The paper investigates the role of soil in the collapse of a 630m segment (Fukae section) of the elevated Hanshin Expressway during the severe Kobe earthquake of 1995. From a geotechnical viewpoint, the earthquake has been associated with extensive liquefactions (notably of reclaimed ground), lateral soil spreading, and damage to waterfront structures. However, there is evidence that soil-foundation-structure interaction (SFSI) in non-liquefied ground played a detrimental role in the seismic performance of local structures, including the one under investigation. The bridge consisted of single circular concrete columns monolithically connected to a concrete deck, founded on pile groups in alluvium sand and gravel. There were 18 spans in total, all of which suffered a spectacular pier failure and transverse overturning. Several factors associated with poor structural design have already been identified. The scope of this paper is to complement the earlier studies by examining the role of soil in the collapse. Specifically, the following issues are discussed: (1) seismological and geotechnical information pertaining to the recorded ground- motions; (2) soil amplification; (3) response of soil-foundation-superstructure system; (4) response of nearby structures that did not collapse. Results indicate that the role of soil in the collapse was triple: First, it modified the bedrock motion so that the frequency content of the resulting surface ground motion became disadvantageous for the particular structure. Second, the compliance of soil and foundation altered the vibrational characteristics of the bridge and moved it to a region of stronger response. Third, ductility demand on the pier was higher than the ductility demand of the system. The increase in seismic demand on the piers may have exceeded 100% in comparison with piers fixed at their base. The results of the study contradict the widespread view of an always-beneficial role of soil-foundation-structure interaction on seismic response
