Foundation–structure systems over a rupturing normal fault: Part II. Analysis of the Kocaeli case histories

Motivated by the observed (successful and unsuccessful) performance of numerous structures on top of, or immediately next to a normal fault that ruptured during the Kocaeli 1999 earthquake, this paper: (i) develops a two-step finite element methodology to study the propagation of a fault rupture through soil and its interplay with the foundation–structure system, denoted hereafter “Fault Rupture–Soil– Foundation–Structure Interaction” (FR–SFSI), (ii) provides validation of the developed methodology through successful Class “A” predictions of centrifuge model tests, and (iii) applies the centrifuge-validated methodology to study one-by-one the Kocaeli case histories of the first paper (Part I). It is shown that the presence of a structure on top of an outcropping fault may have a significant influence on the rupture path: with heavy structures founded on continuous and rigid foundations, the fault rupture diverts substantially and may avoid rupturing underneath the structure. The latter undergoes rigid body rotation, with its foundation sometimes loosing contact with the bearing soil, but in most cases retaining its structural integrity. In stark contrast, buildings on isolated footings and, perhaps surprisingly, piles exert a smaller diversion of the rupture which is thus likely to outcrop between the footings or pile caps; the latter may thus undergo devastating differential displacements. It is shown that structures in the vicinity of faults can be designed to survive significant dislocations. The “secret” of successful performance lies on the continuity, stiffness, and rigidity of the foundation.