Rubber Products Presentation on Bridges


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Rubber Products Presentation on Bridges

  1. 1. Bridge Bearing Pads Expansion Joints Dowel Bars Bridge Parapets Bridge Drainage System Fascia Contact us: Plot # 377, Nawab Siddiq Ali Khan Road, Lasbella, Garden West, Karachi-74550, Sindh-Pakistan Landline: Fax: Cell: +92.321.821.8443 Web: -
  2. 2. <ul><li>About Rainbow: </li></ul><ul><li>Rainbow Developers, was founded in 2006 with aim to try out new ideas, unique and reliable infrastructure, road construction and other constructional products. “ Rainbow” Group is the pioneer of manufacturing in many products of construction since last four decades. After all that successful hard work into family business I decided to launch, new and unique products which I was doing from assorted firms and intending through local ventures and international joint ventures. </li></ul><ul><li>The aim of making Rainbow Developers was to establish a platform to cover the shortage of constructional products in the local markets and introduce new ideas and technology in Pakistan. Rainbow Developers is a manufacturer, importer and also full service specializing in managing high image, technically difficult and mega projects. </li></ul><ul><li>Rainbow Developers is providing services in bridges, complete road construction products and apparatus support, consumer rubber products, re-installation of products, technical support & staff, contractors consultants architectures, designer and planner, project coordinators also plan to provide services in Highways, Dams, and steel structures as well as Rainbow Developers serve in different products like; Bridge Bearing Pads, Pot Bearings, Expansion joints, Aluminum & Plastic Road Studs, Rubber Humps, Rubber Fender, Rubber & PVC Water Stop, Traffic Sign Plates, Anti Glare Screen, Guardrail Reflectors, Delineator Posts, Construction Machines and Turbines. </li></ul><ul><li>Using a variety of delivery methods to meet specific needs of clients including construction management, program management, design-build, general contracting and special facility in construction consultancy with support of our International joint ventures. </li></ul><ul><li>Rainbow Developers work with clients to provide the solutions at the affordable price to improve Clients Company’s efficiency, productivity and the bottom line, serving effectively is its top priority. Prior to beginning work with client, we evaluate client is needs, budget, and timeline. </li></ul><ul><li>Rainbow Developers are very proud of the fact that Rainbow’s products are widely used almost every aspect of industry. We believe </li></ul><ul><li>that we can resolve all customers’ inquiries in better and essential way. </li></ul><ul><li>Look forward to get your precious comments on Rainbow Developers merchandise. For more details, visit . </li></ul>
  4. 4. <ul><li>Bridge Bearings : </li></ul><ul><li>Bearings are devices which transmit the load from the superstructure to the substructure and to accommodate movements and displacements. </li></ul><ul><li>In highway bridge, bearings movements are accommodated by the basic mechanisms of internal deformation (elastomeric), sliding (PTFE), or rolling. </li></ul><ul><li>A large variety of bearings have evolved using various combinations of these mechanisms. </li></ul><ul><li>Basic types of Bearings: </li></ul><ul><li>Specific Functions of Bearings: </li></ul><ul><li>To transfer the load from the superstructure (both vertical and horizontal) to the substructure. Bridges with span less than 10m do not normally require any bearings. </li></ul><ul><li>To accommodate translational movements (expansion and contraction) e.g. movement due to temperature (can be large in steel bridges, up to 300mm); due to dead load & live load especially sloping road; shrinkage and creep etc. </li></ul>Elastomeric Bearing Plane Sliding Bearing Multiple Roller Bearing Rubber Bearings Steel Bearings
