CN114441074A - Effective prestress determination method for prestressed concrete beam based on acoustic emission monitoring - Google Patents
Effective prestress determination method for prestressed concrete beam based on acoustic emission monitoring Download PDFInfo
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- CN114441074A CN114441074A CN202111633395.5A CN202111633395A CN114441074A CN 114441074 A CN114441074 A CN 114441074A CN 202111633395 A CN202111633395 A CN 202111633395A CN 114441074 A CN114441074 A CN 114441074A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
- G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
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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
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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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- 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
- G01N2203/0001—Type of application of the stress
- G01N2203/0003—Steady
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- 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
- G01N2203/0019—Compressive
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- 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
- G01N2203/0067—Fracture or rupture
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- 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
- G01N2203/0658—Indicating or recording means; Sensing means using acoustic or ultrasonic detectors
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- 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
- G01N2203/0676—Force, weight, load, energy, speed or acceleration
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Abstract
The invention discloses a method for determining effective prestress of a prestressed concrete beam based on acoustic emission monitoring, wherein an acoustic emission technology is sensitive to the generation and development of micro cracks on the surface or in the prestressed concrete beam, a bending test is carried out on the prestressed concrete beam, an acoustic emission sensor is connected with an acoustic emission acquisition device, the acoustic emission sensor is adhered to the side surface and the bottom surface of the prestressed concrete beam, and the acoustic emission sensor is vertical to the surface of the prestressed concrete beam; applying a load to the prestressed concrete beam, and recording the load when the prestressed concrete beam starts to crack from the inside, namely the crack load F of the prestressed concrete beamcr(ii) a From the recorded cracking load FcrCalculating the cracking bending moment M of the prestressed concrete beamcrFinally determining the effective pre-pressureStress sigmapcThe size of (2). The method is simple to operate, and can accurately determine the effective pre-stress of the prestressed concrete beam.
Description
Technical Field
The invention relates to the technical field of acoustic emission monitoring, in particular to a method for determining effective prestress of a prestressed concrete beam based on acoustic emission monitoring.
Background
The prestressed reinforcement is an important stressed member of the prestressed concrete beam, and the tensile stress in the prestressed reinforcement can cause prestress loss due to the material performance, the anchoring of a tension process and the like in the processes of manufacturing, transporting, installing and using the prestressed concrete beam.
The key for evaluating the working performance of the prestressed concrete beam is to evaluate and determine the actual effective prestress of the prestressed reinforcement. The effective pre-stress of the prestressed concrete beam is determined, and the method is of great importance to the design of the prestressed concrete bridge structure and the evaluation of the bearing capacity.
In the prior art, the method of firstly loading to fracture the lower edge of the midspan section, then unloading and then reloading is proposed to calculate the pressure-eliminating bending moment; however, the method needs to perform secondary loading, and the concrete beam often cracks from the inside and then expands to the surface, so that the method cannot accurately judge the concrete cracking time, and further cannot obtain accurate pressure relief bending moment and cracking bending moment.
Therefore, a simple, fast and accurate method for determining the effective pre-stress of the prestressed concrete beam is urgently needed.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for determining the effective pre-stress of a prestressed concrete beam based on acoustic emission monitoring, which is convenient and fast to operate and can accurately determine the effective pre-stress of the prestressed concrete beam.
In order to solve the technical problem, the invention provides a method for determining the effective prestress of a prestressed concrete beam based on acoustic emission monitoring, which comprises the following steps:
step 1) adhering acoustic emission sensors to the side surface and the bottom surface of the prestressed concrete beam, wherein the acoustic emission sensors are vertical to the surface of the prestressed concrete beam;
step 2) applying a load to the prestressed concrete beam, and recording the load when the prestressed concrete beam starts to crack from the inside, namely the crack load F of the prestressed concrete beamcr；
Step 3) from the recorded cracking load FcrCalculating the cracking bending moment M of the prestressed concrete beamcrFinally determining the effective pre-stress sigmapcThe size of (2).
Further, in the step 2), a load is applied to the prestressed concrete beam, an acoustic emission ringing count time scatter diagram and/or an acoustic emission energy time scatter diagram are recorded by an acoustic emission collecting device, a load time curve is recorded at the same time, and a time node of the prestressed concrete beam starting to crack from the inside is determined according to the recorded data.
