CN107036522B - Apparatus and method for measuring vertical displacement of medium- and small-span bridges over water - Google Patents

Abstract

The invention discloses a device and a method for measuring the vertical displacement of a water structure of a middle-span and small-span bridge, which are suitable for the field of bridge detection, in particular to the deflection measurement of a bridge structure of a river. The invention comprises a telescopic bracket and a displacement acquisition device, wherein the telescopic bracket can be telescopic and foldable; the displacement acquisition device can effectively measure the vertical displacement of the bridge and realize the vertical displacement information of the long-distance oblique measurement structure through the cable-stayed lead; the measuring method is characterized in that the pre-measurement is realized through the extension and retraction of the telescopic bracket, the correction coefficient of the displacement meter is given, and the actually measured vertical displacement is accurately calculated according to the correction coefficient of the displacement meter. The invention is convenient for carrying engineering vehicles and on-site installation and use of measuring staff, is suitable for complex and dangerous environment measurement, and greatly improves the measuring environments of the measuring staff and measuring equipment.

Description

A device and method for measuring vertical displacement of small and medium span bridge water structures

Technical Field

The present invention relates to the field of detection of small and medium span bridges, and in particular to a device and method for measuring the vertical displacement of a small and medium span bridge aquatic structure.

Background Art

With the development of society, bridges are playing an increasingly important role as an important part of current transportation. However, in recent years, many bridge structures built in the past need to be fully inspected, one of which is the load-bearing capacity assessment. The most direct method to ensure the reliability of the load-bearing capacity assessment result is the load test. In the load test, deflection (vertical displacement) is a comprehensive reflection of the operating status of the bridge structure and one of the most direct and intuitive safety indicators of the bridge structure. However, the environment and topography under the bridge structure are often very complex, and displacement meters and inspection personnel cannot work directly under it. In order to measure the deflection of the bridge, it is often necessary to place a scaffold directly under it, which is time-consuming and labor-intensive. If there is too much river water under the bridge, the stability of the scaffolding is difficult to guarantee, threatening the safety of personnel.

Summary of the invention

The purpose of the present invention is to provide a device and method for measuring the vertical displacement of a medium- and small-span bridge structure above water. The invention enables the displacement meter to provide accurate and reliable displacement measurement without contacting the bridge and being directly below the measurement position.

The specific scheme of the present invention is: a vertical displacement measuring device for a medium- and small-span bridge water structure, comprising a telescopic bracket and a displacement acquisition device; the telescopic bracket comprises a fixed column foot, a fixed column, a telescopic arm, a crossbeam, a pulley and a rigid bottom plate; the fixed column foot and the fixed column of the telescopic bracket are connected by bolts; the telescopic arm of the telescopic bracket is fixed by a fixing cap on the fixed column; the crossbeam and the telescopic arm of the telescopic bracket are connected by a circular shaft, and there is a 5mm gap between the lower surface of the crossbeam and the telescopic arm; there are ejector pin grooves at both ends of the crossbeam of the telescopic bracket; the displacement acquisition device comprises a displacement meter, a correction displacement meter, a signal acquisition instrument, a weight, a magnetic table seat and an indium steel wire; one end of the weight is connected to the indium steel wire, and the displacement meter at the other end is pushed under the weight; two correction displacement meters are respectively pushed in the ejector pin grooves on the crossbeam, and three magnetic table seats are arranged on the rigid bottom plate, respectively clamping two correction displacement meters and one displacement meter; the displacement meter and the correction displacement meter are connected to the signal acquisition instrument through a hydraulic cable.

Furthermore, a pulley is provided between the beams, and the axis of the pulley is colinear with the center line of the beam.

Furthermore, a steel sleeve is provided on the outer side of the weight, and both sides of the steel sleeve are fixed to the crossbeam through sleeve hangers.

Furthermore, the displacement meter and the corrected displacement meter are both resistive displacement meters.

Furthermore, the signal acquisition instrument is a resistive strain gauge.

