Risk targeting in seismic design codes: the state of the art, outstanding issues and possible paths forward

Over the past decade there have been various studies on the development of seismic design maps using the principle of “risk-targeting”. The basis of these studies is the calculation of the seismic risk by convolution of a seismic hazard curve for a given location (derived using probabilistic seismic hazard analysis) with a fragility curve for a code-designed structure (ideally derived from structural modelling). The ground-motion level that the structure is designed for is chosen so that the structure has a pre-defined probability of achieving a certain performance level (e.g. non-collapse). At present, seismic design maps developed using this approach are only widely applied in practice in the US but studies have also been conducted on a national basis for France, Romania, Canada and Indonesia, as well as for the whole of Europe using the European Seismic Hazard Model. This short article presents a review of the state of the art of this technique, highlighting efforts to constrain better some of the input parameters. In addition, we discuss the difficulties of applying this method in practice as well as possible paths forward, including an empirical method to estimate an upper bound for the acceptable collapse and yield risk.