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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 Four square burners Natural Gas
16.22
5,047
8,034
15minRamp_R2 Four square burners Natural Gas
20.00
4,850
7,980
60minRamp_R1 Four square burners Natural Gas
76.48
37,631
10,317
CompositeFloorTest_No1 Four square burners Natural Gas
107.33
63,542
11,496
CompositeFloorTest_No2 Four square burners Natural Gas
160.43
86,908
12,776
CompositeFloorTest_No3 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(link is external)

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

Last Updated October 23, 2023