Steel pin connections have been commonly used on bridges in US since the 1930s. The stress distribution and failure mechanism of a pinned connection are complex, so design code provisions are based on previous tests conducted by Johnston (1939) and Blake (1981). The AISC and AASHTO codes provide different bearing capacities for pin plates based on selected deformation limit states for pin holes, as shown in the table herein. However, they do not provide designers clear pictures of the levels of stress concentrations, limits of plastic zones and maximum strains, etc.
Recent advancements in finite element analysis (FEA) methods allow for modeling both nonlinear contact behaviors between pins and pin plates, and inelastic behaviors of steel. To study bearing failures in the pin plates of a compression truss member, a high-fidelity, nonlinear FE model was created by CHI. The results show the growth of plastic zone and elongation of pin holes with the increase of applied load. The FEA method can yield more data than that can be obtained through conventional prototype tests and is a valuable tool for future research and design of pin connections. It helps to identify the stress concentration zone, provide clear picture about the failure modes of pin connections, optimize the design and achieve the required factor of safety.
