混凝土梁桥的动力快速评定方法研究

发布时间：2018-11-14 20:28

【摘要】：荷载试验评定桥梁虽然可以全面反映结构的实际工作状况，但耗费较大，因此动力测定试验快速评定法就成了目前研究的热点。由于动力法进行钢筋混凝土结构的评估更能真实反映其与结构在移动荷载作用下的实际工作状况，因此动力测试方法和系统识别理论的研究与应用具有广阔的前景。本文从动静力试验着手，以探索钢筋混凝土矩形梁快速动力评定的可行性。阐述了动态损伤识别的典型方法，冲击弹性波检测技术的基本理论，振动结构测试与频谱分析方法。基于上述理论进行模型试验的设计，包括试验梁的参数、测点布置、试验流程安排及数据采集等方面。运用实测回弹值对试验梁的强度进行计算，测试各个工况下试验梁的加载全过程应变云图、裂缝开展情况及分布特征，计算出裂缝的宽度大小，并测试出梁体破坏时的极限承载力，从而全面分析了梁体从弹性阶段到破坏阶段的工作特性。对冲击弹性波的测试和梁的应变分布及裂缝特征的分析，其规律可以归结为梁体在试验加载前，锤击所产生的冲击弹性波信号存在着初始的微小时间差。当采用两个较小量级荷载对梁进行反复加载后，，所测得的弹性冲击波的信号的时间差与梁体空载前的激振结果并无明显的变化。梁体产生裂缝后，弹性冲击波的信号出现了比较明显的差异，这种差异主要与裂缝的分布位置及裂缝的宽度的大小有关。这样，就可以实现对结构的完整性检测，识别损伤的位置和损伤程度的大小。通过对梁的跨中最大冲击动挠度的测试，计算出瞬态冲击曲率均处在较小的水平，而且破坏后梁的曲率较弹性阶段有所增大，这正是动位移增大的另一方面的反映。再者，通过数学上的多元线性回归分析，梁体瞬态冲击最大动挠度和梁的极限承载力之间存在着线性关系。试验梁在破坏阶段较弹性工作阶段的跨中最大冲击动挠度有一定的增量，这种增量与裂缝宽度之间存在着线性关系。从而，在确定的冲击荷载作用下，结构损伤前后的动挠度增量可以识别结构的完整性及损伤程度的大小。最后基于研究成果，建立了一套钢筋混凝土和预应力混凝土梁桥的动力评定方法，为实际桥梁结构安全性能快速评定提供指导。
[Abstract]:Although the load test evaluation bridge can reflect the actual working condition of the structure completely, but the cost is large, so the fast evaluation method of dynamic measurement test has become the hot spot of the research at present. Because the evaluation of reinforced concrete structure by dynamic method can reflect the actual working condition of the reinforced concrete structure and the structure under moving load, the research and application of dynamic test method and system identification theory have a broad prospect. In this paper, the feasibility of rapid dynamic evaluation of reinforced concrete rectangular beams is explored by means of dynamic and static tests. The typical methods of dynamic damage identification, the basic theory of shock elastic wave detection technology, the method of vibration structure test and spectrum analysis are described. Based on the above theory, the design of the model test is carried out, including the parameters of the test beam, the layout of the measuring points, the arrangement of the test flow and the data acquisition. The strength of the test beam is calculated by using the measured rebound value, the strain cloud diagram of the whole loading process of the test beam under various working conditions is tested, the crack development and distribution characteristics are calculated, and the width of the crack is calculated. The ultimate bearing capacity of the beam is tested, and the working characteristics of the beam from the elastic stage to the failure stage are analyzed. The measurement of the shock elastic wave and the analysis of the strain distribution and crack characteristics of the beam can be attributed to the initial small time difference of the impact elastic wave signal produced by the hammer before the test loading. The time difference between the measured elastic shock wave signals and the excitation results before the beam is left unloaded has no obvious change after repeated loading on the beam with two smaller loads. There are obvious differences in the signals of elastic shock waves after the cracks occur in the beam body, which are mainly related to the distribution of the cracks and the width of the cracks. In this way, the integrity of the structure can be detected and the damage location and damage degree can be identified. Through the measurement of the maximum impact dynamic deflection of the beam in the span, it is found that the transient impact curvature is at a smaller level, and the curvature of the beam after the failure is larger than that of the elastic stage, which is another reflection of the increase of the dynamic displacement. Furthermore, through multiple linear regression analysis, there is a linear relationship between the maximum dynamic deflection of the beam and the ultimate bearing capacity of the beam. There is a certain increment in the maximum impact deflection of the test beam in the failure stage than in the elastic working stage, and there is a linear relationship between the increment and the crack width. Therefore, the dynamic deflection increment before and after damage can identify the integrity of the structure and the magnitude of the damage under a certain impact load. Finally, based on the research results, a set of dynamic assessment method of reinforced concrete and prestressed concrete beam bridges is established, which provides guidance for rapid evaluation of the safety performance of practical bridge structures.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U448.33;U441

【参考文献】