预应力轴心受拉钢构件高温性能试验及理论研究

进行了3根预应力轴心受拉钢构件高温试验研究。试验结果表明，高温下预应力轴心受拉构件中内置拉索和钢管所承受荷载比例随温度的变化而不断变化。升温初期拉索张力随温度升高不断增大，预应力轴心受拉钢构件轴向位移平稳发展，在达到峰值后，拉索张力随升温时间的延长而不断降低。在临界状态下，轴向位移增长很快， 预应力受拉构件中拉索均被拉断，外部钢管发生不同程度的颈缩现象。在试验结果的基础上，建立了预应力轴心受拉钢构件的有限元分析模型，得到了高温作用下预应力轴心拉杆中拉索张力和预应力钢杆轴向位移的时程全曲线。参数分析的结果表明：在其他条件相同时，预应力轴心受拉钢构件失效时的临界温度随着荷载比的增加而降低；当预应力比小于08时，预应力比对预应力轴心受拉钢构件失效时的临界温度的影响较小，当预应力比等于08时，预应力轴心受拉钢构件失效时的临界温度显著的提高；在其他条件相同时，预应力轴心受拉钢构件失效的临界温度随约束刚度比的增大而增大。最后对高温下预应力轴心受拉钢构件进行了理论分析，推导出预应力轴心受拉钢构件高温下差分计算方法，并以此为基础编写程序。通过计算结果与试验结果的对比，证明了差分计算方法的正确性。

Experimental and theoretical research on fire resistance of prestressed steel tension member

To study fire resistance of prestressed tensile steel members, three prestressed tensile steel members were fabricated and tested at high temperature. The test results show that the proportion of share loads between the inner strands and steel tube varied with increasing of temperature. Axial stress in the cable strands increases with temperature at the cable strands in the initial stage and the elongation of the column increases. The tension force beyond its peak value in the cable strands decreases with increasing of temperature. The outside steel pipes are necked and the cable strands are ruptured simultaneously at critical states. A numerical model has been developed and verified by the test results at high temperature. Parametric analyses were conducted on the basis of the previous numerical model. The results of analysis demonstrate that the critical temperatures decrease with the ratio of tension applied to the prestressed steel members when other conditions are identical. Similarly, the prestressing ratio has little influence on the critical temperature when the ratio is less than 0.8; the critical temperature rises enormously when the prestressing ratio is 0.8. The critical temperature increases with the increasing of the restraint stiffness when other conditions are identical. At last, theoretical analyses of the response were carried out for the prestressed tension members at high temperature. The effectiveness of the difference method is verified by comparing the analysis results and the tested results at high temperature.