WO2020253449A1 - 混凝土受拉裂缝宽度监测和区域自定位装置及方法 - Google Patents

混凝土受拉裂缝宽度监测和区域自定位装置及方法 Download PDF

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WO2020253449A1
WO2020253449A1 PCT/CN2020/091011 CN2020091011W WO2020253449A1 WO 2020253449 A1 WO2020253449 A1 WO 2020253449A1 CN 2020091011 W CN2020091011 W CN 2020091011W WO 2020253449 A1 WO2020253449 A1 WO 2020253449A1
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concrete
self
conductive electrodes
voltage
width
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English (en)
French (fr)
Inventor
丁一宁
柳根金
李东升
曾伟
王庆轩
于有川
刘倩文
晏楚
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Dalian University of Technology
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Dalian University of Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G01N3/06—Special adaptations of indicating or recording means
    • G01N3/066—Special adaptations of indicating or recording means with electrical indicating or recording means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0014—Type of force applied
    • G01N2203/0016—Tensile or compressive
    • G01N2203/0017—Tensile
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G01N2203/0062—Crack or flaws
    • G01N2203/0064—Initiation of crack
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/006—Crack, flaws, fracture or rupture
    • G01N2203/0062—Crack or flaws
    • G01N2203/0066—Propagation of crack
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/0617—Electrical or magnetic indicating, recording or sensing means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/06—Indicating or recording means; Sensing means
    • G01N2203/067—Parameter measured for estimating the property
    • G01N2203/0682—Spatial dimension, e.g. length, area, angle

Definitions

  • the invention belongs to the technical field of civil engineering, and relates to a device and technology for self-positioning and self-monitoring of crack width changes of concrete components.
  • Concrete has good compressive strength and mainly bears compressive stress in the structure, but the tensile performance of concrete is low, and its tensile strength is only about one-tenth of the compressive strength.
  • the tension zone of concrete structural members is working with cracks in the normal use stage, and the continuous expansion of cracks under load will weaken the effective section of the member, directly affecting the deformation, durability and bearing capacity of the structure; therefore, the concrete Real-time tracking of cracks is of great significance.
  • the more widely used crack detection and monitoring technologies in concrete structure engineering mainly include: manual detection, ultrasonic, acoustic emission and optical fiber sensor monitoring. The application of these technologies may be limited by the accuracy and frequency of manual detection, or rely on complex and expensive sensors and signal demodulation equipment.
  • Concrete is a poor conductor of electricity.
  • the existing cement-based material strain self-monitoring technology uses conductive materials such as carbon fiber, carbon black, and nickel powder to reduce the resistivity of concrete.
  • conductive materials such as carbon fiber, carbon black, and nickel powder to reduce the resistivity of concrete.
  • carbon fiber >0.5% volume content, carbon nanotubes>1% cement volume content
  • concrete is not strictly an insulator, and the resistance of the matrix changes significantly after the concrete is pulled and cracked.
  • the invention is based on the real-time monitoring of the resistance change rate of the concrete itself, and realizes the self-monitoring of the crack positioning and the crack expansion width of the tension zone of the concrete member under load.
  • the technical problem to be solved by the present invention is to provide a device and technology for concrete crack width monitoring and crack area positioning, which can accurately monitor the crack width changes of concrete members under load in real time, and has high accuracy and Sensitivity, low cost; at the same time, it can also realize the device of cracking area positioning. It is especially suitable for crack monitoring of different concrete structures including tunnels, urban underground pipe corridors, subsea immersed pipes and other underground structures.
  • a self-positioning and self-monitoring device for crack width changes of concrete under tension comprises: a DC stabilized power supply 1, a fixed-value resistor 2, an outer conductive electrode 3, an inner conductive electrode a 1 , a 2 ,... , A n-1 , a n , concrete component 4, voltage conversion module 5, data acquisition system 6, computer 7, wire 8.
  • Said tension member concrete base 4 is disposed conductive electrode region, comprising two outer electrically conductive electrodes 3 and arranged inside the outer conductive electrode 3 within the n conductive electrodes a 1 ⁇ a n (n ⁇ 2) .
