CN111366457A - A device and method for measuring long-term creep of steel cables - Google Patents

Abstract

The invention provides a device and method for measuring long-term creep of a steel cable, including a measuring device for marking and displacement measurement of a creep specimen; an auxiliary device for fixing; the measuring device includes two Marking structure and two mechanical dial indicators or dial indicators, the marking structure has a structure connected with the steel cable, the marking structure is provided with a position that can be aligned with the marking position on the steel cable and is connected with the mechanical dial indicator or dial indicator. The measuring working part corresponding to the dial indicator; the auxiliary device is provided with the mechanical dial indicator or the fixing device of the dial indicator, so that the mechanical dial indicator or the dial indicator can be stably measured at the measuring position Measure the displacement of the working part. The invention can be used for long-term creep measurement of steel cables for several years to more than ten years, and can also be used for monitoring the creep of completed structural steel cables.

Description

A device and method for measuring long-term creep of steel cables

technical field

The invention relates to a device and method that can be used for long-term measurement of steel cable creep, mainly applicable to steel cables of steel wire, steel wire bundle, steel wire rope, steel strand and the like, and belongs to the technical field of cable performance testing.

Background technique

Steel cables are widely used in cable-rod structure building systems, roads and bridges, mechanical structures and other fields. Among them, cable-rod structures are mostly used in large public buildings such as stadiums, transportation buildings, and convention and exhibition centers, and their structural importance is self-evident. Roads and bridges are also important structures related to the safety of public life and property, and mechanical structures also have high requirements for stability and safety. Therefore, it is of great social and epochal significance to determine the performance of steel cables to ensure the safety and applicability of structures using steel cables.

However, stress relaxation due to material creep is inevitable over the life of the structure. The existing cable creep test results show that although the tensile prestress can initially tighten the cable section and obtain uniform elastic strain, all cables will still creep under the service load. The change of cable length and the reduction of stress caused by the creep of the steel cable will have an impact on the safety and applicability of the structure. Therefore, it is necessary to clarify the creep elongation law of the steel cable over time and monitor the cable creep of the built structure. Elongation is very important.

Existing creep measurement devices and testing machines can be used for creep measurement under certain specific conditions, but they are not suitable for long-term creep measurement or creep monitoring of built structures. The utility model patent "Steel Strand Relaxation Testing Machine" with the application number CN201920183606.1 represents the principle of the steel cable relaxation testing machine that is widely available on the market. The continuous measurement time is less than 1000 hours, which is not suitable for measuring the creep of steel cables for a long time, nor can it be used for creep monitoring of steel cables in built structures. The invention patent application with the application number CN200510108349.8 "A Device and Method for Automatic Data Acquisition and Tensile Creep Testing" needs to put the test piece into the heating element, which is not suitable for monitoring the built structure; and it needs to use a temperature controller to maintain Constant temperature, using displacement sensors and computers to record data, is also difficult to use for long-term creep measurements lasting more than a few years.

SUMMARY OF THE INVENTION

In order to meet the requirements of measuring the long-term creep of steel cables and monitoring the creep of built-in structural steel cables, the invention proposes a device and method for measuring the long-term creep of steel cables that can be widely and conveniently performed relatively accurately. It consists in fixing a marking structure at both ends of the measuring section of the stressed steel cable, the marking structure can be aligned with the marking position on the steel cable and has a measuring working part corresponding to the mechanical dial indicator or dial indicator, and then use two A mechanical dial indicator or dial indicator measures the displacement of the working part along the length of the wire rope. The body of the watch can be fixed on a stable structure with a magnetic base, so that the measurement length can be flexibly selected according to the situation. Due to the use of mechanical gauges, long-term measurement for several years or even ten years can be carried out. After reading, the creep elongation of this section of steel cable can be obtained according to the difference between the displacements of the two gauges, and then calculated from the length of the measuring section to obtain For the creep strain of the steel cable, the creep strain time curve of the steel cable can be obtained by measuring multiple readings according to the requirements, and then the creep performance and law of the steel cable can be summarized.

