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Composite slab

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    Composite slab Composite slab Presentation Transcript

    • BEHAVIOUR OF COMPOSITE SLABS WITH PROFILED STEEL DECKING PRESENTED BY SHEIK FARHAN(271298) SANDIPAN SINHA(271316) MANIVEL S(271324) KARTHIKEYAN V(271342)
    • INTRODUCTION • The composite slabs have now become a common form of construction of floor decks in major buildings. • In composite slabs, the profile sheet is used as permanent formwork and as tensile reinforcement. • In this composite slab, there is 30% saving in concrete material, resulting in reduced structural weight. • It favours fast and easy construction and also it proves to be economical
    • Profiled Deck steel • Thin-walled cold-formed profiled steel decks • Quality steel sheets conforming to ASTM A653 (2008) and IS 1079 (1994) • A galvanized surface coating with an average thickness of 0.0254 mm is finished on each face of the steel deck • Yield strength of sheet = 250 N/sq.mm As per EN 1993-1-1, 3.2.6. • Shape= Trapezoidal type sheeting • Embossments= Oval and concave
    • Size of sheeting = 1.8mx0.830m Thickeness = 1.1mm (a min. of 0.7 mm ie recommended)
    • Thickness of slab • Based on the satisfactory performance of floors that had previously been constructed in a wide range of countries, EN 1994-1-1 specifies the following minimum slab thicknesses that should be used in design: • Where the slab acts compositely with a beam, or is used as a diaphragm: o the overall depth of the slab h ≥ 90 mm; and o the thickness of concrete above the top of the ribs of the sheeting hc ≥ 50 mm.
    • Where the slab does not act compositely with a beam, or has no other stabilising function: o the overall depth of the slab h ≥ 80 mm; and o the thickness of concrete above the top of the ribs of the sheeting hc ≥ 40 mm.
    • • Here the depth of deck alone is 52mm and so 40mm to 50mm is the minimum thickness of concrete above deck sheet. • Hence over all slab thickness will be 110mm. • This is much less than conventional rcc slab • As per Euro code 4 (part 2) a slab thickness of 110mm will have a fire resistance of 90 minutes
    • LIVETIME EXAMPLE Site: Coimbatore Type: Two way steel bridge Span: 20m
    • TEST CRITERIA • Three slabs with different reinforcement conditions are to be tested for negative bending. • Negative bending is very essential in deck slab design as it is laid as continuous slab at site. • Usually positive bending tests will be carried out and they give least importance to negative bending.
    • • Here in deck slab, the deck sheet is at the bottom and hence during negative bending, it will be subjected to compression and top flange to tension. • 1st slab - Plain concrete with no reinforcement • 2nd slab - Concrete with bar reinforcement • 3rd slab - Concrete with steel macro fibre reinforcement
    • Properties of Fibre S.no Fibre Properties Steel Fibre 1. Length (mm) 30 2. Shape Wavy 3. Size/Diameter (mm) 0.5 4. Aspect Ratio 60 5. Density (Kg/cubic m) 7850 6. Youngs Modulus 210 GPa 7. Tensile strength 532 MPa
    • • As per Euro code 4 (Part 2) the dosage of steel macro fibres is 20kg/m3 to 30 kg/m3 for increasing the flexural strength and crack control • Here, we have chosen 20kg/m3 • Also beyond 30kg/m3, increase in fibre content does not have any effect in the strength of composite slabs
    • TEST SETUP
    • END SLIP
    • TEST RESULT TYPE OF SLAB ULTIMATE LOAD PCC 1.183 RCC 3.55 FIBRE REINFORCED 4.1
    • LOAD DEFLECTION GRAPH FOR PCC
    • LOAD DEFLECTION GRAPH FOR RCC
    • LOAD DEFLECTION GRAPH FOR FIBRE REINFORCED CONCRETE
    • CONCLUSION • The use of fibres in the composite slab increased its load carrying capacity to nearly 2.5 times of the capacity of plain concrete composite slab. • Also the fibres played an important role in crack control.
    • Code books & Refernces 1. For steel sheet properties - ASTM & IS codes 2. For Composite slab design and experiment inference - Euro code 4 (Part 1) 3. ASCE portal LITERATURE: 1. Composite Slab behaviour and strength analysis, Part I: Calculation procedure, Byton j. Daniels and Michel Crisinel. 2. The use of profiled steel sheeting in Floor Construction, H.D. Wright, H.R. Evans and P.W.Harding, University College, South Wales, UK
    • THANK YOU