Experimental Investigation of the Tensile Capacity for Anchor Groups with Different Spacing Between Cast-in-Place Headed Anchors of High Strength and Deep Embedment

The overall objective of this study is to investigate the tensile capacity for anchor groups of cast-in-place headed anchors with high strength and deep embedment at different spacing between anchors. Experimental tensile load tests were conducted on 12 reinforced concrete specimens for the anchor groups of cast-in-place headed 42CrMo anchor bolts of 36, 48, and 60 mm in diameter with an identical embedment of 35 times the anchor diameter. The spacing between the anchors of the test specimens varied from 2 to 5 times the outside diameter of the anchor. The applied tensile loadings, the anchor displacements relative to concrete surface, the strains along the embedment length of anchor bolts, the failure loads, and the failure modes were documented comprehensively. The tensile load–displacement curves of the anchor groups approximately followed a three-phase pattern: an initial linear segment, a curvilinear transition, and a final linear sector. The interpreted tensile load-carrying capacities of elastic limit and failure threshold were obtained. The interpreted elastic limit increased as the anchor spacing increased. However, the spacing between anchors had a different effect on the interpreted failure threshold of anchor groups. All the test specimens of anchor groups failed via concrete splitting rather than concrete cone breakout, following a brittle cracking failure pattern.