EXPERIMENTAL RESEARCH ON BOND PROPERTIES OF LARGE-DIAMETER PRESTRESSED STEEL STRANDS

Under the condition of large-tonnage prestressing, the large-diameter prestressed steel strands has obvious advantages compared with the ordinary diameter prestressed steel strands (1×7 structure, nominal diameter 15.2 mm). At present, many types of large-diameter prestressed steel strands have been used in engineering in China, but its bond performance in concrete (pretensioning method) or in cement paste (post tensioning method) is not very clear. The bond performance is very important to the crack and stiffness control of prestressed members. To this end, the large-diameter prestressed steel strands with a 1×19 structure and a nominal diameter of 21.8 mm was taken as the object, and a static pull-out test was conducted on 30 specimens. Through the analysis of the test results, the bond failure modes were obtained,and the influence of the diameter, bonding length and bonding method of the steel strands on the bonding performance of the steel strands was investigated, and the bonding stress-slip curve and the relative bonding characteristic coefficient of the steel strands were obtained. Combined with the experimental results of the flexural crack of the relevant concrete members, it was believed that the post-tensioned large-diameter prestressed steel strands had a lower bonding performance than the that of ordinary prestressed steel strands, but it had little effect on the normal performance of the members.