This paper presents an experimental program investigating the behavior of single screw and adhesive anchors embedded in thin concrete with full thickness embedment depth subjected to shear load toward the free edge. Variables included:

concrete thickness, concrete compressive strength, anchor diameter, anchor type, and edge distance. Anchors were embedded through the full thickness of the concrete member and the effects of back-face blowout due to drilling were considered. Based on the experimental results of 149 tests, it was shown that concrete capacity design (CCD) method underestimates the shear capacity of the anchors.

Application of the thickness modification factor from ACI 318-14 overcorrects for the conservatism in the CCD approach and can lead to unconservative calculated capacities. An alternative thickness modification factor is presented which results in more accurate calculations of shear capacity. Finally, a design model is proposed for shear capacity of a single anchor installed in thin uncracked concrete members with full thickness embedment. The design model is based on 5% fractile of the experimental capacities.

Read More