Further, setting an acoustic emission ringing count threshold value and/or an acoustic emission energy threshold value, judging that the prestressed concrete beam starts cracking at the time node when the acoustic emission ringing count is larger than the acoustic emission ringing count threshold value and/or the acoustic emission energy is larger than the acoustic emission energy threshold value, and then obtaining a cracking load F at the time node by using a load time curvecr。
Furthermore, a prestressed concrete beam is placed on the support, a distribution beam is arranged in the middle of the top surface of the prestressed concrete beam, and the distribution beam is matched with the oil cylinder to apply load to the prestressed concrete beam.
Furthermore, vaseline is coated at the position where the acoustic emission sensor is adhered to the prestressed concrete beam.
Further, the effective pre-stress σpcObtained by the following formula:
in the formula, W0To convert the elastic resisting moment of the tension edge of the section; gamma is the conversion section resistance moment plasticity influence coefficient; f. oftkThe standard value of the tensile strength of the concrete is obtained.
Furthermore, the converted section resists the moment plastic influence coefficient gamma and the cracking bending moment M of the prestressed concrete beamcrObtained by the following formula:
Mcr＝k*Fcr*l
in the formula, h is the height of the cross section, when h is 400mm, h is taken to be 400mm, and when h is more than 400mm, h is taken to be 1600 mm; gamma raymThe basic value of the cross section resistance moment plastic influence coefficient is converted; fcrLoad of cracking F for prestressed concrete beamcr(ii) a l is the distance from the support to the load action point; when the beam is a four-point bending beam, k is 1; when the beam is a three-point bending beam, k is 0.5.
The invention has the beneficial effects that:
when the interior of the prestressed concrete beam is transmitted and broken, strain energy is released and is transmitted in the form of elastic waves, the elastic waves are transmitted to the surface of the structure and are received by the acoustic emission system, then acoustic emission signals are analyzed, and therefore the time and the cracking load when the interior of the prestressed concrete beam starts to crack are determined.
The method for determining the effective pre-stress of the prestressed concrete beam based on acoustic emission monitoring can accurately determine the crack initiation load of the prestressed concrete beam, and further accurately determine the effective pre-stress sigma of the prestressed concrete beampcThe size of (2). By means of a determined effective pre-stress sigmapcThe actual prestress loss of the prestressed concrete beam can be estimated.
Drawings
FIG. 1 is a schematic view of an acoustic emission testing apparatus for a prestressed concrete beam according to the present invention;
FIG. 2 is a four-point bending test load time chart of the prestressed concrete beam of the present invention;
FIG. 3 is an acoustic emission ringing count determination crack load scatter plot of the present invention;
FIG. 4 is a graph of the acoustic emission energy determination of crack load scatter for the present invention.
Detailed Description
The present invention is further described below in conjunction with the drawings and the embodiments so that those skilled in the art can better understand the present invention and can carry out the present invention, but the embodiments are not to be construed as limiting the present invention.
Referring to fig. 1, in an embodiment of the method for determining the effective pre-stress of the prestressed concrete beam based on acoustic emission monitoring, the prestressed concrete beam 2 is placed on a support, a distribution beam 4 is arranged in the middle of the top surface of the prestressed concrete beam, the distribution beam and an oil cylinder are matched to apply a load to the prestressed concrete beam, an acoustic emission sensor 1 is connected with an acoustic emission acquisition device 3, the acoustic emission sensors are adhered to the surface of the prestressed concrete beam for six, four of the acoustic emission sensors are positioned on the surface of the prestressed concrete beam, the other two acoustic emission sensors are positioned on the surface of the bottom of the prestressed concrete beam, the acoustic emission sensors are perpendicular to the surface of the prestressed concrete beam, and vaseline is coated at the adhering position of the acoustic emission sensors and the prestressed concrete beam to serve as a coupling agent;
and then setting an acoustic emission ringing count threshold value and/or an acoustic emission energy threshold value, wherein the acoustic emission ringing count and/or the acoustic emission energy value are small in the elastic bending stage under the bending condition of the reinforced concrete beam, and the acoustic emission signal is mainly generated by environmental noise and vibration of a loading machine, so that the threshold value only needs to be larger than background noise, and the background noise is collected before formal loading. And when the acoustic emission ringing count is greater than the acoustic emission ringing count threshold value and/or the acoustic emission energy is greater than the acoustic emission energy threshold value, judging that the prestressed concrete beam starts to crack, and then obtaining the cracking load at the moment by using a load time curve. Namely the cracking load F of the prestressed concrete beamcr. Based on the ringing count time scatter diagram and the energy time scatter diagram of the acoustic emission technology, the cracking time of the concrete can be accurately determined, and then the cracking load value of the prestressed concrete beam can be accurately determined through the load value corresponding to the time.
