PITA Fiscal Year 2013 Projects

Effect Of Earthquake-Induced Damage On The Behavior And Performance Of Steel Gravity Frame Beam-Column Connections During Fire Exposure  

Lead University: Lehigh University
PI: Stephen P. Pessiki, Dept. of Civil and Environmental Engineering
Co-PI(s): Wesley J. Keller, Dept. of Civil and Environmental Engineering
PA Industry: LaSalle Engineering

Spray-applied fire-resistive material (SFRM) for steel frame buildings is prone to cracking, debonding, and spalling during inelastic seismic response. Earthquake-induced damage to SFRM insulation near bolted gravity frame beam-column connections is particularly concerning because conventional bolt materials are more sensitive to thermal degradation than structural steel. Experimental studies have shown that bolted gravity frame beam-column connections are susceptible to a low energy bolt shear fracture failure mode at elevated temperatures that can occur well below the anticipated capacity under normal ambient conditions. In addition to thermal degradation, force and deformation demands in gravity frame beam-column connection regions are exacerbated during fire exposure due to thermal distortion of the heat-affected components.

In order to address this potential vulnerability for SFRM-insulated steel gravity frame systems, a series of large-scale experimental beam-column assembly tests are performed to determine the extent of insulation damage that can be expected for a given deformation demand. Experimental data regarding the fragility of SFRM insulation is then incorporated in a series of numerical post-earthquake fire simulations in order to identify recurring design practices that may be linked to deficient performance. A numerical model for simulating fracture and debonding behavior of SFRM insulation is developed so that the vulnerability assessment can be extended to a broader range of connection types and geometries.