![]() ![]() ![]() Traditional strategy of dynamics penalty function is that the penalty value is increased as the generation progresses. on the frame joints are not taken into account in this study.įor sophisticated penalty approaches, the use of dynamics penalty function to handle the constraint of optimization problems is generally quite successful in locating the region of the search space containing the global optimum but not the true optimum itself. It is worth mentioning that some effects of thermochemical treatment of screws, low-torque and uneven distribution of screw etc. In this paper, this influence on apex joint is considered for the optimum design of long-span CFS portal frames. Therefore, the effect of joint’s flexibility on the frame design should be taken into account, in order to obtain a realistic performance of such general steel portal framing system. However, for CFS portal frames, the joints are semi-rigid owing to the deformation of the bolt holes in the web of channel-sections and brackets under applied moments. In practical design, the stiffness of such frame joints can be improved using the haunch, welding to rafters at eaves and apex connection. Structural design of hot-rolled steel portal frames having long-span requires a large stiffness of the joints at the knees and apex to transfer the applied loads through bending action of the members. The minimum weight of main frame obtained from optimization process is approximate 19.72% lighter than a Benchmark Frame used in the full-scale experimental test. The optimum configuration for knee brace joint can reduce the section size of rafter and so the lighter frame could be obtained especially for long-span portal frame. The result showed that the proposed routine for design optimization effectively searched the near global optimum solution with the computational time is approximate 50% faster than methods being popularly used in literature. A novel method in handling design constraints integrated with genetic algorithm is proposed for searching the optimum design of cold-formed steel portal frames. The cold-formed steel portal frames are designed using Eurocode 3 under ultimate limit states. In this paper, the influence of knee brace configuration on the optimum design of long-span cold-formed steel portal frames is investigated. Experimental tests showed that such structures with long-span up to 20 m can be achieved when knee brace joints are included. The application of cold-formed steel channel sections for portal frames becomes more popular for industrial and residential purposes. ![]()
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