CN112146980B - System and method for judging initial tension force and pressure stabilizing time of prestressed steel strand - Google Patents
System and method for judging initial tension force and pressure stabilizing time of prestressed steel strand Download PDFInfo
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- 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
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- 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
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Abstract
The invention discloses a system and a method for judging initial tension force and voltage stabilization time of a prestressed steel strand, wherein a curve of the change of initial tension load and voltage stabilization time along with the length of the steel strand is drawn through a test for testing the change of the initial tension load and the voltage stabilization time under different lengths of the steel strand; analyzing the influence rule of the length of the steel strand on the initial tensioning load and the voltage stabilization time, and performing data fitting regression on the test curve to respectively obtain a mathematical regression model of the length of the steel strand, the initial tensioning load and the length of the steel strand and the voltage stabilization time. Can be according to the accurate judgement steel strand initial tension load of length and steady voltage time of tensile steel strand through this model, be favorable to improving prestressing force steel strand tension quality, the practicality is strong, improves the engineering quality of actual bridge.
Description
Technical Field
The invention relates to a system and a method for judging initial tension and voltage stabilization time of a prestressed steel strand.
Background
Under the drive of rapid development of domestic economy, bridge construction also enters a rapid development stage. The prestressed concrete bridge structure is widely popularized in the field of highway and railway bridge construction due to good service performance and superior crossing capacity. As prestressed bridges have been developed, various problems have been discovered. According to research, the technical specification of highway, bridge and culvert construction (JTG/TFSO-2011) stipulates that: in order to effectively ensure that the tensioning construction quality of the prestressed steel strands with different lengths meets requirements and avoid effective prestress loss, the initial tensioning load and the pressure stabilizing time need to be effectively controlled. The research for the initial tension load and the pressure stabilizing time of the ultra-long strand at home and abroad is less, the research result is only limited to the steel strand test in specific engineering, a unified calculation mode is not formed, and the initial tension load and the pressure stabilizing time have a very key influence on the prestress loss of the bridge in the operation period, so that the research for the initial tension load and the pressure stabilizing time of the prestressed steel strands under different lengths is particularly important.
The inventor finds that the research on initial tension load and pressure stabilizing time of the prestressed steel strand is blank at present and needs to be further researched.
Disclosure of Invention
In order to solve the problems in the prior art, the invention discloses a system and a method for judging the initial tension force and the voltage stabilization time of a prestressed steel strand, and provides a test method for carrying out the research on the initial tension load judgment and the voltage stabilization time of the prestressed steel strand of a beam body.
The method for judging the initial tensioning load and testing the pressure stabilizing time of the prestressed steel strand is simple, convenient and quick, has accurate test data, does not influence the tensioning construction process, does not damage the steel strand and is not limited by a construction site. The system and the method provide important basis for initial tension load and voltage stabilization time judgment of the prestressed steel strand.
The invention aims to provide a system for judging initial tensioning load and voltage stabilization time of a prestressed steel strand, which can be applied to research on initial tensioning load and voltage stabilization time of steel strands with different lengths so as to guide tensioning construction of the steel strands with different lengths and effectively improve the quality of the prestressed tensioning construction.
In order to achieve the first object, the present invention adopts the following technical means:
the invention provides a system for testing initial tension load and pressure stabilizing time of a prestressed steel strand, which comprises a tension jack, a feed-through pressure sensor, a working anchor, a limiting plate, a tool anchor and a high-precision displacement meter,
the two tensioning jacks respectively apply certain tensioning force to two ends of the steel strand extending out of the beam body, and a working anchor and a limiting plate are arranged between the tensioning jacks and the beam body;
the feed-through pressure sensor is arranged on a steel strand extending out of the beam body, is positioned between the tensioning end working anchor and the tensioning jack and is used for measuring tensioning load; the high-precision displacement meter is arranged on the tensioning jack and used for testing the elongation of the steel strand in the tensioning process of the prestressed steel strand.
The method comprises the steps of testing the tension force and the elongation in the tensioning process, drawing a tension force-elongation relation curve according to a test result and comparing the curve with a fitting curve; and testing the data of the voltage stabilization time and the tension force, and analyzing the voltage stabilization time to obtain the tension voltage stabilization time under different lengths of the steel strand.