  5. 5. <ul><li>Specific Functions of Bearings: </li></ul><ul><li>To accommodate rotational movements of deck girders. Rotation occurs as the deck deflect under load. Also, some relative rotations occur in composite section due to different properties of concrete and steel. Differential settlement may also cause some rotational movement. </li></ul><ul><li>To limit forces transmitted to the substructures by suitable design. </li></ul><ul><li>To provide damping of vibrations and minimize effects of impact loading in case of elastomeric bearings </li></ul><ul><li>Choice of Bearings </li></ul><ul><li>There are two broad types of bridge bearings, either ‘elastomeric’ or ‘mechanical’ . Intermediate (combination) types of bearings are also used where an elastomer is used to provide rotational capacity and horizontal movement occurs mechanically. </li></ul><ul><li>In elastomeric bearings, movements and rotations are accommodated by compressing or shearing layers of rubber, so these bearings are always deforming elastically. </li></ul><ul><li>The mechanical bearing permits translation and rotation by sliding, rolling or rocking on metal parts, and these bearings are virtually incompressible. </li></ul>General Criteria for Initial Selection
  6. 6. <ul><li>Fixed & Sliding Bearings: </li></ul><ul><li>Bearings are arranged to allow the deck to expand and contract, but retain the deck in its correct position on the substructure. </li></ul><ul><li>A 'Fixed' Bearing does not allow translational movement. </li></ul><ul><li>'Sliding Guided' Bearings are provided to restrain the deck in all translational directions except in a radial direction from the fixed bearing. This allows the deck to expand and contract freely. </li></ul><ul><li>'Sliding' Bearings are provided for vertical support to the deck only. </li></ul><ul><li>Typical Bearing Layout </li></ul>
  7. 7. <ul><li>Elastomeric Bearings: </li></ul><ul><li>An elastomer is either vulcanized rubber or synthetic material called neoprene having rubber-like characteristics. Movements and rotations are accommodated by compressing or shearing of the layers. </li></ul><ul><li>Laminated Bearing – consists of one or more elastomer slabs bonded to metal plate so as to form a sandwich. </li></ul><ul><li>Bearing pad – a single unreinforced elastomer slab. </li></ul><ul><li>Bearing strip – a continuous bearing pad for which B/L is greater than 5. </li></ul>Plain Pad Bearing Laminated Elastomeric Bearing Strip Bearing B/L > 5 <ul><li>Laminated bearings are recommended for most cases since they give more reliable performance and better stability. </li></ul><ul><li>Plain pad and strip bearings are suitable only for low loads and small shear strains. </li></ul>
  8. 8. Details of Elastomeric Bearing Pad: Bridge spanning The plan size of bearing is normally governed by the width of the beam it supports and the width of the abutment seating in the direction of span. Outer Steel Plate Inner steel plate Inner Elastomer slab Outer Elastomer Slab Shape Factor: B = effective width of bearing L = effective length of bearing A = effective plan area of elastomer (BxL) Ao = actual plan area of elastomer T = total thickness of bearing t = actual thickness of an elastomer Σ t = total thickness of elastomer slabs tn = effective thickness of an elastomer slab in compression (tn = t for an inner slab, tn=1.4t for outer slab, tn=1.6t for pad or strip bearing) T B L
  9. 9. S = (BxL) 2(B + L) tn Behaviour of Elastomeric Bearing Pads: The Shape Factor: S = shape factor = ratio of effective plan area to force-free surface area of an elastomer.
