Experimental investigation on the anchorage performance of hooked high-strength steel strands for beam-to-column connection

Abstract

To explore the anchorage performance of hooked steel strands used in the beam-to-column connection of the precast prestressed assembled structural (PPAS) system, considering the influence of the various research variables, such as anchorage length and the length of the vertical segment of the steel strand, 16 specimens were designed and tested under the pull-out loading. The failure modes, pull-out load-slip curves, peak point loads, and the corresponding slips of the tested specimens were obtained accordingly. Besides, by means of portable X-ray detection technology, the shape evolution of hooked steel strands in the concrete columns under various pull-out loads were imaged and compared, and the anchorage failure mechanism of hooked steel strands was further clarified. The test results demonstrated that three failure modes were observed in all test specimens. Besides, the hooked steel strands can significantly improve its ultimate anchorage capacity and material strength utilization efficiency. When the anchorage length is not less than 500 mm, and the length of the vertical segment is 5d, 10d and 15d, the conical fracture failure of the steel strand always occurs in the test specimens, and the material strength utilization efficiency is always not less than 90 %, far higher than that of the straight steel strands. In addition, the relative slip at the loaded end is obviously related to the anchorage parameters of the steel strands. In details, whether the length of the vertical segment is 5d, 10d or 15d, the relative slip of the hooked steel strand is significantly lower than that of the straight steel strand, which is strongly related to the unique anchoring mechanism of hooked steel strand. However, the necessary anchorage length is needed for hooked steel strands to achieve the ideal anchorage effect, which should generally not be less than 500 mm.