Inverse Sustainable Seismic Design

Abstract

Inverse sustainable seismic design (ISSD) is a new concept that reverses the steps involved in conventional analysis (CSD) for determination of ultimate capacities at target distortions to working backward from incipient collapse, to investigate the best options for seismic sustainability. CSD aims at compliance with codes with no guaranties for life safety nor collapse prevention. ISSD assures collapse prevention with a view to aftershock safety, environmental protection and post-earthquake realignment and repairs (PERR). The difference between the two is in the inverse method where postearthquake abilities of the structure are as important as its response during the event. The quest for sustainable seismic design (SSD) began two decades ago and is still not part of contemporary collage curricula nor seismic design guidelines (SDGs). The paper presents ISSD as an efficient approach that results in higher performance levels than those recommended by current SDGs. SSD can be accomplished using commonly available means and materials of construction without overlooking mainstream requirements. In the interim the concepts of P-delta suppression, removal of residual effects. effective stiffnesses, and ultimate load distribution have also been introduced. Concept details for SSD have been presented in the appendices. Sustainable seismic design is a new concept that is rapidly gaining interest worldwide. Here, it means the ability that allows structures to remain functional after repairs. The design of conventional structures for seismic sustainability is difficult by standard methods of approach. Earthquakes are unforeseeable, dynamic events, whereas postearthquake realignment and repairs are purposeful and static operations. The combination of these issues calls for development of new archetypes and methods of design, A few such systems have already been introduced, among others, by the authors. This paper presents a new method of analysis that not only reduces the task of otherwise cumbersome computations to that of simple arithmetic, but also provides insight into the state of the structure at incipient failure. Conventional design usually begins by assessing the seismic loading, followed by sizing the members of the system in such a way as to satisfy the prescribed drift ratio. In inverse design the same drift ratio plays the central role, where the pertinent analytical steps are worked backward to establish the corresponding ultimate loading, the preload, and the most favorable framing and member sizes for the given drift ratio.