  • One of the outer conductive electrodes 3 is connected to the positive electrode or the negative electrode of the DC stabilized power supply 1, and the other outer conductive electrode 3 is connected in series with one end of the fixed value resistor 2.
  • the other end of the fixed value resistor 2 is connected to the negative or positive pole of the DC power supply 1.
  • two wires 8 are connected in parallel to the voltage conversion module 5 at both ends of the fixed value resistor 2 to measure the voltage of the fixed value resistor 2.
  • the two adjacent inner conductive electrodes a i and a i+1 are connected to the voltage conversion module 5 through two external wires 8 to measure the voltage of the corresponding area a i - a i+1 .
  • the voltage conversion module 5 is connected to the data acquisition device 6, and the data acquisition device 6 is connected to the computer 7 through a wire; the voltage conversion module 5 linearly converts the received voltage signal into a voltage of 0-5v, and inputs the data acquisition device 6, The data acquisition device 6 transmits the voltage signal to the computer 7 and realizes signal visualization.
  • the described DC regulated power supply 1 can provide a stable DC voltage, and the adjustable range of voltage is 0- 60V.
  • the fixed value resistor 2 is a cement resistor, and the resistance range of the resistor is 5k ⁇ -10k ⁇ .
  • the electrodes can be made of copper, stainless steel, conductive tape and other materials with good conductivity.
  • the form can be grid or sheet, and the combination with concrete can be Choose internally embedded or externally attached type; when internally embedded, the thickness of the protective layer does not exceed 5mm; when externally attached, it can be fixed with graphite glue.
  • the distance between the inner conductive electrodes is 40-1000 mm, and the distance between the outer conductive electrode 3 and the adjacent inner conductive electrodes is 30-50 mm.
  • the width of the conductive electrode should not exceed 20mm, the length should be greater than the width of the measured concrete part, and the thickness should generally not exceed 0.5mm.
  • the concrete component 4 can be reinforced concrete, fiber concrete, fiber reinforced concrete and other components.
  • the voltage conversion module 5 is an S1105H high-frequency differential isolation transmitter, with a maximum input range of 0-60V, and a linear output range of 0-5v according to the input voltage.
  • the specific technical parameters are: accuracy: 0.2%, response frequency: 1KHz, working temperature: -20°C ⁇ 70°C.
  • the data acquisition system 6 is a data acquisition device that can receive 0-5V voltage signals, and the acquisition frequency is not less than 5HZ.
  • a method for self-monitoring the change of concrete crack width and locating the cracked area includes the following steps:
  • the first step connecting lines, the individual elements: a DC power supply, fixed-value resistor 2, the conductive outer electrode and the inner conductive electrode 3 a 1 ⁇ a n, voltage conversion module 5, the data acquisition system 6, a computer 7, using The wire 8 is connected with the concrete member 4 to be tested into a closed loop.
  • the second step is to turn on the DC stabilized power supply 1, adjust the voltage to 12-60V, and the concrete member 4 starts to polarize.
  • the computer 7 records the output voltage, wait for 20-30 minutes until the output voltage between the inner conductive electrodes a i and a i+1 and both ends of the fixed value resistor 2 are stable, and the polarization in the concrete member 4 tends to be stable.
  • the third step is to load the concrete member 4, and the computer 7 starts to record the output voltage between the inner conductive electrodes a i and a i+1 and the two ends of the fixed value resistor 2 to obtain the resistance change rate curve-time curve, and perform the target concrete member 4.
  • Crack monitoring Specifically, by directly measuring the resistance change rate of the concrete target area, determine whether there are cracks in the concrete tension zone, the area where the cracks occur, and the expansion width of the cracks:
  • Component 4 conducts self-monitoring of cracks;
  • the invention can directly measure the resistance change rate of the concrete target area to determine whether there are cracks in the concrete tension zone, the area where the cracks appear, and the expansion width of the crack.
