The FRACOF Composite Slab Test

Transcription

1 The FRACOF Composite Slab Test Experiment, Predictions & Results Anthony Abu & Ian Burgess

2 Fire Resistance Assessment of partially protected COmposite Floors - FRACOF Introduction To increase the use of Steel in multi-storey construction from 18% to about 65% in continental Europe Difference mainly due to adopted Fire Safety approach

3 Introduction Introduction to Eurocodes Use of optimised structural systems Education of people in the construction industry FRACOF Test Objectives of the Test 1. Investigate the performance of slab panels in SCI P Observe the impact of different construction details on slab panel capacity

4 Test Setup Primary Beams S355 IPE 400 Secondary Beams S235 IPE 300 Columns S235 HEB 260 Protection Material Cerablanket Density = 128kg/m 3 Specific Heat Capacity = 1130J/kgK Thermal Conductivity = W/mK 8.735m 6.66m

5 Test Setup 58mm 155mm COFRAPLUS 60 C30/37 Φ7mm 150 c/c S500 50mm cover (top) Reinforcement welded to S235 HEB 200 flanges to ensure continuity

6 Test Setup Shear Studs Φ = 19mm Primary beams studs spaced at 100mm centres h = 125mm Secondary beams studs spaced at 207mm centres f y = 350N/mm 2 f u = 450N/mm 2

7 Test Setup Applied Loading = 3.87kN/m 2 Assumed Dead Load = 3.254kN/m 2 Furnace ISO 834 curve

8 Vulcan Prediction Before Test IPE400 sections

9 Vulcan Prediction Before Test VulcanLite Concrete Topping Vulcan - Effective Stiffness Central Displacement (mm) Time (min)

10 The Experiment - Observations Edge continuity Condition not achieved on one side

11 The Experiment - Observations Debonding of Concrete from the steel deck

12 The Experiment - Observations Buckling of exposed reinforcement

13 The Experiment - Observations Central Crack across short span at about 105mins

14 The Experiment - Observations Large crack in the centre of the slab panel due to failure of the welded joint between lapped reinforcements along that line.

15 The Experiment - Observations Test Conclusions 1. Even with the fracture of reinforcement the test showed that the slab panel could sustain more than 2 hours of exposure to the standard fire 2. The integrity and insulation criteria of the slab were lost after 105 minutes, when the crack occurred due to the loss of the bond between the lapped reinforcement 3. Provided the continuity of reinforcement is guaranteed, reinforced slab panels will survive their specified duration once state of the art construction details are used.

16 VulcanLite Concrete Topping Vulcan Prediction Vulcan - Effective Stiffness Central Displacement (mm) Test Result Time (min)

17 Protected secondary beam Temperature 600 Secondary beam Temperature Temperature ( o C) Test Temperatures Time (min)

18 Revised Prediction Before Test Slab thickness = 160mm f cu = 40N/mm 2 2 welded beams for continuity Imposed load = 3.75kN/m 2 Revised Prediction Slab thickness = 155mm f cu = 37N/mm 2 1 welded beam for continuity Imposed load = 3.87kN/m 2 Protection material Thermal conductivity = 0.2W/mK Thickness = 50mm Protection material Thermal conductivity = 0.06W/mK Thickness = 50mm

19 Protected secondary beam Temperature 600 Initial Uniform Secondary beam Temperature IPE 300 Temperature ( o C) Revised Beam Temperature Test Temperatures Time (min)

20 Revised Prediction Revised Prediction with lower edge beam temperature 500 Central Displacement (mm) Test Result TSLAB Limit Bailey-BRE Deflection Time (min)

21 Non-uniform beam temperatures 600 Temperature ( o C) Vulcan Bottom flange, web and top flange temperatures for the protected secondary beams IPE 300 Test Temperatures Time (min)

22 Non-uniform beam temperature Non-uniform protected beam temperatures 500 Central Displacement (mm) Uniform protected beam temperatures Test Result Time (min)

23 Mesh Temperature & Slab Thickness Full depth Vulcan Effective stiffness approach Average depth Closest comparison with TSLAB Temperatures Thin Continuous concrete depth Most conservative approach Increasing Reinforcement Temperature and decreasing slab thickness

24 Mesh Temperature & Slab Thickness Thin Concrete Topping Average Depth 500 Temperature ( o C) Effective Stiffness Reinforcement Temperature range - Test Time (min)

25 Mesh Temperature & Slab Thickness Thin Concrete Topping Average Depth 500 Central Displacement (mm) Effective Stiffness Time (min)

26 Mesh Temperature & Slab Thickness 57mm 50mm 14mm 57mm 0.514mm Physical Representation Vulcan Representation

27 Mesh Temperature & Slab Thickness Temperature ( o C) Reinforcement at average depth of mm Reinforcement at average depth of 57mm Time (min)

28 Mesh Temperature & Slab Thickness Reinforcement at average depth of mm Central Displacement (mm) Reinforcement at average depth of 57mm Time (min)

29 Conservative Estimate VulcanLite estimate with uniform protected beam temperatures, thermal conductivity 0.06W/mK and a thin concrete slab TSLAB Limit Bailey-BRE Deflection

30 Conclusions Vulcan and VulcanLite give good predictions of slab panel behaviour Vulcan predictions and Test results differ by the observed integrity failure of the test Need to incorporate a plausible localised concrete failure criterion in finite elements Care must be taken in the selection of assumptions for finite element analyses

31 Thank You!