CN207317990U - The cable force measurement device of low frequency micro breadth oscillation drag-line - Google Patents

Abstract

The utility model relates to a cable force measuring device for a low-frequency micro-amplitude vibration cable, which belongs to the field of bridge cable force detection. The device includes: the cable under test, the cable capture unit, the cable capture unit joint, the vibration transmission unit, the auxiliary bracket, the main sliding unit, the main sliding groove, the main rotating rod, the rotating bracket, the rotating connector, the slave rotating rod, From the sliding unit, from the sliding groove, the displacement head, the displacement measuring unit, the main body base and the data analysis unit; the device realizes the cable force measurement under the condition that the amplitude of the cable is small. The device has a vibration amplification function, which can amplify the small vibration of the cable in proportion, and is convenient for measuring and recording the vibration by using a displacement measuring unit. The patent can effectively detect the low-frequency vibration of the cable, solve the problem that the vibration sensor has extremely poor measurement capability at low frequencies, and can directly detect the fundamental frequency vibration. The cost of this patent is lower than the method commonly used at present.

Description

Cable Force Measuring Device for Low-Frequency Micro-amplitude Vibration Cable

technical field

The utility model relates to a cable force measuring device for a low-frequency micro-amplitude vibration cable, which belongs to the field of bridge cable force detection.

Background technique

With the rapid development of my country's economic construction and opening to the outside world, the continuous progress of bridge technology and people's requirements for bridge aesthetics, cable technology is increasingly widely used in long-span bridges. Typical applications include main cables and suspension cables of suspension bridges, inclined cables of cable-stayed bridges, suspension cables of arch suspension bridges, etc. As the core component of the above-mentioned large-scale bridge structure, most of the weight of the bridge span structure and the live load on the bridge are transmitted to the tower column through the cables. According to incomplete statistics, there are more than 300 long-span cable-type bridges in my country, and most of the cables have various degrees of disease. In recent years, serious accidents of bridge collapses caused by bridge cable breaks have also occurred. In 2011, the suspender of the Xiaonanmen Jinsha Yangtze River Bridge in Yibin broke and the bridge deck collapsed; in 2010, the Nanping Yuping Bridge broke and replaced the cables. It can be seen that due to long-term exposure to alternating stress, corrosion, and wind-induced vibration, the cables are prone to local fatigue and damage, which not only shortens their service life, but also directly affects the internal force distribution and structural alignment of the structure, endangering the safety of the entire structure. As a flexible component, the cable has different mechanical characteristics from rigid components: it has no compressive stiffness, can only bear tension, has obvious geometric nonlinearity, and is prone to relaxation and stress loss. The stress and working status of bridge cables are one of the important signs that directly reflect whether the bridge is in normal operation. During the design and construction, it is necessary to detect and optimize the force of the bridge cables so that the towers and beams are in the best stress state. After the bridge is completed, it is also necessary to continuously monitor the change of the cable force, understand the working status of the cable, and make timely adjustments to make it meet the design requirements. The People's Republic of China industry standard CJJ99-2003 "Technical Specifications for Urban Bridge Maintenance" 5.9.5 requires: "The cable force must be measured once a year, and the cable force of the last cable adjustment after the completion of the bridge should be compared with the design cable force." The industry recommendation standard JTG/T J21-2011 of the People's Republic of China clearly states that the cable force is one of the main loading test items of cable-stayed bridges and suspension bridges, and is one of the important parameters reflecting the state of bridges. . Therefore, the bridge cable force testing business is an indispensable testing item and basic capability of each testing agency.

1) Jack pressure gauge measurement method

At present, the draglines are stretched using hydraulic jacks. Since the tensioning cylinder of the jack is directly related to the tensioning force, the cable force can be obtained by measuring the hydraulic pressure of the tensioning cylinder with a precision pressure gauge or a hydraulic sensor.

2) Pressure sensor measurement method

When the cable is stretched, the tension force of the jack is transmitted to the cable anchor through the connecting rod, and a through-hole pressure sensor is sleeved on the connecting rod. The sensor can output voltage after being pressed, and it can be read on the secondary instrument Out of the tension of the jack.

3) Cable force dynamic tester method

The cable force dynamic tester method is based on the characteristics of the corresponding relationship between the cable force and the vibration frequency of the cable. When the parameters such as the length of the cable, the constraints at both ends, and the distribution quality are known, a high-sensitivity frequency sensor is placed on the cable. Detect the vibration signal of the cable under vibration excitation, and after digital signal processing, the natural vibration frequency of the cable can be measured, and then the cable force can be obtained. Due to its convenience, the cable force dynamic tester is mostly used in engineering for measurement.

