Study on neutral axis location of common bolts of flush end-plate connections

Abstract

The external load eccentricity and the end-plate thickness were employed as the research parameters, and experimental studies on the tensile properties of the bolts with flush end-plate in the beam-column joints was conducted under the action of eccentric pulling force (group A) or pure bending moment (group B). Through the analysis of failure mode, the force distribution of bolts and the offset ratio of the neutral axis, the variations of neutral axis location for common bolts with flush end-plate connections were investigated. Based on the load-displacement curves and the joints tensile performance, the finite element (FE) analysis was used for the two sets of tests. A good agreement exists between the numerical results and the experimental results. The neutral axis of bolts continuously moved continuously to the compression zone as the load increased. Increasing the bolts eccentric distance could significantly increase the bolt axial force increment and accelerate the offset of neutral axial to compression zone. Increasing the thickness of end-plate could reduce the bolt axial force increment and delay the offset of neutral axial to compression zone. The simplified elastic calculation method is more conservative in predicting the stress state of common bolted end-plate connections Under the action of eccentric pulling force or pure bending moment. The modified formulae for the bolt force for flush end-plate connections are presented, and the modified results agree well with the experimental results. Under the premise of ensuring the safety of the structure, the modified formulae provide a more accurate description of the stress state of the common bolted end-plate connections, while requiring less material and reducing the joint cost. It is expected that this study will serve as a reference for the structural design and construction of common bolted end-plate connections.