Search

This paper aims to guide structural engineers on how to apply the rapid nonlinear time history analysis (RNLTHA) procedure effectively to predict seismic demand, taking into account ductility and overstrength, and effects of dynamic phenomena including cyclic degradation of strength and stiffness in structures, in a direct and expedient manner. The shortcoming of the conventional force-based approach of design involving the use of a force reduction factor to account for nonlinear effects is well recognised. Nonlinear static (pushover) analysis and dynamic nonlinear time history analysis (NLTHA) are offered as alternative methods of analysis by major codes of practices to achieve better optimisation in the use of materials. NLTHA has advantages over pushover analysis in being more direct and capable of capturing cyclic response behaviour. Despite the merits of NLTHA, its adoption in the industry has been limited, mainly because of the complexity and the higher analysis cost involved. RNLTHA proposed in this article uses a macroscopic model of the building to fulfil the purpose of NLTHA, whilst saving computational time and achieving a good degree of accuracy, as verified by comparison with results generated from SeismoStruct.

This paper is aimed at giving structural designers guidance on how to make use of elastic site-specific response spectra for the dynamic modal analysis of a structure in support of its structural design. The use of response spectra in support of the pushover analysis of an RC building forming part of the non-linear static analysis procedure (that can be used to predict seismic demand without relying on the code-stipulated default R factor) is also presented. Seismic analysis of structures based on the use of site-specific response spectra can help to achieve a more optimised, and cost-effective, structural design compared to the conventional approach employing a response spectrum model stipulated by the code for different site classes. Currently, the methodology is only adopted in major projects in which enough resources are available to engage experts who are skilled in operating the procedure; thus, the use of site-specific response spectra in structural engineering practice is still limited despite the merits of the procedure. Deriving a site-specific response spectrum requires a database of representative ground motion records to be developed. Extra analytical tasks to be undertaken include the processing of bore log data, site response analyses, and selection/scaling of bedrock accelerograms for input into site response analyses. Guidelines for implementing this design methodology are currently lacking. To promote the wide adoption of site-specific seismic design, this article presents the procedure for developing the required site-specific design spectra, as well as guidelines for applying these spectra for seismic design based on analyses of linear, or nonlinear, models of the building. Non-linear analysis can be accomplished by dealing with macroscopic models as illustrated in a case study.