  • the main advantages are the following points: 1) The location of the cracking area and the expansion width are realized Self-monitoring can provide an accurate method for judging the initial cracks of fiber reinforced concrete components, reinforced concrete components, fiber reinforced concrete components, etc.; 2) This concrete crack monitoring technology does not require additional crack sensors on the components, eliminating The tedious work of arranging sensors; 3) There is no need to add a large amount of conductive materials to the concrete matrix, which has no negative impact on the construction of the concrete structure and can save costs; 4) The electrodes can be conveniently and flexibly placed in the tension zone of the structure according to internal forces The arrangement can also save costs; 5) Avoid the problem that a large number of conductive phases are difficult to disperse in concrete.
  • the above points can provide guarantee for real-time monitoring of cracks in important concrete structural components.
  • Figure 1 is a schematic diagram of a device for self-positioning and self-monitoring of crack width changes in concrete tension zone
  • Figure 2 is a schematic diagram of a device for realizing concrete crack width monitoring when the number of internal electrodes is equal to 2 in Embodiment 1.
  • Figure 3 is the load-time-resistance change rate curve of the steel fiber concrete beam in Example 1;
  • Figure 4 is the load-crack propagation width-resistance change rate relationship curve of the steel fiber concrete beam in Example 1;
  • Fig. 5 is a schematic diagram of a device capable of realizing the positioning of the concrete cracking area when the number of internal electrodes is equal to 3 in embodiment 2;
  • Figure 6 is the load-time-resistance change rate relationship curve of the concrete beam in Example 2.
  • this embodiment describes a self-monitoring technology for the expansion width of concrete cracks.
  • the specific implementation is as follows:
  • the second step is to turn on the DC stabilized power supply 1, adjust the voltage to 12V, and the concrete member 4 starts to polarize.
  • the computer 7 records the output voltage, wait for 20 minutes until the output voltage between the inner conductive electrodes a 1 and a 2 and both ends of the fixed-value resistor 2 is stable. At this time, the internal polarization of the concrete member 4 becomes stable.
  • the third step is to load the concrete member 4, and the computer 7 starts to record the voltage signal between the two ends of the constant-value resistor 2 and the inner conductive electrodes a 1 and a 2 and convert it into the resistance change rate of the corresponding area a 1 - a 2 -Time real-time curve, while measuring the width of cracks on the tension side of the concrete member 4.
  • the fourth step is to obtain the relationship between the resistance change rate and the crack propagation width, and fit the relationship between the two. As shown in Figure 3 and Figure 4, they are the relationship curves of load-time-resistance change rate, load-crack propagation width-resistance change rate. It can be seen from Figure 3 that before the concrete cracks, the resistance change rate remains near zero with no obvious change. When the concrete cracks, the resistance change rate increases rapidly. As the crack width continues to expand, the rate of resistance change keeps increasing, but the rate of increase slows down.
  • the fifth step is to realize the self-monitoring of concrete cracks, that is, to convert the crack propagation width through the rate of resistance change.
  • two external electrodes 3 are arranged in the tension zone of the fiber reinforced concrete member 4, and three internal electrodes a 1 , a 2 , a 3 (Built-in type, brass mesh 12 mesh 0.38mm wire diameter, 15mm width), the distance between adjacent inner electrodes is 42.5mm, and the distance between outer electrode and adjacent inner electrode is 30mm.
  • the second step is to turn on the DC stabilized power supply 1, adjust the voltage to 12V, and the concrete member 4 starts to polarize.
  • the computer 7 records the output voltage, wait for 20 minutes until the output voltage between the inner conductive electrodes a 1 and a 2 , a 2 and a 3 and the two ends of the fixed value resistor 2 is stable. At this time, the internal polarization of the concrete member 4 becomes stable.
  • the third step is to load the concrete member 4, record the voltage signals between the two ends of the fixed value resistor 2 and the internal electrodes a 1 and a 2 , a 2 and a 3 and transform to obtain the corresponding areas a 1 - a 2 and a 2- a 3 Resistance change rate-time curve.