Further, the invention also provides a method for testing initial tension load and voltage stabilization time of the prestressed steel strand, which comprises the following specific operation steps:
(1) installing a pressure sensor: after the steel strand wires are threaded, a pressure sensor is installed under a working anchor, the feed-through pressure sensor is placed between a tool anchor and a jack before the tensioning construction process, steel base plates are placed on two sides of the sensor, and the contact surface of the sensor is guaranteed to be evenly stressed.
(2) Installing a high-precision displacement meter: after the jack is installed, a high-precision displacement meter is installed above the jack, and a thimble of the displacement meter is in contact with a baffle in front of the jack.
(3) Connecting an acquisition instrument: and connecting the acquisition instrument after the installation of the straight-through pressure sensor and the high-precision displacement meter is finished.
(4) And after the installation is finished, tensioning construction is started, graded tensioning is started by using intelligent tensioning equipment, and tensioning force and elongation collection work is started.
(5) Based on the field measured data, a calculation formula for judging initial tensioning loads of prestressed steel bundles with different lengths in actual engineering is provided.
Further, in the method, the quantitative relation between the length of the prestressed steel strand and the initial tensioning load is determined in the step (5), and the linear regression fitting is performed on the test data by taking the length of the steel strand as an independent variable. And determining the value range of the initial tension of different lengths of the steel strand by taking the upper and lower limit values of the 90% guarantee rate of the fitting formula.
Furthermore, the quantitative relation between the length of the prestressed steel strand and the load-holding and voltage-stabilizing time is determined, and linear regression fitting is carried out on the voltage-stabilizing time by taking the length of the steel strand as an independent variable. And determining the voltage stabilization time value range of different steel strand lengths by taking the upper and lower limit values of the 90% guarantee rate of the fitting formula of the steel strand lengths and the voltage stabilization time.
Compared with the prior art, the invention has the beneficial effects that:
the method for testing the prestress and the elongation under the anchor is simple, convenient and quick, has accurate test data, does not influence the tensioning construction process, does not damage the beam body and is not limited by the construction site.
The test system and the test method provide important scientific research basis for researching the initial tension force and the pressure stabilizing time of the prestressed steel strands, and the content of the invention can determine the initial tension load and the pressure stabilizing time of the prestressed steel strands with different lengths so as to guide the actual tension construction process in a bridge and effectively improve the prestressed tension construction quality.
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The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic view of the overall connection of a tensioning system;
FIG. 2 is a schematic view of a high precision displacement gauge mounting;
FIG. 3(a) is a tension load test curve of No. 1 beam prestressing tendons;
FIG. 3(b) is a No. 2 beam prestress tendon tension load test curve;
FIG. 3(c) is a No. 3 beam prestressing tendons tensile load test curve;
FIG. 4(a) is a No. 1 prestressing tendon load-sustaining time curve;
FIG. 4(b) is the load sustaining time curve of No. 2 prestressing tendons;
FIG. 4(c) is the holding load time curve of No. 3 tendon;
FIG. 5 shows the fitting result of the length of the steel strand and the initial tension load;
FIG. 6 shows the fitting result of the length of the steel strand and the voltage stabilization time;
in the figure: 1 is a beam body; 2 is a prestressed steel strand; 3 is a working anchor; 4, a limiting plate; 5 is a jack; 6 is a pressure sensor; 7 is a tool anchor; 8, a high-precision displacement meter; and 9 is a displacement meter baffle.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As introduced in the background art, research shows that the research on initial tension load and voltage stabilization time of the ultra-long beam is less at home and abroad, and research results are only limited to steel strand testing in specific engineering, and a unified calculation mode is not formed. The inventor finds that the research on the initial tension load and the pressure stabilizing rule of the prestressed steel strands with different lengths is blank at present and needs to be further researched.
