基于频率测试及压电阻抗技术的预应力测试研究

发布时间：2018-03-30 05:10

本文选题：竖向预应力　切入点：张力测试　出处：《湖南大学》2015年硕士论文

【摘要】：在我国的桥梁建设当中大量采用了预应力混凝土连续箱梁桥,该桥型在经济合理性以及施工工艺方面均具有很大的优越性,但主梁的竖向预应力不足导致的梁体腹板开裂问题严重影响着桥梁的运营使用,严重制约了该桥型的发展。为了监督施工时的竖向预应力筋质量,防止竖向预应力损失过大而引起腹板开裂,需要提出一套方便快捷、准确可靠实用的检测方法,进一步制定出相应配套的现场检测及质量评定标准。本文主要进行了以下几项研究工作:(1)竖向预应力筋外露段的刚度会随张力发生变化,基于此提出了两种外露段的力学模型,即变截面刚度系数模型和变转角刚度模型,进一步阐述了基于频率测试方法的预应力筋张力测试原理,详细推导了欧拉梁理论及铁木辛柯梁理论,利用这两种梁理论分别建立运动方程,并通过代入两种模型的边界条件来求得螺纹钢外露段的振动方程;(2)介绍了压电智能材料的材料特性及其参数,依据其独特的压电效应建立了压电运动方程,进一步采用一维阻抗模型推导了压电陶瓷片-结构耦合系统的阻抗值公式,基于所得压电系统的阻抗值公式阐述了基于压电阻抗技术的预应力筋张力测试原理;(3)基于频率测试方法的预应力筋张力测试原理及其振动方程,设计并进行了预应力混凝土实验,实验采集了长度不一的外露段端部在不同张力下的自振频率,并对频率测试结果进行分析处理,通过振动方程得出模型刚度,拟合了两种函数来表达频率与刚度、刚度与张力之间的关系,基于拟合函数提出了张力计算公式并进行了复核;(4)基于压电阻抗技术进行了预应力筋的张力测试实验,实验采集了锚固端处粘贴于不同位置的压电陶瓷片的阻抗信号,对实验结果进行了阻抗指标计算与处理,找出了压电陶瓷片的敏感位置,同时得出了阻抗指标随张力改变的变化规律。
[Abstract]:The prestressed concrete continuous box girder bridge is widely used in the bridge construction in our country. The bridge type has great superiority in economic rationality and construction technology. However, the cracking of girder web caused by insufficient vertical prestressing of main beam seriously affects the operation and use of the bridge and seriously restricts the development of the bridge type. In order to supervise the quality of the vertical prestressed tendons during construction, To prevent the web from cracking due to the excessive loss of vertical prestress, it is necessary to put forward a set of convenient, accurate, reliable and practical testing methods. In this paper, the following research work is carried out: the stiffness of the exposed segment of the vertical prestressed tendons will change with the tension. Based on this, two kinds of mechanical models of the exposed segments are put forward. That is, variable cross-section stiffness coefficient model and variable rotation angle stiffness model, the principle of tension testing of prestressed tendons based on frequency measurement method is further expounded, and the theory of Euler beam and Temuxinko beam are deduced in detail. The equations of motion are established by using these two kinds of beam theories, and the vibration equation of the exposed section of rebar is obtained by inserting the boundary conditions of the two models.) the material characteristics and parameters of piezoelectric intelligent materials are introduced. According to its unique piezoelectric effect, the equation of piezoelectric motion is established, and the impedance formula of piezoelectric ceramic plate-structure coupling system is derived by using one-dimensional impedance model. Based on the impedance formula of piezoelectric system, the principle of tension testing of prestressed tendons based on piezoelectric impedance technique and its vibration equation are described. The experiment of prestressed concrete is designed and carried out. The natural vibration frequency of the end of the exposed segment with different lengths under different tension is collected, and the results of the frequency measurement are analyzed and processed, and the model stiffness is obtained by the vibration equation. Two kinds of functions are fitted to express the relationship between frequency and stiffness, stiffness and tension. Based on the fitting function, the tension calculation formula is put forward and the tension test of prestressed tendons is carried out based on piezoelectric impedance technique. The impedance signals of the piezoelectric ceramic plates affixed to different positions at the anchoring ends were collected experimentally. The impedance index of the experimental results was calculated and processed, and the sensitive position of the piezoelectric ceramic plates was found out. At the same time, the change law of impedance index with tension is obtained.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U446;U445.57

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