girder strength – high tensile steel High freeboard Worlds largest engines (100 000 BHP) High Speed Light loads Value of cargo up to 5 times value of ship Liner Trade • Panamax Any proposals? 18.02.2005 Post Panamax
    • Container Ships Historical Fleet Development Container Carriers, Bulk Carriers and Oil Tankers Mill. TEU Mill. Dwt. 500 6 Container Carriers (TEU) Bulk Carriers (Dwt.) Oil Tankers (Dwt.) 5 4 400 300 3 200 2 100 1 0 0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 Average growth 1997 - 2002: Container Carriers: Bulk Carriers: +9.3 % +3.1 % 2002 - Year-end figures Slide 4 Source: Fairplay/Clarkson 18.02.2005 Oil Tankers: + 3.2 %
    • Container Ships Slide 5 It started in the late 50’s 18.02.2005
    • Container The Container Ship Development Ships • • • • • Container ship era started late 60’s 70 ship below 2000 TEU delivered before 1970 In the 70’s ships up to 3000 TEU Big Panmax built in the 80’s, exceeding 4000 TEU Post Panmax ships today designed with capacity exceeding 8000 TEU • 10000 TEU now contracted at HHI Slide 6 18.02.2005
    • Container Ships Types of Container Ships Feeder • • • • • • Loa 100 - 200 m long Open Top Service speed range is 18 to 22 Knots in general Cranes are often arranged to achieve flexible operating ability Damage stability criteria influence on hatch cover tightness and subdivision of hold area Fully aft located deckhouse can be seen often Mixed stowage (Russian stowage) in hold is Panamax common Post Panamax Slide 7 18.02.2005
    • Container Ships Types of Container Ships Feeder • • • • • Open Top 3800 – 4800 TEU Max Loa = 294 m Service speed 24 knots 11 rows in hold in general, but 12 rows is possible 8 tiers in hold, 5 tiers on deck Panamax Post Panamax Slide 8 18.02.2005
    • Container Ships • • • • Types of Container Ships Feeder Loa 270 m (5,500 TEU) to 340 m (9000 TEU) Open 5,500 TEU has been popular size, but it’s a trend that the ships become bigger and bigger Service speed 25-26 knots HT40 steel is often used to upper deck and hatch coaming Top Panamax Post Panamax Slide 9 18.02.2005
    • Container The Cargo Ships Total value = Ship + Cargo = 100 + 500 = 600 000 000 USD Slide 10 18.02.2005
    • Container Ships The Cargo Post Panamax Container Ship in Typhoon Babs - Pacific, October 98 • 300 containers lost Slide 11 18.02.2005 • ab. 100 more damaged • Cargo claim ~ 50mUSD (or even higher) • New ship price ~ 92mUSD
    • Container Ships Structural breakdown of hull - A vessel’s hull can be divided into different hull structural elements - Each element has its own function in the total hull integrity - In order to assess the structure of a Container Ship you need to understand the function of the structural element you are looking at Slide 12 18.02.2005
    • Container Hull Structural Breakdown Ships 1. Bottom 2. Side 3. Hatch 4. Deck & hatch coaming 5. Transverse Bulkhead Slide 13 18.02.2005
    • Container Hull Structural Breakdown Ships 1. Bottom 2. Side 3. Hatch 4. Deck & hatch coaming 5. Transverse Bulkhead Slide 1 18.02.2005 1. Bottom
    • Container Ships Structural functions of bottom 1. Bottom 1. Watertight integrity (local strength bottom / inner bottom) - Resist external sea pressure (bottom) - Resist internal pressure from ballast & fuel oil 2. Carry net load on double bottom girder structure - Inner bottom / bottom plate & stiffn. are girder flanges - Double bottom floors / girders are webs in double bottom girders 3. Bottom flange in hull girder (global strength) - Bottom and inner bottom structure is the bottom flange in the hull girder Slide 2 18.02.2005
    • Container Ships Structural build up of bottom Bottom plating w/ longitudinals Longitudinal girders Floor Slide 3 18.02.2005 Hopper Tank 1. Bottom
    • Container Structural functions of bottom Ships Stress distribution in a double bottom structure follows the hierarchy: → Plating → Longitudinals → Floors / girders → Bulkheads /side Slide 4 18.02.2005 1. Bottom
