Adverse effect of too-small edge distances on tensile capacity of screw anchors

摘要

ABSTRACT Due to space limitations, screw anchors may be used closer to the edge of the substrate than distances recommended by manufacturers, e.g. to connect bottom plates, base plates or handrails in residential buildings. This paper intends to investigate some of the adverse effects of such improper practices on the performance of screw anchors in such special close-to-edge applications that are common in the Australian residential building industry. This paper is therefore not intending to overrule the product prequalification/approval documents or the specifications provided by anchor manufacturers. More than 60 tests are carried out. The experimental results are compared with the predicted values from the literature and provided by the manufacturer. The type of failure modes and the effect of anchor installation method are scrutinised. It is found that the tensile strength reduces by up to 50% when anchors are installed closer to edge than the edge distances recommended by the manufacturer. Using the described installation method, single anchors of the type investigated in this study could potentially be installed as close as 2.2 the nominal diameter of the anchor to the edge of the substrate. For an edge distance of three times the diameter, the tensile strength is found to be slightly less than the value suggested by the manufacturer.