After setting is finished, a load can be applied to the prestressed concrete beam, an acoustic emission acquisition device is used for recording an acoustic emission ringing count time scatter diagram and/or an acoustic emission energy time scatter diagram, and a load time curve is recorded at the same time as shown in figures 3 and 4 and shown in figure 2; when the prestressed concrete beam starts to crack from the inside, namely the threshold value is triggered, the time node of the prestressed concrete beam starting to crack from the inside can be determined, and the corresponding load under the time node is found on the load time curve according to the time node, namely the cracking load F of the prestressed concrete beamcr；
Followed by the recorded cracking load FcrCalculating the cracking bending moment M of the prestressed concrete beamcr；
Mcr＝k*Fcr*l
Wherein, FcrLoad of cracking F for prestressed concrete beamcr(ii) a l is the distance from the support to the load action point; the prestressed concrete beam is a four-point bending beam, and k is 1; when the three-point bending beam is adopted, k is 0.5;
according to the cracking bending moment M of the prestressed concrete beamcrCalculating the effective pre-stress sigmapcObtained by the following formula:
in the formula, W0To convert the elastic resisting moment of the tension edge of the section; gamma is the conversion section resistance moment plasticity influence coefficient; f. oftkThe standard value of the tensile strength of the concrete is obtained.
Wherein, the converted section resists the moment plastic influence coefficient gamma and the cracking bending moment M of the prestressed concrete beamcrObtained by the following formula:
in the formula, h is the height of the cross section, when h is 400mm, h is taken to be 400mm, and when h is more than 400mm, h is taken to be 1600 mm; gamma raymIs a basic value of the converted section resistance moment plasticity influence coefficient.
Compared with the prior art, the method can judge the concrete cracking time more accurately, effectively improve the acquisition precision of the cracking load of the prestressed concrete beam, avoid the operation steps of multiple loading tests, and can determine the effective pre-compressive stress of the prestressed concrete beam more simply, conveniently and accurately.
The above embodiments are merely preferred embodiments for fully illustrating the present invention, and the scope of the present invention is not limited thereto. The equivalent substitution or change made by the technical personnel in the technical field on the basis of the invention is all within the protection scope of the invention. The protection scope of the invention is subject to the claims.
Claims (7)
1. A method for determining effective pre-stress of a prestressed concrete beam based on acoustic emission monitoring is characterized by comprising the following steps:
step 1) adhering acoustic emission sensors to the side surface and the bottom surface of the prestressed concrete beam, wherein the acoustic emission sensors are vertical to the surface of the prestressed concrete beam;
step 2) applying a load to the prestressed concrete beam, and recording the load when the prestressed concrete beam starts to crack from the inside, namely the crack load F of the prestressed concrete beamcr；
Step 3) from the recorded cracking load FcrCalculating the cracking bending moment M of the prestressed concrete beamcrFinally determining the effective pre-stress sigmapcThe size of (2).
2. The method for determining the effective pre-stress of the prestressed concrete beam based on acoustic emission monitoring as claimed in claim 1, wherein in step 2), a load is applied to said prestressed concrete beam, an acoustic emission ringing count time scatter diagram and/or an acoustic emission energy time scatter diagram are recorded by using an acoustic emission collecting device, a load time curve is recorded at the same time, and a time node at which the prestressed concrete beam starts to crack from the inside is determined according to the recorded data.