4) Magnetic flux measurement method

The magnetic flux measurement method to measure the cable force is based on the principle of magnetoelastic effect of ferromagnetic materials. When an external force is applied, mechanical stress or strain is generated inside the ferromagnetic material, and its magnetic permeability changes accordingly. By measuring the magnetic permeability Changes to reflect changes in stress (or cable force).

Current technology has the following disadvantages:

1) It is not suitable for the dynamic measurement and long-term measurement of the cable force after the bridge is completed. Due to the problems of the pressure gauge itself, the pointer deflects too fast, the pointer shakes violently, there are artificial random errors in the reading, and the oil does not return to zero. At the same time, the cable has been stretched after the bridge is completed, so it is not convenient to remove the cable to install the pressure gauge. , so this method is not suitable for dynamic measurement and long-term measurement after the bridge is completed.

2) Expensive. Due to the relatively expensive price of the pressure sensor, short useful life, poor dynamic response and other problems, this measurement method is only suitable for specific occasions.

3) The measurement capability cannot meet the demand. In 2006, Wu Kangxiong and others pointed out in the literature that the vibration signal of the cable is a composite vibration signal composed of multi-harmonic vibration signals. The vibration frequency of the cable is generally (0.3-50) Hz, and the high-frequency components are likely to cause confusion when the instrument is sampled. Frequent phenomena should generally be filtered out. In 2016, according to the model parameters of high-strength steel wire cables provided by GB/T 18365 "Technical Conditions for Hot-Extruded Polyethylene High-Strength Steel Wire Cables for Cable-Stayed Bridges", Zhou Yi selected the thinnest and thickest cable parameters recommended by the code, and established The ANSYS finite element model simulates the natural vibration characteristics of the cable. The cable density, cross-sectional area, diameter, elastic modulus, Poisson's ratio, and cable force are constant, and the cable length is adjusted from 10m to 200m in steps of 1m. Simulation calculations show that the ranges of the first-order natural natural frequencies are (14.39307-0.69740) Hz and (16.28878-0.71355) Hz, respectively, and the cable length is inversely proportional to the frequency. Apparently, to measure the cable force using the cable force dynamic tester method, the vibration sensor equipped with it needs to cover the low frequency range of 0.3 Hz to 10 Hz. The sensor with this measurement capability is very expensive and is generally not equipped with this sensor.

4) The accuracy of the measurement result is low. Due to the lack of technological development, the magnetic flux method has low measurement accuracy and cannot meet the actual engineering needs.

Contents of the invention

The technical problem solved by this application:

Measurement capability to cover long cables with low vibration frequencies;

It can be applied to the detection and monitoring of bridges under construction and completed bridges;

Improved measurement accuracy.

The cable force measurement device of the low-frequency micro-amplitude vibration cable is mainly composed of a data analysis unit, a displacement measurement unit, and a vibration transmission unit. The hardware connection diagram is shown in Figure 1.

The cable catch unit can tightly lock the cable so that it does not move on the cable during work. A cable capture unit connector is installed on the cable capture unit. A vibration transmission unit can be installed on the joint of the cable capture unit to transmit the vibration of the cable to the device of this patent. The vibration transmission unit is fixed by the auxiliary support, so that the vibration transmission unit and the auxiliary support are kept horizontal, and the vibration transmission unit can generate horizontal displacement with the auxiliary support. The lower end of the vibration transmission unit is connected with a main slide groove. The main slide unit can move horizontally in the main slide groove along the long side direction. The main rotating rod is connected to the main sliding unit and forms an included angle with the slave rotating rod. The connection between the main rotating rod and the secondary rotating rod is a rotating connection, and the rotating connecting part makes the relative position between the main rotating rod and the secondary rotating rod unchanged, and the structure formed by the main rotating rod and the secondary rotating rod can be connected by rotation The piece rotates around the center of the circle. A slave sliding unit is connected with the other end of the slave turning rod. The slave sliding unit is installed in the slave sliding groove, and the slave sliding unit can move horizontally in the slave sliding groove according to the long side direction. Connect to the displacement head from one end of the sliding groove. The displacement head moves on the displacement measurement unit. The displacement measurement unit measures the displacement of the displacement head, and transmits the displacement information to the data analysis unit. The data analysis unit has the functions of displaying displacement curve, displaying frequency spectrum, displaying frequency, displaying cable force value and data calculation. The base of the main body is used to fix the displacement measurement unit, the rotating bracket and the auxiliary bracket.

The main sliding groove can use air bearing guide rail or magnetic bearing guide rail to realize the smooth movement of the main sliding unit on the main sliding groove without friction and vibration. The slave sliding groove can choose air bearing guide rail or magnetic bearing guide rail to realize the frictionless and vibration-free smooth movement of the slave sliding unit on the slave sliding groove.

The displacement measuring unit can choose high-precision grating ruler, capacitive digital displacement sensor, laser distance measuring sensor, pull wire encoder, etc.

