混凝土连续梁(板)中无粘结预应力钢筋应力增长规律研究

把握无粘结预应力钢筋应力增长规律是准确计算无粘结预应力混凝土梁(板)刚度、裂缝开展宽度及受弯承载力的基础。首先定义了正常使用阶段无粘结预应力钢筋应力增量与有粘结非预应力钢筋增量的比值为无粘结预应力钢筋等效折减系数。然后针对无粘结部分预应力混凝土受弯构件在受荷过程中无粘结预应力钢筋不符合变形平截面假定的特点,应用等刚度法及弯矩-曲率非线性分析法,编制了可分别用于考察正常使用阶段和承载能力极限状态无粘结预应力钢筋应力增长规律的计算程序。最后基于模型试验结果和仿真分析结果,得到了无粘结预应力钢筋等效折减系数与非预应力钢筋配筋指标βs和预应力钢筋配筋指标βp的关系式,以及无粘结预应力钢筋极限应力增量与非预应力钢筋配筋指标sβ、预应力钢筋配筋指标pβ和跨高比l/h的关系式。

Research on law of stress increment of unbonded tendons in continuous prestressed concrete beam and slab

Comprehension of law of stress increment of unbonded tendon is the basis to accurately calculate stiffness,crack width and flexural load capacity of unbonded prestressed concrete beam and slab.Equivalent reduction coefficient of tendons was defined as the ratio of unbonded prestressed reinforcement stress increment to non-prestressed reinforcement stress increment.Considering plane-section assumption can not be applied to tendon strain in unbonded prestressed concrete flexual member subjected to loading,equivalent stiffness method and moment-curvature nonlinear analysis method are used to compile calculation programs of the law of stress increment of unbonded tendons which can be used in serviceability phase and strength limit state respectively.Based on results of model test and large numbers of simulation analysis,the relationship among equivalent reduction coefficient of tendons,non-prestressed reinforcement index βs and prestressed reinforcement index βp was formulated,and the relationship among ultimate stress increment of unbonded tendons,non-prestressed reinforcement index βs,prestressed reinforcement index βp and ratio of span to depth l/h was also formulated.