Effect of span length on behavior of MRF accompanied with CBF and MBF systems

Abstract

The main objective of this study is to quantify effects of variations of aspect ratio (ratio of span length to story height) and lateral resisting system on response of high-rise steel structures. In the present research two goals of finding optimum aspect ratio in the smallest sensible system and suitable strengthening system have been followed. In order to compare sensitivity of different lateral systems, twelve 15-story structures equipped with the following three systems were modelled: a) special moment resisting frames (SMRFs), b) dual system of intermediate moment resisting frames and special concentrically braced frames (MRF-CBF) and c) dual system of intermediate moment resisting frames and mega braced frames (MRF-MBF). Analytical results show that using MRF-CBF system not only does not reduce lateral displacement and drift of the SMRF system, but also increases these parameters. If design is based on lateral displacement and drift, using the MRF-CBF system is not appropriate decision for reinforcement while the MRF-MBF system is extremely useful for this purpose.