Optimum design of semi-rigid steel frames using genetic algorithm

vııı SUMMARY In this study, an algorithm has been developed for optimum design of semi-rigid steel frames. A computer program which follows the instructions of the algorithm has also been prepared and presented. Frame drift constraints and stress constraints in the Turkish Steel Design and Construction Specification TS 648 (1980) are used in the optimization. In the first chapter, the importance and the reasons for the research has been stated. In the second chapter, previous research works related to this subject are mentioned briefly. In the third chapter, basic concepts regarding optimization problem and optimization methods are explained briefly. Genetic Algorithm, an optimization method, is inspected in detail in this chapter. In the fourth chapter, semi-rigid behaviour of connections is examined in detail and the most common types of beam-to-column connections currently employed in the steel structures industry are given. The equations and member stiffness matrices required for the analysis of steel frames with incorporating the semi-rigid connections have been obtained. In the fifth chapter, the stress interaction formulas considered in the optimum design taken from TS 648 (1980) are expressed. In the sixth chapter, a nonlinear analysis method depending on the load incremental approach with secant stiffness concept is explained in which the system equilibrium equations are satisfied for the deformed system in every load increment. Nonlinear analysis algorithm is also given in this chapter. In the seventh chapter, optimum design algorithm for the nonlinear semi-rigid frames is presented. A computer program developed in this study is introduced. Information on input data of the program and sample frame data are given herein. In the eighth chapter, optimum designs of various frames are performed by the computer program and the results are presented. The same frames with rigid connections are also designed and results are compared. In the ninth chapter, conclusions drawn from this study are given. The important conclusions are as follows; i^-5 ^ i^ WW*'IX Semi-rigid frames have been found economic when compared to rigid frames, but there has been considerable increase in their displacements. Moreover, designs are performed changing the connections parameters. Frames with more flexible, connections result in heavier optimum frames. End moments decrease span moments increase in the beams when compared to the beams with rigid connections. This leads to a more economic beam design.