【作者】 李荣；

【导师】 李奉阁；

【作者基本信息】 内蒙古科技大学 ， 结构工程， 2012， 硕士

【摘要】 随着科技的进步，预应力结构应用越来越广泛。但是预应力结构在使用过程中，预应力会逐渐地损失，将使工程结构的使用安全受到严重威胁。因此对预应力混凝土结构中的有效预应力进行检测，是预应力混凝土结构健康监测的一个重要课题。本文通过对无粘结预应力钢筋混凝土简支梁动力性能的试验研究和理论分析，来探讨无粘结预应力梁自振频率和模态振型与预应力之间的关系。本文对五根无粘结预应力混凝土简支梁进行了动力性能的试验研究。利用动力检测方法测试了预应力混凝土梁在各级预应力水平下的固有频率。分析结果表明，偏心距不为零的预应力混凝土梁随着预应力增加，梁的各阶频率减小；预应力筋布置在梁的中心，一阶、二阶频率不随预应力变化而变化。利用钢分配梁在试验梁的三分点上对称加载，造成梁不同程度的损伤，随着混凝土裂缝的增大，频率逐渐减小，振型也出现突变。根据结构动力学理论分析了简支梁在轴向力影响后梁的弯曲振动方程，并在此基础上根据达朗伯原理，建立了在偏心预应力作用下的钢筋混凝土简支梁的振动微分方程，得出了具有偏心距和预应力参数的简支梁自振频率公式，这一公式也表明了频率随着预应力的增大而减小，这与试验结果相符合。采用有限元软件ANSYS分析了无粘结预应力混凝土梁，计算结果表明：预应力梁固有频率也随着预应力的增大而降低，但是降低的幅度微小，并对计算结果和试验实测数据作了对比分析，一阶频率相对误差不大，在工程上有一定的参考价值。更多还原

【Abstract】 With the development of technology, pre-stressed concrete structures are being appliedmore and more widely. But the pre-stress forces in tendons will loss gradually in the usingprocess, and the structure safety is threatened. So the detection of pre-stress loss is theimportant problem of the health monitoring and detection of pre-stressed concrete structure.The relation between force of pre-stressed tendons and dynamic characteristic is discussedthrough theoretical analysis and experimental research for unbonded pre-stressed concretesimply supported beam.In this paper dynamic characteristic of five pre-stressed concrete simply supportedbeam is researched. According to the analysis of natural frequency in levels pre-stressedforce through the technique of dynamic test, the test results indicate that the frequencies ofthese beams with eccentricity are reducing with the increasing of the pre-stress force, but thefirst and second steps frequencies in every grade pre-stressed force are not change when thepre-stressed tendons is placed in the center of the beam. Static load was put on the beamthrough two symmetric points for the pre-stressed beam, causing these beams to differentdegrees of damage, the frequencies of these beams are reducing with the increasing of thecrack, and vibration mode appears mutationThe flexural vibrate equation of simply-supported beam which is subjected to the axialcompressive force is analyzed by the theory of structural dynamics. On this foundation, thevibrate equation is established according to D’ Alembert’s principle, considered that steelconcrete simple supported beams is subjected to the eccentric compressive force. Theformula which is used to calculate natural frequency of simple supported beams is derivedunder both pre-stressing force and the influence of position of pre-stressed tendons. Theresults of calculation indicate that the calculated frequencies of pre-stressed concrete beamsare reducing gradually with the increasing of the pre-stress force. This conclusion is identicalto the result of test.In the end, the model of unbonded pre-stressed concrete beam has been established byANSYS, and then the frequencies of test beams were calculated by it. The results ofcalculation indicate that the calculated frequencies of these beams are reducing graduallywith the increasing of the pre-stress force, but reduced of the frequencies is very poor. Andthe analysis of theoretical calculation result and experimental data is carried. It is reasonable that the relative error of the first order natural frequency and it has good reference value onproject.更多还原