  • the fourth step is to determine the cracked area of the concrete beam by observing the real-time resistance change rate-time curve of each area to be tested in the tension zone of the concrete beam, and realize the location of the cracked area. Judgment basis: when concrete cracks in a certain area, the resistance change rate corresponding to this area will increase sharply, and the resistance change rate of other areas will remain stable after a small change.
  • FIG. 5 shows the load-time-resistance change rate relationship curve of the concrete beam in this embodiment, and it can be obtained: 1) There are cracks in the area ( a 1 - a 2 ) represented by the significantly increased resistance change rate-time relationship curve It can be judged that the cracking time is 426s; and after a small decrease (within 10%), a stable resistance change rate-time curve indicates that no cracks appear in the area ( a 2 - a 3 ).

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Abstract

一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置及方法，自监测装置包括直流稳压电源(1)，定值电阻(2)，外导电电极(3)，内导电电极a 1、a 2、...、a n-1、a n，混凝土构件(4)，电压转换模块(5)，数据采集系统(6)，电脑(7)；混凝土构件(4)底部受拉区域布置两个外导电电极(3)和设于外导电电极(3)内部的n个内导电电极a 1～a n，n≥2；其中一个外导电电极(3)接直流稳压电源(1)的正极或负极，另一个外导电电极(3)与定值电阻(2)的一端串联连接；定值电阻(2)的另一端连接直流稳压电源(1)中的负极或正极；同时定值电阻(2)两端并联引出导线(8)接入电压转换模块(5)，测量定值电阻(2)的电压；相邻两个内导电电极a i、a i+1通过导线(8)与电压转换模块(5)连接，测量对应区域a i-a i+1的电压；电压转换模块(5)通过数据采集设备(6)与电脑(7)连接。通过实时监测混凝土目标区域在荷载作用下电阻变化率，实现混凝土裂缝宽度的自监测和裂缝出现区域定位的目标。无需在构件上额外布置裂缝传感器，无需在混凝土基体中添加大量的导电材料，为重要混凝土结构构件的裂缝实时监测提供保障。

Description

混凝土受拉裂缝宽度监测和区域自定位装置及方法 技术领域
本发明属于土木工程技术领域，涉及一种混凝土构件开裂区域自定位与裂缝宽度变化自监测的装置和技术。
 背景技术