    • Container Ships Functions of inner bottom 1. Bottom Cargo hold boundary (local strength) The internal loads from tanks induce shear forces and bending moments in the inner bottom longitudinals as single beams (between floors) BM and SF distribtion for a single beam with distributed load and fixed ends Slide 5 18.02.2005
    • Container Ships Functions of inner bottom 1. Bottom External loads from container sockets induce shear forces and bending moments in the floors and girders Slide 6 18.02.2005
    • Container Ships Load response double bottom 1. Bottom Stresss flow shortest way to support Slide 7 18.02.2005
    • Container Ships Double bottom girders load response 1. Bottom • girders & floors carry the net load to hopper tank and support- and water tight bulkhead •longitudinal girders carry most of the load towards transverse bulkhead • length / width ratio is important for the distribution of loads between girders & floors • the stiffest elements are taking most of the load / stresses seek the shortest way to supports Slide 8 18.02.2005
    • Container Ships Functions of double bottom girder Net Load on double bottom Slide 9 Longitudinal girders represented by springs 18.02.2005 1. Bottom
    • Container Ships Functions of double bottom girder Net Load on double bottom Shear Force Bending Moment Slide 10 18.02.2005 1. Bottom
    • Container Ships Functions of double bottom girder 1. Bottom Net Load on double bottom Shear Force Bending Moment Slide 11 18.02.2005
    • Container Ships Functions of bottom 1. Bottom Bottom flange in hull girder (global strength) The bottom and inner bottom longs and longitudinal girders are carrying the vertical bending moments from still water and wave induced bending moments along the vessel length Slide 12 18.02.2005 Global loads are acting on the hull girder beam Bottom structure is acting as flange in hull girder beam
    • Container Functions of bottom Ships 1. Bottom Post-Panamax Container Ship Shear Force [t] Bending Moment [tm] Moment & Shear Force Diagram ENGINE ROOM Slide 13 18.02.2005
    • Container Total BM acting on a vessel Ships 1. Bottom Total hull girder bending moment = Mstill water + M wave Slide 14 Hogging Mstill water Sagging BM limits Mwave 18.02.2005
    • Container Ships Highly stressed areas Deck 1. Bottom •Bottom plate/longs middle of empty holds (compression ) •Bottom plate in loaded holds (tension) NA •Inner bottom plate middle of loaded holds (compression ) Inner Bottom Bottom Global bending Slide 15 18.02.2005 Double bottom bending
    • Container Ships Hull damages bottom / inner bottom 1. Characteristic damages for bottom are: 1. Crack at connection of longitudinals to floors 2. Indents of inner bottom plate Slide 16 18.02.2005 Bottom
    • Container Ships Crack at connection of longitudinal to floor 1. Bottom • Floor in way of high shear stress • Connection at bottom longitudinals • Areas exposed to high fatigue loading Slide 17 18.02.2005
    • Container Ships Crack of floor 1. Impact on function • Loss of support of longitudinals – increased stresses in adjacent structure • Large crack in floor – increased stresses in adjacent floors and girders Slide 18 18.02.2005 Bottom
    • Container Ships Slide 19 Indents of inner bottom plate 18.02.2005 1. Bottom
    • Container Ships Indents of inner bottom plate • Severe indents – cracks – leakage • Impact on buckling capacity of panel Slide 20 18.02.2005 1. Bottom
    • Container Ships Slide 21 Contact damages in bottom plate 18.02.2005 1. Bottom
    • Container Ships Contact damages of bottom plate Impact on function • Severe indents – cracks – leakage • Impact on buckling capacity of panel Slide 22 18.02.2005 1. Bottom
    • Container Hull Structural Breakdown Ships 1. 2. Side 3. Hatch 4. Deck & hatch coaming 5. Slide 1 Bottom Transverse Bulkhead 2. Side
