ON THE EFFECTS OF CIRCULAR BOLT PATTERNS ON THE ...

Figure 2-2 Free-Body Diagram Of A T-Stubs Connection.
Bending – The bending relation will be developed for the cases of a tension angle within a
connection; a similar relationship can be derived for other connections. Figure 2-3 shows the free-body
diagram of the angle member. As the applied force T works to overcome the contact forces at the bolt
line, a moment initiates which tends to increase the contact force (prying) at the far side of the bolt line
and decreases contact on the near side. The bolt pretension gradually overcome as the contact surface
recedes. In addition to the tensile force T and the prying force Q, moment Ma from the angle curvature
and a proportion (α) of the total connection shear Vconn exist. The details of these analyses are presented
in research paper by Fleischman et al. [61].
Nair et al. [4] conducted 27 full-scale experimental tests to investigate the effect of the prying forces
on the overall behavior of the T-Stubs. The four-bolted T-Stubs were tested under both static and fatigue
loading. The static testing was involved loading the specimens to the failure and monitoring the applied
force versus the elongation of the bolts. While the dynamic loading involved loading the specimens
cyclically through up to 3-million cycles or fracture. They concluded that the capacity of the connection
could reduce substantially due to the prying forces and fatigue strength of the bolts in the connections.
Using the geometry and the thickness of the T-Stubs, they introduced and empirical relation between the
flange forces and prying forces, which was recommended to used while designing the connection bolt
forces.
Bolt Force B
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Applied Force T
M
b
Prying Force Q