混凝土具有良好的抗压强度, 在结构中主要承受压应力, 但混凝土的抗拉性能较低，其抗拉强度仅为抗压强度的约十分之一。混凝土结构构件的受拉区在正常使用阶段是带裂缝工作的，而裂缝在荷载作用下的不断扩展将削弱构件的有效截面，直接影响到结构的变形、耐久性与承载力；所以对混凝土进行裂缝实时跟踪意义重大。目前混凝土结构工程上应用较为广泛的裂缝检测、监测技术主要有：人工检测、超声波、声发射以及光纤传感器监测等。这些技术的应用或受限于人工检测的精度和频次、或依赖于复杂且昂贵的传感器和信号解调设备。
一种成本较低、更方便的方法获得了人们的重视，即通过在水泥基复合材料中掺加导电纤维、导电颗粒以实现应变和损伤的自感知：利用电阻的变化规律对水泥基试件及水泥砂浆等材料受压或受拉时的应变进行监测。但目前国内外针对水泥基复合材料应变自感应技术无法实现对混凝土裂缝的开裂位置、裂缝宽度进行判断与实时监测，这就存在不能及时发现结构物安全隐患的弊端，无法实现对混凝土结构的耐久性和安全性进行科学的评估，影响对受损结构的维修与加固。
混凝土属于电的不良导体，已有水泥基材料应变自监测技术借助碳纤维、碳黑、镍粉等导电材料降低混凝土的电阻率，通常要达到导电渗滤阈值需要的导电材料掺量较高（碳纤维＞0.5%体积掺量，碳纳米管>1%水泥质量掺量），主要集中在受压时的应变，且成本昂贵。实际上，混凝土并不是严格意义上的绝缘体，且混凝土受拉开裂后基体电阻变化比较明显。本发明基于对混凝土自身电阻变化率的实时监测，实现对荷载作用下的混凝土构件受拉区的裂缝定位和裂缝扩展宽度的自监测。
 技术问题
本发明要解决的技术问题是提供一种用于混凝土裂缝宽度监测和裂缝区域定位的装置和技术，它可实时精确地监测混凝土构件在荷载作用下的裂缝宽度变化，具有较高的准确性和灵敏度、低成本；同时还可实现开裂区域定位的装置。尤其适用于包括隧道、城市地下管廊、海底沉管等地下结构在内的不同混凝土结构的裂缝监测。
 技术解决方案
为了达到上述目的，本发明采用的技术方案为：
一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，所述装置包括：直流稳压电源1，定值电阻2，外导电电极3，内导电电极 a 1、 a 2、...、 a n-1、 a n，混凝土构件4，电压转换模块5，数据采集系统6，电脑7，导线8。
所述的混凝土构件4底部受拉区域布置导电电极，包括两个外导电电极3和设于外导电电极3内部的n个内导电电极 a 1 ~ a n（n≥2）。其中一个外导电电极3接直流稳压电源1的正极或负极，另一个外导电电极3与定值电阻2的一端串联连接。定值电阻2的另一端连接直流稳压电源1中的负极或正极。同时定值电阻2两端并联引出两条导线8接入电压转化模块5，测量定值电阻2的电压。所述的相邻两个内导电电极 a i、 a i+1通过外接两根导线8与电压转化模块5连接，测量对应区域 a i- a i+1的电压。所述的电压转化模块5与数据采集设备6连接，数据采集设备6通过导线与电脑7连接；电压转化模块5将接收到的电压信号线性转换成0-5v的电压，输入数据采集设备6，数据采集设备6将电压信号传输给电脑7并实现信号可视化。
所述的直流稳压电源1，可提供稳定的直流电压，电压可调节的范围为0 - 60V。
所述的定值电阻2为水泥电阻，电阻的阻值大小范围为5kΩ - 10kΩ。
所述的外导电电极3以及内导电电极 a 1 ~ a n，其电极可选择铜、不锈钢、导电胶带等导电性能良好的材料，形式可为网格状或片状，与混凝土的结合方式可以选择内埋式或采用外贴式；当采用内埋式时，保护层厚度不超过5mm；当采用外贴式时, 可用石墨胶等固定。
所述的内导电电极相互间距40-1000mm，外导电电极3与相邻内导电电极之间距离30-50mm。且导电电极宽度不超过20mm，长度需要大于所测混凝土部位的宽度，厚度一般不超过0.5mm。
所述的混凝土构件4，可为钢筋混凝土、纤维混凝土、纤维筋增强混凝土等构件。
所述的电压转换模块5为S1105H 高频差分隔离变送器，最大输入范围0-60V，可以根据输入电压的大小线性输出范围为0-5v的电压。具体技术参数为：精度：0.2%，响应频率：1KHz，工作温度：-20℃～70℃。
所述的数据采集系统6为可接收0-5V电压信号的数据采集设备，采集频率不小于5HZ。
