A Framework for Design and Optimization of Bolted Connection Assemblies using the Simplified Finite Element Model

Abstract

Bolted joint is one of the most common joint type in structures and mechanical systems. This joint type has a long history of development with a complete guideline for bolted connection design. In these conventional methods, parameters such as number of bolts, bolt type, bolts patterns etc. are chosen firstly and the design safety is then verified by analytical methods with a lot of assumptions. These methods are useful for the design step as they are simple and fast. However, analytical calculations in these methods are applicable for simple bolted connection only (eg: symmetric patterns, connected parts with simple geometry). Besides, due to the involvement of many assumptions (eg: equal load distribution, assumed rotation center.), there may be a possibility of high error during the calculation. With the development of modern computers and many advanced computational methods, the behavior of bolted connections with complicated designs can now be predicted more accurately. The most popular method used for the bolted connection assessment is the Finite Element Method (FEM) with the capability of simulating parts having complex geometries. However, since a full 3D analysis for bolted connections is a highly nonlinear problem, this analysis type is quite time-consuming, not suitable for large scale structures and also requires a comprehensive knowledge to setup and handle the analysis. In this thesis, a new framework using the simplified FE model for bolted connection design is proposed. The proposed method combines the tradition method using analytical calculations with the FEM to achieve an innovative bolted connection design solution which is simple, fast but still accurate enough. The number of required assumptions is also reduced hence lower the calculation error. Unlike many existed simplified models for bolted joint, the simplified model presented in this study requires only basic parameters thus make it particularly suitable for bolted connection design step. In addition, this model has the capability of accurately capturing the joint stiffness in multiple direction. The capability of the proposed method with the simplified FE model is demonstrated by the validation process with result from many different papers and experiment. Two optimization examples using the simplified FE model are performed also in order to show a further application of the presented method in bolted connection design.