Modeling Crushed Concrete Depth and Its Impact on Anchors Shear Capacities

Abstract

Concrete anchors in base plate connections may develop large bending moments under shear. The moments were shown to be proportional to the length of laterally unsupported anchor shafts, referred to as the effective exposed length in this paper. This length includes an apparent exposed length measured from bottom of plate or leveling nut to the concrete surface in a stand-off connection and a crushed concrete depth below concrete surface. The paper reports a total of 12 shear tests of single anchors and 101 finite-element analyses to determine the factors critical to crushed concrete depths, including concrete and anchor materials, anchor diameters, and stand-off heights. The study shows that the crushed concrete depth increases with an increase in the diameter of an anchor and its ultimate tensile strength, and decreases with an increase in concrete strength and the stand-off height. Equations are proposed to estimate the effective exposed lengths and the shear capacities of anchors governed by steel. The design equations reasonably predicted the shear capacities of 153 experimental tests. The proposed concept of crushed concrete depths facilitates future research on the shear capacities of anchors governed by steel, although other models are available in the literature to explain the existing tests.