Strength Determination and Fracture Characteristics of Bolted Connections

Abstract

Bolted connections are commonly used for attaching structural elements in various civil and mechanical engineering applications. Despite their popularity, various studies raised concerns over the adequacy of design provisions in capturing connection strength. Design provisions to accurately predict connection strength could be refined through experimental tests and/or the use of highly nonlinear analysis that can simulate stress redistribution and ductile fracture in the connections. Recently, an effective numerical method for accurately predicting ductile fracture of bolted connections under any stress state was proposed and validated. In this study, using the validated numerical prediction framework, a comprehensive study on typical bolted connections is conducted. Parameters relevant to connection behavior, including bolt spacing in the tensile and shear planes as well as the edge/end distances, are varied in the analysis. It is found that plastic bearing deformations facilitate shear fracture initiation, and significant uneven stress might occur along the shear failure path. Based on the findings, new design equations pertaining to bolted connection strength are proposed. The design equations not only indicate better correlation with the experimental data than current code equations but also reflect more accurately the actual failure mechanisms in the connections. The results can be useful for assessing in-service connections and achieving reliable yet economical structural design at a consistent safety level.