The effect of head plate details on the pull-out behaviour of headed bars

This paper presents the pull-out behaviour of headed bars having various head details and the prediction of pull-out failure capacity governed by concrete breakout failure, reinforcing bar failure and pull-through failure. It is becoming increasingly common to anchor reinforcing bars by welding a plate to the end of the bar. This paper presents a study of the influence of the shape and thickness of the plate on the pull-out behaviour of bars anchored in this way. A total of 58 pull-out tests were conducted on four slab-like specimens and 13 beam-like specimens containing headed bars. The test variables were the reinforcing bar diameters connected to the headed plate, the head plate shapes, the dimensions of head plates and the types of welding scheme connecting the reinforcing bars and head plates. Concrete compressive strengths and embedment depths were also taken into consideration. Headed bars were manufactured with varying details of head according to ASTM 970-98 and the embedment depths were based on CSA 23.3-94. Since there is no relevant specification governing the headed bars, pull-out failure capacities through the static tensile load test are compared to the values predicted by the current design methods for anchor systems connected to concrete, such as ACI-349, ACI-349R and the Concrete Capacity Design (CCD) Method. Failure modes and the respective effect of each test variable are discussed.