Abstract
A novel method to improve the robustness of steel end plate connections is presented in this paper. Existing commonly adopted techniques alter the stiffness of the beam or the end plate to improve the connection’s robustness. In this study, the robustness is enhanced by improving the contribution of the bolts to the rotational capacity of connections; the higher the bolts’ elongation, the higher the rotational capacity that can be achieved. However, the brittleness of the bolt material, combined with its small length, results in negligible elongation. Alternatively, the load path between the end plate and the bolts can be interrupted with a ductile element to achieve the required elongation. This can be achieved by inserting a steel sleeve with a designated length, thickness, and wall curvature between the end plate and the washer. The proposed sleeve should be designed so that its ultimate capacity is less than the force in the bolt at failure; accordingly, the sleeve develops a severe bending deformation before the failure of any connection components. Using a validated finite element model, end plate connections with various parameters are numerically investigated to understand the performance of the sleeve device. The proposed system substantially enhances the rotational capacity of the connections, ranging between 1.37 and 2.46 times that of the standard connection. It is also concluded that the sleeved connections exhibit a consistent elastic response with the standard connections, indicating the proposed system is compatible with codified elastic design approaches without modification. Furthermore, for a specific connection, various ductile responses can be achieved without altering the connection capacity nor configuration.
Highlights
The performance of steel structures subjected to extreme loading has received increased attention in recent years [1,2,3,4]
Due to the limited ductility provided by the connection components, researchers have often focused on various methods to enhance the ductility of connections by increasing their rotational capacity; see Figure 1
The relatively small length of the bolt leads to a reduced contribution to the connection’s rotational capacity in comparison to the end plate. This present study proposes a novel technique to increase the rotational capacity of end plate connections by enhancing the bolt contribution to the system behaviour
Summary
The performance of steel structures subjected to extreme loading has received increased attention in recent years [1,2,3,4]. Connections for fire and seismic actions are included to illustrate the various concepts to enhance the ductility under different extreme load scenarios. The rotational capacity of the steel connection is largely controlled by the least ductile members within the load path These are usually the bolts [12,13]. There are countless numbers of geometrical configurations, including the wave form and the number of waves, the practical constraints posed by the manufacturability, the cost and optimum structural performance can limit these alternatives. The previous analysis concluded that the proposed sleeve significantly improves the rotational capacity of connections, required for the survival of the beam to avoid progressive collapse, without changing the initial stiffness of the standard configuration of the connection. A sine wave is considered as it is frequently used to define the initial imperfection profile of shells for buckling analysis [19]
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