Post-Earthquake Fire Performance of Buildings: Summary of a Large-Scale Experiment and Conceptual Framework for Integrated Performance-Based Seismic and Fire Design

Abstract

A full-scale, five-story reinforced concrete building test specimen was erected on the large outdoor high performance shake table at the University of California, San Diego, and outfitted with various nonstructural components and systems. The specimen was subjected to a series of thirteen earthquake motions: seven with base-isolation and six with fixed-base (FB), with peak accelerations up to 0.8 g and peak inter-story drift ratios of up to about 6% reached during the largest FB motion. Damage to the structure following the largest motion included densely concentrated cracking in the slabs around columns resulting in punching shear failure, concrete spalling at the base of columns and the ends of beams where the large rotations occurred, as well as fractured and yielded longitudinal rebar in the Floor 2 and Floor 3 frame beams. Nonstructural component and system damage included loss of stair connections at Floors 3 and 4 due to weld fractures, loss of elevator function due to damaged doors on Floors 2 and 3, widespread damage to gypsum wallboard and joints, with about a 900% increase in effective leakage area measured in one compartment, varying degrees of damage to ceiling system based on type, including loss of 20% of ceiling tiles on the Floor 1, extensive damage to the balloon-framed facade system which enclosed Floors 1, 2 and 3, and displacement of unanchored contents. Following the motion tests, designated areas on Floor 3 were subjected to fires ranging in size from 500 kW to 2000 kW. Many fire protection systems, such as the sprinkler system and most firestop systems performed well. However, loss of compartmentation due to ground motions provided means for smoke spread, and loss of the stairs and the elevator rendered the means of egress unusable. Post experiment analysis illustrates how such damage could impact occupant life safety and emergency response during fires in earthquake-damaged buildings, and how the understanding of expected earthquake damage could be integrated into a risk-informed performance-based approach to building fire safety design in earthquake prone areas.