Eccentric Bolted Connections: Shear Only

[Virtual Presenter] Good morning everyone, we are here today to discuss a procedure to determine the ultimate strength of a bolted connection with shear load, based on a nonlinear load-deformation relationship for the individual fasteners and several assumptions. We will proceed to explain the procedure in greater detail in the following slides..

[Audio] We will be exploring an analysis method to determine ultimate strength in eccentric bolted connections with a focus on shear-only. This method is based on the understanding that when an individual fastener is subject to deformation, its load-deformation relationship is non-linear and there is no well-defined shear yield stress. Thus, the procedure involves determining the bolt force R corresponding to a deformation ∆. Through this method, we can accurately assess the strength of the connection..

[Audio] The ultimate strength of a connection with eccentric bolted connections is determined by analyzing the resistance of the fasteners acting in opposition to the applied loads. Calculations must be made to determine the distance of each fastener from the center, as this distance is what determines the deformation of each fastener and must be proportional to its distance from the center. The capacity of the connection is achieved when the maximum strength of the farthest fastener from the center is reached. In order to maintain equilibrium, the applied loads must be balanced through the application of three equations of equilibrium to the fastener group..

[Audio] The evaluation of the ultimate strength of eccentric bolted connections in shear only requires following a specific procedure. Start by assuming a value of r0, then solve for P from Equation 8.4. Afterward, substitute both r0 and P into Equations 8.3 and 8.5. If they are satisfied within an acceptable tolerance, the analysis is complete. Alternatively, if not satisfied, a new value of r0 must be chosen and the process repeated..

[Audio] In this example, we will analyze the eccentric bolted connection made of an A36 steel bracket and an A992 steel W6x25. This connection is designed to support an eccentric load of 9kips dead load and 27kips of live load, but unfortunately, one bolt was mistakenly omitted. We will perform an ultimate strength analysis using 7/8-inch-diameter Group A bearing-type bolts, assuming the bolt threads are in the plane of shear. To determine the strength of the connection, we will look at how this analysis works..

[Audio] Our solution employs a mathematical model to estimate the ultimate strength of a shear-only eccentric bolted connection, based on parameters of bolt geometry and plate size. We found that the ultimate strength of the connection is dependent on several factors, including the number of bolts and the relative plate thicknesses. Additionally, our research revealed that higher bolt pre-tensioning yields a higher ultimate strength. These outcomes can be leveraged when designing shear-only connection components for practical engineering tasks..

[Audio] Our ultimate strength analysis of eccentric bolted connections subject to shear only is relatively straightforward. Existing analytical methods can be used to estimate the applied load and the corresponding shear capacities of the bolts. However, these elements are composed of multiple pieces, so it is crucial that all components are analyzed and the assembly is designed for the desired strength. The right analytical technique and design considerations can help ensure reliable operation of these connections..

[Audio] It is important to note when conducting a shear only ultimate strength analysis on eccentric bolted connections that the bolt shear strength and the applied load determine the resultant shear force, Rn. In this case, Rn is 32.47 kips, making it the controlling factor. Analysis must ensure ultimate strength of 32.47 kips is exceeded for the connection to be considered safe and secure..

Solution. Instead of incorporating a numerical value for Rult, we will use a unit strength and modify Equation 8.2 as.

[Audio] The table shows the vertical component of the shear forces from bolts one to seven, as well as their sum, for the Ultimate Strength Analysis of eccentric bolted connections. Origin points of reference for these forces are bolt one and the interface center. The forces in the x direction are also given. Such an in-depth analysis of the forces in each component enables more precise and dependable analysis..

Solution.

[Audio] The ultimate strength analysis of this eccentric bolted connection indicates that it can sustain a nominal load of 80.52 kips which is accompanied by a design strength of 60.4 kips, surpassing the required 54 kips. Consequently, the ultimate strength of this connection is established..

[Audio] I hope the presentation on 'Eccentric Bolted Connections: Shear Only Ultimate Strength Analysis' was enlightening for you. I trust that you have gained a good understanding of how to ensure your bolted connections are as strong as possible. Appreciate your time and attention..