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Title: Design optimisation of steel portal frames using real-coded niching genetic algorithm
Author: Phan , Thanh Duoc
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2013
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Abstract:
This thesis is concerned with the design optimization of single-storey steel portal frame buildings. In the UK, such buildings account for 90% of all single-storey buildings and 50% of all constructional steelwork used. Two different types of steel portal frames are considered: conventional hot-rolled steel portal frames, which can achieve spans of up to 50 m, and cold-formed steel frames, which while less popular in the UK, may be more efficient for spans around 12 m. A real-coded niching genetic algorithm is used for the purposes of the design optimization. By adopting a niching strategy, the diversity of the population is effectively maintained and so increases the probability in searching for the optimum solution in the design space. The efficiency of the real-coded niching genetic algorithm is demonstrated through design examples of both hot-rolled steel and cold-formed steel portal frames. For the design optimization of hot-rolled steel portal frames, the optimization algorithm is used to minimize the material cost of the portal frame, per square m on plan, taking into account both the hot-rolled steel cross-sections and the eaves haunch size. In all cases, a frame spacing of 6 m is adopted. Both ultimate and serviceability limit states are considered, with deflection limits recommended by the Steel Construction Institute. It is shown that serviceability deflections govern for the design of a 50 m span portal frame, where material costs increase by 60% compared to an ultimate limit state design only. For small span frame, i.e., span of 10m, material cost only increases by 19%. For the design optimization of the cold-formed steel portal frame, the same algorithm is applied to minimize the material cost of the main frame members. In addition, frame spacings of both 4 m and 6 m are considered. For the case of a 12 m span frame, with rigid joints, it is shown that the frame design is not sensitive to serviceability deflections and that the frame is 24% cheaper (in terms of material costs per square m) than using hot-rolled steel. When the effects of semi-rigid joints and stressed-skin action are included, it is shown that the cost of members is further reduced by 32%.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.602785  DOI: Not available
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