Development of a component method for calculating the initial stiffness of friction end-plate connections

One of the practical and useful methods that is used in Eurocode 3 to analyze the bending behavior of connections is the component method. Based on this method, the moment-rotation curves of joints are estimated bilinearly based on the two parameters of bending strength and initial stiffness. Therefore, one of the most important parameters to evaluate the moment-rotation curve using the component method is to find the exact initial stiffness of the connection (Sj,ini ). An issue that is not mentioned in the Eurocode 3 and causes the obtained results to be insufficiently accurate is the issue of pre-tensioning bolts. The main goal of this research is to add the effect of prestressing bolts to the component method. For this purpose, the stiffness of the spring elements modeling the column flange in bending, the end plate in bending, and the bolt in tension, which are necessary to predict the rotational stiffness of connections with the end plate with prestressed bolts, should be investigated. For this purpose, first, relationships are presented to consider the effect of prestressing bolts in the component method. Then, several end plate connections that have been investigated by the researchers are evaluated in two cases without considering the effect of pre-tensioning of the bolts and considering this effect in order to verify the correctness of the presented relationships. The results show that the presented method for considering the prestressing of bolts is a suitable and efficient method, which makes the accuracy of the developed component method more accurate than the conventional component method. So that the rotational stiffness difference of the laboratory model with the component method without considering the effect of pre-tensioning of the bolts was reduced to -13.81% and by considering the effect of pre-tensioning of the bolts to -2.41%.