Direct estimation of the seismic demand and capacity of MDOF systems through Incremental Dynamic Analysis of an SDOF approximation

Introducing a fast and accurate method to estimate the seismic demand and capacity of first-mode dominated multi-degree-of-freedom (MDOF) systems by approximating the Incremental Dynamic Analysis (IDA) through the Static Pushover (SPO) analysis. While the computer-intensive IDA would require several nonlinear dynamic analyses under multiple suitably-scaled ground motion records, the simpler SPO helps approximate the MDOF system with a single-degree-of-freedom (SDOF) oscillator whose backbone matches the structure’s SPO curve far beyond its peak. Thanks to the empirical equations implemented in the SPO2IDA software, the summarized IDA curves of the resulting system are effortlessly generated, enabling an engineeruser to obtain accurate estimates of seismic demands and capacities for limit-states such as global dynamic instability. Using a nine-storey building as a case study, the methodology is favorably compared to the full IDA.