Effect of Assembly Size, End Restraints, and Fireproofing Thickness onFire Endurance Testing of Floor Systems

摘要

As part of the National Institute of Standards and Technology’s building and firernsafety investigation of the World Trade Center disaster, four standard fire resistancerntests were conducted on the composite floor system used in the towers. The firernresistance tests were conducted to study three factors, the effect of (1) fireproofingrnthickness, (2) scale of the test, and (3) test restraint conditions. Two full-scale tests,rn35 ft (10.7 m) span, and two reduced-scale tests, 17 ft (5.2 m) span, were conducted.rnThree tests were conducted under restrained conditions and one under unrestrainedrnconditions. Additionally, two fireproofing thicknesses were applied, the specifiedrnthickness and the average applied thickness. Results showed that 1) a fire rating ofrn? h was determined from the reduced-scale restrained test with the specifiedrnfireproofing thickness which would not have satisfied 1968 New York City buildingrncode rating requirement of 2 h for the WTC towers, 2) the full-scale restrained floorrnsystem obtained a fire resistance rating of 1? h, and 3 h) the full-scale unrestrainedrnfloor system achieved a 2 h rating. Past experience with the ASTM E 119 testrnmethod would lead one to expect that the unrestrained floor assembly would notrnperform as well as the restrained assembly, and therefore, would receive a lower firernrating.