一种混凝土裂缝宽度变化自监测和开裂区域定位方法，包括以下步骤：
第一步，连接线路，将各个元件：直流稳压电源1，定值电阻2，外导电电极3和内导电电极 a 1 ~ a n，电压转换模块5，数据采集系统6，电脑7，采用导线8与待测混凝土构件4连接成闭合回路。
第二步，打开直流稳压电源1，调节电压至12-60V，混凝土构件4开始极化。电脑7记录输出电压前，等待20-30分钟直至内导电电极 a i与 a i+1间以及定值电阻2两端的输出电压稳定，此时混凝土构件4内极化趋于稳定。
第三步，对混凝土构件4进行加载，电脑7开始记录内导电电极 a i与 a i+1间和定值电阻2两端的输出电压，得出电阻变化率曲线-时间曲线，进行目标混凝土构件4的裂缝监测。具体为通过直接测量混凝土目标区域电阻变化率，判断混凝土受拉区是否出现裂缝、裂缝出现的区域以及裂缝的扩展宽度：
当实现混凝土裂缝宽度的自监测时，n=2，通过获取电阻变化率与裂缝扩展宽度关系，进行数据拟合得到上述二者关系，即通过电阻变化率换算裂缝扩展宽度，即可实现对混凝土构件4进行裂缝的自监测；
当判断开裂区域或监测裂缝区域时，n>2，判断目标区域混凝土电阻变化率的关系，电阻上升明显的区段为开裂区段；即可实现对混凝土构件4裂缝区段的自定位。
 有益效果
本发明的有益效果是：
本发明可通过直接测量混凝土目标区域电阻变化率，判断混凝土受拉区是否出现裂缝、裂缝出现的区域以及裂缝的扩展宽度，主要优势在于下列各点：1）实现了开裂区域位置和扩展宽度的自监测，可对纤维混凝土构件、钢筋混凝土构件、纤维筋混凝土构件等的初裂点的判断提供一种准确的判断方法；2）该混凝土裂缝监测技术无需在构件上额外布置裂缝传感器，免去布置传感器的繁琐工作；3）无需在混凝土基体中添加大量的导电材料，对混凝土结构的施工没有负面影响，且能够节约成本；4) 电极可根据内力图在结构的受拉区方便、灵活地布置，同时还可节约成本；5）避免了大量导电相在混凝土中难以分散的问题。以上各点可为重要混凝土结构构件的裂缝实时监测提供保障。
 附图说明
图1为一种混凝土受拉区开裂区域自定位与裂缝宽度变化自监测的装置示意图；
图2为实施例1，内电极数量等于2时，实现混凝土裂缝宽度监测装置示意图；
图3为实施例1中钢纤维混凝土梁荷载-时间-电阻变化率曲线；
图4为实施例1中钢纤维混凝土梁荷载-裂缝扩展宽度-电阻变化率关系曲线；
图5为实施例2，内电极数量等于3时，可实现混凝土开裂区域定位的装置示意图；
图6为实施例2中混凝土梁的荷载-时间-电阻变化率关系曲线。
图中：1直流稳压电源，2定值电阻，3外导电电极，内导电电极 a 1 ~ a n，4混凝土构件，5电压转换模块，6数据采集系统，7电脑，8导线。
本发明的实施方式
为利于理解本发明的技术方案，以下结合附图及两个实施例进行说明。
实施例1
当本发明涉及的装置中内电极的数量为2时（n=2），可实现混凝土受拉侧裂缝宽度的自监测。参照附图2，本实施例所述为一种混凝土裂缝扩展宽度自监测技术，具体实施方式如下：
第一步，连接线路，将各个元件：直流稳压电源1，定值电阻2 (阻值=5 kΩ)，外导电电极3 (内埋置式，黄铜网12目0.38mm丝径，宽度为15mm），外电极与内电极间距30mm，内导电电极 a 1、 a 2 (内埋置式，黄铜网12目0.38mm丝径，宽度为15mm，间距100mm)，钢纤维混凝土构件4（40kg/m 3钢纤维），电压转换模块5，数据采集系统6，电脑7，按照说明书附图2用导线8连接成闭合回路。
第二步，打开直流稳压电源1，调节电压至12V，混凝土构件4开始极化。电脑7记录输出电压前，先等待20分钟直至内导电电极 a 1与 a 2之间以及定值电阻2两端的输出电压稳定，此时混凝土构件4内极化趋于稳定。
第三步，对混凝土构件4进行加载，电脑7开始记录定值电阻2两端和内导电电极 a 1与 a 2之间的电压信号并转换成对应区域 a 1- a 2段的电阻变化率-时间实时曲线，同时测量混凝土构件4受拉侧裂缝宽度扩展。