  10. 10. <ul><li>Properties of Elastomer : </li></ul><ul><li>Basic assumptions and requirements of ASTM 4014-3 for elastomeric bearings are : </li></ul><ul><li>The elastomer is an elastic and almost incompressible material; its bulk modulus has to be taken into account where appropriate. </li></ul><ul><li>The thickness of bearing pads and strips shall be not less than 10mm nor greater than 25mm (not counting inner rubber slabs of laminated bearings). </li></ul><ul><li>The thickness of steel plate reinforcement shall not be less than 3mm. </li></ul><ul><li>Internal plates shall have edge cover of not less than 6.0mm of elastomer. </li></ul><ul><li>Dowel holes in bearings shall be filled either with close fitting dowels or with elastomer plugs of the same properties as the elastomer of the bearing. </li></ul><ul><li>Properties of Elastomer: </li></ul><ul><li>The thickness of steel plate reinforcement shall not be less than 2(t 1 + t 2 )V/A 1 f s but the thickness shall not be less than 3mm for outer plates and not less than 1.5mm for internal plates. A greater thickness of internal plates may sometimes be necessitated by manufacturing considerations. </li></ul><ul><li>Where, t 1 & t 2 are actual thickness of adjacent elastomer slabs. </li></ul><ul><li>f s = the permissible tensile stress in the steel plate of a laminated bearing. </li></ul><ul><li>V = vertical reaction on laminated bearing or bearing pad. </li></ul>
  11. 11. Properties of Elastomer Values from AASHTO M251 ASTM D4014-03: Limiting Values ASTM (D4014-03 (2007) D2240
  12. 12. <ul><li>Specifications of Elastomeric Bearing: </li></ul><ul><li>The bearings can either be designed from first principles, selecting proprietary products or by specifying the requisite loads, movements and rotations and approving the bearing details submitted by the contractor. </li></ul><ul><li>Selecting a standard proprietary product is simpler and cheaper than designing a bearing which is based on trial and error process. </li></ul><ul><li>Technical data of proprietary products is available from manufacturer’s catalogue and a sample is appended. </li></ul><ul><li>Loads on Bearings: </li></ul><ul><li>Loads transferred to the substructure through C/L of the bearing are : </li></ul><ul><li>DL (dead load & superimposed) </li></ul><ul><li>LL (live load HA & HB) </li></ul><ul><li>Loads per bearing are determined from grillage analysis or manual method. </li></ul><ul><li>Movements in Bridges: </li></ul><ul><li>Temperature variations </li></ul><ul><li>Concrete shrinkage and creep </li></ul><ul><li>Effect of pre-stressing </li></ul><ul><li>Dead Load and Live Loads </li></ul><ul><li>Tilt, settlement and seismic disturbances </li></ul><ul><li>Displacements can be longitudinal, transverse and vertical directions, rotational modes or combination thereof. </li></ul><ul><li>Rainbow practice in design of elastomeric bearing is to consider only longitudinal movements due to temperature, creep and shrinkage. </li></ul>
  13. 13. <ul><li>Movement due to Temperature & Shrinkage: </li></ul><ul><li>Coefficient for concrete, α t = 5.5x10-6/F/m </li></ul><ul><li>Assume temperature difference, to = 20oF </li></ul><ul><li>δ t = α t x to x length of beam </li></ul><ul><li>Shrinkage coefficient, </li></ul><ul><li>α s = 300x10-6 (pre-tensioned concrete) </li></ul><ul><li> = 200 x 10-6 (post-tensioned) </li></ul><ul><li>δ s = α o x length of beam </li></ul><ul><li>Movement due to Creep: </li></ul><ul><li>Creep coefficient for concrete, </li></ul><ul><li>α c = 400 to 600 x10-6 depending on type of beam. </li></ul><ul><li>δ c = α c x length of beam </li></ul><ul><li>2/3 of shrinkage + ½ of creep are assumed to occur at the time of placing of beam. </li></ul><ul><li>Effective shortening, δ es= δ s/3 + δ c/2. </li></ul><ul><li>Hence, total beam movement, δ b= δ t + δ es </li></ul><ul><li>Rotation, θ (radian): </li></ul><ul><li>Rotation of girders are due to the effect of DL and LL. </li></ul><ul><li>Rotation capacity of the bearing shall be equal to or greater than the rotation of girder at the support. </li></ul><ul><li>(obtained from grillage analysis). </li></ul><ul><li>An additional tolerance of 0.005 radian is added to the rotation to cater for the seating allowance </li></ul>
