RESEARCH ON BOND-SLIP BEHAVIOR BETWEEN CONCRETE AND STEEL REBAR UNDER UNIAXIAL LATERAL PRESSURE AFTER HIGH TEMPERATURES

The bond performance between concrete and steel rebar after high temperatures (HT) affects the safety evaluation of reinforced concrete structure. In practical engineering, the reinforced concrete is often subjected to lateral pressure (LP). Therefore, forty-eight pull-out tests of steel rebar embedded in concrete were carried out with HT and LP as parameters. The effects of LP on failure pattern, peak bond stress, peak slip and residual bond strength of specimens after HT were analyzed, and the empirical formula for peak bond stress with HT and LP was also established. The bond stress field of reinforced concrete under lateral pressure was deemed as linear superposition of concrete extrusion pressure in front of ribs and lateral pressure, and the bond strength of specimens with/without uniaxial LP were then calculated based on the microscopic transfer model and multi-axis strength failure criteria of concrete after HT. The results show that: LP and HT have significant effect on failure pattern of specimens. As LP increases, the peak bond stress, residual bond strength and peak slip gradually increase, but the peak slips of specimens with LP are smaller than those of specimens without LP when HT reaches 500 ℃. The theoretical calculations agree well with test results, indicating that it can predict the bond strength between concrete and steel bar after HT.