冲击回波法在预应力混凝土结构无损检测中的应用研究

发布时间：2018-06-02 13:02

本文选题：冲击回波法 + 无损检测　；参考：《北京交通大学》2017年硕士论文

【摘要】：近年来,后张预应力混凝土结构以其特有的优势在桥梁工程中占有重要地位,然而实际工程中由于预应力管道压浆不密实易导致预应力钢筋发生锈蚀,由此带来的结构安全问题日益突出。此外,作为结构质量评价的重要指标,混凝土强度传统的检测方法包括钻芯法和回弹法,钻芯法对结构有一定损伤而回弹法误差较大。基于此,实际工程中需要一种准确、方便的无损检测方法对预应力孔道压浆质量和混凝土强度进行检测。冲击回波法是一种基于应力波的无损检测方法,基于该检测方法,本文进行了预应力管道压浆质量和混凝土强度及弹性模量检测的试验研究及工程应用。论文主要工作和结论如下:(1)利用有限元软件对冲击回波法进行模拟分析,结果表明冲击回波法检测中冲击点和信号接收点的理想间距为4cm-8cm;对不同尺寸的灌浆缺陷进行模拟,结果表明当缺陷尺寸小于1cm时冲击回波法无法对缺陷进行定位检测,当缺陷尺寸超过2cm时冲击回波法可以对缺陷进行准确定位;通过改变冲击点相对缺陷轴线位置的偏移距离进行模拟分析,结果表明当冲击点偏移距离不超过0.7D(D为内部缺陷尺寸)时冲击回波法可以对灌浆缺陷进行定位。(2)通过分析试验模型板中不同灌浆工况预应力孔道的检测特征频谱图,得出结论:当预应力孔道存在灌浆缺陷时,板厚反射频率有增大趋势,试验测试中冲击回波法可以对孔道灌浆缺陷进行准确定位;对比不同材质预应力孔道测试特征频谱图发现波纹管材质对检测结果影响较小可以忽略;预应力孔道灌浆密实的测试特征频谱图和密实混凝土板的测试特征频谱图基本一致,通过这一结果可以对灌浆密实的预应力孔道进行判定;对箱梁顶板横向预应力筋灌浆孔道的检测结果表明,冲击回波法能够准确的对灌浆缺陷进行定位检测。(3)通过对不同混凝土试件的测试特征频谱图进行分析得出不同强度及不同骨料类型混凝土的应力波波速,建立了混凝土应力波波速-抗压强度/弹性模量基本计算公式;相同强度条件下不同骨料类型混凝土中应力波波速的关系为:普通混凝土波速海水珊瑚骨料混凝土波速陶粒混凝土波速ECC混凝土波速;波速-强度基本计算公式的工程检测应用表明:波速法能够准确的推算出混凝土结构的抗压强度值,测试误差小于7%。
[Abstract]:In recent years, post-tensioned prestressed concrete structures have played an important role in bridge engineering with their unique advantages. As a result, the structural safety problems are becoming more and more prominent. In addition, as an important index of structural quality evaluation, the traditional testing methods of concrete strength include the core drilling method and the rebound method. The core drilling method has some damage to the structure, but the rebound method has a big error. Based on this, a kind of accurate and convenient nondestructive testing method is needed in practical engineering to detect the grouting quality and concrete strength of prestressed channel. Impact echo method is a non-destructive testing method based on stress wave. Based on this method, the test research and engineering application of grouting quality, concrete strength and elastic modulus of prestressed pipeline are carried out in this paper. The main work and conclusions are as follows: (1) the impact echo method is simulated by finite element software. The results show that the ideal distance between the shock point and the signal receiving point is 4cm-8 cm, and the grouting defects of different sizes are simulated. The results show that the impact echo method can not locate the defect when the size of the defect is smaller than 1cm, and the impact echo method can accurately locate the defect when the size of the defect exceeds 2cm. By changing the offset distance of the impact point relative to the defect axis, the simulation analysis is carried out. The results show that the impact echo method can locate the grouting defects when the offset distance of the impact point is less than 0.7D(D. It is concluded that the reflection frequency of slab thickness increases when there are grouting defects in the prestressed channel, and the impact echo method can accurately locate the grouting defect in the test. Comparing with the characteristic spectrum diagram of different materials, it is found that the corrugated pipe material has little influence on the test results, and the spectrum of the test characteristic spectrum of the prestressed channel grouting density is basically the same as the test characteristic spectrum diagram of the dense concrete slab. Through this result, we can judge the prestressed holes with dense grouting, and the test results of the transverse prestressed tendons grouting holes in the roof of box girder show that, The impact echo method can accurately detect the grouting defects. (3) by analyzing the characteristic spectrum of different concrete samples, the stress wave velocity of concrete with different strength and different aggregate type can be obtained. A basic formula for calculating the stress-wave velocities, compressive strength and elastic modulus of concrete is established. Under the same strength condition, the relationship of stress wave velocity in concrete of different aggregate types is as follows: ordinary concrete wave velocity, seawater coral aggregate concrete wave velocity, ceramic concrete wave velocity, ECC concrete wave velocity; The application of the basic formula of wave velocities to strength calculation shows that the wave velocity method can accurately calculate the compressive strength of concrete structures, and the test error is less than 7.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU378

【参考文献】