Application of Large-scale Layout Optimization Techniques in Structural Engineering Practice

A number of promising techniques which allow treatment of very large-scale plastic truss layout optimization problems incorporating multiple load cases, self weight and practical nodal stability constraints have been developed recently and collaboration with innovative structural engineering consultants Buro Happold has now provided an invaluable opportunity to investigate the effectiveness of these in practice. In use it was found that the recently developed member adding technique in particular was pivotal in permitting real-world scale problems to be tackled in the first place (this allows single load-case problems containing up to approx. 1,000,000,000 potential truss members to be solved on a desktop PC). However, many practically important issues requiring resolution were identified, and these are briefly discussed in the paper. One specific issue is considered in more detail in the paper; this concerns the specification of external applied loads, something which appears to have received scant attention in the literature to date. Whereas in a conventional layout optimization problem the spatial locations of external applied loads are predefined, in practice, e.g. for roof structures, this may be inappropriate since this strongly influences the form of the resulting ’optimum’ structure. In an attempt to overcome this, loads were instead applied to groups of nodes. The technique proved to be remarkably successful, and typical results are presented in the paper.