Structural optimization with reliability-based durability constraints

This paper describes a reliability-based design optimization methodology for structural durability that directly considers expected variations in service loads, material characteristics and finite element analysis modeling. The methodology is based on the development of a stochastic durability limit state model. For a given field reliability target this model can be easily evaluated for known (or assumed) variations; yielding an equivalent deterministic limiting stress. This limiting stress is then used as input (in the form of a durability stress constraint) to an existing structural design optimization tool which, in turn, is used to generate a mass efficient structural design. Because the variations considered are completely comprehended by the stress constraint, the reliability analysis and the structural optimization procedure are uncoupled. Therefore, the methodology is computationally efficient. As a demonstration, the new methodology is used to design a typical automobile shock tower interface structure.