Simplified pushover-based seismic risk assessment methodology for existing infilled frame structures

The evaluation of seismic risk in structures requires information on both site hazard and structural vulnerability. Hazard can be quantified via probabilistic seismic hazard analysis, while seismic vulnerability can be quantified using structural analysis; the former is typically specified via predefined national hazard models, whereas the latter is more structure-specific and can be computationally expensive depending on the numerical modelling and analysis procedure complexity. As a compromise, various simplified seismic response evaluation methods have emerged and been implemented in assessment codes and guidelines (e.g., N2 method in Eurocode 8, SPO2IDA in FEMA P695). Furthermore, the seismic assessment and rehabilitation of existing structures have seen the introduction of risk classification guidelines. These are tools to primarily assist practitioners and decision-makers in understanding and managing seismic risk and the possible implications of different retrofitting schemes. Risk classification guidelines typically use loading-based quantities such as the seismic capacity-to-demand ratio. However, several drawbacks are associated with adopting loading-based quantities, namely the lack of uniformity of the actual seismic risk, expressed as a mean annual frequency of limit state exceedance. To address these drawbacks, this paper outlines a relatively simple pushover-based methodology for the direct evaluation of seismic risk (PB-Risk) for non-ductile infilled frame structures. The article describes a step-by-step framework for the simplified characterisation of hazard, vulnerability and subsequently seismic risk. It is quick and easy to implement within a practical and code-based setting and can be adopted within risk classification guidelines. The application of the proposed PB-Risk methodology is demonstrated via several case study applications, and its robustness in characterising seismic risk with respect to other simplified non-linear static formulations for infilled frame buildings is shown.