CN109975118A - A kind of test method for surveying fracture energy of concrete based on four_point bending beam - Google Patents
A kind of test method for surveying fracture energy of concrete based on four_point bending beam Download PDFInfo
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- CN109975118A CN109975118A CN201910266242.8A CN201910266242A CN109975118A CN 109975118 A CN109975118 A CN 109975118A CN 201910266242 A CN201910266242 A CN 201910266242A CN 109975118 A CN109975118 A CN 109975118A
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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
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Abstract
A kind of test method the present invention relates to pipe based on four_point bending beam survey fracture energy of concrete, comprising: installation experimental rig and test specimen, be further applied load test, record test data, calculating energy to failure and etc..This invention ensures that test specimen stress is freely-supported, and according to the test result of applicant, complete load-deflection curves can be obtained when initial seam height is than more than or equal to 0.4, and what International Structure and investigation of materials federation (RILEM) the Fracture Mechanics of Concrete committee (TC-50FMC) were recommended uses three-point bending beam test specimen to survey the initial seam height ratio of energy to failure as 0.5.
Description
Technical field
The present invention relates to a kind of test methods that fracture energy of concrete is surveyed based on four_point bending beam, belong to material mechanical performance
The field of test technology.
Background technique
Currently, the energy to failure of test concrete is mostly based on three-point bending beam test specimen.International Structure is combined with investigation of materials
Meeting (RILEM) the Fracture Mechanics of Concrete committee (TC-50FMC), which gives, surveys fracture energy of concrete based on three-point bending beam test specimen
Standard test method.But from the point of view of the test result of many scholars, the energy to failure of concrete is surveyed using three-point bending beam test specimen
When, the extensions path of pre-formed joint often because big aggregate there are due to there is deflection, and according to the stress of three-point bending beam it is found that
Deflection, which once occurs, in crack will make to split effect of the point simultaneously by moment of flexure and shearing, and the presence sheared will make the extension road in crack
There is bigger deflection in diameter, thus the fracture energy of concrete measured leads to the actual plane of disruption because of the deflection of the extensions path in crack
Product is big compared with area of fracture used when calculating and causes the concrete fracture measured that can reflect that concrete material really supports
The ability of Resisting fractre.
Summary of the invention
The invention solves technical problems to be: the shortcomings that overcoming the prior art, provides a kind of survey based on four_point bending beam and mixes
The method of solidifying soil energy to failure.
In order to solve the above-mentioned technical problem, technical solution proposed by the present invention is: one kind surveying coagulation based on four_point bending beam
The test method of native energy to failure, using four_point bending beam experimental rig, the four_point bending beam experimental rig include loading device,
Pedestal, movable bearing support, hold-down support and two pressure heads being mounted on loading device, the movable bearing support and hold-down support peace
On pedestal；It the described method comprises the following steps:
(1) hold-down support and movable bearing support are installed respectively in two predeterminated positions of pedestal；
(2) there is the test specimen of pre-formed joint to be mounted on hold-down support and movable bearing support bottom, and makes the prefabricated crack
Positioned at the middle of the hold-down support and movable bearing support；The spaning middle section top that displacement meter is fixed on the test specimen is corresponded into institute
State the position in prefabricated crack；
(3) be arranged in below the loading device two pressure heads are pressed on the test specimen, the position of one of pressure head
It sets and is located between hold-down support and prefabricated crack, another pressure head is between movable bearing support and prefabricated crack, two pressures
Head is equal with the distance between the prefabricated crack respectively；
(4) it is further applied load by the loading device to test specimen, it is P, each pressure that the loading device, which applies pressure,
The external load that head applies is P/2, according to the amount of deflection measured when applying pressure, draws load-deflection curves；
Energy to failure G is obtained according to the following formulaF:
In formula, W0For the function that external load is done, δmaxTo measure displacement when the obtained test specimen destroys, WERefer to that function is quasi-
Obtained end segment area is closed, H is height of specimen, a0For pre-formed joint length, t is specimen width, and m is test specimen hold-down support and work
Quality in span scope between dynamic support, g is acceleration of gravity, takes g=9.81m/s2。
Above scheme is further improvement is that the WEExponential function fitting formula are as follows:
Y=Ae-Bx；
Wherein, A, B are fitting constant.
