Anchorage failure mechanism and uplift bearing capacity of L- & J-anchor bolts in plain concrete

Abstract

This paper studies the anchorage failure mechanism and bearing capacity characteristics of hooked (L- & J-) anchor bolts in plain concrete under uplift load. Static tests on L- & J- anchor bolts were carried out to study the influence of different parameters (such as bolt diameter, anchorage depth, and bolt hook length) on the failure mode of hooked anchor bolts. The test results show that the uplift bearing capacity of L- & J- anchor bolts is greatly improved compared with that of smooth bolts. Two typical failure modes, that is, concrete breakout and bolt failure. In specific, the concrete breakout occurred in the L- & J- anchor bolts with anchorage depth of 5d, and the failure mode changed from concrete breakout to bolt failure as the anchorage depth increased. The finite element model was further established to investigate the stress development of the anchorage bolt and concrete and thus reveal the anchorage failure mechanism. Furthermore, a calculation method was proposed to accurately predict the uplift bearing capacity for the hooked anchor bolts with concrete breakout, where the change rule of the breakout cone diffusion angle θi and concrete crack propagation were mainly discussed. It reveals that the anchorage depth greatly influenced the diffusion angle when the concrete breakout occurs, and the diffusion angle on both sides of L- & J- anchor bolts presented an asymmetric distribution. Compared with the code ACI318, the proposed formula considered the effect of breakout cone diffusion angle on bearing capacity, and the calculation results coincided well with the experimental and numerical results, implying that the proposed formula in this paper can be considered reliable to guide the practical engineering design.