The embodiment provides a system and a method for judging initial tensioning load and pressure stabilizing time of a prestressed steel strand, wherein the system is shown in fig. 1 and fig. 2 and comprises a tensioning jack 5, a feed-through pressure sensor 6, a working anchor 3, a limiting plate 4, a tool anchor 7 and a displacement meter 8; the two tensioning jacks 5 respectively apply certain tensioning force to two ends of the prestressed steel strand 2 extending out of the beam body, a working anchor 3 and a limiting plate 4 are arranged between the front end of the tensioning jack 5 and the beam body, and a tool anchor 7 is arranged at the rear end of the tensioning jack 5; the straight-through pressure sensor 6 is arranged on a steel strand extending out of the beam body, is positioned between the tensioning end tool anchor 7 and the tensioning jack 5, and is used for measuring tensioning load; and the displacement meter 8 is arranged on the tensioning jack 5 and used for testing the elongation of the steel strand in the tensioning process of the prestressed steel strand, and the cross-core pressure sensor and the displacement meter are connected with the acquisition instrument after installation is completed. Steel base plates are arranged between the feed-through pressure sensor and the jack and between the feed-through pressure sensor and the tool anchor, so that the front contact surface and the rear contact surface of the pressure sensor are uniformly contacted with the beam body and the anchorage, and the accuracy of the prestress test data under the anchor is ensured. And the thimble of the displacement meter is contacted with a baffle in front of the tensioning jack.
According to the method, initial tension load and voltage stabilization time test data of prestressed steel strands with different lengths are combined to draw a tension load P relation curve of the elongation length delta L-of the steel strands and a tension load P relation curve of the voltage stabilization time T-of the steel strands; firstly, summarizing the rule of the length to the initial tensioning load and the voltage stabilization time, analyzing the influence of the length of the prestressed steel strand on the initial tensioning load and the voltage stabilization time, finally performing data fitting regression on the initial tensioning load and the voltage stabilization time of the steel strands with different lengths, and finally respectively obtaining the initial tensioning load P of the length L-of the steel strand0And a mathematical regression model of the length L of the steel strand and the voltage stabilization time T.
The principle of initial tension load and voltage stabilization time test is as follows: the first stage of tensioning in the tensioning construction process of the post-tensioning method prestressed steel strand is called as initial tensioning, and the stage has the function of eliminating the inelastic deformation of the prestressed steel strand and is used as a starting state for measuring the elongation of the steel strand. In the elastic deformation process of the steel bundle, the tension and the elongation are in one-to-one correspondence, so that a tension-elongation relation curve can be drawn. Considering the operability of a field test, in the prestress tensioning process, a single-end tensioning mode is adopted, and the accumulated displacement of the jack piston is equivalent to the elongation of the steel strand. For a relation curve of the tension force and the elongation, the rear half part of the relation curve is similar to a straight line, namely, the relaxation of the strand penetration and the slippage factor of the anchorage device are proved to be eliminated, the stress of the steel strand at the moment becomes a direct proportion, the straight line is extended towards the original point direction, the force value corresponding to the separation point of the straight line and the actually measured curve is the starting point of the initial elastic deformation of the prestressed steel strand, namely the initial tension force of the prestressed steel strand, and the initial tension load is identified at the moment; in the process of stabilizing the pressure of the ultra-long bundle of steel strands, the stress of the steel strands at the position of the anchoring end is gradually transmitted to the midspan part, and finally the stress of the whole bundle of steel strands is uniform, so that the stress of the steel strands at the position under the anchor in the process of stabilizing the pressure is tested, and when the tension force tends to be stable or does not change along with the time, the load-holding and pressure-stabilizing time is obtained.
The method for judging the initial tension load comprises the following steps:
setting the tensile force percentage P as [ F/F ═ Fcon]X 100% (F: each tension, F)con: design of tension control force), the elongation of the ultra-long prestressed steel strand measured in the test process is delta L. From the experimental principle, it can be seen that the second half of the P- Δ L relationship for each test bundle is approximately a straight line, and the stress and strain are proportional. Therefore, the test data of the latter half part of the curve is subjected to linear fitting, and the separation critical point of the fitted straight line and the curve is found to be the initial tensile stress.
