Behavior of Bolted Connections in Cold Formed Steel Trusses

Abstract

The usage of cold-formed steel members in structural applications has increased considerably in recent years, due to its high strength and stiffness to weight ratio. However, the structural behavior of the bolted cold-formed bearing connections is affected by rotational stiffness, and by axial stiffness of joints, in the direction of web members' axial forces. In this research, an investigated numerical analysis is made to study the behavior of the bearing connections assembled by bolts for K and T joints in the cold-formed trusses. An overall literature review was done to identify the state of knowledge and gather the required data. A three dimensional model accounts both geometrical and material non-linearities are developed to justify the finite element model. In addition, a comparison of the previous experimental studies and the finite element is performed. From these results, a good agreement is observed between the finite element model results and the previous experimental results. A simply supported warren truss with three-point loads is tested using numerical simulation. The warren truss chords are formed from cold-formed hat section. Moreover, the web members were cold-formed lipped channels. Different parameters such as width-depth ratios as well width-thickness ratios of the hat cold-formed chord members, truss length, detail configurations of K joint and the arrangement of bolts in the K and T joints are used in this study. Ultimate strength and behavior of the web and chord members is studied. In addition, different failure modes of the bolted bearing connections are investigated. According to the comparison between the finite element results and the design rules the connections are classified into semi-rigid or pin. Eventually, moment- rotation and joint stiffness are deduced for the K and T joints. Key words: Cold-formed steel trusses; Finite element numerical modelling; truss connections; Bolted bearing connections; K connection; T connection and steel structures.