The Effects of Load Intensity and Restraint on the Fire Resistance of Steel and Composite Beams

Abstract

The paper presents the results of sixteen fire resistance tests (in accordance with ASTM E119 and ANSI/UL 263 standards) on structural steel beams and composite steel/concrete beams conducted by the authors in 2015 at the Underwriters Laboratories facility in Northbrook, Illinois. The described experimental program was designed to investigate the effects of load intensity and restraint on the fire resistance of steel and composite beams in the context of contemporary construction materials and structural design standards. In terms of the scope and the range of investigated parameters, such experimental study was carried-out in North America for the first time. The test results confirmed the beneficial effects of reduced loads and restraint on the performance of beams in standard fire resistance tests and quantified these beneficial effects in terms of critical (failure) temperatures. The tests results also confirmed and quantified the long existing knowledge about non-composite structural steel beams performing much better than comparable composite steel/concrete beams in fire resistance tests. The generated experimental data will be used to validate numerical models, conduct parametric studies and develop simplified correlations for load intensity versus fire resistance time (and/or protection thickness). It will be of interest to certification laboratories, product developers and the broader structural fire protection design community.