According to the first aspect of the present invention, the present invention adopts the following technical solutions:

A device for measuring long-term creep of a steel cable, characterized in that it comprises a measuring device for marking and measuring displacement of a creep specimen; an auxiliary device for fixing;

The measuring device includes two marking structures and two mechanical dial indicators or dial indicators, the marking structures have a structure connected with the steel cable, the marking structure is provided with a position that can be aligned with the marking position on the steel cable, and The measuring working part corresponding to the mechanical dial indicator or dial indicator;

The auxiliary device is provided with a fixing device for the mechanical dial indicator or dial indicator, so that the mechanical dial indicator or dial indicator can be stably located at the measuring position to measure the displacement of the working part.

Further, the marking structure adopts a sleeve, and the sleeve is provided with a horizontal top plate of the sleeve, which is used for aligning the marking position on the steel cable and as the measuring working part corresponding to the mechanical dial indicator or dial indicator, The cylindrical part of the sleeve can be clamped as a structure for connecting with the wire rope.

Further, the marking structure adopts a hinge structure, which can be opened and closed to both sides for clamping.

Further, the auxiliary device includes a fixing frame and a connecting frame of a mechanical dial indicator or dial indicator, and the connecting frame is connected with the fixing frame. The fixed frame can be connected to the ground or placed on a stable ground. When measured in the laboratory, it can withstand the load applied by the test and remain stable.

Further, the connecting frame is connected to the fixing frame by a magnet, and its position can be adjusted and fixed arbitrarily.

Further, the fixed pulley of the steel cable is arranged on the top of the fixed frame to wind up the long specimen to reduce the occupied space. The fixed pulley should be as smooth as possible, and the rotation resistance should be small.

For laboratory measurements, the lower end of the measuring wire can be made into a processing section, which can become a port where heavy objects can be suspended. In the specific implementation, the lower end of the measuring wire can be bent into a circle and locked, and then the hook and load can be placed; or A clamp with a hook is fixed on the lower end of the measuring wire.

According to another aspect of the present invention, the present invention adopts the following technical scheme:

In the laboratory, the method for measuring the long-term creep of a steel cable using the above-mentioned device is characterized in that it comprises the following steps:

(1) Fix one end of the creep measurement wire on the fixing frame, select a suitable part on the measurement wire as the measurement section, and the length of the measurement section is represented by L; Mark the structure and align it with the marked position on the cable; connect a counterweight to the other end of the measuring cable;

(2) Connect the two mechanical dial indicators or dial indicators to the appropriate position of the fixing frame through their connecting frame, so that the heads of the two mechanical dial indicators or dial indicators are in vertical contact with the measurement of the marking structure. work site;

(3) Take a certain time after the loading is completed and stabilized as the initial time point, read the readings of the two meters, the reading of the upper table is represented by x1, and the reading of the following table 7 is represented by y1. The gauge reading is represented by x2, the lower gauge reading is represented by y2, and this time interval is represented by t1; then repeat the reading according to the set interval time until the predetermined experimental time is reached;

依次类推，则可得到各个测量时间点的蠕变应变，从而得到测量钢索在应力

下的蠕变应变曲线，其中A为测量钢索的横截面积，F为荷载。Taking the initial time point as 0, the creep strain at time point t1 is:

By analogy, the creep strain at each measurement time point can be obtained, so that the stress of the measured steel cable can be obtained.

The creep-strain curve below, where A is the cross-sectional area of the measuring cable and F is the load.

