Approximate analysis of strength of tehran's tall buildings reinforced with spandrel frame against lateral forces

Spandrel frame system is one of the most applicable resistant systems against lateral forces in tall buildings of Tehran. Usual analysis of these frames is often costly and time-consuming due to involving numerous degrees of freedom. In this paper a method for investigation of shear lag and estimation of stress in constitutive elements of spandrel frame is presented. In this method, with consideration of deformation functions for flange and web frame and then writing stress-deformation function and using the principle of least energy, functions are presented for lateral and vertical displacement of structure. Proposed relations of this study are capable to consider shear lag phenomenon for both flange and web frame. Through consideration of variation of shear lag with elevations, factors are presented as functions of elevation through numerical solution of several structures.