A Finite Element Model for Beam to Column Bolted Connections with Semi Rigid Behaviour

Nowadays it is recognized that connections and members of steel frameworks have a semi rigid and nonlinear behaviour. One of the main concerns is how to incorporate the connection characteristics into an analysis. In the present study, beam-to-column bolted end plate connections, widely used because of the economy and simplicity of fabrication and assembly, are investigated for predicting their rotational behaviour (moment-rotation curve) that can be used in the frame analysis. In order to predict the rotational behaviour of this type of connection, a three-dimensional finite element model has been developed by the COSMOS/M® code. The proposed model takes into consideration the interaction between the various components that are comprised in the connection. Thus, the modelling domain includes the beam, end plate, bolts and nuts and the column. The main novelty now presented consists of accounting for the flexibility of the column components in the analysis. The column is modeled using solid elements. Other authors employ shell elements or use a rigid surface representing the column flange. Besides, the analysis incorporates the effects of material nonlinearity, for the plates and bolts, using the elastic-perfecty plastic stress-strain relationship. The results obtained from the finite element analysis are evaluated and verified by comparing the numerically predicted results with those of the corresponding tests carried out. The numerical results are also compared with a simplified theoretical model based on yield line analysis and the stub-tee analogy. The 3D finite element model presented in this study can be used to generalize the rotational behaviour of the end plate connection through more extensive parametric studies in order to take into consideration the connection flexibility and its effect on the performance of steel frames. So, extension of the methodology now presented may involve an improvement in analysis and design procedures of the proposed type of connection according to modern design codes.