Evolutionary topology optimization for structures made of multiple materials with different properties in tension and compression

Structural optimization techniques for single-material continuum have been well developed and widely applied. However, topology optimization techniques with multiple materials, especially those with distinctly different mechanical properties in tension and compression, require significant improvement. Built on the bi-directional evolutionary structural optimization (BESO) technique for a single material, this paper proposes a method which takes material utilization as the criterion for determining the importance of the materials to the whole structure and assigns a suitable material for each element according to the sum of the principal stresses to obtain an efficient multi-material distribution. Numerical examples are presented to demonstrate the effectiveness of the proposed method in material saving and safety enhancement. The application of the method to the topology optimization of bridges with different support conditions and multi-span continuous bridges shows that the new technique has significant practical value for the conceptual design of multi-material structures.