According to another aspect of the present invention, the present invention adopts the following technical scheme:

The method for measuring long-term creep of a steel cable by using the above device on site is characterized in that the marking structure adopts a hinge structure, which can be opened and closed to both sides and clamped, and the method includes the following steps:

(1) Select a suitable part on the measuring wire as the measuring section, and the length of the measuring section is represented by L; put the corresponding mark structure on the head and end of the measuring section of the measuring wire, and align it with the mark on the wire bit;

(2) Connect the two mechanical dial indicators or dial indicators to the appropriate position of the fixing frame through their connecting frame, so that the heads of the two mechanical dial indicators or dial indicators are in vertical contact with the measurement of the marking structure. work site;

(3) Take a certain time after the loading is completed and stabilized as the initial time point, read the readings of the two meters, the reading of the upper table is represented by x1, and the reading of the following table 7 is represented by y1. The gauge reading is represented by x2, the lower gauge reading is represented by y2, and this time interval is represented by t1; then repeat the reading according to the set interval time until the predetermined experimental time is reached;

依次类推，得到各个测量时间点的蠕变应变，从而得到测量钢索在应力

下的蠕变应变曲线，其中A为测量钢索的横截面积，F为荷载。Taking the initial time point as 0, the creep strain at time point t1 is:

By analogy, the creep strain at each measurement time point is obtained, so as to obtain the stress of the measured steel cable

The creep-strain curve below, where A is the cross-sectional area of the measuring cable and F is the load.

To sum up, the device and method for measuring the long-term creep of steel cables provided by the present invention can be used to measure the long-term creep of steel cables for several years to more than ten years, and can also be used for the creep of existing structural steel cables. It has the advantages of simple device, easy implementation, wide application range, long continuous measurement time, built-up structure can be detected, and it can be combined with other devices.

Description of drawings

Fig. 1 is a flow chart of the present invention for measuring long-term creep of a steel cable.

Figure 2 is a schematic diagram of the structure of the device for measuring long-term creep of a steel cable according to the present invention.

FIG. 3 is a schematic structural diagram (including a fixed pulley) of an embodiment of the present invention.

FIG. 4 is a schematic structural diagram of an embodiment of the present invention (without a fixed pulley).

FIG. 5 is a schematic diagram of a marking sleeve in the device for measuring long-term creep of a steel cable according to the present invention.

Detailed ways

Refer to attached drawings. The device for measuring the long-term creep of a steel cable provided by the present invention includes three parts: a loading device, a measuring device and an auxiliary device. The method for measuring the long-term creep of a steel cable proposed by the present invention also relies on this device. The general process is shown in Figure 1, which includes measuring the cross-sectional area, arranging the experiment, completing the loading, reading the data, and processing the data, and finally the creep is obtained. performance and regularity.

As shown in Figure 2-5, the loading device is used to fix and load the creep specimen, the measuring device is used to mark and measure the displacement of the creep specimen, and the auxiliary device is used to fix the measuring instrument. The magnetic gauge seat on the rigid fixing frame of the auxiliary device is used to fix the gauge of the measuring device. The gauge measures the displacement of the two marking sleeves fixed at both ends of the measuring section of the test piece, so as to obtain the elongation of the measuring section of the test piece for The data is analyzed and processed to finally obtain the creep performance and development law of the specimen.

The loading device includes a loading fixed frame 1 , a fixed pulley 2 (optional), and a load 4 for the treatment section at the lower end of the creep specimen 3 . Wherein, the fixing frame 1 is provided with a structure for fixing the upper end 31 of the test piece 3 , such as a hook, a ring, a clamp and the like.

The upper end 31 of the test piece 3 is fixedly connected to the loading fixture 1 , and the lower end processing section 32 refers to making the lower end of the test piece a port that can hang heavy objects for hanging the load 4 . Both the upper and lower ends should be firm and stable.

The measuring device includes an upper marking sleeve 6 , a lower marking sleeve 7 , an upper gauge 8 and a lower gauge 9 .

The auxiliary device includes a rigid fixing frame 5 , an upper magnetic watch seat 10 , and a lower magnetic watch seat 11 .

As shown in FIG. 5 , the marking sleeves 6 and 7 are rigid members composed of two parts: the clamping part 12 and the horizontal plate 13 . The inner holes of the sleeves 6 and 7 cover the test piece, and are clamped and fixed at the marked point of the test piece 3 by pressing the clamping part. The horizontal plate 13 is perpendicular to the axial direction of the specimen, and should have a large area and a flat surface.

