Equivalent Modeling of Bolted Connections under Transverse Load Using Iwan-Based Material Properties

The nonlinear characteristics of bolted connections are of significant importance for analyzing the mechanical performance of structures. The Iwan model is well-known and has been widely applied; its limitation is that it is not convenient for complex structures with multiple bolted connections. To simplify the modeling process, a material with the force-displacement characteristics of the Iwan model is proposed and applied to the bolted connection region, which can convert the nonlinearity of the bolted connection into the nonlinearity of the material. The constitutive relation of the proposed Iwan-based material is determined by the force-displacement equation of the bolted connection under load and the elastic-plastic hypothesis. The proposed Iwan-based material is implemented using the UMAT subroutine of ABAQUS, and the properties of the Iwan-based material are assigned to a solid finite element for an equivalent modeling of bolted connections. Through comparisons with the s imul ation results of the AIBE, the feasibility of the equivalent modeling method for the force-displacement relationship of the original Iwan model is verified, and through comparisons with the simulation results and experimental results of a detailed 3D FE model of the bolted connection, the universality of the equivalent modeling method is verified. The results show that the equivalent modeling method can well restore the statics characteristics of bolted structures under cyclic loading and can be applied to complex combined structures. The method is more convenient for establishing the finite element model of bolted connections and has more flexibility in adjusting parameters than traditional methods.