JOURNAL OF THE INTERNATIONAL ASSOCIATION FOR SHELL AND SPATIAL STRUCTURES: J. IASS 1 STRUCTURAL OPTIMIZATION OF A THIN-SHELL BRIDGE STRUCTURE Evrard Fauche 1 Sigrid Adriaenssens 2 Jean H. Prevost 3 1 Visiting Student Research Collaborator, Department of Civil and Environmental Engineering, Princeton University 2 Assistant Professor, Department of Civil and Environmental Engineering, Princeton University 3 Professor, Department of Civil and Environmental Engineering, Princeton University ABSTRACT This paper demonstrates the use of topology optimization as a design tool for a thin-shell bridge structure. The presented topology optimization algorithm computes the material distribution within the shell while maximizing its overall stiffness for a given volume of material. The optimization routine is coupled to a Finite Element Method and finds its solution using the Fixed Point Iteration method or Picard Iterations. Besides obtaining the optimal shell thickness distribution, the topology optimization routine also suggests the optimal shape. The optimal shape enhances the mechanical behavior of the structure. The results of this study show that after topology optimization, the deck’s deflection, the shell’s Von Mises stresses, the eigenfrequency of free vibration as well as the deck’s bending moments are improved. This study uses a simplified model of the existing steel shell of the Knokke Footbridge as a case study. Keywords: design tool, thin shell, topology optimization, finite element, Picard iterations, Reissner-Midlin, potential energy, thickness distribution 1. INTRODUCTION This work demonstrates the value of computational methods as a design tool to optimize a thin-shell bridge structure. A typical topology optimization problem consists of distributing a given amount of material in a design domain subject to load and support conditions, such that the stiffness of the structure is maximized. Such topology optimization problems have previously been tackled. F. Belblidia and S. Bulman use a hybrid topology optimization algorithm which combines mathematically rigorous homogenization with intuitive methods [1]. R. Ansola and J. Canales have also implemented a computational method that integrates both shape and topology optimization [2][3]. Furthermore, T. Kimura and H. Ohmori also propose optimization methods for both shape and topology of shell [4]. Our approach focuses on the intuitive interpretation of topology optimization results in order to enhance the shape of a structure. The geometry of the existing 102 m span steel Knokke Footbridge [5] offers the basic static and dynamic model for this research. The footbridge has two 26 m approaching spans and a central span of 50 m. The structure is a steel thin shell with a reinforced 3 m wide concrete structural deck. Figure 1 shows the initial topology of the steel shell without the deck. The method aims at finding the optimal thickness distribution throughout the shell to improve the structural performance (being the deck’s deflection, the shell stresses, the deck’s bending moments and the shell’s dynamic behavior based on the eigenfrequency of free vibration). Figure 1. Thin-shell structure: base geometry to be optimized with topology optimization