重复荷载下部分预应力混凝土构件的变形

Deformation of PPC Members under Repeated Loading

在重复荷载作用下,部分预应力混凝±构件由于疲劳裂缝的发生和发展,以及混凝±动力徐变等的作用,使得刚度随荷载循环次数增大而降低,构件产生较大的变形,以至超过正常使用的极限状态.因而变形计算成为相当重要的问题.目前国内外规范对部分预应力混凝±梁的变形计算还没有统一的模式,一般都忽略重复加载对梁变形的影响.通过对四组不同预应力度的部分预应力混凝±梁进行等幅疲劳试验,本文对重复荷载作用下部分预应力混凝土构件的变形增长规律有一定的认识,提出了反映预应力度及荷载循环次数的变形计算统一模式.

The stiffness of PPC members under repeated loading will degenerate along with the increasing of the number of loadingcycles,due to the development of fatigue cracks and,the dynamiccreep of the concrte.It is important how to predict the deformation of PFC members nuder repeated loading,which is usuallyso great as to violate the serviceability criterion.There is nounified approach for predicting the deformation of PPC membersin the existing model codes,which consider no the effect of repeatedloadig on the deformation of members.Four groups of PPC beams,with different degrees of prestress,are taken for fatiguetest.Based on the test results,some rules of the deformation ofPPC members under repeated loading are round and a unifiedpredicting method including the panameters of prestress degreeand loading cycle unmber is proposed.