  14. 14. <ul><li>Shear Forces: </li></ul><ul><li>Horizontal forces are generated in the bearing due to the movement of beam-slab caused by temperature difference, creep and shrinkage. </li></ul><ul><li>The value of the forces depend on the magnitude of the movement, size of bearing and the shear modulus of the bearing. </li></ul><ul><li>Force due to temperature, FT = ebAoG = δ tAoG/T per beam. Where T=total thickness of bearing. </li></ul><ul><li>Force due to shrinkage & creep, Fsc = ebA0G = δ es AoG/T where δ es = effective shortening. </li></ul><ul><li>Procedure for Design </li></ul><ul><li>Determine trial plan size of bearing. </li></ul><ul><li>Check for friction location criteria. Determine minimum value of total thickness of elastomer. </li></ul><ul><li>Determine bearing thickness. </li></ul><ul><li>Calculate shape factor S. </li></ul><ul><li>Determine DL and LL per bearing. </li></ul><ul><li>Check for compressive strain ec of inner/outer slab where ec1 + ec2 < 0.1 </li></ul><ul><li>Check for shear strain eqll due to compression of inner/outer slab (maximum component of eq due to LL). </li></ul><ul><li>Check for shear strain etmax due to horizontal movement. </li></ul><ul><li>Find overall vertical stiffness, Kc kN/mm </li></ul><ul><li>Find horizontal shear stiffness Kq kN/mm </li></ul><ul><li>Check allowable angle of rotation, θ max (radian) </li></ul><ul><li>Check stability of bearing. </li></ul>
  15. 15. <ul><li>Procedure for Adopting Proprietary Products (ASTM D429): </li></ul><ul><li>Determine trial plan size of bearing from manufacturer’s table. </li></ul><ul><li>Check friction location criteria : determine minimum value of total thickness of elastomer slabs. </li></ul><ul><li>Determine trial bearing thickness from manufacturer’s table. </li></ul><ul><li>Check shear deflection : Maximum shear deflection from table > calculated beam movement, </li></ul><ul><li>Check dead load and live load : Maximum loads from table > calculated loads. Check for DL + HA and DL+HB. </li></ul><ul><li>Check allowable angle of rotation :  max >  actual from grillage analysis. Where,  max = 2  /B where  = total vertical deflection. Check for DL+HA and DL+HB. </li></ul><ul><li>Proprietary Products </li></ul>
  16. 16. Steel Bearings (AASHTO M270 ASTM D 5977-03 ): <ul><li>Steel / Mechanical Bearings: </li></ul><ul><li>Spherical and Cylindrical Bearings: </li></ul><ul><li>Bearings of this type are designed to accommodate large rotational movement and utilize the low frictional characteristics of PTFE (poly-tetra-fluoro-ethylene) sliding on a concave surface. The surface is chosen to be spherical for multi-axial rotation or cylindrical for uni-axial rotations. </li></ul><ul><li>Roller and Rocker Bearings: </li></ul><ul><li>The roller bearing permits uni-axial rotation and uni-directional horizontal movement. Rollers can also be used in combination to increase load capacity, allow multi-directional movements and multi-axial rotational movements. </li></ul><ul><li>The cost is relatively higher than spherical or cylindrical bearings. The rocker bearing can be used to provide uni-axial rotation at the fixed end of a bridge. </li></ul><ul><li>A form of rocker bearing is available which uses spherical surfaces to accommodate multi-axial rotations. Rocker bearings can also be used with a PTFE sliding surface to provide horizontal movement capacity for the free end of a deck. </li></ul><ul><li>The materials used for these bearings is high grade forged and heat-treated alloy steels. </li></ul>
  17. 17. Rubber Pot Bearing Pads AASHTO M251: These bearings incorporate a disc of rubber trapped inside a shallow piston and cylinder assembly. The result is similar to a hydraulic cylinder containing a viscous fluid, and the rubber disc can support pressures. The piston can tilt within the cylinder without damage to itself or the rubber and rotation capacities can be achieved. Horizontal translation can be achieved by using a sliding bearing on one external face. Standard bearings are manufactured which offer a range of vertical load capacities of up to 30,000kN and cater for horizontal movements of more than 50mm.
