Earthquake records for multilevel seismic performance assessment of structures
A method is established to identify critical ground motions that are to be used in physical testing to enable different levels of seismic performances to be assessed. The earthquake identification procedure consists of: choosing a suitable suite of ground motions and an appropriate intensity measure; selecting a computational tool and modelling the structure accordingly; performing Incremental Dynamic Analysis on a nonlinear model of the structure; interpreting these results into 50th (median) and 90th percentile performance bounds; and identifying the critical earthquakes that are close to these probabilistic curves at intensities corresponding to the design basis earthquake and the maximum considered earthquake. An illustrative example of the procedure is given for a reinforced concrete highway bridge pier designed to New Zealand standards. Nonlinear time-history dynamic analyses and pseudodynamic tests are performed on the pier using the three ground motions identified as: (i) a Design Basis Earthquake (10% probability in 50 years) with 90 percent confidence of nonexceedance; (ii) a Maximum Credible Earthquake (2% probability in 50 years) representing a median response; and (iii) a Maximum Considered Event representing 90 percent confidence of nonexceedance.