Optimum design of rib-reinforced composite I-beam

Abstract

The main goal of this study is to develop a methodology for optimum shape design of reinforcing ribs on the web of an I-beam so as to minimize the weight of the structure and maximize the buckling-load carrying capacity of the beam under three-point bending test condition. IM7/8552 carbon-fiber reinforced composite material is selected for the model because of its high strength with low density. A finite element model is developed to simulate the mechanical behavior of the I-beam under three-point bending. The model is validated by comparing its predictions with the results of an experimental study. Then, an I-beam with a large web is considered so that the most critical failure mode is web-buckling due to transverse shear loads. Tsai-Wu criterion is used to predict static failure. By using ANSYS Parametric Design Language (APDL), codes are developed to implement the optimization algorithm and carry out buckling analyses to determine the maximum buckling-load capacity. The design variables are the geometric parameters defining the shape, size, and orientation of the ribs. Three different configurations are considered for the ribs and a parametric study is conducted to select the best rib configuration for optimization. Additionally, another parametric study is done to find the best stacking sequence for the layers of the web. The optimum shape and orientation angle of the ribs are found using modified simulated annealing algorithm, which is a global search algorithm. A considerable improvement is obtained in load-carrying capacity of the I-beam by introducing the optimum rib configuration, which results in an insignificantly small increase in the use material compared to the I-beam with flat web.