火灾下无粘结预应力筋应力-应变全过程分析

火灾下预应力筋的膨胀应变、高温蠕变较大，对其受力的影响也较大。提出了通过对火灾下各时间段、各微段无粘结筋膨胀应变、高温蠕变以及无粘结筋总伸长量的分析来得到无粘结筋应力以及应力引起的应变，从而完成无粘结筋应力一应变全过程分析的方法。计算借助编程完成，将火灾下无粘结筋应力变化的计算值与相关的试验数据进行比较，吻合程度较好。...

Analysis on stress-strain complete process of unbonded prestressing tendons in concrete subjected to fire

In fire, thermal expansion and thermal creep appear obviously in prestressing tendons and affect the mechanical behavior of the tendons. Based on analysis stress and strain caused by stress, thermal expansion, thermal creep of each micro-segment in the unbonded tendons and total elongation of the tendons at each time step in fire, the analysis method for stress-strain complete process of unbonded tendons in concrete subjected to fire was proposed. And computer program was compiled for the calculation. The calculated values of stress variation of unbonded tendons subjected to fire agreed well with the related experimental results. Analysis results showed that the stress variation trend of tensile non-prestressing steel at mid-span in fire was similar to that of unbonded tendons. That is the stress increases in the early stages in fire, and decreases at some time later. All these may be helpful for understanding fire resistance mechanism of unbonded prestressed concrete structures.