Modeling of end-plate bolted composite connection in fire considering axial force effects

This paper proposes the development and validation of a simplified model, which is based on spring-component-based model, in an attempt to calculate the initial stiffness and ultimate moment capacity for flush end-plate composite joints at elevated temperatures. This method may be adopted as the basis of the flush end-plate joint design in high temperature. In this paper, the resulting axial force due to the expansion of the beam at elevated temperatures is considered as a significant influence on the moment bearing capacity of joints. A 3-D finite element model using ANSYS is presented to simulate the real response of flush end-plate composite joints with axial force at elevated temperatures. This model is verified by comparing the simulated temperature distribution and the behavior of the joint at ambient temperature with experimental results. Then the finite element model is used to validate the accuracy of the simplified component model. Close agreement is found between the results of the simplified component-based method and that of the finite-element method. Furthermore, a simplified model based on the three-parameter exponential model proposed by Kishi-Chen [15] to predict the moment–rotation relationship of the composite joint at elevated temperatures considering the effect of the axial force is proposed, the parameters in which is obtained based on the parametric analysis with the FE model. The proposed component model and moment–rotation relationship provide a convenient path for designers to assess the connection behavior in the semi-rigid frame analysis.

► Simplified model to obtain characteristics of composite joints in fire was proposed.
► The resulting axial force due to the expansion of the beam in fire was considered.
► The proposed simplified model was validated by a verified 3-D finite element model.
► Equations to predict the M–θ relationship considering axial force effect were proposed.