Advancements and challenges in direct loss-based seismic design

Abstract

Provisions in seismic design codes generally focus on collapse prevention or life safety for major, rare earthquakes while damage prevention for minor, frequent ones. The evolution of theoretical knowledge, modelling abilities, and actual damage observations led to higher awareness of the implications of code provisions on earthquake risk. The economic consequences of the 1994 Northridge (USA) earthquake symbolically led to a paradigm shift in evaluating structural performance. This led to performance-based earthquake engineering, now considered a standard for risk/loss assessment. Different research efforts improved the common force-based design to include risk-related concepts within the design process, such as: methods targeting displacement, seismic fragility, mean annual frequency of exceeding a given damage state, losses, resilience metrics. This paper focuses on the recently developed direct loss-based design (DLBD), which allows designing structures that achieve a given loss-related metric under the relevant site-specific seismic hazard virtually without design iterations (generally less than three). After describing the design methodology, this paper discusses: 1) the accuracy of the procedure for the design of new reinforced concrete buildings -monolithic or base isolated- and the retrofit of existing ones; 2) the necessary validation studies needed to maximise the scope of DLBD; 3) the methodological advancements needed to improve the accuracy of the embedded loss-estimation method; 4) the operational advances to render DLBD appealing in the practice.