Bond stress distribution analysis between non-prestressed steel strand and concrete in novel beam-to-column connection

Abstract

The Precast Prestressed Assembled Structural (PPAS) system frame is a novel prefabricated concrete structure, which mainly use 15.2-mm high-strength steel strands as the bottom longitudinal reinforcement. In addition, a certain length of non-prestressed steel strands with 90-degree hooked anchorage type are reserved at the beam end and anchored into concrete column to form a novel beam-to-column connection. The good bond and anchorage performance of steel strand in concrete column is the prerequisite for this connection. However, the bond behaviors such as the bond stress distribution, the bond stress transfer mechanism of the steel strand-to-concrete interface etc. has not been fully understood. For this reason, pull-out tests on six specimens, including thirty-six steel strands with various anchorage type, embedment length and anchorage position, were performed in this research. The results indicated that, compared with straight-line anchorage type, the steel strand with 90-degree hooked anchorage type could increase the ultimate average bond stress and bond stiffness. In addition, the embedment length and anchorage position of the steel strands also had different degrees of influence on the average bond stress. The evolution of strain-pullout load behavior of steel strand was strongly related to the bond position. The anchorage type of steel strand greatly affected the distribution pattern of bond stress between steel strand and concrete. However, the bond stress distribution was always non-uniform along the embedment length, regardless of the anchorage type or embedment length.