Effects of Axial Compression on Shear Strengths of Anchors

초록

The influence of axial compression is not incorporated into the design provisions for concrete breakout or pryout strength of anchors under shear. This study experimentally evaluated the shear capacities of anchors subjected to axial compression on a base plate using 10 large-scale specimens. The test variables included axial compression N, edge distances from the anchor shaft in the direction of applied shear, edge distances perpendicular to the applied shear, and the compressive strength of concrete. The results showed little difference in crack initiation and propagation with varying axial compression. However, axial compression significantly improved the concrete breakout strength of anchors in shear. The applied axial compression reached up to 2.5 times the mean concrete breakout strength Vcbgo, as determined by the concrete capacity design (CCD) method, and the average increase in shear strength was approximately 0.6 times the applied compression. In addition, axial compression suppressed concrete pryout failure by preventing the uplift of base plates. Based on the lowest N/Vcbgo ratio used in the tests, if axial compression of at least 0.5Vcbgo is applied to a base plate, pryout failure need not be considered.

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