第四步，获取电阻变化率与裂缝扩展宽度关系，拟合二者关系。如图3、图4所示，分别为荷载-时间-电阻变化率、荷载-裂缝扩展宽度-电阻变化率关系曲线。从图3中可知混凝土开裂前，电阻变化率保持在零附近，无明显变化，当混凝土开裂时，电阻变化率迅速增加。随着裂缝宽度的继续扩展，电阻变化率一直增加，但增速减缓，进行数据拟合可以获得电阻变化率( y)与裂缝扩展宽度( x)之间的定量关系（图4中虚线）为 y=48.75896(1- e (-0.38795/ x) )，拟合效果良好。
第五步，实现混凝土裂缝的自监测，即通过电阻变化率换算裂缝扩展宽度。
实施例2：
当需要判断混凝土构件4受拉侧开裂区域或监测裂缝区域时，本发明涉及的装置可通过增加内电极的方式，实现目标。例如，当内电极的数量为3时（n=3），可实现混凝土两个裂缝区域的裂缝定位，参照附图5，本实施例所述为一种混凝土裂缝区域定位技术，具体实施方式如下：
第一步，在纤维混凝土构件4的受拉区布置两个外电极3（内埋置式，黄铜网12目0.38mm丝径，宽度为15mm），布置三个内电极 a 1、 a 2、 a 3（内埋置式，黄铜网12目0.38mm丝径，宽度为15mm），相邻内电极间距为42.5mm，外电极与邻近内电极间距30mm。连接线路，将各个元件：直流稳压电源1，定值电阻2 (阻值=5 kΩ)，外导电电极3、内电极 a 1、 a 2、 a 3，电压转换模块5，数据采集系统6，电脑7，按照说明书附图5用导线8连接成闭合回路。其中相邻两内电极 a 1、 a 2与 a 2、 a 3分别接入转换模块5，可以测出对应区域 a 1- a 2和 a 2- a 3的实时电压。
第二步，打开直流稳压电源1，调节电压至12V，混凝土构件4开始极化。电脑7记录输出电压前，先等待20分钟直至内导电电极 a 1与 a 2， a 2与 a 3间以及定值电阻2两端的输出电压稳定，此时混凝土构件4内极化趋于稳定。
第三步，对混凝土构件4进行加载，记录定值电阻2两端和内电极 a 1与 a 2、 a 2与 a 3间的电压信号并转化获取对应区域 a 1- a 2和 a 2- a 3的电阻变化率-时间曲线。
第四步，通过观察混凝土梁受拉区待测的各区域的实时电阻变化率-时间曲线，判断混凝土梁开裂的区域，实现开裂区域的定位。判断依据：当某一区域混凝土开裂时，该区域对应的电阻变化率将急剧增加，其它区域的电阻变化率在小幅变化后保持稳定。
本实施例裂缝区域定位判别过程：内电极 a 1、 a 2、 a 3将监测区域划分为2部分，即 a 1- a 2段和 a 2- a 3段，如附图5所示。附图6为本实施例混凝土梁的荷载-时间-电阻变化率关系曲线，可得出：1)显著上升的电阻变化率-时间关系曲线所代表的区域（ a 1- a 2）内有裂缝出现，且可以判定开裂的时刻为426s；而经历小幅下降（10%以内）后维持稳定的电阻变化率-时间曲线表示区域（ a 2- a 3）内无裂缝出现。
以上所述实施例仅表达本发明的实施方式，但并不能因此而理解为对本发明专利的范围的限制，应当指出，对于本领域的技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些均属于本发明的保护范围。

Claims (6)

  1. 一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，其特征在于，所述的自监测装置包括直流稳压电源(1)，定值电阻(2)，外导电电极(3)，内导电电极 a 1、 a 2、...、 a n-1、 a n，混凝土构件(4)，电压转换模块(5)，数据采集系统(6)，电脑(7)；
    所述的混凝土构件(4)底部受拉区域布置两个外导电电极(3)和设于外导电电极(3)内部的n个内导电电极 a 1 ~ a n，n≥2；其中一个外导电电极(3)接直流稳压电源(1)的正极或负极，另一个外导电电极(3)与定值电阻(2)的一端串联连接；定值电阻(2)的另一端连接直流稳压电源(1)中的负极或正极；同时定值电阻(2)两端并联引出导线(8)接入电压转换模块(5)，测量定值电阻(2)的电压；所述的相邻两个内导电电极 a i 、 a i+1通过导线(8)与电压转换模块(5)连接，测量对应区域 a i - a i+1的电压；所述的电压转换模块(5)通过数据采集设备6与电脑(7)连接；