Taking the test data of the pressure sensor as a horizontal coordinate and the elongation of the steel strand at each tension level as a vertical coordinate, drawing a tension-elongation relation curve according to the test result and comparing the curve with a fitting curve to find out an initial tension load point; FIGS. 3(a), 3(b) and 3(c) are graphs for testing tension load of partially prestressed tendons;
taking the length L of the steel strand as a horizontal coordinate and initially tensioning a load P0And drawing a curve for coordinates to obtain a model of the change of the initial tension load along with the length of the steel strand (figure 5).
Further establishing a pre-stress length L-an initial tensile force P0The mathematical regression model has the expression:
P0＝0.0929L+9.4674 (1)
in the formula: p0Represents the initial tension load of the steel strand, unit: kN; length of the L-shaped prestressed steel strand, unit: and m is selected.
Further, by taking the upper and lower limit ranges of the 90% assurance rate of the formula (1), fig. 5 shows that most of the actual test results are within the limit ranges, and only a small portion of the data is outside the limit ranges, but basically approaches to the 90% limit ranges.
The voltage stabilization time judgment method comprises the following steps:
measuring the voltage stabilization time of the prestressed steel strands in the tensioning process, namely the time from tensioning each stage of the prestressed steel strands to the stabilization of the prestress, wherein fig. 4(a), 4(b) and 4(c) are partial prestressed tendon load-holding time curves;
in order to determine the quantitative relation between the length of the prestressed steel strand and the load-holding and voltage-stabilizing time, linear regression fitting is respectively carried out on the measured data, the length L of the steel strand is taken as a horizontal coordinate, the load-holding and voltage-stabilizing time T is taken as a vertical coordinate, and a model (figure 6) of the voltage-stabilizing time along with the length of the steel strand is obtained;
establishing a mathematical regression model of the prestress length L-voltage stabilization time T, wherein the expression is as follows:
T＝0.1212L+9.3302 (2)
in the formula: t represents the load-bearing voltage-stabilizing time, and the unit is: min; l represents the prestressed strand length, unit: and m is selected.
By taking the range of the upper limit value and the lower limit value of the 90% guarantee rate of the formula (2), as can be seen from fig. 6, most of statistical data are located in the range of the 90% limit value, and the fitting results are compared, the linear fitting effect of the method for judging the load holding time by adopting the tension change rate is better, and the method is proved to be more accurate in determining the correlation between the length of the prestressed steel beam and the load holding and pressure stabilizing time.
The technical scheme is utilized to judge the pull-off detection, and the specific method comprises the following steps:
step 1, selecting prestressed tendons with different lengths for testing, and installing instrument equipment in sequence; installing a working anchor → a limiting plate → a tensioning jack → a feed-through pressure sensor → a tool anchor → a high-precision displacement meter;
step 3, in the tensioning process of the ultra-long prestressed steel beam, tensioning force of the active end is graded for tensioning, and the tensioning process is earlier (50% sigma)conWithin), the tension grades are divided densely, 2.5% of each grade is increased progressively, when the tension process is in the middle and later stages, 10% of each grade can be increased progressively, and the initial tension load is finally determined.
Step 4, voltage stabilization time judgment: when the design tension control load is reached to 100 percent sigmaconAt this time, willAnd controlling the stretched oil pump to pause and start to hold load and stabilize pressure. And in the pressure stabilizing process, reading the value of the pressure sensor at intervals of 2-3 minutes until the pressure value is stable.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles defined in the embodiments may be implemented in other embodiments without the use of the specific details or with the use of an extensive range of techniques, the details of which have not been set forth herein in order to avoid obscuring the underlying concepts of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and features disclosed herein.
