Development of frame finite element model for truss structures with semi-rigid connections

The problem of connecting truss structures is one of the major concerns in structural analysis and design. The behavior of truss structures is usually analyzed using a common finite element model, which considers each member as a two-force member. Each truss member connection is treated as a rotational pinned joint, but in the reality, the members of truss structures are usually connected with bolts or by welding. Alternatively, a designer may analyze such a structure using a frame finite element model where joint connections are considered fixed or rigid connections, which provide a connection that is stiffer than the inherent behavior. In this research, instead of using truss or frame finite element models, a substructure technique is employed to develop a more realistic finite element model. Each element is separated into three parts, a main element and two joint elements. The substructure technique is integrated into the frame finite element model to reduce design variables in global equations, to increase deformability of the joint elements, and make the proposed model more realistic. Young’s modulus values of the joints are reduced as a percentage of the modulus of the main elements. Comparison of the results obtained from the proposed model to the truss and frame finite element models are reported