Empirical Damage Classification of Base‐Isolated Buildings Based on Global Postearthquake Observations

ABSTRACT Current seismic damage classification standards do not adequately capture the distinctive damage characteristics inherent to base‐isolated buildings. To bridge this gap, this study collects and analyzes empirical damage observations from 52 base‐isolated buildings affected by 11 destructive earthquakes globally. Operating within the framework of current Chinese seismic damage classification standards, the typical damage patterns of critical and vulnerable components in base‐isolated buildings are summarized, including isolation bearings, supplemental energy‐dissipation devices, nonstructural elements within the isolation layer, and the superstructure. On this basis, we propose a seismic damage classification framework for base‐isolated buildings, which incorporates postearthquake functionality, the conditions of the isolation layer, and the extent of nonstructural damage. The damage state of the isolation layer is derived from discrete damage states and damage rates of its constituent parts, which is subsequently integrated with the state of the superstructure to determine the overall building damage state. It offers a practical foundation for postearthquake field survey, damage statistical analyses, and the future revision of relevant standards.