الفهرس 
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Abstract
Moment resistine steel frames (MRSF); which are widely used as lateral load resisting systems for low- to medium-rise buildings; are one of the simplest ductile systems that can be built without bracing elements. The objective of this study is to evaluate the seismic behavior of two steel office buildings (six- and twelve- story frames), designed according to the Egyptian code with two design models, the strong-joint frame and the weak-joint frame.
The performances of the MRSF’s with strong- and weak-joints are evaluated through global and local performance parameters. The global performance parameters are the base shear coefficient, the roof drift ratio and the maximum story drift ratio. The local performance parameters are the rotational ductility ratios of columns, beams and panel zones.
A static pushover analysis was performed using the DRAIN-2DX program for nonlinear static analysis of building structures. The columns and beams are modeled using the DRAIN-2DX beam-colum’1 element. The connection behavior is modeled using a rotational spring approach, in which the moment-rotation relationship is approximated as a bilinear piece-line curve. The shear response of the panel zone is simulated as tri-linear rotational spring shear model. An inverted triangular lateral force distribution applied to the structural model in each step of the analysis. The results indicated that the deformability characteristics ofthe strong-joint frame are better than those of the weak-joint frame.
The evaluation is also performed by analyzing the building using nonlinear dynamic analysis. Twelve earthquake records are used in the analysis to cover a wide range of ground motion duration and frequency content. The P-l\ effect has been taken into consideration. The element mass is assumed to be lumped at the joints and viscous damping is assumed 3%. The results indicated that the natural periods of the strong-joint frame are less than that of the weak-joint frame and the natural periods increase with the increase of the building height. For the two designed buildings (strong- and weak-joint frames} the higher of the building; the better is of its seismic performance.