Vamvatsikos D., Aschheim M.A., Kazantzi A.K. (2014). Direct performance-based seismic design: Avant-garde and code-compatible approaches. Proceedings of the 9th European Conference on Structural Dynamics (EURODYN 2014), Porto, Portugal
Abstract | Current force-based seismic design codes use design spectra and system-specific behavior factors to satisfy two pre-defined structural limit-states: Serviceability and Life Safety. Instead, performance-based seismic design aims to design a structure to fulfill any number of target performance objectives, defined as user-prescribed levels of structural response, loss or casualties to be exceeded at a maximum rate less than a given mean annual frequency (MAF). Even at its simplest structural response basis, the inverse probabilistic nature of the requirements has not yet allowed a satisfying solution without cumbersome cycles of re-design and re-analysis. An alternative approach is proposed, relying on a new format for visualizing seismic performance, termed Yield Frequency Spectra (YFS). YFS offer a unique view of the entire solution space for structural performance, as indexed by the MAF of exceeding arbitrary ductility (or displacement) thresholds, versus the base shear strength of a structural system with given yield displacement and backbone capacity curve. YFS can be instantly computed for any system that is satisfactorily approximated by a single-degree-of-freedom oscillator, as in any nonlinear static procedure. Thus, stated performance objectives are directly related to the strength and stiffness of the structure while fully incorporating aleatory and epistemic sources of uncertainty, as needed to achieve any required level of confidence. The combination of ductility (or displacement) demand and its exceedance MAF is readily determined, allowing a satisfactory initial design to be realized in a single step. Using a simple safety factor approach given the period and the hazard curve slope, the benefits can also apply to contemporary seismic codes, essentially introducing true performance-based capabilities in a traditional format.