Incremental dynamic analysis applied to seismic financial risk assessment of bridges

Incremental dynamic analysis (IDA) is applied in a performance-based earthquake engineering context to investigate expected structural response, damage outcomes, and financial loss from highway bridges. This quantitative risk analysis procedure consists of: adopting a suitable suite of ground motions and performing IDA on a nonlinear model of the prototype structure; summarizing and parameterizing the IDA results into various percentile performance bounds; and integrating the results with respect to hazard intensity–recurrence relations into a probabilistic risk format. An illustrative example of the procedure is given for reinforced concrete highway bridge piers, designed to New Zealand, Japan and Caltrans specifications. It is shown that bridges designed to a “Design Basis Earthquake” that has a 10% probability in 50 years with PGA=0.4g, and detailed according to the specification of each country, should perform well without extensive damage. However, if a larger earthquake occurs, such as a maximum considered event which has a probability of 2% in 50 years, then extensive damage with the possibility of collapse may be expected. The financial implications of this vulnerability are also given, revealing a fourfold variation between the three countries.