PPC异形曲板中无粘结筋应力增长研究

进行了6块无粘结部分预应力混凝土(PPC)分岔斜弯异形曲板模型静载试验研究,分析了试验模型中无粘结筋应力增长的主要特征,给出了无粘结筋应力增量与截面相对受压高度、综合配筋指标、混凝土的极限压应变、截面曲率等的试验关系,揭示了影响无粘结筋应力增长的重要参数及其相互关系;根据试验结果,综合分析并拟合出无粘结部分预应力混凝土异形曲板试验模型中无粘结筋应力的计算公式,推导出无粘结筋应力增长方程,可对无粘结筋的应力增长全过程进行分析计算,这给出了一种新的分析研究途径;采用两种方法建立了无粘结筋极限应力的计算公式,与试验数据符合较好。本论文的研究结果不仅可用于桥梁工程中的无粘结PPC异形曲板桥,也可用于建筑工程中的无粘结PPC异形曲板结构。

A STUDY ON STRESS INCREASE IN UNBONDED TENDONS FOR PARTIALLY PRESTRESSED CONCRETE SLABS OF IRREGULARITY CURVED SHAPES

In this paper, six partially prestrssed concrete slab models with unbonded tendons are experim entally studied.The main characteristics of stress increase in the unbonded tendons of the test models is analyzed.The relationship between the stress increment in the unbonded tendons and the relative compressi on depth of the cross sectio n,the combined reinforcement index,the ultimate compression strain of the concre t e and the curvature of the cross section are given by the test.Important paramet ers affecting the stress increase in the unbonded tendons and their relationship s are revealed.According to the experimental result,the formula for calculating the stress in the unbonded tendons of the test model is obtained.Stress-increas e equation for the unbonded tendons is derived,wich represents a new approach th at can be used in analyzing the total process of stress in crease in the unbonde d tendons.The formula s for the ultimate stress in the unbonded tendons are obtained by using two meth ods,and the calculated results show good agreement with the test results.The res ults described in this paper may be employed not only for analyzing irregulenly curved,partially prestressed concrete slab bridges with unbonded tendons,but als o for analyzing those slab structures with unbonded tendons in building engineer ing.