高温下无黏结预应力混凝土中钢绞线预应力的损失

Prestressing loss of steel cable in unbonded prestressed RC at high temperature

对高温作用下无黏结预应力混凝土中钢绞线的预应力损失进行了试验研究,根据试验结果分析了高温作用下产生预应力损失的主要因素,并建立了高温作用下无黏结预应力混凝土结构预应力损失的计算模型.结果表明:在高温作用下,预应力混凝土结构会产生预应力损失,钢绞线的预应力损失随温度的升高而增大;试件完全冷却后,钢绞线的预应力损失会有所恢复,但钢绞线经历的温度越高,其恢复值就越小.受高温作用的预应力构件产生附加预应力损失的主要因素有高温作用下预应力钢筋的松弛和蠕变、混凝土的高温徐变和钢筋与混凝土的热膨胀差.高温作用下无黏结预应力混凝土结构预应力损失的计算模型可为无黏结预应力混凝土结构的抗火设计和火灾后预应力混凝土结构的评估提供参考.

From the experimental study on the prestressing loss of steel cable in unbonded prestressed RC at high temperature, the main influencing factors of the prestressing loss were analyzed, and a calculation model for the prestressing loss at high temperature was established. The results show that the prestressing loss occurs in the prestressed concrete structure at high temperature, and it increases with the rise of temperature, and that the prestressing loss can be recovered partly as the specimens are cooled completely, and the higher the temperature of steel cable being heated, the less the recovery of the prestressing loss. It is also indicated that the main influencing factors of the prestressing loss of prestressed members at high temperature are the relaxation and creep of prestressed steel cable, the thermal creep of concrete and the thennal expansion difference between steel cable and concrete. The calculation model for the prestressing loss at high temperature provides some references for fire control design and post-flre evaluation of unbonded partial prestressed concrete structures.