Finite strip modeling for optimal design of prestressed folded plate structures

The optimal limit state design of prestressed thin-walled folded plate structures under multiple loading conditions is presented. The design variables include (a) geometrical quantities, like the thickness and the dimensions of the structural members, (b) topological parameters, which define the location and the connectivity of such elements, and (c) the characteristics of the eventual prestressing system, described by the prestressing forces and the cables profile. Besides the physical and technological limits on such variables, the design constraints account for given limit states on both the stress and the displacement states which define the structural behavior. The objective of the design process is to find the structural layout which minimizes the structural volume and/or the total prestressing force according to the mentioned side and behavioral constraints. The solution of the corresponding non-linear optimization problem is achieved by using a numerical procedure based on the complex method. The structural analyses required during the optimization process are performed by using the finite strip method. Some applications to the optimal design of beams, vaults and box-girder bridges show the effectiveness of the proposed procedure.