Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Steel-Concrete Composite Floor Systems Subject to Fire – Phase 2 (Test #2)

CF Test 2 Report Cover

Test #2 investigates the influence of the slab reinforcement on the structural integrity of the 9.1 m × 6.1 m steel-concrete composite floor subjected to combined mechanical loads and compartment fire exposure. The fire test bay was situated on the ground floor in the middle edge bay of the two-story test building. The floor slab in the test bay was reinforced with 9.5 mm diameter deformed bars placed 30 cm on-center (230 mm2/m). The test floor was hydraulically loaded to 2.7 kPa to mimic the code-prescribed gravity loads for fire conditions. Natural gas burners created a peak gas temperature exceeding 1100 °C below the test floor. The test fire lasted about 131 min, but the hydraulic loading was not removed until the test floor cooled down over 2 hours after the fire was extinguished. This experiment confirmed that the steel reinforcement played a vital role in maintaining the integrity of the composite floor under prolonged compartment fire exposure. The mid-panel vertical displacement increased at a rate less than 1 mm/°C as the protected steel beams were heated to 850 °C on average. The peak vertical displacement of the test slab was recorded 475 mm surpassing the displacement limit prescribed in the standard fire test. Although the test slab developed extensive surface cracks, it successfully contained the test fire underneath while sustaining the imposed loads. When the test floor was loaded again after it cooled down to room temperature, it retained the post-fire flexural strength exceeding 90 % of the ambient strength, calculated using the measured mechanical properties, of the composite secondary beam prior to fire exposure.

Fire Resilience of a Steel-Concrete Composite Floor System: Full-Scale Experimental Evaluation for Influence of Slab Reinforcement (Test #2) - Experiment Overview
Fire Resilience of a Steel-Concrete Composite Floor System: Full-Scale Experimental Evaluation for Influence of Slab Reinforcement (Test #2) - Experiment Overview
This video shows a time-lapse of a structural-fire experiment conducted at the National Fire Research Laboratory (NFRL). The test structure is a two-story, two-bays by three-bays gravity frame with a story height of 3.3 m. The test bay (at the center of the building) measures 6.1 m by 9.1 m and is hydraulically loaded to service gravity loads. The fire is produced by natural gas-fueled burners with a total maximum capacity of 16 megawatts. A standard fire-resistance test time-temperature curve is used to generate baseline data for current U.S. practice. For more information and other videos, please visit the project website. [no audio]


Spreadsheets containing the Test #2 data can be downloaded here (Click Link).

Video Gallery 

Created June 9, 2022, Updated October 4, 2022