Failure analysis of one-story precast structures for near-fault and far-fault strong ground motions

Failure of one-story precast structures consisting of cantilever columns connected by simply supported beams was widely reported throughout the epicentral regions of the last devastating earthquakes in Turkey. As a single degree of freedom system, precast columns are designed by using the elastic spectrum given in the seismic code and by considering a seismic load reduction factor which takes into account the inelastic behavior of the columns under seismic loads. Although the existing seismic codes consider near-fault shaking effects in the development of elastic response spectra, they do not currently consider the increased inelastic demands that may occur during near-fault ground motion. The current study consists of nonlinear time history analyses of various hypothetical columns having geometric and mass properties which are being used in Turkish precast industry and the evaluation of damage indexes (DI) in terms of peak ground velocity (PGV) and peak ground acceleration (PGA) of the used strong ground motions. It is achieved that near-fault earthquakes create more damages on the columns. This might be one of the main reasons for the collapse of several one-storey precast buildings which were well designed according to the seismic codes in the district of existing faults. The obtained PGV versus DI charts prove that if one increase the sectional dimensions and/or longitudinal reinforcement ratio of the column, the possible damage from near-fault shaking effects could be reduced.