Optimization of frame structures with flexible joints

In the traditional approach to analysing and optimizing frame structures, joints are assumed to be rigid. Research has shown, however, that flexibility in the joints of a structure has a great effect on its behaviour. In this paper we present a formal method for optimizing frame structures to account for joint flexibilities and their design parameter sensitivities. We also present a simplified method that accounts for joint flexibility in the initial configuration, but neglects sensitivities to the design parameters. In a case study on an automotive sub-frame structure we compare optimization results using the traditional rigid joint model and the flexible joint methods proposed here. Results suggest that the simplified flexible joint method is more accurate than the traditional rigid joint model, and provides a more conservative design than the full flexible joint method while saving physical and computational effort.