摘要
大跨度结构和超高层建筑结构裂缝无损检测越来越受到学术界和工程界的重视。在我国,钢筋混凝土结构的检测、鉴定评估以及加固研究等工作起步较晚,已有结构的安全性评定标准还不完善。因此,对于钢筋混凝土结构的检测、安全性评价以及加固等方面作进一步的研究十分有必要。
本文从混凝土结构的质量要求出发,阐述了混凝土结构检测的内容,在对各种钢筋混凝土结构检测方法进行总结和归纳的基础之上详细介绍了混凝土裂缝的检测手段。并通过应用碳纤维智能传感器作为混凝土裂缝检测试验,来分析试件裂缝宽度的变化情况。具体研究内容概述如下:
1介绍工程结构裂缝的形成和危害性,提出了关于混凝土缺陷无损伤检测的几种常见方法,并加以比较。同时选用碳纤维智能层作为本文智能检测的主要研究方法。
2制作了预置碳纤维智能层的工程试件并进行三弯点试验,分析了各测量参数随增幅荷载的变化规律、电阻变化率与应变之间的关系以及电阻变化率与切口端部张开位移的关系,同时给出了根据试验构件的电阻变化率预测切口端部张开位移的经验公式。
3运用ANSYS有限元计算软件结合断裂力学理论建立了不同参数构件的三维有限元模型,模拟了具有初始裂缝构件三维电-力耦合场,得到不同工况下构件的应力强度因子与电阻变化率。
4选用改进的阻尼最小二乘法拟合出计算应力强度因子。
The nondestructive detection of large-span structures and high-rise buildings get more and more attention in academic studies and engineering field. In China, the detection, identification assessment and strengthening research work of the reinforced concrete structures were started late, and the security of the existing structure evaluation standard is not perfect. Therefore, further studies of the detection of reinforced concrete structures, safety evaluation, and reinforcement areas were necessary.
In this paper, according to the requirements of concrete structures quality, the contents of the concrete structure inspection was described, and various detection methods for reinforced concrete structures based on the summary details on concrete flaw detection methods was introduced. Meanwhile, through the application of carbon fiber as the concrete cracks smart sensor, the detection tests to analyze the specimen changes in crack width was conducted. Specific studies were outlined below:
1. The formation of cracks in engineering structures and the dangers was described. Several common methods of non-destructive testing of concrete defects was presented and compared to each other. Meanwhile using the carbon fiber intelligent layers as the intelligent detection were selected as the major research method.
2. The carbon-fiber-Intelligent pre-engineering test pieces were manufactured and the three-point bending tests were conducted. The measured parameters changed with the increasing of load variation, and either the relationship between the change of resistance rate and the strain or the relationship between the rate of resistance change and the incision open end displacement relations was analyzed and explained in detail. The empirical formulas for notch tip opened displacement were presented.
3. The different three-dimensional finite element models, were created by using of ANSYS finite element software combining with the theory of fracture mechanics. And the three-dimensional structures with initial cracks in power-mechanical coupled field were simulated. The stress intensity factors and the resistance change rate in different conditions were obtained in simulations.
4. The improved damping least squares were selected to fit the empirical formulas of the calculation of stress intensity factors. The sub-end opening displacement of the incision and the correctness of the formulas were verified by using these test data.
引文
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