The FRACOF Composite Slab Test
Anthony Abu & Ian Burgess
Experiment, Predictions & Results
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Introduction
Fire Resistance Assessment of partially protected
COmposite Floors - FRACOF
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
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Introduction
Introduction to Eurocodes
Objectives of the Test
1. Investigate the performance of slab panels in SCI P-288
2. Observe the impact of different construction details on slab
panel capacity
Education of people in the construction industry
• FRACOF Test
Use of optimised structural systems
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Test Setup
6.66m8.735m
Primary Beams – S355 IPE 400
Secondary Beams – S235 IPE 300
Columns – S235 HEB 260
Protection Material – Cerablanket
Density = 128kg/m3
Specific Heat Capacity = 1130J/kgK
Thermal Conductivity = 0.06 – 0.27 W/mK
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Test Setup
58mm155mm
COFRAPLUS 60
C30/37
Φ7mm – 150 c/c – S500
50mm cover (top)
Reinforcement welded to S235 HEB 200
flanges to ensure continuity
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Shear Studs
• Φ = 19mm Primary beams – studs spaced at 100mm centres
• h = 125mm Secondary beams – studs spaced at 207mm centres
• fy = 350N/mm2
• fu = 450N/mm2
Test Setup
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Furnace
ISO 834
curve
Applied Loading
= 3.87kN/m2
Test Setup
Assumed Dead
Load = 3.254kN/m2
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Vulcan Prediction – Before Test
IPE400 sections
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Central Displacement (mm)
VulcanLite – Concrete Topping
Vulcan - Effective
Stiffness
Vulcan Prediction – Before Test
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
The Experiment - Observations
Edge continuity Condition not achieved on
one side
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Debonding of Concrete from
the steel deck
The Experiment - Observations
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Buckling of exposed
reinforcement
The Experiment - Observations
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Central Crack across short
span at about 105mins
The Experiment - Observations
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Large crack in the centre of the slab panel due to failure of the
welded joint between lapped reinforcements along that line.
The Experiment - Observations
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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.
The Experiment - Observations
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Central Displacement (mm)
VulcanLite – Concrete Topping
Vulcan - Effective
Stiffness
Test Result
Vulcan Prediction
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Tem
perature (oC)
Protected secondary beam Temperature
Test
Temperatures
Secondary beam
Temperature
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Revised Prediction
Before Test
Slab thickness = 160mm
fcu = 40N/mm2
2 welded beams for continuity
Imposed load = 3.75kN/m2
Protection material
Thermal conductivity = 0.2W/mK
Thickness = 50mm
Revised Prediction
Slab thickness = 155mm
fcu = 37N/mm2
1 welded beam for continuity
Imposed load = 3.87kN/m2
Protection material
Thermal conductivity = 0.06W/mK
Thickness = 50mm
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Tem
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Protected secondary beam Temperature
Test
Temperatures
IPE 300
Initial Uniform Secondary
beam Temperature
Revised Beam
Temperature
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Revised Prediction
Time (min)
Central Displacement (mm)
Test Result
TSLAB Limit
Bailey-BRE
Deflection
Revised Prediction with lower
edge beam temperature
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Tem
perature (oC)
Non-uniform beam temperatures
IPE 300
Test
Temperatures
Vulcan Bottom flange, web and
top flange temperatures for the
protected secondary beams
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Central Displacement (mm)
Non-uniform beam temperature
Test Result
Uniform protected beam
temperatures
Non-uniform protected
beam temperatures
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Tem
perature (oC)
Mesh Temperature & Slab Thickness
Reinforcement
Temperature range -
Test
Effective
Stiffness
Thin Concrete
ToppingAverage Depth
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Central Displacement (mm)
Effective Stiffness
Thin Concrete
Topping Average Depth
Mesh Temperature & Slab Thickness
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Physical
Representation
50mm57mm14mm
Vulcan
Representation
57mm0.514mm
Mesh Temperature & Slab Thickness
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Tem
perature (oC)
Mesh Temperature & Slab Thickness
Reinforcement at
average depth of 57mm
Reinforcement at average
depth of 63.743mm
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Time (min)
Central Displacement (mm)
Mesh Temperature & Slab Thickness
Reinforcement at average
depth of 63.743mm
Reinforcement at average
depth of 57mm
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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Conservative Estimate
VulcanLite estimate with uniform protected
beam temperatures, thermal conductivity
0.06W/mK and a thin concrete slab
TSLAB Limit
Bailey-BRE
Deflection
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
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
15th April 2008 © The University of Sheffield - Structural Fire Engineering Group
Thank You!
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