An Investigation on Ultimate Strength of High Strength Aluminum Alloys Four-Bolted Connections with Out-of-plane Deformation

An experimental study for the structural behaviors of high strength aluminum alloys (7075-T6) single shear bolted connections with three types of bolt arrays has been carried out by authors. Out-of-plane deformation in the direction of plate thickness (hereafter, curling) occurred in some specimens with long end distances parallel to the direction of applied force. It is known that the curling reduced ultimate strength for curled specimens and it contributed to deciding the ultimate state of 7075-T6 bolted connections. In this paper, finite element analysis model has been developed based on the previous experimental results of 7075-T6 four-bolted connections and previous finite element analysis procedures related to singe shear bolted connections. The validation of finite element analysis method for predicting the ultimate behaviors of 7075-T6 bolted connections was verified through the comparison of test results and analysis results. Additional analyses with extended parameters of end and edge distances were conducted. As a result, strength reduction ratio (up to maximum 19%) by curling was investigated quantitatively and the curling occurrence conditions for end distance and edge distance were presented. In addition, analysis strengths were compared with design strengths by AAA (American Aluminum Association), AISI (American Iron Steel Institute) design specifications and proposed equation for 6061-T6 aluminum alloys four-bolted connections. Lastly, revised strength equation was suggested considering the actual fracture mechanism at ultimate state and curling influence (strength drop) by bolt bearing action.