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Steel-Concrete Composite Floor Systems Subject to Fire, Phase 2

Research Overview

A series of large compartment fire tests was performed to investigate the behavior and fire-induced failure mechanisms of full-scale composite floor assemblies with a two-story steel gravity frame, two bays by three bays in plan. A total of three 9.1 m × 6.1 m composite floor specimens with varying slab reinforcement and fire protection schemes for the secondary beam were tested under combined mechanical loads and compartment fire exposure. The first experiment (Test #1) was designed to achieve a 2-hour fire resistance rating per current U.S. practice and create baseline data for the behavior of the building. Test #1 specimen had the minimum specified reinforcement permitted in the U.S. for the composite slabs with profiled steel decks. Test #2 was conducted to study the effect of enhanced slab reinforcement with larger area and ductility on the fire resilience of the composite floor systems. Test #3 was conducted to study the effect of enhanced slab reinforcement as well as unprotected secondary beams on the fire resilience of the composite floor systems. Similar to Test #2, the floor slab in the test bay was reinforced with 9.5 mm diameter deformed bars with a center-to-center spacing of 30 cm. Unlike in Test #1 and Test #2, the secondary beam and its end connections in the test bay were left unprotected in Test #3.

Experiment Name Plot of Heat Release Rate Ignition Photo Date/Time Sort descending Specimen Fuel Type Test Duration (min) Total Heat Released (MJ) Peak HRR (kW)
15minRamp_R1
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
Ignition
Four square burners Natural Gas
16.22
5,047
8,034
15minRamp_R2
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
Ignition
Four square burners Natural Gas
20.00
4,850
7,980
60minRamp_R1
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
Ignition
Four square burners Natural Gas
76.48
37,631
10,317
CompositeFloorTest_No1
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
Ignition
Four square burners Natural Gas
107.33
63,542
11,496
CompositeFloorTest_No2
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
Ignition
Four square burners Natural Gas
160.43
86,908
12,776
CompositeFloorTest_No3
Plot of Fire Heat Release Rate with event markers. Uncertainty bar shown at peak value.
horn
Four square burners Natural Gas
145.28
90,480
12,124

Bryant, R. and Bundy, M. The NIST 20 MW Calorimetry Measurement System for Large-Fire Research, Technical Note (NIST TN) 2077, 2019
https://doi.org/10.6028/NIST.TN.2077

NIST Fire Calorimetry Database (FCD)
https://doi.org/10.18434/mds2-2314

Last Updated October 23, 2023