    所述的内导电电极相互间距40-1000mm，外导电电极(3)与相邻内导电电极之间距离30-50mm。
  2. 根据权利要求1所述的一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，其特征在于，所述的定值电阻(2)为水泥电阻，电阻的阻值大小范围为5kΩ - 10kΩ。
  3. 根据权利要求1所述的一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，其特征在于，所述的外导电电极(3)以及内导电电极 a 1 ~ a n，其电极形式为网格状或片状，与混凝土的结合方式选择内埋式或采用外贴式；当采用内埋式时，保护层厚度不超过5mm；当采用外贴式时, 进行胶接。
  4. 根据权利要求1所述的一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，其特征在于，所述的内外导电电极宽度不超过20mm，长度大于所测混凝土部位的宽度，厚度不超过0.5mm。
  5. 根据权利要求1所述的一种混凝土受拉开裂区自定位与裂缝宽度变化自监测装置，其特征在于，所述的电压转换模块(5)为S1105H 高频差分隔离变送器，最大输入范围0-60V，根据输入电压的大小线性输出0-5v的电压；具体技术参数为：精度：0.2%，响应频率：1KHz，工作温度：-20℃～70℃。
  6. 一种采用权利要求1-5任一所述的自监测装置进行混凝土裂缝宽度变化自监测和开裂区域定位方法，其特征在于，包括以下步骤：
    第一步，连接线路，将各个元件：直流稳压电源(1)，定值电阻(2)，外导电电极(3)和内导电电极 a 1 ~ a n，电压转换模块(5)，数据采集系统(6)，电脑(7)，采用导线(8)与待测混凝土构件(4)连接成闭合回路；
    第二步，打开直流稳压电源(1)，调节电压至12-60V，混凝土构件(4)开始极化；电脑(7)记录输出电压前，等待20-30分钟直至内导电电极 a i与 a i+1间以及定值电阻(2)两端的输出电压稳定，此时混凝土构件(4)内极化趋于稳定；
    第三步，对混凝土构件(4)进行加载，电脑(7)开始记录内导电电极 a i 与 a i+1间和定值电阻(2)两端的输出电压，得出电阻变化率曲线-时间曲线，进行目标混凝土构件(4)的裂缝监测；具体为通过直接测量混凝土目标区域电阻变化率，判断混凝土受拉区是否出现裂缝、裂缝出现的区域以及裂缝的扩展宽度：
    当实现混凝土裂缝宽度的自监测时，n=2，通过获取电阻变化率与裂缝扩展宽度关系，进行数据拟合得到上述二者关系，即通过电阻变化率换算裂缝扩展宽度，即可实现对混凝土构件(4)进行裂缝的自监测；
    当判断开裂区域或监测裂缝区域时，n>2，判断目标区域混凝土电阻变化率的关系，电阻上升明显的区段为开裂区段；即可实现对混凝土构件(4)裂缝区段的自定位。
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CN206096020U (zh) * 2016-08-30 2017-04-12 浙江广川工程咨询有限公司 快速测试心墙坝表层裂缝空间特征的装置
CN106839958A (zh) * 2017-01-24 2017-06-13 东南大学 一种简易混凝土裂缝监测与量测装置及方法
CN109813210A (zh) * 2019-01-22 2019-05-28 长安大学 半刚性基层内部裂缝监测系统及裂缝宽度、位置确定方法
CN110208084A (zh) * 2019-06-17 2019-09-06 大连理工大学 混凝土受拉裂缝宽度监测和区域自定位装置及方法

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