火灾下平行钢丝束温度膨胀及高温蠕变试验研究

采用非接触式应变视频测量系统,对常用于实际工程的1670级平行钢丝束进行了15个温度水平下的温度膨胀试验以及多应力水平下的高温蠕变试验,并对历经2 h高温蠕变试验后冷却至室温的平行钢丝束试件进行了抗拉强度测试,获取了平行钢丝束热膨胀应变历程及高温蠕变应变历程曲线.试验结果表明:平行钢丝束热膨胀应变随着温度升高呈非线性增...

EXPERIMENTAL INVESTIGATION ON THE CREEP RESPONSE AND THERMAL EXPANSION OF PARALLEL STEEL WIRES AT ELEVATED TEMPERATURES

The thermal expansion at 15 different temperatures and the high temperature creep at multiple stress levels of 1670 MPa parallel steel wires, which are widely used in practical engineering, were experimentally investigated by a charge-coupled device camera (CCDC) system. The tensile strength of the specimens which experienced 2-hour’s high temperature creep investigation was measured at the ambient temperature. The curves of thermal expansion strain and high temperature creep strain of the parallel steel wires were obtained. The test results show that the thermal expansion strain of the parallel steel wires increased nonlinearly with the increase of the temperature and the microstructure changed at 750 ℃. Both the heating temperature and the stress level significantly affected the high temperature creep strain. At a higher temperature, the effect of the stress level on the residual tensile strength of the parallel steel wires was more significant. Compared with the 1860 MPa pre-stressed twisted steel wires, the 1670 MPa parallel steel wires had a lower creep strain at a high temperature. Based on the test data, the function of the thermal expansion coefficient of parallel steel wires with respect to the temperature and the high temperature creep model are proposed. The thermal expansion coefficient and the high temperature creep model proposed in this paper can benefit the mechanical response analysis of pre-stressed steel structures at elevated temperatures.