Parametric study of steel flush and extended end-plate joints under column loss scenario

Abstract

In steel-framed structures, joints play an essential role in providing a frame response to loading under persistence scenarios and especially in robustness analysis, which is very often executed in column loss scenarios. A type of joint used in framed structures is a bolted end-plate joint with extended and flush end plates. Experimental tests of six configurations of extended and flush end-plate joints were conducted to understand the actual joint behaviour under loading based on bending moment and tension force from catenary action. An advanced 3D FEM model of the joints was created using Abaqus software. Validated to own results of the experimental tests models were used in a wide parametric study to investigate the effect of the arrangement and thickness of the end plate, number, placement, and grade of bolts. The results provide practical recommendations for improving the joint characteristics required in accidental scenarios, for example, for enhanced resistance and rotation capacity under bending moment and tension force. The change from brittle to ductile failure mode was analysed as the second major parameter of joint ultimate behaviour. The thicker end plate and higher bolt diameter as the main component of the connection with the unstiffened column web was recommended to increase capacity in an accidental scenario. Finally, few proposals were presented to create innovative joints that demonstrate better performance in the column loss case: additional channels, saddles, and rings at bottom beam flanges. A significant increment in the load capacity and rotation capacity of the modified joints was achieved. The failure mode of the modified joints was changed moving the damage outside the joint zone. Further, the brittle destruction of bolts and end-plate fracture were avoided in the innovative models of joints.