  18. 18. <ul><li>Bearing Installation & Replacement: </li></ul><ul><li>The principal causes of bearing failure are : </li></ul><ul><li>Damage during installation </li></ul><ul><li>Poor bedding </li></ul><ul><li>Inaccurate positioning </li></ul><ul><li>In many cases there has been little provision made for access to bearings and possible bearing replacement. </li></ul><ul><li>There are mainly 2 techniques used to install bearing systems : </li></ul><ul><li>1) A 5-10mm plinth is constructed on the concrete surface using an epoxy or polyester resin. The bearing surface is then covered with a thin layer of resin adhesive. Any excess resin is squeezed out as the bearing is lowered onto the plinth, and uniform distribution of load occurs over the whole bearing area. </li></ul><ul><li>2) The bearing is correctly positioned and leveled on steel shims and the remaining space filled with a grouting material. The shims are then removed after grouting to avoid the possibility of point loading. </li></ul>Worked Example on Bearing
  19. 19. Worked Example on Bearing:
  20. 20. Worked Example on Bearing:
  21. 21. Worked Example on Bearing:
  22. 22. TEST METHOD OF BRIDGE BEARING: Hardness: ASTM D 2240 Tensile: ASTM D 412 Elongation: ASTM D 412 Heat Resistance: ASTM D 573 Compression Set ASTM D 395 Ozone ASTM D 1149 Low Temperature Brittleness ASTM D 746 Instantaneous Thermal Stiffening ASTM D 1043 STANDARDS: ASTM D 4014-03: Specification for Plain and Steel-Laminated Elastomeric Bearings for Bridges ASTM D 5977-03: Specification for High Load Rotational Spherical Bearings for Bridges and Structures. AASHTO M 251-06 UL: Plain and Laminated Elastomeric Bridge Bearings.
  24. 24. <ul><li>Expansion joints provide continuity of the road surface at the interface between the bridge deck and the abutments. </li></ul><ul><li>Expansion joints are used to accommodate movements and withstand loadings as well as for operational requirements. An expansion joint should be designed to withstand a combination of vertical and horizontal loads. </li></ul><ul><li>The sources of movements to be accommodated are identical to that of bearings and therefore, expansion joints and bearings for a particular bridge span should be compatible. </li></ul><ul><li>Expansion joints provide continuity of the road surface at the interface between the bridge deck and the abutments. </li></ul><ul><li>Expansion joints are used to accommodate movements and withstand loadings as well as for operational requirements. An expansion joint should be designed to withstand a combination of vertical and horizontal loads. </li></ul><ul><li>The sources of movements to be accommodated are identical to that of bearings and therefore, expansion joints and bearings for a particular bridge span should be compatible. </li></ul><ul><li>Design Considerations: </li></ul><ul><li>Designers need to consider the following points: </li></ul><ul><li>The resistance of the joint and of the anchoring points in the structure to the fatigue loading due to the traffic. </li></ul><ul><li>Waterproofing of the attachment between the joint and the waterproofing facing. </li></ul><ul><li>Ease of maintenance and replacement. </li></ul><ul><li>Silence and comfort. (The best joint is the one which is not apparent). </li></ul>
  25. 25. <ul><li>Movements of Expansion Joint): </li></ul><ul><li>The type of expansion joint to be used is dependent on the total range of movement to be expected. </li></ul><ul><li>Movements are categorized as follows : </li></ul><ul><li>< 5mm Very small movement – no expansion joint required </li></ul><ul><li>5 – 10mm Small movement </li></ul><ul><li>10-75mm Medium movement – majority of expansion joints used </li></ul><ul><li>> 75mm Large movement </li></ul><ul><li>Design Load for Joints: </li></ul><ul><li>Design Loads: </li></ul><ul><li>Vertical load – Two 112kN wheel loads, 0.9m apart with a contact area of 265 x 265mm. The load shall be applied to the edge of the expansion gap. It may be spread transversely over such a length as is justified by the continuity and rigidity of the joint subject to a maximum of 450mm on either side of the centerline of each wheel. </li></ul><ul><li>Horizontal load – A traffic force of 80 kN/m run of the joint acting at road level. </li></ul><ul><li>Choice of Bridge Expansion Joints: </li></ul><ul><li>Current practice is to make decks integral with the abutments. The objective is to avoid the use of joints over abutments and piers. </li></ul><ul><li>Expansion joints are prone to leak and allow the ingress of corrosion agents into the bridge deck and substructure. </li></ul><ul><li>In general all bridges are made continuous over intermediate supports and decks under 60m long with skews not exceeding 30° are made integral with their abutments. </li></ul>