3. The method for determining the effective prestressing of a prestressed concrete beam based on acoustic emission monitoring of claim 2, wherein an acoustic emission ringing count threshold value and/or an acoustic emission energy threshold value is set, and when the acoustic emission ringing count is greater than the acoustic emission ringing count threshold value and/or the acoustic emission energy is greater than the acoustic emission energy threshold value, it is determined that the prestressed concrete beam starts to crack at the time node, and then a crack load F at the time node is obtained by using a load-time curvecr。
4. The method for determining the effective pre-stress of the prestressed concrete beam based on acoustic emission monitoring as claimed in claim 2, wherein the prestressed concrete beam is placed on a support, a distribution beam is arranged in the middle of the top surface of the prestressed concrete beam, and the distribution beam cooperates with the oil cylinder to apply a load to the prestressed concrete beam.
5. The method for determining the effective pre-stress of a prestressed concrete beam based on acoustic emission monitoring as claimed in claim 1, wherein the position where said acoustic emission sensor is attached to said prestressed concrete beam is coated with vaseline.
6. The method of determining the effective pre-stress of a prestressed concrete beam based on acoustic emission monitoring of claim 1, wherein said effective pre-stress σ ispcObtained by the following formula:
in the formula, W0To convert the elastic resisting moment of the tension edge of the section; gamma is the conversion section resistance moment plasticity influence coefficient; f. oftkThe standard value of the tensile strength of the concrete is obtained.
7. The method of claim 1 for determining the effective pre-stress of a prestressed concrete beam based on acoustic emission monitoring, wherein the cross-sectional resistance moment-plasticity influence coefficient γ and the cracking bending moment M of the prestressed concrete beam are convertedcrObtained by the following formula:
MCr＝k*Fcr*l
in the formula, h is the height of the cross section, when h is 400mm, h is taken to be 400mm, and when h is more than 400mm, h is taken to be 1600 mm; gamma raymThe basic value of the cross section resistance moment plastic influence coefficient is converted; fcrLoad of cracking F for prestressed concrete beamcr(ii) a l is the distance from the support to the load action point; when the beam is a four-point bending beam, k is 1; when the beam is a three-point bending beam, k is 0.5.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6391557A (en) * | 1986-10-07 | 1988-04-22 | Onoda Cement Co Ltd | Method for measuring strength and breaking tenacity of concrete structural member on job-site |
| DD284287A5 (en) * | 1988-08-03 | 1990-11-07 | Tu Dresden,Direkt. Forsch.,Dd | METHOD AND ARRANGEMENT FOR THE QUASI DISTORTION-FREE DETERMINATION OF CONCRETE STRENGTH IN SITU |
| US20030145659A1 (en) * | 2001-12-10 | 2003-08-07 | Moe Momayez | Remote structural material evaluation apparatus |
| CN2644558Y (en) * | 2003-09-30 | 2004-09-29 | 杨庆国 | Pre-tension broken line prestressing force concrete component made by mixing tension technology |
-
2021
- 2021-12-29 CN CN202111633395.5A patent/CN114441074A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6391557A (en) * | 1986-10-07 | 1988-04-22 | Onoda Cement Co Ltd | Method for measuring strength and breaking tenacity of concrete structural member on job-site |
| DD284287A5 (en) * | 1988-08-03 | 1990-11-07 | Tu Dresden,Direkt. Forsch.,Dd | METHOD AND ARRANGEMENT FOR THE QUASI DISTORTION-FREE DETERMINATION OF CONCRETE STRENGTH IN SITU |
| US20030145659A1 (en) * | 2001-12-10 | 2003-08-07 | Moe Momayez | Remote structural material evaluation apparatus |
| CN2644558Y (en) * | 2003-09-30 | 2004-09-29 | 杨庆国 | Pre-tension broken line prestressing force concrete component made by mixing tension technology |
Non-Patent Citations (2)
| Title |
|---|
| 范宇恒: "基于声发射技术的混凝土试件弯曲损伤研究", 《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》, pages 21 - 34 * |
| 袁锦根等: "《混凝土结构与砌体结构学习指导》", 中国矿业大学出版社, pages: 253 - 254 * |
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