Combined with Figure 3 and Figure 4, the specific methods and steps for measuring long-term creep of steel cables are as follows:

a. Cut out a section of steel cable 3 with the same specification and standard as the creep measurement specimen, measure its weight and length, and then calculate the actual cross-sectional area of the steel cable according to the material density, which is represented by A;

b. The upper end of the creep measurement specimen is fixed and vertically suspended on the fixing frame 1, and the lower end of the specimen is made into a port that can hang heavy objects (such as bending into a circle, and setting a hook) and locking it. If the specimen is long and the space is limited, the form shown in Figure 3 is adopted, and the upper end of the specimen is fixed to the middle and lower part of the fixing frame, and then the fixed pulley 2 that is also fixed at the upper end of the fixing frame is wound to the bottom;

c. Select a suitable part on the test piece as the measurement section, and the length of the measurement section is represented by L. Put the corresponding size marking sleeves 6 and 7 on the two marks. The direction of the sleeves 6 and 7 is based on the clamping part outside the measuring section. position alignment. Then squeeze the clamping part to fix the marking sleeves 6 and 7;

d. Suspend a certain mass of weight 4 at the lower end of the specimen for loading, the loading should be kept stable, and then start timing;

e. Adsorb the two magnetic watch bases 10 and 11 to the appropriate positions on the rigid fixing frame 5 , corresponding to the two marking sleeves 6 and 7 . Fix two gauges 8 and 9 with suitable ranges on the cantilevers of the magnetic gauge bases 10 and 11 respectively, and adjust the positions so that the two gauge heads are in vertical contact with the horizontal plates 13 of the marking sleeves 6 and 7;

f. Take 3-5 minutes after the loading is completed and stabilized as the initial time point, read the readings of two meters, the reading of the upper meter 6 is represented by x1, and the reading of the lower meter 7 is represented by y1;

g. Set the reading interval according to your needs, read the readings of two meters after a period of time, the reading of the upper meter is represented by x2, the reading of the lower meter is represented by y2, and the time interval is represented by t1; then repeat the reading according to the set time interval, until the scheduled experimental time is reached;

依次类推，则可得到各个测量时间点的蠕变应变，从而得到试件在应力

下的蠕变应变曲线。根据蠕变应变曲线则可以归纳得到该钢索的蠕变性能与发展规律。Taking the initial time point as 0, the creep strain at time point t1 is:

By analogy, the creep strain at each measurement time point can be obtained, so that the stress of the specimen can be obtained.

The creep strain curve below. According to the creep strain curve, the creep performance and development law of the steel cable can be summarized.

If the steel cable of the completed structure is measured, since the two ends of the steel cable are fixed and subjected to force, the above loading device is not required, and the marking sleeve is changed to a hinge-type deployable structure. fixed at the mark.

From the above, the present invention provides an experimental device and method for measuring the long-term creep of steel cables, which can be used for creep experiments for several years to more than ten years, and can also be used for steel cables that have been constructed. The cable creep monitoring supplements and improves the method of steel cable creep measurement in some cases. It has the advantages of simple device, easy implementation, wide application range, long continuous measurement time, built-up structure can be detected, and it can be combined with other devices.

The above description of the drawings and the specific implementation methods and steps describe the content of the present invention. However, it should be understood that the present invention is not limited to specific materials, dimensions and partial structures. When other persons make certain modifications and variations to the present invention, if these modifications and variations are within the scope of the claims of the present invention and its equivalent technology within the scope of protection of the present invention.

Claims (8)

1. A device for measuring long-term creep of a steel cable is characterized by comprising a measuring device for marking a creep test piece and measuring displacement; auxiliary means for fixing;

the measuring device comprises two marking structures and two mechanical dial indicators or dial indicators, wherein each marking structure is provided with a structure connected with the steel cable, and each marking structure is provided with a part capable of aligning with a marking position on the steel cable and a measuring working part corresponding to the mechanical dial indicator or the dial indicator;

the auxiliary device is provided with a fixing device of the mechanical dial indicator or the dial indicator, so that the mechanical dial indicator or the dial indicator can be stably positioned at a measuring position to measure the displacement of a measuring working position.