    • Container Ships Structural functions of ship side 2. 1. Watertight integrity (local strength) - Resist external sea pressure - Resist internal pressure from ballast / fuel oil tanks 2. Carry net load on double side structure - Inner side / side plate are girder flanges - The webs act as web in double side girder 3. Web in hull girder (global strength) - Side plating and inner side act as the web in the hull girder beam Slide 2 Side
    • Container Ships Structural build up of ship side Strength deck Side shell Side longitudinal Side stringer Side frame Slide 3 Longitudinal bulkhead Hopper structure Flat, recess or step 2. Side
    • Container Ships Local function: Watertight integrity 2. Side External static and dynamic loads induces shear forces and bending moments in the side and inner side longitudinals as single beams (between each web frame) Side long.as a single beam between two web frames BM and SF distribtion for a single beam with distributed load and fixed ends Slide 4
    • Container Ships Local function: Webs in a double side 2. Side -Side longs are supported at the web frames - Web frames are supported at the stringers and at the deck and bottom Shear force L High Shear Slide 5 Bending moment
    • Container Ships Local function: Stringers in a double side Stringers contribute to the stiffness of the double hull ship side, which means: High shear stress in stringers towards the transverse bulkhead Slide 6 2. Side
    • Container Ships Loads on the ship side 2. Side tainers m con e fro et forc N Net force Min cargo / max draught Max cargo / min draught Slide 7
    • Container Ships Global function: Web in hull girder 2. Side Web in hull girder (global strength) Ship side is taking up global shear forces resulting from the hull girder bending moment and weight/buoyancy distribution along the vessel length Global loads are acting on the hull girder beam Side plating is acting as web in hull girder beam Slide 8
    • Container Ships Global function: Web in hull girder Web in hull girder (global strength) Ship side is taking up global shear forces resulting from the hull girder bending moment and weight/buoyancy distribution along the vessel length 2. Side Global loads are acting on the hull girder beam Side plating is acting as web in hull girder beam Slide 9
    • Container Ships Function of ship side 2. Shear force Shear Force Distribution Slide 10 Be n mo ding me nt Side
    • Container Ships Global function: Web in hull girder 2. Global shear forces resulting from the distribution of cargo and buoyancy are taken up in the ship side plating Area effective in transferring shear force Slide 11 Shear stress distribution resulting from global loads for midship section Side
    • Container Ships Hull damages in ship side Characteristic damages for ship side: 1. 2. Fatigue Cracks in side longitudinals 3. Slide 12 Indents in ship side Fatigue Cracks in web frame cut out 2. Side
    • Container Ships Indents of side shell with stiffeners 2. Side Mainly from contact damages: The terms indents and buckling should not be mixed up with each other, as the cause for these damages are different: Indents: Caused by lateral forces. Slide 13 Buckling: Due to excessive in-plane stresses
    • Container Ships Acceptance Criteria 2. Deformations Side Local Plate Indents (contact / slamming deformations); Maximum Depth S/12 provided; smooth indent no cracks Less than 15deg New IS 5.1 Technical survey Guide Slide 14 Small deformation (less than 15 deg) out of plane for stiffeners and girders
    • Container Ships Consequense of indents Sharp indents may lead to cracks and possible leakage Large area set in (plating and stiffeners) gives reduced buckling capacity Adjacent areas may then be overloaded Slide 15 2. Side
    • Container Ships Fatigue cracks in longitudinals • • • Side Cracks have been detected due to FO leakage to the sea 270 cracked longitudinals Ship was 7 years of age This could be the future problem in many container ships! Slide 16 2.