  26. 26. Choice of Bridge Joints: Where the deck and substructure have been designed to incorporate deck joints then the following guidance is given in M 213 for the range of movements that can be accommodated by the various joint types: 3 * 25 7. Cantilever comb or tooth joint. 3 * 5 6. Elastomeric in metal runners. 3 * 5 5. Reinforced Elastomeric. 3 40 5 4. Nosing with preformed compression seal. 3 12 5 3. Nosing joint with poured sealant. 3 40 5 2. Asphaltic Plug joint. 1.3 20 5 1. Buried joint under continuous surfacing. Maximum (mm) Minimum (mm) Maximum Acceptable Vertical Mvement Between Two Sides of Joint (mm) Total Acceptable Longitudinal Movement JOINT TYPE
  27. 27. Types of Joints: This type gives a very comfortable riding surface, but the capacity of movement is restricted to 30mm. Only light or semi dense traffic can be carried. An elastomeric profile with steel plate inserts is fastened on two steel plates and anchored in the slab. Movements of up to 300mm are possible.
  28. 28. Types of Joints: Two thick and firmly anchored sheets slide one into the other. They are in the form of straight or biased teeth which allow movements of 25 to 350mm. Larger joints require intermediate support of the teeth.
  29. 29. <ul><li>Thermal Movements: </li></ul><ul><li>BS 5400 Part 2 Chapter 5.4 specifies maximum and minimum effective bridge temperatures which have to be accommodated in the bridge structure. </li></ul><ul><li>The width of joint between the end of the deck and the abutment is set during construction of the bridge; usually when the concrete curtain wall is cast. </li></ul><ul><li>The maximum expansion of the deck is therefore determined from the minimum effective temperature at which the curtain wall is allowed to be cast; usually 2°C. </li></ul><ul><li>Hence if a maximum effective temperature of 40°C is calculated from BS 5400 Part 2 then a joint width will have to be provided at the end of the deck to allow for an expansion caused by a temperature increase of </li></ul><ul><li>(40-2)=38°C. </li></ul><ul><li>Design Standards for Joints </li></ul><ul><li>Design Manuals </li></ul><ul><li>AASHTO HL93: AASHTO LRFD Bridge Design Specifications (Loading on simple spans between 1 and 200 feet) </li></ul><ul><li>AASHTO HL 93:Live Load Moments, Shears, and Reactions Simple Spans, One Lane, w/o Dynamic Load Allowance </li></ul><ul><li>AASHTO 1999: Art of designing bridges with controlled damage </li></ul><ul><li>AASHTO M 85: Standard of concrete durability for LRFD </li></ul><ul><li>AASHTO M 95: Specific gravity and false set. </li></ul><ul><li>ASTM C 150: Standard of concrete durability test </li></ul>
  30. 30. DOWEL BARS
  31. 31. Dowel Bars AASHTO M 31 : Fixed end supports in bridges are provided for by dowel bars. At the free end, the support members can rotate and move horizontal whereas at the fixed end only rotation is allowed while all horizontal movements are restrained. The dowel bars pass from the beams to the abutment and are normally placed between bearings to facilitate easy replacement of bearings. Sometimes where space is restricted, elastomeric bearings are provided with holes for dowel bars to pass through. Design Criteria for Dowel Bars: Longitudinal movements of the deck will be accommodated by the bearings at the free ends and horizontal loads will be carried by the dowel bars at the fixed ends. The dowel bars shall be designed to resist a combination of horizontal loads due to tractive load (Tr), wind load (W) and loads due to shrinkage, temperature and creep (FSTC). The dowel bars are specified by suitable diameter and minimum embedded length ( usually made to reach the main reinforcement in the support).
