composite slab
DESCRIPTION
TRANSCRIPT
BEHAVIOUR OF COMPOSITE SLABS WITH PROFILED STEEL DECKING
PRESENTED BYSHEIK 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.mmAs per EN 1993-1-1, 3.2.6.• Shape= Trapezoidal type sheeting• Embossments= Oval and concave
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
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
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 & Refernces1. For steel sheet properties - ASTM & IS codes2. 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