Above scheme is further improvement is that the WEIt can also be obtained by power function fitting.
Above scheme is further improvement is that energy to failure G in the step (4)FIt can also be obtained by RILEM recommended method
Come:In formula, W0For the function that external load is done, δmaxTo measure position when the obtained test specimen destroys
It moves, H is height of specimen, a0For pre-formed joint length, t is specimen width, m span scope between test specimen hold-down support and movable bearing support
Interior quality, g are acceleration of gravity, take g=9.81m/s2, WEFunction done in fracture process, W are focused on certainly for test specimenE=wgS
δmax/2。
It is provided by the invention based on four_point bending beam survey fracture energy of concrete test method, by four_point bending beam test specimen by
Power state aware, span centre crack section are nearby in simple bending section, thus even if crack extensions path because encountering big aggregate
In the presence of and there is a small amount of deflection, will not lead to split point is influenced by shearing, therefore, it can be stated that four_point bending beam test specimen measures
Fracture energy of concrete more can really reflect the ability that concrete material resists fracture compared with three-point bending beam test specimen.The present invention protects
Having demonstrate,proved test specimen stress is freely-supported, and according to the test result of applicant, can be obtained when the high ratio of initial seam is more than or equal to 0.4
To complete load-deflection curves, and International Structure and investigation of materials federation (RILEM) the Fracture Mechanics of Concrete committee
(TC-50FMC) that recommends uses three-point bending beam test specimen to survey the high ratio of initial seam of energy to failure as 0.5.
Detailed description of the invention
The present invention will be further explained below with reference to the attached drawings.
Fig. 1 is the structural schematic diagram of four_point bending beam experimental rig.
Fig. 2 is the structural schematic diagram of movable bearing support.
Fig. 3 is the structural schematic diagram of supporter.
Fig. 4 is the schematic diagram of support connecting plate and the first U-lag.
Fig. 5 is the structural schematic diagram of hold-down support.
Fig. 6 is test specimen stress model.
Fig. 7 is P- δ curve.
Specific embodiment
Embodiment
The test method that fracture energy of concrete is surveyed based on four_point bending beam of the present embodiment, using as shown in Figure 14 points
Bent beam experimental rig, comprising: loading device 1, installation loading device on two pressure heads 2, movable bearing support 8, hold-down support 4 and
Pedestal 5, movable bearing support 8, hold-down support 4 are installed on pedestal 5.It when in use, can be according to the size adjustment activity branch of test specimen 3
The distance between seat 8, hold-down support 4 and two pressure heads 2.Concrete test part 3 is placed on support movable bearing support 8, hold-down support 4
On, it is tested by the load span of the corresponding test specimen of the pressure head 2 of loading device 1.
Specific step is as follows:
(1) hold-down support 4 and movable bearing support 8 are installed respectively in two predeterminated positions of pedestal 5；
(2) there is the test specimen 3 of pre-formed joint to be mounted on fixed branch 4 and movable bearing support 8 bottom, and makes prefabricated crack position
In the middle of hold-down support 4 and movable bearing support 8；Displacement meter 7 is fixed on to the span centre of test specimen by L-type support and Magnetic gauge stand
Section top corresponds to the position in prefabricated crack；
(3) be arranged in below loading device 1 two pressure heads 2 are pressed on test specimen 3, the position difference of one of pressure head
Between hold-down support and prefabricated crack, another pressure head is between movable bearing support and prefabricated crack, two pressure head difference
The distance between prefabricated crack is equal；
(4) be further applied load by loading device 1 to test specimen, the pressure head of loading device correspond to the load span of test specimen into
Row test；It is P that loading device, which applies pressure, and the external load that each pressure head applies is P/2, is scratched according to what is measured when applying pressure
Degree, by drafting load-deflection curves；It should be pointed out that being different from three-point bending beam test specimen surveys fracture energy of concrete, for four
Point bent beam test specimen, the function W that external load is done0And WEThe area that load-amount of deflection (P- δ) curve not surveyed is surrounded, by Fig. 6
Shown in rigid model it is found that load(ing) point amount of deflection δ1=δmax/ 2, so, W0And WEIt should be the face that the P- δ curve of actual measurement is surrounded
Long-pending half, as shown in Figure 7.