  32. 32. é é é w w Dowel Bar (Plan View) 45 o 45 o Dowel Bars AASHTO M 31: Embedded length = l beam For Inverted T-beams, é = ½ (Total length of beam – effective length) For I-beams, é= ½ (thickness of end diaphragms)
  33. 33. <ul><li>Length of Dowel Bar: </li></ul><ul><li>Area of bar = H/(fst.n) </li></ul><ul><li>where, </li></ul><ul><ul><ul><ul><li>H = maximum horizontal forces </li></ul></ul></ul></ul><ul><ul><ul><ul><li>fst = allowable stress in dowel bar </li></ul></ul></ul></ul><ul><ul><ul><ul><li>n = number of dowel bars </li></ul></ul></ul></ul><ul><li>Π d2/4 = H/(fst.n) thus, d = √ [4H/(n Π .fst)] </li></ul><ul><li>Shear area = 2(ℓ x w) = H/(n. σ ) </li></ul><ul><li>where σ = shear stress of concrete. Hence ℓ = H/(2nw σ ) </li></ul><ul><li>Total length of dowel = ℓ + thickness of bearing and epoxy layer. </li></ul>
  35. 35. <ul><li>Bridge Parapets AASHTO M111 & M232: </li></ul><ul><li>Parapets are necessary to protect both the users and the carriageways and railways. There are several types: </li></ul><ul><li>pedestrian parapets; </li></ul><ul><li>crash barriers for light vehicles; </li></ul><ul><li>vehicular barriers for heavy lorries. </li></ul><ul><li>This equipment which is needed to meet general safety requirements, has to conform to detailed specifications. Acceptance by official inspection bodies is usually based on full scale testing. </li></ul><ul><li>The Design Manual for Roads and Bridges AASHTO M111 & M232 defines a parapet as ‘a protective fence or wall at the edge of a bridge or similar structure’. </li></ul><ul><li>Manufacturers have developed and tested parapets to meet the containment standards specified in the codes. </li></ul><ul><li>The weight of vehicle, speed of impact and angle of impact influence the behavior of the parapet. </li></ul><ul><li>A level of containment has been adopted to minimize the risk to traffic using the bridge (above and below the deck). </li></ul>Pedestrian Parapets: Pedestrian parapets are dedicated to the safety of people. Their shapes vary depending on their use and requirements of appearance. Whether made of steel or aluminium alloy, all pedestrian parapets should conform to the same strength and safety requirements.
  36. 36. Crash Barriers: To be efficient, both sliding rails and barriers should: Absorb the shock of a crash; permit vehicles to slide on them; retain and re-direct the vehicle. Crash barriers are usually bolted to the structure through an anchorage incorporated in the deck slab. The fastening is designed to ensure the structure is not damaged in case of an accident so that a quick and easy repair is possible. <ul><li>Safety Fences: </li></ul><ul><li>Depending on their purpose and the structural materials of which they are constructed, safety fences may be of various types: </li></ul><ul><li>a rigid fence in reinforced concrete; </li></ul><ul><li>a very flexible fence consisting of a chain of pre-stressed concrete blocks; </li></ul><ul><li>a flexible steel fence. </li></ul>
  37. 37. Rainbow Bridge Parapets: New Jersey Parapet with galvanized iron railing Standard kerb with railing The Design Manual for Roads and Bridges AASHTO M111 & M232 Specifies a Group Designation for various containment levels.