The present invention provides a method for measuring the vertical displacement of a medium-span bridge structure above water, wherein the steps of implementing the method are as follows:

Step 1: Manually loosen the fixing cap, lift the telescopic arm upward according to the estimated displacement of the structure to be measured, and then tighten the fixing cap to fix it;

Step 2: Collect the reading changes S1 and S2 of the two corrected displacement meters, and the reading change △H of the displacement meter;

其中△S＝(S1+S2)/2，η>1；Step 3: Calculate the displacement meter correction factor

Where △S＝(S1+S2)/2, η>1;

Step 4: Manually loosen the fixing cap, retract the telescopic arm to the initial state and fix it to reduce system error;

Step 5: Load on site and collect the displacement meter reading change △H;

Step 6: Calculate the actual displacement of the structure S = η*△H.

The beneficial effects of the present invention are: under the premise of ensuring accurate and reliable measurement, it can save manpower and material resources, reduce the difficulty of detecting displacement during bridge load testing and the dangerous factors in the detection process, and facilitate detection in complex terrain and environmental conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the structure of the present invention;

Fig. 2 is a diagram of a measuring device of the present invention;

FIG3 is a partial enlarged view of the key part A in FIG2 ;

FIG4 is a partial enlarged view of the key part B in FIG2;

FIG5 is a partial enlarged view of the key part C in FIG2;

Fig. 6 is a schematic diagram of the implementation of the forecast measurement;

FIG. 7 is a diagram showing the principle of calculating the calibration coefficient of the displacement meter.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the accompanying drawings.

As can be seen from Figures 1 and 2, the implementation method of the present invention is that the measuring device is placed at any position below the measured structure 19, and an indium steel wire 13 is bonded to the measured structure 19 and obliquely pulled to the pulley 5, and a heavy hammer 12 is hung around the pulley 5.

As shown in Figures 2 to 5, the measuring device of the present invention is composed of a telescopic bracket and a displacement acquisition device, wherein the telescopic bracket is composed of a rigid base plate 17, a fixed column foot 1, a fixed column 2, a telescopic arm 3 that can be raised and lowered, a crossbeam 4, a pulley 5, a steel sleeve 6, a sleeve suspension rod 7 and a fixed cap 8. The inner diameter of the fixed column 2 is slightly larger than the outer diameter of the telescopic arm 3, and there is a screw hole on the fixed column 2. Rotating the fixing cap 8 can squeeze the telescopic arm to facilitate fixing the telescopic arm 3, ensuring that the telescopic arm 3 can be telescoped; the telescopic arm 3 and the crossbeam 4 are connected by a circular shaft 16, and the lower surface of the crossbeam 4 is 5mm away from the telescopic arm, so that the telescopic arm 3 and the crossbeam 4 are hinged, ensuring that the crossbeam 4 does not deform when the telescopic arm 3 is freely telescoped; the fixed column 2 and the fixed column foot 1 are connected by bolts 15, and rotating the nut can make the fixed column foot 1 clamp the fixed column 2, and the width of the fixed column foot 1 is slightly larger than the width of the fixed column 2, ensuring that the telescopic bracket can be folded; there are pin grooves 18 of the displacement meter at both ends of the lower part of the crossbeam 4, which are used to fix and correct the pin of the displacement meter 10 to prevent the pin from being displaced; a sleeve hanger 7 is welded near the middle of the crossbeam 4, and the sleeve hanger 7 is welded on both sides of the steel sleeve 6, and the steel sleeve 6 is used to stabilize the heavy hammer 12.

The displacement acquisition device is composed of a displacement meter 9, a modified displacement meter 10, a signal acquisition instrument 11, a weight 12, an indium steel wire 13 and a magnetic base 14. The magnetic base 14 clamps the displacement meter 9 and two modified displacement meters 10, and the pins of the modified displacement meters 10 at both ends of the beam 4 are placed in the pin grooves 18 of the beam shown in Figure 4. The middle displacement meter 9 is pressed against the bottom surface of the weight 12, and the weight 12 is suspended in the steel sleeve 6 through the indium steel wire 13. The displacement meter 9 and the modified displacement meter 10 are connected to the signal acquisition instrument through a hydraulic cable, and the connection method is a full-bridge connection. The signal acquisition instrument 11 collects the data of each displacement meter and transmits it to the computer through a USB conversion line, and the computer is used to save the data.

As shown in FIG6 , a pre-measurement is required before formally measuring the displacement to obtain the displacement meter correction coefficient.

Before measurement, the vertical displacement (deflection) of the structure is estimated in advance, and then the telescopic arm 3 is adjusted and the lifting (lowering) heights S1 and S2 at both ends of the beam 4 are measured by the modified displacement meter 10, as well as the weight displacement difference ΔH (close to the estimated deflection) measured by the resistive displacement meter 9 under the weight 12, where ΔS = (S1+S2)/2.

