Finite element analysis and optimization of bonded post-tensioned concrete slabs

Abstract

Optimization techniques may be effective in finding alternative design of post-tensioned slabs to improve their mechanical behaviour, particularly reducing the bending moments. Post-Tensioned (PT) concrete one-way slabs are one of the widely used slabs because of their good performance and cost effectiveness compared with other slab types. The objective of this study is to develop three-dimensional Finite Element (FE) model for the optimization of bonded PT concrete one-way slab. The FE software package ANSYS was used to find the optimum strain energy and area of PT tendons. The interface between PT tendon and the surrounding concretes was also modeled, allowing the tendon to keep its shape during slab deformation. Contact algorithm and material nonlinearity were considered in the FE model. The total strain energy of bonded PT concrete slab was considered as the objective function. The design variables are the area of PT tendons, the initial stress in tendons and the eccentricity of the tendon profile while the constraints are the normal stress in concrete, the stress in steel tendon, the shear stress in concrete and the displacement at mid-span of the slab. The optimization results indicate that the area of PT tendons may be reduced by approximately 38% using an appropriate optimization algorithm. We conclude that the optimization of area of PT tendons of the post tensioned slab is very important because, it enable us to find the optimal area of PT tendon with low cost and suitable service conditions