Overall pull-out behavior of group anchored steel strands with 90-degree hooked type

Abstract

The Precast Prestressed Assembled Structural (PPAS) system is a novel prefabricated structure system, which mainly adopts the group anchor technology for 90-degree hooked steel strands in the connection of beam-column members. For this connection, however, the anchorage performance of the group anchored steel strands with 90-degree hooked type has not been fully understood. For this reason, the overall pull-out tests on the 12 test specimens of group anchored 90-degree hooked steel strands were carried out by adopting the overall pull-out test device. The test results indicated that with the increase of the layout quantity of the steel strands in the concrete column from one row of one column (1 steel strand) to three rows of four columns (12 steel strands), the anchorage capacity, anchorage stiffness and energy dissipation capacity of the group anchor specimens were significantly improved, but its anchoring efficiency presents a three-stage change rule of slow attenuation (0.065) - gentle attenuation (0.025) - fast attenuation (0.105). The variation of the anchorage depth of the steel strands in the concrete column has more pronounced effects on the failure mode and pull-out load-overall slip response, indirectly affecting its ultimate anchorage capacity, overall slip, anchorage stiffness, and anchoring efficiency, but hardly affecting its energy dissipation capacity. Additionally, the anchoring efficiency is strongly related to the failure mode of the test specimens. For the failure mode of the steel strand fracture, the anchoring efficiency is always not less than 0.85, which is significantly higher than that of the overall pulling out of the steel strands, always between 0.70 and 0.80. • The overall pull-out tests on the group anchored 90-degree hooked steel strands were successfully carried out. • The multiple 90-degree hooked steel strands with smaller anchorage lengths tended to be overall pulled out. • Increasing the layout quantity of steel strands in the concrete column can effectively improve the anchoring capacity. • Group anchored 90-degree hooked steel strands exhibited higher anchoring efficiency. • The influence of the group anchor effect on its anchorage performance cannot be negligible.