Effect of Earthquake-Induced Damage on the Sidesway Response of Steel Moment-Frame Buildings during Fire Exposure

Abstract

Spray-applied fire-resistive material (SFRM) is prone to debonding, cracking, and spalling in steel moment-frame plastic hinge regions during inelastic seismic response. To evaluate the effect of experimentally observed earthquake-induced SFRM spall patterns on building sidesway response during an ensuing fire, an analytical case study is developed for a steel special moment-frame building with a seismic hazard representative of coastal California. Response data from numerical earthquake simulations indicate that damage to SFRM insulation in beam hinge regions should be anticipated following ground shaking representative of the maximum considered seismic hazard. Thermomechanical post-earthquake fire simulations demonstrate that earthquake-induced SFRM spalling significantly increases thermal degradation in the affected beam hinge regions during fire exposure, leading to pronounced softening of moment-rotation response for the beam-column assemblies. This temperature-induced moment-frame connection softening increases the flexibility of the structural system for sidesway motion and exacerbates drift demands under the action of residual destabilizing forces.