    • Container Ships Fatigue cracks in longitudinals Side longs connection to web frame & transverse bhd. Slide 17 2. Side
    • Container Ships Cause for cracking in side longitudinals 2. Fatigue Damages are caused by Dynamic Loading Slide 18 Side
    • Container Ships Cause for cracking in side longitudinals 2. Side Potential problem area Ex. P ana ma x •High alternating bending stresses towards the end supports (web frames) •Highly stressed areas created around geometric ’hard points’ (bracket toes, scallops, flat bars) Slide 19
    • Container Stress concentration factors Ships 2. • Kg : Gross Geometry (from FEM analysis or standard values) • Kw : Weld Geometry (typical 1,5) • Kte : Eccentricity tolerance (production tolerances) • Ktα : Αngular mismatch (production tolerances) • Kn : Unsymmetrical Stiffeners (L & bulb-profiles) Slide 20 Side
    • Container Ships Fatigue Life N ⎛ 1 ⎜ ≈ C⎜ ⎜ σK ⎝ 2. ⎞ ⎟ ⎟ ⎟ ⎠ 3 Where: N = Fatigue life (normally 20 years) σ = Nominal Stress (dynamic stress amplitude) K = Stress Concentration Factor C = Constant (including the environment and mean stress level i.e. compression / tension) Slide 21 Side
    • Container Ships Slide 22 Standard repair proposal longs / web frames 2. Side
    • Container Consequence of damage Ships 2. Cracks in side longitudinals: Slide 23 oil leakage and pollution longitudinal may break off in worst case (a series of cracks in same area) could induce a larger fracture (loss of ship side) Side
    • Container Ships Fatigue cracks in web frames 2. Side Cracks around openings for side longitudinals in web frames Cr Slide 24 ac ks
    • Container Ships Cause for cracking in cut outs for longitudinals 2. Side Sea loads induce shear stresses in the web frame Shear stress High shear stresses around openings etc, where shear area is reduced Shear stress Slide 25
    • Container Ships Consequence of fatigue crack in webs 2. Side How does the damage impact on the function? Side longitudinals loose their support Re-distribution of shear stresses in web frame May lead to overloading of adjacent structure Slide 26
    • Container “Rules of Thumb” Regarding Fatigue Ships • Fatigue is not an exact science – ±10% stress → ±30% fatigue life • • • • Slide 27 High tensile steel ≈ Mild steel Corrosive environment → (Fatigue life / 2) North Atlantic/Pacific → (Fatigue life / 2) Symmetric profiles have longer fatigue life 2. Side
    • Container Ships “Rule of thumb” regarding fatigue crack repairs 2. • Workmanship has a significant impact on fatigue life • Repair as function of time for crack to develop: Years 0-5 5-10 Design improvement recommended 10-15 Repair to original standard normally acceptable, grinding out and re-welding may also be considered towards 15 years * < 15 * Design improvement recommended, check misalignment, possible vibration related Repair by re-welding normally acceptable * Note! cracks in main deck / hatch opening corners to be specially considered Slide 28 Side
    • Container Hull Structural Breakdown Ships 1. 2. Side 3. Hatch 4. Deck & hatch coaming 5. Slide 1 Bottom Transverse Bulkhead 3. Hatch
    • Container Ships Structural functions 3. 1. Load on hatch covers (local strength) • must withstand static and dynamic loads from containers 2. Allow for hull deformations 3. Weather tightness • Resist water pressure Slide 2 Hatch
    • Container Ships Structural build up Support Pads (Vertical support) Longitudinal stopper (Pitching) Slide 3 3. Hatch Pin stopper (Rolling / pitching) Hold down device (Vertical support)
    • Container Ships Structural functions: Container load (local strength) 3. Hatch A-A A A Shear Force Bending Moment Hatch cover with container load Slide 4
    • Container Ships Structural functions: Container load (local strength) Wind 3. Transverse Acceleration Ph Slide 5 Hatch
    • Container Ships Structural functions: Allow for Hull Deformations 3. Hatch Hull deformation looking down at deck Ship Size Diagonal deflection (mm) Slide 6 Panamax. + 7000 TEU + 9000 TEU 70 100 150
    • Container Ships Slide 7 Structural functions: Allow for Hull Deformation 3. Hatch
    • Container Ships Structural functions: Weather tightness 3. Hatch • Weather tight hatches are to have packing • Some hatches are not weather tight, i.e. no packing. In case of non weather tight hatches, this is written in the Load Line report. Slide 8
    • Container Hull damages Ships Characteristic damages related to the hatch cover are damages to the: • Slide 9 Hatch Cover Support 3. Hatch
