Pryout Capacity of Cast-in Headed Stud Anchors

Pryout is a failure mode for headed studs that occurs when short, stocky studs are usedin an anchorage loaded in shearaway from an edge. As part of a PCI research program, Wiss, Janney, Elstner Associates, Inc. (WJE) studied a number of testing programs reported in the literature. Pushoff tests of headed stud connections from the 1960s and early 1970s, focusing on composite beam design, were reviewed to determine the steel capacity of headed stud anchorages away from all edge effects. This extensive database was further evaluated to examine the pryout failure mode. As a result of a careful analysis of this historic data, a modified pryout formula rooted in a shear type failure mode is proposed. The database was also found to be lacking in pryout tests having a variable spacing parallel to the applied shear load. To further evaluate the effect, eight laboratory tests were conducted focusing on this variable. Six anchorages with four studs and two anchorages with six studs were tested to examine individual y-spacing and the overall Y-spacing projection of the anchorage. From these tests and others reported recently, the influence of y-spacing was evaluated, and a modification factor is proposed to the basic pryout capacity equation.

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