The four_point bending beam test specimen of the present embodiment surveys the test of fracture energy of concrete, and it is mixed to be similar to the survey of three-point bending beam test specimen
Solidifying soil energy to failure is equal to the principle that crack extends consumed energy according to external work, by the load-deflection curves surveyed
The fracture energy of concrete that four_point bending beam test specimen measures is obtained, since four_point bending beam test specimen force way and three-point bending beam try
Part is different, therefore different from three-point bending beam test specimen for the calculation formula of four_point bending beam test specimen energy to failure.It is adopted in the present embodiment
Method is influenced with load-amount of deflection (P- δ) the curve tail section for considering not measure,
Energy to failure G is obtained according to the following formulaF:
In formula, W0For the function that external load is done, δmaxTo measure displacement when obtained test specimen destroys, WERefer to that Function Fitting obtains
The end segment area arrived, H are height of specimen, a0For pre-formed joint length, t is specimen width, and m is test specimen hold-down support and activity branch
Quality in span scope between seat, g is acceleration of gravity, takes g=9.81m/s2。
Wherein, WEExponential function fitting formula are as follows:
Y=Ae-Bx；
Wherein, A, B are fitting constant.
Likewise, WEIt can also be obtained by power function fitting.Its result has no difference.
Further, energy to failure G in step (4)FIt can also be got by RILEM recommended method:In formula, W0For the function that external load is done, δmaxTo measure displacement when the obtained test specimen destroys,
H is height of specimen, a0For pre-formed joint length, t is specimen width, and m is between test specimen hold-down support and movable bearing support in span scope
Quality, g are acceleration of gravity, take g=9.81m/s2, WEFunction done in fracture process, W are focused on certainly for test specimenE=wgSδmax/
2。
From the narration of above two method it is found that the two represents the average value of crack extension the consumed energy of unit area.
Moreover, for four_point bending beam test specimen, according to the calculated result of applicant, the above two available essentially identical knot of method
Fruit, and resulting energy to failure does not change with the variation for initially stitching high ratio.
For the ease of adjustment, as shown in Figure 2-5, movable bearing support 8 by be fixed on pedestal 5 support connecting plate 2b, fixation
The supporter 2a that the first U-lag 2c and bottom on support connecting plate 2b are inserted into the first U-lag 2c is constituted, the supporter
2a is equipped with second pin hole 2d corresponding with the first pin hole equipped with the side wall of the first pin hole 2e, the first U-lag 2c；By pin shaft
Being inserted into the first pin hole and the second pin hole can be rotated the movable bearing support, to guarantee that test specimen 3 and pedestal 5 completely attach to.
In addition, supporter 2a and the structure, shape and mounting means of pressure head 2 are almost the same, only direction when in use
On the contrary.That is, being connected with the second downwardly open U-lag on loading device 1, the top of pressure head 2 is inserted into the second U-lag, pressure
First 2 are equipped with third pin hole, and the second U-lag is equipped with the 4th pin hole corresponding with third pin hole；Pin shaft is inserted into third pin
Hole and the 4th pin hole can be rotated the pressure head 2 to install pressure head 2, to guarantee that test specimen 3 and loading device 1 completely attach to.