2. The device for measuring long-term creep of steel cable according to claim 1, wherein the marking structure is a sleeve, the sleeve is provided with a sleeve horizontal top plate for aligning the marking position on the steel cable and serving as a measuring working position corresponding to the mechanical dial indicator or the dial indicator, and a part which can be clamped by the sleeve part of the sleeve is used as a structure connected with the steel cable.

3. A device for measuring long term creep of a steel cord as claimed in claim 1 or 2 wherein said marking means is of hinge construction allowing the clamping to be opened and closed to both sides.

4. The device for measuring long-term creep of steel cable according to claim 1, wherein said auxiliary device comprises a fixing frame and a connecting frame of a mechanical dial indicator or a dial indicator, said connecting frame is connected with the fixing frame.

5. The apparatus for measuring long-term creep of a steel cable according to claim 1, wherein said connecting frame is connected to said fixing frame by a magnet, and the position of said connecting frame can be arbitrarily adjusted and fixed.

6. The apparatus for measuring long-term creep of a steel cable according to claim 1, wherein a fixed pulley of the steel cable is provided on the top of the fixed frame.

7. A method for measuring long term creep in a steel cord in a laboratory using the apparatus of claim 1, comprising the steps of:

(1) fixing one end of a creep measurement steel cable on the fixing frame, selecting a proper part on the measurement steel cable as a measurement section, and expressing the length of the measurement section by L; sleeving the head end and the tail end of a measuring section of the measuring steel cable with corresponding mark structures, and aligning the mark structures to mark positions on the steel cable; the other end of the measuring steel cable is connected with a balance weight;

(2) connecting the two mechanical dial indicators or the dial indicator at a proper position of the fixing frame through the connecting frame of the two mechanical dial indicators or the dial indicator, so that the gauge heads of the two mechanical dial indicators or the dial indicator are vertically contacted with the measuring working part of the marking structure;

(3) taking a certain time after the completion of the loading and stabilizing as an initial time point, reading two meter readings, wherein the reading of the upper meter is represented by x1, the reading of the lower meter is represented by y1, the reading of the two meters is later read according to the reading interval time, the reading of the upper meter is represented by x2, the reading of the lower meter is represented by y2, and the time interval is represented by t 1; then repeating the reading at set intervals until a predetermined experimental time is reached;

with an initial time point of 0, the creep strain at time t1 is:

by analogy, the creep strain of each measurement time point can be obtained, and the stress of the steel cable can be measured

Creep strain curve, where A is the cross-sectional area of the steel cord measured and F is the load.

8. Method for measuring long-term creep of a steel cable in situ by means of the device according to claim 1, characterized in that the marking means are hinge means allowing the clamping to be opened and closed on both sides, the method comprising the following steps:

(1) selecting a proper part on the measuring steel cable as a measuring section, wherein the length of the measuring section is represented by L; sleeving the head end and the tail end of a measuring section of the measuring steel cable with corresponding mark structures, and aligning the mark structures to mark positions on the steel cable;

(2) connecting the two mechanical dial indicators or the dial indicator at a proper position of the fixing frame through the connecting frame of the two mechanical dial indicators or the dial indicator, so that the gauge heads of the two mechanical dial indicators or the dial indicator are vertically contacted with the measuring working part of the marking structure;

(3) taking a certain time after the completion of the loading and stabilizing as an initial time point, reading two meter readings, wherein the reading of the upper meter is represented by x1, the reading of the lower meter is represented by y1, the reading of the two meters is later read according to the reading interval time, the reading of the upper meter is represented by x2, the reading of the lower meter is represented by y2, and the time interval is represented by t 1; then repeating the reading at set intervals until a predetermined experimental time is reached;

with an initial time point of 0, the creep strain at time t1 is:

analogizing in turn to obtain creep strain of each measurement time point, thereby obtaining the stress of the measured steel cable

Creep strain curve, where A is the cross-sectional area of the steel cord measured and F is the load.

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