The data analysis unit can be a computer, an industrial computer, a single-chip microcomputer, a mobile phone, etc.

The cable capture unit, the cable capture unit joint, the vibration transmission unit and the auxiliary bracket described in this patent are used to transmit the vibration of the cable in equivalent value.

The main sliding unit, main sliding groove, main rotating rod, rotating bracket, rotating connector, slave rotating rod, slave sliding unit, slave sliding groove and displacement head described in this patent are used to transmit the vibration of the cable at a certain ratio. Among them, the size of the ratio is positively correlated with the lengths of the main rotating rod and the slave rotating rod; if the length of the main rotating rod is L and the rotation angle θ, then the vertical distance of the main rotating rod is The same can be deduced from the rotation rod.

The data analysis unit described in this patent records the displacement information transmitted by the displacement measurement unit, draws the time history curve, and calculates the multi-order frequency of the vibration of the cable under test by using the wavelet change calculation. Measure the tension of the cable.

The cable capturing unit may be a pair of semi-cylindrical rings, the inner diameter of the semi-cylindrical rings is the same as the outer diameter of the measured cable. The vibration transmission unit may be a rigid optical shaft. The auxiliary support is vertical to the ground, and the moving direction of the displacement head is also vertical to the ground.

Initialization means that the indication value of the displacement measurement unit is reset to zero, the records of the data analysis unit are cleared and reset to zero, and the master rotating rod and the slave rotating rod reach a balance. Balance means that the master and slave turning rods cannot rotate without the cable not vibrating. In order to achieve balance, the positions of the main rotating rod, the slave rotating rod, the master slide groove and the slave slide groove can be adjusted by hand. Angle θ is the angle at which the main rotating rod rotates clockwise with the rotating connecting piece as the center. 5. The displacement head moves on the displacement measurement unit.

The device for measuring the force of the cable described in this patent is composed of a data analysis unit, a displacement measurement unit, a vibration transmission unit and other parts.

The implementation process of the overall technical solution is as follows:

(1) Install the cable capture unit on the cable under test so that the cable capture unit and the cable under test fit closely.

(2) Place the base of the main body on a stable ground, and make the long side of the vibration transmission unit perpendicular to the ground.

(3) The device is powered on and initialized, and the master rotating rod and the slave rotating rod reach a balanced state.

(4) Use methods such as hammering to excite the tested cable to make the cable vibrate.

(5) The vibration transmission unit produces up and down displacement with the vibration of the cable, and the displacement direction should be parallel to the auxiliary support.

(6) The main sliding groove is displaced by the push-pull force generated by the movement of the vibration transmission unit, so that the main sliding unit is forced to reciprocate left and right in the main sliding groove, and the movement direction should be parallel to the main sliding groove.

(7) The movement of the main sliding unit drives the main rotating rod to reciprocate around the connecting piece.

(8) The secondary rotating rod reciprocates due to the rotation of the main rotating rod, and the rotating direction is consistent with the rotating direction of the main rotating rod.

(9) When the slave rotating rod reciprocates, it drives the slave sliding unit to generate displacement.

(10) The secondary sliding unit reciprocates left and right in the secondary sliding groove, and the moving direction is horizontal to the secondary sliding groove.

(11) receiving the force applied from the sliding unit from the sliding groove, thereby driving the displacement head to reciprocate along the vertical direction;

(12) The displacement measuring unit measures the movement of the displacement head.

(13) The displacement measurement unit transmits the measured displacement information to the data analysis unit.

(14) The data analysis unit displays the time history curve of the displacement in real time according to the displacement data transmitted by the displacement measurement unit.

(15) The data analysis unit uses algorithms such as FFT to calculate and draw the frequency spectrum.

(16) The data analysis unit is based on the theory of string vibration, using algorithms such as wavelet transform to calculate the frequency and cable force value of the displacement curve.

Description of drawings

Figure 1 schematic diagram of the device

In the figure, 1 is the tested cable, 2 is the cable capture unit, 3 is the cable capture unit joint, 4 is the vibration transmission unit, 5 is the auxiliary bracket, 6 is the main sliding unit, 7 is the main sliding groove, 8 is the The main rotating rod, 9 is the rotating bracket, 10 is the rotating connector, 11 is the slave rotating rod, 12 is the slave sliding unit, 13 is the slave sliding groove, 14 is the displacement head, 15 is the displacement measuring unit, 16 is the main body base, 17 is the data analysis unit.

Figure 2 is a flow chart of the technical scheme of the device and method for measuring the force of the cable

Example 1 flow chart shown in Fig. 3.

Detailed ways

Referring to the flowchart of Example 1 shown in Figure 3, the implementation process of the technical solution of Example 1 is as follows:

(1) Install the cable capture unit on the cable under test so that the cable capture unit and the cable under test fit closely.