Claims (7)
1. A method for testing initial tension load and pressure stabilizing time of prestressed steel strands is characterized in that,
installing a prestressed steel strand initial tensioning load and voltage stabilization time testing system, wherein the prestressed steel strand initial tensioning load and voltage stabilization time testing system comprises a tensioning jack, a feed-through pressure sensor, a working anchor, a limiting plate, a tool anchor and a displacement meter;
the tensioning jacks comprise two tensioning jacks, certain tensioning forces are respectively applied to two ends of the steel strand extending out of the beam body, a working anchor and a limiting plate are arranged between the front ends of the tensioning jacks and the beam body, and tool anchors are arranged at the rear ends of the tensioning jacks; the feed-through pressure sensor is arranged on a steel strand extending out of the beam body, is positioned between the tensioning end tool anchor and the tensioning jack and is used for measuring tensioning load; the displacement meter is arranged on the tensioning jack and used for testing the elongation of the steel strand in the tensioning process of the prestressed steel strand;
carrying out a change test of the initial tensioning load and the pressure stabilizing time, and drawing a change curve of the initial tensioning load and the pressure stabilizing time along with the length of the prestressed steel strand;
summarizing the rule of the length of the steel strand on the initial tensioning load, and analyzing the influence of the length change of the prestressed steel strand on the initial tensioning load to obtain a mathematical regression model of the length of the steel strand and the initial tensioning load;
and summarizing the rule of the length of the steel strand on the voltage stabilization time, and analyzing the influence of the length change of the prestressed steel strand on the voltage stabilization time to obtain a mathematical regression model of the length of the steel strand and the voltage stabilization time.
2. The method for testing initial tension load and voltage stabilization time of the prestressed steel strand as claimed in claim 1, wherein the method for installing the system for testing initial tension load and voltage stabilization time of the prestressed steel strand comprises the following steps:
(1) installing a pressure sensor: before the tensioning construction process, the feed-through pressure sensor is placed between the tool anchor and the jack, and steel base plates are placed on two sides of the feed-through pressure sensor to ensure that the contact surface of the sensor is uniformly stressed;
(2) mounting a displacement meter: after the jack is installed, a displacement meter is installed above the jack, and a thimble of the displacement meter is in contact with a baffle in front of the jack;
(3) connecting an acquisition instrument: connecting an acquisition instrument after the installation of the straight-through pressure sensor and the high-precision displacement meter is finished;
(4) and after the installation is finished, tensioning construction is started, graded tensioning is started by using intelligent tensioning equipment, and tensioning force and elongation collection work is started.
3. The method for testing initial tension load and voltage stabilization time of the prestressed steel strand as recited in claim 1, wherein linear regression fitting is performed on the test data by taking the length of the steel strand as an independent variable, and the value range of the initial tension of different lengths of the steel strand is determined by taking the upper and lower limit values of the 90% guarantee rate of a fitting formula.
4. The method for testing initial tension load and voltage stabilization time of prestressed steel strands according to claim 1, wherein a quantitative relationship between the length of the prestressed steel strands and the load-holding and voltage stabilization time is defined, linear regression fitting is performed on the voltage stabilization time by taking the length of the steel strands as an independent variable, and the upper and lower limit values of the 90% guarantee rate of a fitting formula of the length of the steel strands and the voltage stabilization time are taken to determine the voltage stabilization time value ranges of different lengths of the steel strands.
5. The method for testing initial tension load and pressure stabilizing time of the prestressed steel strand as recited in claim 1, wherein steel tie plates are placed between the feed-through pressure sensor and the jack, and between the feed-through pressure sensor and the tool anchor.
6. The method for testing initial tension load and pressure stabilizing time of the prestressed steel strand as recited in claim 1, wherein the through pressure sensor and the displacement gauge are connected with a collecting instrument after installation.
7. The method for testing initial tension load and pressure stabilizing time of prestressed steel strands according to claim 1, wherein the thimble of the displacement gauge is in contact with a baffle in front of the tension jack.
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| CN114414381B (en) * | 2021-12-04 | 2024-09-10 | 中铁九局集团第五工程有限公司 | Intelligent bridge tensioning test device |
| CN114319114B (en) * | 2021-12-14 | 2023-11-17 | 中交二公局第一工程有限公司 | Improved stay cable equivalent tensioning construction method based on deformation control |
| CN114428015B (en) * | 2022-01-06 | 2024-02-06 | 中国建筑第八工程局有限公司 | Device and method for testing prestress loss of carbon fiber reinforced composite bar |
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| CN112146980A (en) | 2020-12-29 |
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