    • Container Ships Hull damages - hatch cover support 3. Hatch Heavily worn steel to steel Damaged low friction pad Damage due to corrosion and high forces Slide 10
    • Container Ships Hull damages - hatch cover support Low friction bearing pad Slide 11 3. Hatch Lubripads for big ships
    • Container Ships Consequence of damage 3. Hatch • Damages to friction pad may cause an undesired stiff connection • Introduction of new forces • Potential cracks in the coaming Slide 12
    • Container Hull Structural Breakdown Ships 1. 2. Side 3. Hatch 4. Deck & hatch coaming 5. Slide 1 Bottom Transverse Bulkhead 4. Deck and coaming
    • Container Ships Structural build up Hatch end coaming Hatch coaming top 4. Deck and coaming Hatch side coaming Coaming stay Hatch side coaming Slide 2
    • Container Ships Structural functions 1. Watertight integrity (local strength) - Resist external sea pressure 2. Carry and transfer loads from hatch (local strength) - Coaming stays are main load carrying element 3. Global strength -Bending and torsion Slide 3 4. Deck and coaming
    • Container Ships Structural functions 1. Watertight integrity (local strength) Deck plate and hatch coaming must be watertight Slide 4 4. Deck and coaming
    • Container Ships Structural functions 4. 2. Carry and transfer loads from hatch (local strength) Hatch cover with container load Slide 5 Deck and coaming
    • Container Ships Structural functions: Container load (local strength) 4. Stays Slide 6 Deck and coaming Support
    • Container Ships Structural functions: Global Strength 4. Deck and coaming What kind of global loads are we talking about and which effects do they have? Vertical Bending Moment Slide 7
    • Container Ships Structural functions: Global Strength Horizontal Bending Moment Slide 8 4. Deck and coaming
    • Container Ships Structural functions: Global Strength Torsion Slide 9 4. Deck and coaming
    • Container Structural functions: Incorporate hull deformation Ships 4. Deck plate and coaming must be strong enough to withstand the combination of all the loadcases! A typical combination of stresses could be: • • • • Slide 10 Max Still water bending moment (vertical + horizontal + torsion) 45% vertical wave bending moment 100% horizontal wave bending moment 100% wave torsion Deck and coaming
    • Container Hull damages Ships 4. Characteristic damages related to deck & hatch coaming are: 1. 2. Hatch and Deck Corners 3. Knuckle at Side Hatch Coaming 4. Slide 11 Hatch Coaming Stays Coaming Termination Deck and coaming
    • Container Ships Cracks in hatch coaming stays 4. Deck and coaming High Dynamic stress due to friction between hatch and bearing pad Coaming stay Upper deck Slide 12 Hatch Coaming Stays Upper deck
    • Container Ships Consequence of damage 4. • Hatch coaming may loose its transverse strength • The cracks may propagate into the deck Slide 13 Deck and coaming
    • Container Ships Cracks in Hatch corners 4. Deck and coaming High global stress (vertical and horizontal bending) in addition to torsion may result in fatigue damages in the hatch corners Slide 14
    • Container Ships Cracks in Hatch corners 4. Deck and coaming High global stress (vertical and horizontal bending) in addition to torsion may result in fatigue damages in the hatch corners Slide 15
    • Container Ships Cracks in Hatch corners 4. Deck and coaming Forward Cargo Hold Insert plate IWO hatch corners is to be 25 % thicker than adjacent deck plate Hatch Corner Insert Plate Slide 16
    • Container Ships Cracks in hatch corners Consequence • Cracks in hatch and deck corners should be taken serious! (Contact MTPNO864 if in doubt) • Crack in hatch corners could indicate a design problem. It is therefore most likely to find similar damages other places too. • The cracks may develop rapidly in a highly utilized structure Repair • Thickness increase • Edge grinding • Improved shape Slide 17 4. Deck and coaming
    • Container Ships Cracks in Hatch Coaming Knuckle 4. Deck and coaming Upper Deck Additional force due to knuckle brings stress concentration at upper deck connection Cause of Damages: • The transverse member was arranged 100 mm away from the knuckle line • Fine mesh F.E. analysis results show high stress concentration factor of K = 3.5 (75 mm offset distance and 20° of knuckle angle) at the knuckle point Slide 18
    • Container Ships Cracks in Hatch Coaming Knuckle Upper Deck Knuckle in Coaming Hatch Coaming Cracks Upper Deck Slide 19 4. Deck and coaming
