Reliability analysis of single-headed anchor bolts

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Virginia Polytechnic Institute and State University

Several design equations for predicting the capacity of a single-headed anchor bolt embedded in plain concrete have been recommended in the United States. The capacities computed by these different recommendations, in some cases, differ significantly. The existing differences in current design criteria for anchor bolts subjected to tensile or shear loading is discussed with emphasis on the ACI, the PCI and the proposed Load and Resistance Factor Design (LRFD) equations. Available data from test results on the anchor bolts and welded studs were analyzed. Then, based on the analysis of these data and statistical information on basic design variables, a reliability analysis was performed. Using the advanced first-order second-moment reliability analysis method, risk levels implied in these design equations were computed for a dead and maximum live load combination.

It was found that there are inconsistencies in the levels of safety implied by both the ACI and the PCI design equations, and that the level of safety depends on the loading and the failure mode under consideration. By comparing reliability indices for these design equations, it is thus possible to make an objective evaluation of current design criteria.