Abstract: Ground motions at liquefied sites exhibit distinct characteristics. Clarifying their impact on the damage to superstructures is fundamental for rational seismic fortification in engineering. Using actual seismic-damage data, this study reveals how ground motions at liquefied sites influence structural damage via fragility analysis of typical building types. Against the backdrop of the 2011 M6.3 earthquake in New Zealand, we have compiled actual seismic records from both liquefiable and non-liquefiable sites, and constructed fragility analysis models for two archetypal buildings: a single-story residence and a six-story structure. Using the widely used OpenSees software, we compute the seismic fragility of structures under records from liquefied and non-liquefied sites, respectively. The difference between the results is defined as the fragility increment due to liquefaction and is compared with observed seismic damage. The influence mechanism and degree of seismic ground motion in liquefiable sites on the vibration response of two typical buildings are proposed. The findings enhance the understanding of the influence of liquefied sites on engineering structural damage and can provide guidance for advancing the theoretical development of seismic design for structures on liquefiable sites.

Key words: actual seismic damage, ground motion on liquefied sites, fragility of typical building, damage exceedance probability increment