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Modern seismic codes rely on performance-based seismic design methodology which requires from the structures to withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation for various inelastic spectra. The purpose is to investigate the ratio between the inelastic and elastic maximum lateral displacement demands. Three options are considered in the present work to express the inelastic response spectra in terms of the ductility demand, yield strength reduction factor and inelastic deformation ratio. This later, a new non dimensional parameter called inelastic deformation ratio (Cη), depends on the natural period (T), the post-to-preyield stiffness ratio (a), the normalized yield strength coefficient (t) and the peak ground acceleration (PGA). The inelastic deformation ratio (Cη), is not evaluated for a fixed ductility ratio or for a fixed strength reduction factor. Though the ductility demand and yield strength reduction factor differ greatly for given ranges of T and r“ they take close values for systems for any T value when η > 1. It confirms also previous studies stating that they take unity value for periods T ≥ 1sec. [ABSTRACT FROM AUTHOR]

In seismic codes, the acceleration demand of nonstructural components is commonly expressed in terms of floor response spectra and estimated by means of simple predictive equations. By using the latter, response-history analysis of the structure is not required, being floor spectra calculated directly from the peak ground acceleration expected at the site. The price for this simplicity in the method used for the estimation of floor spectra is the generally poor approximation of the obtained predictions. Codes’ equations, in fact, do not explicitly account for important factors influencing floor spectra, such as the contribution of the higher modes of vibration of the structure and the actual value of the nonstructural components’ damping ratio. Alternative spectrum-to-spectrum methods for direct generation of floor spectra have been proposed, which include these factors and improve the accuracy of the predictions. Different approaches have been used and several methods developed. Despite large research effort, however, a comparative evaluation of the currently available proposals is still lacking. The objective of this paper is to fill this gap, by reviewing selected proposals representative of practice-oriented spectrum-to-spectrum methods. A case study consisting in a six-story frame is analyzed and predictions obtained with the investigated methods are compared with exact floor spectra derived from time-history analyses of the structure, as well as spectra calculated using the Eurocode 8 equation. [ABSTRACT FROM AUTHOR]

Abstract: The nonlinear static procedure, based on pushover analysis, has become an important tool to characterize the seismic demand and the performance of structures. The standard pushover procedure is restricted to single-mode response, a valid supposition for symmetrical or low-rise buildings, where the response is dominated by the fundamental vibration mode. The standard pushover procedures become misleading when the response of the structure is influenced by higher vibration modes. This is the case of tall or non-symmetrical buildings. Several pushover procedures, able to take into account the effects of higher vibration modes, have been lately developed to overcome this drawback. This paper presents a comparison between standard, advanced pushover analyses and the exact results obtained by nonlinear time history analysis. The analyses have been conducted on a series of moment-resisting steel frames with stiffness irregularities, with different number of stories, designed according to EC8 and the Romanian Seismic Design Code for Romania''s Vrancea Seismic Area. [Copyright &y& Elsevier]

Abstract: This paper presents the vulnerability of public buildings in Sabah which are subjected to earthquakes from Sumatra and the Philippines. Tremors in Peninsular Malaysia and East Malaysia due to Sumatra and Philippine earthquakes have been reported several times. Engineers are concerned of the seismic vulnerability of public buildings due to lack of earthquake consideration in Malaysia‟s building design procedure. 8 (eight) reinforced concrete buildings which are mostly categorized as moment resisting frames has been selected for vulnerability study. A case study has been conducted on low rise, medium rise, and high rise buildings. The buildings are analyzed using Finite Element Modeling (FEM) under different types of analyses including Time History Analysis (THA) considering low to medium earthquake intensities. Different intensities of earthquake load, 0.05g, 0.10g, 0.15g and 0.20g are applied to the structures to know the maximum allowable earthquake load intensities for the buildings. In the non-linear analysis of modal frames, it indicates that most of the buildings are categorised in the moderate damage level where there is no structural damage but some non-structural damage are expected. The performances of the structure are shown by the yield point at beam-column connections where the internal forces at beam elements exceed the design capacity of the beams. The Labuan Airport building was performed the early yielding point at 3.85 sec for column element at intensity 0.05g. The study indicates that the plastic hinge initially formed on the column at the lower storey level for both low and high rise building frames. [Copyright &y& Elsevier]