η>1。其中ΔS相对测量点高度、斜向引线长度基本可以忽略不计。进行预测量后算出位移计修正系数，回缩(回升)伸缩臂3至初始状态，减少系统误差。然后开始现场加载试验，采集位移计9的读数变化△H，根据修正系数η，计算实际结构位移，其中计算公式为：S＝η*△H。As can be seen from Figure 7, when the rising distance of the middle of the beam 4 is ΔS, the lead length of the weight 12 increases by ΔL, and when the structural displacement of the weight 12 is vertical displacement, the displacement meter correction coefficient is

η>1. ΔS can be basically ignored relative to the height of the measuring point and the length of the oblique lead. After the pre-measurement, the displacement meter correction coefficient is calculated, and the telescopic arm 3 is retracted (raised) to the initial state to reduce the system error. Then the on-site loading test is started, and the reading change △H of the displacement meter 9 is collected. According to the correction coefficient η, the actual structural displacement is calculated, and the calculation formula is: S＝η*△H.

Claims (6)

1. A vertical displacement measuring device for medium and small-span bridges above water, characterized in that: comprise a telescopic support and a displacement acquisition device; said telescopic support comprises a fixed column foot (1), a fixed column (2), a telescopic arm (3 ), crossbeam (4), pulley (5) and rigid base plate (17); the fixed column foot (1) of described telescopic bracket and the fixed column (2) are connected by bolt (15); the expansion and contraction of described telescopic bracket The arm (3) is fixed by the fixed cap (8) on the fixed column (2); the crossbeam (4) of the telescopic support and the telescopic arm (3) are connected by a circular shaft (16), and the lower surface of the crossbeam (4) and There is a 5mm gap between the telescopic arms (3); there are thimble grooves (18) at both ends of the crossbeam (4) of the telescopic support; the displacement acquisition device includes a displacement meter (9), a correction displacement meter (10) , signal acquisition instrument (11), weight (12), magnetic table base (14) and indium steel wire (13); one end of described weight is connected with indium steel wire (13), and the displacement meter (9) at the other end The top is placed under the weight (12); the two correction displacement gauges (10) are respectively placed in the thimble grooves (18) on the beam (4), and the three magnetic bases are set on the rigid base plate (17), respectively Two correction displacement gauges (10) and one displacement gauge (9) are clamped; the displacement gauges (9) and correction displacement gauges (10) are connected to the signal acquisition instrument through hydraulic cables. 2. The device for measuring the vertical displacement of a medium- and small-span bridge over water structure according to claim 1, characterized in that: a pulley (5) is arranged between the crossbeams (4), and the axis of the pulley (5) and the crossbeam The centerlines of (4) are collinear. 3. The device for measuring the vertical displacement of a medium- and small-span bridge over water structure according to claim 1, characterized in that: a steel sleeve (6) is provided on the outside of the weight (12), and the steel sleeve (6) The two sides of both sides are fixed on the crossbeam by sleeve suspender (7). 4. The device for measuring the vertical displacement of a medium- and small-span bridge over water structure according to claim 1, characterized in that: the displacement gauge (9) and the correction displacement gauge (10) are both resistive displacement gauges. 5 . The device for measuring vertical displacement of medium- and small-span bridges above water according to claim 1 , wherein the signal acquisition instrument ( 11 ) is a resistive strain gauge. 6 . 6. a kind of medium and small span bridge water structure vertical displacement measuring device according to claim 1, the steps that its measuring method implements are as follows: Step 1: Loosen the fixing cap (8) manually, lift up the telescopic arm (3) according to the estimated displacement of the structure under test (19), and then tighten the fixing cap (8) to fix it; Step 2: Collect the reading changes S1 and S2 of the two corrected displacement meters (10), and the reading change ΔH of the displacement meter (9); Step 3: Calculate the Displacement Gauge Correction Factor

Where ΔS=(S1+S2)/2, η>1; Step 4: Loosen the fixing cap (8) manually, retract the telescopic arm (3) to the initial state and fix it to reduce system errors; Step 5: On-site loading, collecting the reading change ΔH of the displacement meter (9); Step 6: Calculate the actual displacement of the structure S=η*ΔH.

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