Quantifying seismic risk in structures via simplified demand–intensity models

Abstract

Performance-based earthquake engineering (PBEE) has traditionally implied the verification of limit states at different earthquake intensities, where recent developments advocate a more risk-consistent approach. This has been primarily investigated for assessing existing structures and typically involves extensive analyses using detailed numerical models and ground motions. For new design, structures must be sized and detailed before more advanced numerical verifications are performed and the final design solution is established. In assessment, simplified procedures have been developed to incorporate further aspects of PBEE and typically comprise extensions to traditional structural analysis methods. Displacement-based assessment is one such method and while it has been extended for PBEE in the past, its use in a risk-oriented context still requires some validation. This article presents such a study, where recent developments in simplified analysis to estimate the exceedance rates of both storey drift and floor acceleration in reinforced concrete frames are described. This gives a method that is simple in its application, since it doesn’t require extensive and detailed numerical modelling or analysis, but also sufficiently accurate in its quantification of performance. While not intended as a substitute to extensive verification analysis, such a method for quantifying structural demand exceedance rates can be used to check results and provide better understanding to risk analysts. The work described herein can also be used in simplified verification analysis of new designs, whereby trial solutions may be verified in a relatively easy manner before more extensive verifications are carried out via non-linear dynamic analysis. It represents a further extension to existing simplified methods that strive toward more advanced performance quantification in line with the needs and goals of PBEE.