Anchorage performance of group anchored 1860-grade high-strength steel strands for beam-column connection

Abstract

• An overall pull-out test device for group anchored steel strands is developed. • The influence law of the layout quantity of steel strands on the pull-out load and average bond stress is analyzed. • The influence law of the embedment length of steel strands on the pull-out load and average bond stress is investigated. • The calculation formula for the critical anchorage length of the group anchored steel strands embedded in the concrete column is also proposed. • The difference of stress development of steel strands at different positions in group anchor specimens is revealed. To determine the rational anchorage form of group anchored 1860-grade high-strength steel strands adopted in the beam-column connection of the Precast Prestressed Assembled Structural (PPAS) system frame, the overall pull-out test was carried out to investigate the influence of the anchorage type, embedment length and arrangement form (layout quantity) of steel strands on the overall pull-out behavior of group anchored steel strands. Test results indicated that the influence of the interaction of multiple steel strands in concrete columns (i.e., group anchor effect) on the anchorage performance should be taken into consideration. The layout quantity and embedment length of the steel strands have a significant influence on the anchorage performance of group anchored steel strands, such as the overall slip, ultimate anchorage capacity, and average bond stress at each characteristic point, but the influencing law is different obviously. In addition, a calculation formula for critical anchorage length of the group anchored steel strands embedded in the concrete column was also proposed, and relevant design suggestions for anchorage length were recommended for various arrangement forms of steel strands. The bond properties of the steel strands in concrete columns vary with their positions in group anchor specimens, which indirectly affects the anchorage performance of the group anchored steel strands, but its influence degree is strongly related to the stress development level of steel strands at that position.