In seismic codes, the capacity of structures is calculated using capacity design procedure based on the concept of base shear. The critical parameter in this procedure is the behaviour factor (q-factor), which allows designing the structures at the ultimate limit state accounting for their ductility and reserve strength. In this paper, the q-factor is evaluated for medium ductile steel moment-resisting frames (SMRF) using pushover analysis. The influence of specific parameters, such as the stories number, the "Column/Beam" capacity and the local response of structural members, is studied. The results show that the most important parameter that affects the q-factor is the local response of first-storey columns, while the "Column/ Beam" capacity has a less effect on this factor. Furthermore, it is observed that the q-factor value assigned to the studied frames in Eurocode-8 is systematically underestimated for low-rise frame, while the use of this value for high-rise frame is potentially unsafe.
A study is carried out to evaluate the storey drift evaluation methods of the seismic code of Algeria (RPA 99) and France (PS 92) for multi-storey steel rigid-frame buildings with set-back towers. The evaluation is based on a comparison of the storey drift obtained from the procedures of codes with those obtained from the nonlinear dynamic analysis of the buildings with set-back and a uniform building served as a reference. The results of the nonlinear dynamic analysis show in particular that the code methods of RPA 99 and PS 92 lead generally to an underestimation of storey drifts for the "tower" portion but provide such estimates of those for the "base" portion.Key words: storey, drift, code, seismic, building, set-back, response, analysis.
The inelastic deformation of structural elements is generally permitted in the case of the design of structures subjected to earthquakes. In this context, the resistance of such structures increases when plastic hinges are formed in their structural elements. The resistance that occurs during the formation of plastic hinges is none other than the overstrength that plays a significant role in the seismic design of structures. As a result, their overstrength and the influence of X-braces on this overstrength are not well understood. This present study tries to evaluate the overstrength factor obtained from inelastic pushover analyses of concentrically X-braced steel frames. The effects of some parameters influencing the value of overstrength factor, including the number of stories, are investigated. The results show that overstrength factor depends closely on this parameter. Finally, based on the findings presented in the study, tentative of overstrength factors are proposed for X-braced steel frames.
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