The Influence of Short Embedment and Close Spacing on the Strength of Hook Bar Anchorages

Larry A. Johnson and James O. Jirsa


The development of bars in reinforced concrete beams and/or slabs framing into relatively thin walls presents a special design problem. In anchoring bars in walls, standard 90 degree hooked bars are generally used. In some cases, the wall thickness will be sufficient to permit a short straight embedment between the hook and wall face. In thin walls the hook may start at the face (critical section) of the supporting wall. Full development of yield is highly unlikely in either case. Currently, no data concerning the efficiency of hooked anchorages with short embedment lengths exists. Design recommendations for such embedments are needed to cover the broad range of design situations encountered.

From the data obtained in earlier investigations conducted under Reinforced Concrete Research Council Project 33, equations were developed for the capacity or the required embedment length for a hooked bar failing in a sice splitting mode.

In this investigation the behavior of hooked bar anchorages with short embedment lengths was evaluated. The specimens were intended to simulate (in full scale) typical anchorages in walls. In the study, the range of variable previously investigated under Project 33 was extended and design recommendations developed previously were examined to determine applicability to short embedments. The bar diameter, concrete strength, beam depth, lead embedment, transverse reinforcement, unbonded straight lead lengths, and spacing between hooked bars were varied.

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