【作者】 蔡利建；

【导师】 张耀庭；

【作者基本信息】 华中科技大学 ， 结构工程， 2005， 硕士

【摘要】 随着我国交通运输事业的发展,预应力混凝土桥梁负荷日益加重,不少桥梁发生了不同程度的损坏,同时,土木行业的其他预应力混凝土结构也存在着与桥梁工程类似的结构隐患。因此,对预应力砼结构进行损伤检测和健康评估显得非常迫切,而预应力砼构件的失效是由预应力钢筋和砼二者之一或两者共同失效造成,其中砼的损伤诊断技术已趋完善并应用于工程实践,而对主要受力部件—预应力钢筋受力状况的检测则相对落后。鉴于此,本文将对预应力混凝土梁预应力筋有效预应力的检测进行试验及理论研究。论文进行了两根无粘结和三根有粘结的预应力混凝土简支梁的试验及相应的材料试验。试验设计时主要考虑了有效预应力大小、荷载情况等对梁自振频率的影响。结果表明:对全预应力梁,随着有效预应力的增加,梁的自振频率也略有增加; 相同预应力情况下,随着荷载的增加,频率的降低非常明显。梁加载开裂之后,频率呈不规律变化。论文采用有限元分析软件ANSYS 对预应力混凝土简支梁进行了动力分析,得到了不同预应力作用下梁的自振频率及试验难于测得的模态振型。将有限元分析结果与试验结果进行了对比,结果表明:有限元分析结果可以很好地作为试验数据的补充。论文针对现有预应力混凝土梁动力分析方法存在的不足,从结构动力学的基本原理出发,推导出直线筋无粘结全预应力混凝土简支梁的自振频率数学分析模型; 采用摄动法求解梁的自振频率,建立了预应力筋受力与梁自振频率的关系; 最后,对数学模型进行了反向求解,得到了通过频率的变化预测梁中预应力筋有效预应力大小的公式。计算结果表明:由预应力预测频率能达到较高的精度,而通过频率预测预应力筋的受力尚存在一定的误差,需进行进一步的研究工作。更多还原

【Abstract】 With the development of transportation project in our country, the carrying load of the bridge is more and more heavier day by day, so most of the prestressed concrete bridges are damaged in different levels. Meanwhile, other civil construction facilities used prestressed concrete has the same problems as the bridges. So, it’s very urgent to detect the damage state of the structure and give a health evaluation. The failure of the prestressed concrete is caused by the tendons failure or concrete failure, or both of them. At present, the detecting techniques for concrete have been perfectly developed and used in existed structures, but for tendons, it is backward. In view of that, the dissertation does the experimental investigation and theoretical research on the effective prestress detecting of the prestressed concrete beams. In the present dissertation, the experiment of two unbonded prestressed simple concrete beams, three bonded beams and the relevant material property test are carried. The dynamic experiment mainly considers the influence to the natural frequency caused by effective prestress and load state. The result indicates that, as the effective prestress growing, the natural frequency of the beam increasing slowly, and in the same effective prestress state, as the load increasing, the natural frequency decreasing obviously. After the cracking of the beam, the natural frequency varies irregularly. Through the finite element modal analyzing by ANSYS software, the natural frequencies and mode shapes of the unbonded prestressed simple concrete beam in different prestress levels are gotten. Then, the analysis result has been compared with the experimental result to prove that the finite element analysis is reliable and the analysis result can be the supplement to the experimental data. Due to the shortage of the existed dynamic analysis methods of prestressed concrete beam, the dissertation deduces a natural frequency mathematical model for straight unbonded full prestressed simple concrete beam, proceeding from the basic theory of structural dynamics. Then, the relation between prestress and the natural frequency is also established by using perturbation to solving the model. Last, through the inverse solution of model, an equation for predicting the effective prestress by the frequency is founded. The result shows that it is feasible to predict the frequency by effective prestress, but to predict the effective prestress by frequency have to do much more work.更多还原