(2) Place the base of the main body on a stable ground, and make the long side of the vibration transmission unit perpendicular to the ground.

(3) The device is powered on and initialized, and the master rotating rod and the slave rotating rod reach a balanced state.

(4) Use methods such as hammering to excite the tested cable to make the cable vibrate.

(5) The vibration of the cable is transmitted to the displacement head through a certain amplitude amplification of the device. The displacement measurement unit of the device measures the displacement of the displacement head and transmits it to the data analysis unit of the device.

(6) The data analysis unit displays the time history curve of the displacement in real time according to the displacement data transmitted by the displacement measurement unit, and calculates the cable force value of the displacement curve based on the string vibration theory and using algorithms such as wavelet transform.

The patent realizes the measurement of the cable force under the condition that the amplitude of the cable is small. The device has a vibration amplification function, which can amplify the small vibration of the cable in proportion, and is convenient to measure and record the vibration by the displacement measurement unit. The patent can effectively detect the low-frequency vibration of the cable, solve the problem that the vibration sensor has extremely poor measurement capability at low frequencies, and can directly detect the fundamental frequency vibration. The cost of this patent is lower than the method commonly used at present.

This patent invents a cable force measuring device for low-frequency micro-amplitude vibration cables.

The existing method of measuring the cable force with the cable force dynamic tester method, because the vibration sensor has a very poor measurement capability in the low frequency range of 0.3 Hz to 10 Hz, after the high-order vibration frequency is obtained through the measurement of the vibration pickup, it is calculated by different The frequency difference between the order frequencies is used as the fundamental frequency of the cable vibration, so as to calculate the force value of the cable. According to a large number of experiments and literature records, it can be known that the maximum measurement error of the traditional cable force dynamic measuring instrument can reach 2.1%, and the measurement error of the existing method is relatively large, which cannot meet the actual needs. The maximum measurement error of this patent is about 1.5%.

Claims (5)

1. The cable force measuring device of the low-frequency micro-amplitude vibration cable, which is characterized in that it includes: the measured cable, the cable capture unit, the cable capture unit joint, the vibration transmission unit, the auxiliary bracket, the main sliding unit, and the main sliding groove , a main rotating rod, a rotating bracket, a rotating connector, a slave rotating rod, a slave sliding unit, a slave sliding groove, a displacement head, a displacement measurement unit, a main body base and a data analysis unit; The cable capture unit can lock the cable tightly so that it does not move on the cable during work; the cable capture unit is equipped with a cable capture unit joint; the cable capture unit joint can be equipped with a vibration transmission unit; the vibration transmission The unit is fixed by the auxiliary bracket, so that the vibration transmission unit and the auxiliary bracket are kept horizontal, and the vibration transmission unit can generate horizontal displacement with the auxiliary bracket; the lower end of the vibration transmission unit is connected with a main sliding groove; the main sliding unit can move in the main sliding groove along the length Move horizontally in the side direction; the main rotating rod is connected to the main sliding unit and forms an included angle with the slave rotating rod; the connection between the main rotating rod and the slave rotating rod is a rotating connector, and the rotating connector makes the master rotating rod and the slave rotate The relative position between the rods does not change, and the structure formed by the main rotating rod and the slave rotating rod can rotate with the rotating connector as the center of the circle; the slave sliding unit is connected to the other end of the slave rotating rod; the slave sliding unit is installed on the slave In the sliding groove, the slave sliding unit can move horizontally in the longitudinal direction in the slave sliding groove; one end of the slave sliding groove is connected to the displacement head; the displacement head moves on the displacement measuring unit; the displacement measuring unit measures the displacement of the displacement head, And transmit the displacement information to the data analysis unit; the base of the main body is used to fix the displacement measurement unit, the rotating bracket and the auxiliary bracket. 2. The device according to claim 1, characterized in that the main sliding groove or the secondary sliding groove adopts an air-floating guide rail or a magnetic floating guide rail. 3. The device according to claim 1, wherein the displacement measurement unit can be a high-precision grating ruler, a capacitive digital displacement sensor, a laser ranging sensor or a wire-drawn encoder. 4. The device according to claim 1, wherein the data analysis unit can be a computer, an industrial computer, a single-chip microcomputer or a mobile phone. 5. The device according to claim 1, characterized in that, the main sliding unit, the main sliding groove, the main rotating rod, the rotating bracket, the rotating connector, the rotating rod, the sliding unit, the sliding groove and the displacement head , used to transmit the vibration of the cable according to a certain ratio; wherein, the ratio is positively correlated with the length of the main rotating rod and the length of the slave rotating rod; if the length of the main rotating rod is L and the rotation angle θ, then the vertical distance of the main rotating rod for