    • Container Ships Cracks in Hatch Coaming Knuckle Consequence of crack • May influence the load carrying characteristics of the hatch coaming with regard to support of hatch • Reduced longitudinal strength Slide 20 4. Deck and coaming The knuckle has to be supported. A possible repair is insert of a support bracket
    • Container Ships Slide 21 Hatch Girder / Coaming Termination 4. Deck and coaming
    • Container Ships Hatch Girder / Coaming Termination 4. Deck and coaming Crack Slide 22
    • Container Ships Hatch Girder / Coaming Termination Consequence Crack may develop and penetrate the deck Repair proposal – Meeting angle of bracket to be less than 15 degrees – Bracket toe and flange end to be grinded after welding – Full penetration welding to be carried out for min. 500 mm IWO flange and 1000-1500 mm for bracket toe Slide 23 4. Deck and coaming
    • Container Ships Slide 24 Damages to the wave breaker 4. Deck and coaming
    • Container Ships Damages to the wave breaker 4. Deck and coaming Possible buckling problems Sea pressure Slide 25
    • Container Ships Damages to the wave breaker Impact of function 4. Deck and coaming • Collapse of wave breaker could lead to damages to the containers or leakage into cargo hold Slide 26
    • Container Hull Structural Breakdown Ships 1. 2. Side 3. Hatch 4. Deck & hatch coaming 5. Slide 1 Bottom Transverse Bulkhead 5. Transverse Bulkhead
    • Container Ships Structural build up Transverse watertight bulkhead Box beam 5. Transverse Bulkhead Pillar or support bulkhead Box beam web (diaphragm) Bulkhead stringer Vertical girder Slide 2
    • Container Ships Structural functions 1. Cargo hold boundary (local strength) - Watertight integrity - Support of container stacks - Support the bottom - Support the stringers in ship side 2. Stiffness to the hull girder (global strength) Slide 3 5. Transverse Bulkhead
    • Container Ships Structural functions: Watertight integrity (local strength) Transverse Bulkhead Watertight bulkhead Damaged condition Shear Force Slide 4 5. Bending Moment
    • Container Ships Structural functions: Support of container stacks (local strength) 5. Transverse Bulkhead Pillar bulkhead Shear Force Bending Moment High stress lower / upper end & midfield Slide 5
    • Container Ships Structural functions: Support of container stacks (local strength) Racking Tipping Stringer Slide 6 5. Transverse Bulkhead
    • Container Ships Structural functions: Support the bottom (local strength) High compression Slide 7 5. Transverse Bulkhead
    • Container Ships Structural functions: Transverse strength of hull girder 5. Transverse Bulkhead Deformation Torsion Slide 8
    • Container Ships Hull damages 5. Transverse Bulkhead Characteristic damages for transverse bulkheads: 1. Damages to cell guide 2. Damages to webs and stringers 3. Overstressed / buckled support bulkhead Slide 9
    • Container Ships Slide 10 Damages to cell guide 5. Transverse Bulkhead
    • Container Ships Damages to cell guide 5. Consequences of damages? • Difficulties in loading / unloading the cargo holds • Loss of support of containers Slide 11 Transverse Bulkhead
    • Container Ships Damages to webs 5. Transverse Bulkhead Damages to webs due to wrong loading of containers Slide 12
    • Container Ships Typical design 5. Transverse Bulkhead From Specification: “7th tier in cargo holds shall be suitable for 40ft long 9 feet 6 inches high container loading.” Slide 13
    • Container Ships Typical design 5. Transverse Bulkhead 8’6’’Bulkhead Slide 14
    • Container Ships Slide 15 Damages to webs 5. Transverse Bulkhead
    • Container Ships Damages to webs 5. Consequences of damages • Difficulties in loading / unloading the cargo holds • Damages to webs and stringers could reduce the container support • Reduced vertical support of bottom Slide 16 Transverse Bulkhead
    • Container Ships Overstressed / buckled support bulkhead 5. Transverse Bulkhead Crack repaired by welding and additional stiffener • • The support bulkheads are highly stressed in shear and equivalent stress in the outer part Areas with lightening holes are to be specially checked Slide 17 Critical area of support bulkhead
    • Container Ships Overstressed / buckled support bulkhead Impact of function 5. Transverse Bulkhead • Damages may lead to cracks and hence leakage from bottom / wing tank • Containers may shift due to reduced support • Reduced support of bottom and consequently other overloaded areas Slide 18
    • Container Ships Slide 19 5. Transverse Bulkhead