Optimal folding of cold formed steel cross sections under compression

This paper introduces manufacturing constraints into a recently developed evolutionary algorithm for shape optimisation of CFS profiles. The algorithm is referred to as "self-shape optimisation" and uses Genetic Algorithm (GA) together with the Augmented Lagrangian (AL) method to avoid ill-conditioned problems. Simple manufacturing rules derived from the limitations of current cold-forming processes, i.e. a limited ability to form continuously curved surfaces without discrete bends, are described in the paper and incorporated into the algorithm. The Hough transform is used to detect straight lines and transform arbitrarily drawn cross-sections into manufacturable ones. Firstly, the algorithm is verified against a known optimisation problem and found to accurately converge to a manufacturable optimum solution. Secondly, the algorithm is applied to singly-symmetric CFS columns each of which is subject to an axial compressive load of 75kN and has a uniform wall thickness of 1.2 mm. The strength of the columns is evaluated by the Direct Strength Method (DSM) and all buckling modes are considered. Various column lengths (from 500 mm to 3000 mm) and numbers of roll-forming bends were investigated. The optimised cross-sections are presented and discussed. ABSTRACTThis paper introduces manufacturing constraints into a recently developed evolutionary algorithm for shape optimisation of CFS profiles. The algorithm is referred to as "self-shape optimisation" and uses Genetic Algorithm (GA) together with the Augmented Lagrangian (AL) method to avoid illconditioned problems. Simple manufacturing rules derived from the limitations of current coldforming processes, i.e. a limited ability to form continuously curved surfaces without discrete bends, are described in the paper and incorporated into the algorithm. The Hough transform is used to detect straight lines and transform arbitrarily drawn cross-sections into manufacturable ones. Firstly, the algorithm is verified against a known optimisation problem and found to accurately converge to a manufacturable optimum solution. Secondly, the algorithm is applied to singly-symmetric CFS columns each of which is subject to an axial compressive load of 75 kN and has a uniform wall thickness of 1.2 mm. The strength of the columns is evaluated by the Direct Strength Method (DSM) and all buckling modes are considered. Various column lengths (from 500 mm to 3,000 mm) and numbers of roll-forming bends were investigated. The optimised cross-sections are presented and discussed.2

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“…al. [7] improved the study in [6] by introducing various types of boundary conditions into the algorithm. Gilbert et.…”

Section: Generalmentioning

confidence: 99%

Shape optimisation of cold-formed steel columns with manufacturing constraints using the Hough transform

Wang

Gilbert

Molinier

et al. 2016

Thin-Walled Structures

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“…Previous optimisation research has been carried out for steel frames and truss structures [28]- [32] but not on portal frames with asymmetry and tapering. The weight of the frame depends on the cross-section sizes of members.…”

Section: Optimisation Modelmentioning

confidence: 99%

Comparison of optimal designs of steel portal frames including topological asymmetry considering rolled, fabricated and tapered sections

McKinstray

Lim

Tanyimboh

et al. 2016

Engineering Structures

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General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. AbstractA structural design optimisation has been carried out to allow for asymmetry and fully tapered portal frames. The additional weight of an asymmetric structural shape was found to be on average 5 to 13% with additional photovoltaic (PV) loading having a negligible effect on the optimum design. It was also shown that fabricated and tapered frames achieved an average percentage weight reduction of 9% and 11%, respectively, as compared to comparable hot-rolled steel frames. When the deflection limits recommended by the Steel Construction Institute were used, frames were shown to be deflection controlled with industrial limits yielding up to 40% saving.

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“…The cross-section shapes converged to "bean", "oval" or rounded "Σ" shape types, in a relatively low number of generations (around 70). Moharrami et al [8] extended the work by Leng et al [5] by investigating the effect of different boundary conditions on the optimal geometry of the cold-formed steel columns. The design space was searched via a hybrid strategy composed of a stochastic search algorithm, used to arrive at near-optimal designs, and gradient descent, used to fine-tune the near optimal designs.…”

Section: Introductionmentioning

confidence: 99%

“…The computation of these critical loads for an arbitrary cross-section can be made using the finite strip software CUFSM [3]. This DSM/CUFSM procedure led several authors to study the optimization of cold-formed steel sections under compression [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%