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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 • Yield strength of sheet = 250 N/sq.mm 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 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 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 (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 Length (mm) 30 Shape Wavy Size/Diameter (mm) 0.5 Aspect Ratio 60 Density (Kg/cubic m) 7850 Youngs Modulus 210 GPa Tensile strength 532 MPa • • • As per Euro code (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 For steel sheet properties - ASTM & IS codes For Composite slab design and experiment inference - Euro code (Part 1) ASCE portal LITERATURE: Composite Slab behaviour and strength analysis, Part I: Calculation procedure, Byton j Daniels and Michel Crisinel 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