Title: Tensile Capacity of Anchors with Partial or Overlapping Failure Surfaces: Evaluation of Existing Formulas on an LRFD Basis

Author(s): C. Ben Farrow and Richard E. Klingner

Publication: Structural Journal

Volume: 92

Issue: 6

Appears on pages(s): 698-710

Keywords: anchor bolts; anchors (fasteners); safety; structural design.

DOI: 10.14359/9664

Date: 11/1/1995

Abstract:
This study concerns the prediction of tensile capacity, as governed by concrete cone failure, of single anchors located close to a free edge and multiple anchor groups located far from a free edge and installed in uncracked, unreinforced concrete. A total of 160 data points is available for single anchors close to a free edge, while 18.5 data points are available for multiple anchors. A total of 31 data points consisting of data on high-strength anchors previously compiled by Klingner et al., Collins et al., and Cannon is accessible from tests on single anchors failing by fracture of the anchor Using common definitions and nomenclature for all variables and material properties, each data set is placed in a data base using SI units and concrete cube strengths. The concrete failure data are then compared with capacities predicted by the three existing methods: the 45 deg cone method of ACI 349-90, Appendix B; a variable angle cone (VAC) method; and the concrete capacity (CC) method. Observed data are compared against these existing methods in terms of average square error and load and resistance factor design (LRFD). Finally, using the principles of LRFD, and following the design procedure of ACI 349-90, the probability of steel failure or concrete cone failure under known loads and concrete cone failure under unlimited loads is calculated. Based on those comparisons, each approach is evaluated with respect to accuracy and suitability for use in design. For single anchors located near a free edge and for multiple closely spaced anchors, the CC method fits most of the data better than either the ACI 349-90 method or the VAC method, and gives lower and more consistent probabilities of failure. This is especially evident.at very shallow and very deep embedments.