Abstrait

Optimum Design of Steel Moment Resisting Frames Subjected to Seismic Excitation

G. Lalitha, K.Suresh K.Vijaya Bhaskar Reddy

The main aim of this project is to develop an interior penalty function (IPF) based algorithm to multi-storey steel frames for minimum weight of frames. The frames are intended for resisting lateral sway due to seismic loading along with gravity forces. Many structural systems are used for resisting seismic (lateral) forces; however steel moment resisting frames (MRF) are considered for the present work. The design methodology incorporates codal provisions of IS 800-2007, thereby obtains the frames with optimum weight for in-plane moments with lateral support of beam elements. Strength and buckling criteria are considered as behaviour constraints along with side constraints in formulating optimization problem. A computer program is developed that uses an interior penalty function (IPF) for weight minimization of two-dimensional moment resisting steel framed structures. The program uses MATLAB, performs one dimensional search, and structural design in an iterative procedure. The design examples have shown that the proposed algorithm provides an efficient tool for the practicing structural engineers. The program is applied to 6 and 9 storey (4 bays) moment resisting frames (MRFs). The program demonstrated its capability of optimizing the weight of two medium size frames. To obtain member forces in frames an analysis procedure has to be applied. In the present work Equivalent Lateral Force procedure (ELF) and material nonlinear time history analysis (NTH) are applied and optimum values obtained from both the analyses are compared.