  38. 38. <ul><li>Choice of Parapets: </li></ul><ul><li>Concrete parapets are ideal for high containment parapets due to their significant mass. </li></ul><ul><li>Steel parapets are generally the cheapest solution for the normal and low level containment. This is significant if the site is prone to accidents and parapet maintenance is likely to be regular. The steelwork does however require painting and is usually pretreated with hot-dip galvanizing. </li></ul><ul><li>Aluminium parapets do not require surface protection and maintenance costs will be reduced if the parapet does not require replacing through damage. The initial cost is however high and special attention to fixing bolts is required to prevent them from being stolen for their high scrap value. </li></ul><ul><li>Design Standards for Parapet: </li></ul><ul><li>AASHTO HB17: Standard Specifications for Highway Bridges. </li></ul><ul><li>Design Manuals: Testing: </li></ul>ASTM A 123: Accordance with Galvanized ASTM B 696: Accordance with cadmium plate ASTM A 153: Accordance with galvanize wood components ASTM F2049-09b: Fences/Barriers for Public, Commercial, Multi-Family Residential Use and Outdoor Play Areas. AASHTO M 111 : Accordance with Galvanized AASHTO M 299: Accordance with cadmium plate AASHTO M 232 : Accordance with galvanize wood components.
  40. 40. <ul><li>Bridge Drainage System: </li></ul><ul><li>The surface water to be drained away from earth retaining structures or backfill. Any water percolating through the fill is collected in a perforated drainpipe, not less than 150mm diameter, which is located at the rear of the vertical stem of the wall at the level of the top of the footing. </li></ul><ul><li>Weep holes are often provided as a safeguard in the event that the drainpipe is blocked; they also provide a visual check that the system is working. </li></ul><ul><li>Unless the backfill to the wall is highly permeable then a vertical drainage layer is provided at the rear of the wall and is connected with the perforated drainpipe. </li></ul><ul><li>Drainage of Rainwater: </li></ul><ul><li>Drainage is carried out by means of: </li></ul><ul><li>a transverse profile of both the carriageway and the footway with a slope of 2 – 2.5%, which leads the rainwater </li></ul><ul><li>into gutter and along the kerb of the footway; </li></ul><ul><li>a longitudinal profile which eases the drainage downstream; </li></ul><ul><li>water gully's and water traps under the gutter channels whose location and dimensions are determined as a </li></ul><ul><li>function of slope and of water volume to be drained; </li></ul><ul><li>water downpipes which may be connected to collectors and to outfall sewers in towns or pollution-protected </li></ul><ul><li>areas. </li></ul>
  41. 41. Drainage System:
  42. 42. <ul><li>Bridge Drainage System: </li></ul><ul><li>The vertical permeable layer may take the form of any of the following: </li></ul><ul><li>Precast hollow concrete blocks. </li></ul><ul><li>Cast in-situ porous no fines concrete. </li></ul><ul><li>Granular drainage layer. </li></ul><ul><li>Special consideration to the drainage layer is required when the backfill contains materials susceptible to piping such as silt, chalk or PFA. Under these conditions, a granular drainage layer only is recommended; hollow blocks or no fines concrete are unsuitable. </li></ul><ul><li>Design Standards for Drainage: </li></ul><ul><li>ASTM D4071 - 84(2005) Standard Practice for Use of Portland Cement Concrete Bridge Deck Water Barrier Membrane Systems </li></ul>
  43. 43. FASCIA
  44. 44. <ul><li>Fascia: </li></ul><ul><li>The fascia are built on the deck edge and perform several functions : </li></ul><ul><li>Functional role - the fascia includes a drip stone which prevents water falling on them from flowing onto the underface of the slab and then onto the girders; </li></ul><ul><li>Aesthetical role - the fascia mark the crown line of the bridge. By associating them with the parapets the architect may design the shapes, material qualities and aspects of the facings in order to enhance the impression of the structure in the environment. </li></ul>
  45. 45. Plot: 377, Street: Nawab Siddiq Ali Khan Road, Area: Lasbella, Garden West, City: Karachi. Postal Code: 74550 Province: Sindh Country: Pakistan Landline: Fax: Website: - Email: [email_address] - [email_address] Contact us:
  46. 46. C a l e n d a r 2010 Contact us: Plot # 377, Nawab Siddiq Ali Khan Road, Lasbella, Garden West, Karachi-74550, Sindh-Pakistan. Landline: Fax: Cell: +92.321.821.8443 email: [email_address] - [email_address]