Abstract
The application of cold-formed steel channel sections for portal frames becomes more popular for industrial and residential purposes. Experimental tests showed that such structures with long-span up to 20 m can be achieved when knee brace joints are included. In this paper, the influence of knee brace configuration on the optimum design of long-span cold-formed steel portal frames is investigated. The cold-formed steel portal frames are designed using Eurocode 3 under ultimate limit states. 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 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. 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 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.
Highlights
The use of cold-formed steel members for low-rise building construction has increased significantly in recent years
Etc. purposes to provide large spaces, portal frame buildings are a popular form of construction, which are often composed of hot-rolled steel sections, or alternatively can be constructed from cold-formed steel (CFS) sections for spans up to 20 m [1,2]
Where g1 is constraint for sectional buckling, namely, local or distortional buckling of section; g2 is constraint for lateral buckling of members; g3 is constraint for combined axial compression and bending moment; g4 is constraint for crushing at the frame joints; g5 is constraint for lateral torsional buckling of bending members; g6 is constraint for buckling of member in both bending and compression
Summary
The use of cold-formed steel members for low-rise building construction has increased significantly in recent years. 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. While most classical optimization methods, i.e., Another group of optimization techniques that have emerged recently are heuristic approaches, mathematical programming methods, generate a deterministic sequence of computation based on i.e., genetic algorithms, simulated annealing, evolution optimization, the gradient or higher-order derivatives of objective function, strategies, GAs perform particle a multipleswarm directional tabu search, ant colony optimization and harmony search. The application of genetic algorithm (GA) for optimizing hot-rolled steel portal frame buildings programming methods, generate deterministic sequence of computation basedachieved on the gradient or was considered in the literaturea[8,9,10,11,12]. Enough to scale the penalty to the same order with the objective function value
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