Performance assessment of bridges under a sequence of seismic excitations

This study utilizes the current Pacific Earthquake Engineering Research (PEER) Performance-based Earthquake Engineering (PBEE) methodology to address the significance of considering a sequence of ground motions as the representation of seismic hazard in PBEE design and assessment frameworks. The current state of the art in design and assessment of structures, via PBEE, is founded on the conditional relationships between Intensity Measure (IM), Engineering Demand Parameter (EDP), Damage Measures (DM) and Decision Variable (DV stringed together in a triple integral representing total probability theorem. Aside from presenting theoretical background, this study is conducted on two reinforced concrete (RC) ordinary highway bridges in California which are subjected to a sequence of earthquakes determined randomly using ARIMA model fitted to the history of events in Southern California. In contrast, the traditional PBEE approach, the non-linear analysis of the bridges is conducted without resetting the damage to the bridge models due to earlier ground motions. Methodologic risk assessment is conducted using Column Drift Ratio (CDR) as the primary EDP, to generate analytical functions that can assist engineers in the decision making of whether to repair the bridge after a ground motion or otherwise. This is achieved by providing a functional form to predict the amplification of EDP in a pre-damaged bridge due to a future unobserved ground motion given the last observed ground motions. Conclusions are based on this amplification factor which is described as the ratio of the EDP of a pre-damaged bridge to that of a repaired bridge under the influence of a certain history of ground motion intensity measures.