The present invention is not limited to the above embodiment the specific technical solution, and in addition to the implementation, the present invention may be used also
To there is other embodiments.It is all using equivalent replacement formed technical solution, be the present invention claims protection scope.
Claims (4)
1. a kind of test method for surveying fracture energy of concrete based on four_point bending beam, it is characterised in that: tried using four_point bending beam
Experiment device, the four_point bending beam experimental rig include loading device, pedestal, movable bearing support, hold-down support and be mounted on plus
Two pressure heads set are carried, the movable bearing support and hold-down support are mounted on the base；It the described method comprises the following steps:
(1) hold-down support and movable bearing support are installed respectively in two predeterminated positions of pedestal；
(2) there is the test specimen of pre-formed joint to be mounted on hold-down support and movable bearing support bottom, and is located at the prefabricated crack
The middle of the hold-down support and movable bearing support；The spaning middle section top that displacement meter is fixed on the test specimen is corresponded to described pre-
The position in crack processed；
(3) be arranged in below the loading device two pressure heads are pressed on the test specimen, the position point of one of pressure head
Not between hold-down support and prefabricated crack, another pressure head is between movable bearing support and prefabricated crack, two pressure heads point
It is inequal with the distance between the prefabricated crack；
(4) it is further applied load by the loading device to test specimen, it is P that the loading device, which applies pressure, and each pressure head is applied
The external load added is P/2, according to the amount of deflection measured when applying pressure, draws load-deflection curves；
Energy to failure G is obtained according to the following formulaF:
In formula, W0For the function that external load is done, δmaxTo measure displacement when the obtained test specimen destroys, WERefer to that Function Fitting obtains
The end segment area arrived, H are height of specimen, a0For pre-formed joint length, t is specimen width, and m is test specimen hold-down support and activity branch
Quality in span scope between seat, g is acceleration of gravity.
2. the test method according to claim 1 for surveying fracture energy of concrete based on four_point bending beam, it is characterised in that: institute
State WEExponential function fitting formula are as follows:
Y=Ae-Bx；
Wherein, A, B are fitting constant.
3. the test method according to claim 1 for surveying fracture energy of concrete based on four_point bending beam, it is characterised in that: institute
State WEIt can also be obtained by power function fitting.
4. the test method according to claim 1 for surveying fracture energy of concrete based on four_point bending beam, it is characterised in that: institute
State energy to failure G in step (4)FIt can also be got by RILEM recommended method:In formula, W0For outer lotus
Carry the function done, δmaxTo measure displacement when the obtained test specimen destroys, H is height of specimen, a0For pre-formed joint length, t is examination
Part width, quality, g are acceleration of gravity, W to m in span scope between test specimen hold-down support and movable bearing supportEIt is focused on certainly for test specimen
Function done in fracture process, WE=wgSδmax/2。
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261226A (en) * | 2019-07-09 | 2019-09-20 | 武汉理工大学 | A kind of ultra-high performance concrete cracking resistance system safety testing device and method |
| CN110455650A (en) * | 2019-07-10 | 2019-11-15 | 河海大学 | A method of quickly determining prefabricated cracked concrete beam fatigue life |
| CN113075060A (en) * | 2021-04-01 | 2021-07-06 | 中国石油天然气集团有限公司 | Interface crack II type shearing dynamic stress intensity factor testing system and method |
| CN113218789A (en) * | 2021-04-13 | 2021-08-06 | 同济大学 | Reinforced concrete beam post-crack fatigue performance testing system and method |
| CN113218754A (en) * | 2021-04-23 | 2021-08-06 | 河海大学 | Device and method for testing deflection of precast crack concrete specimen |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110261226A (en) * | 2019-07-09 | 2019-09-20 | 武汉理工大学 | A kind of ultra-high performance concrete cracking resistance system safety testing device and method |
| CN110455650A (en) * | 2019-07-10 | 2019-11-15 | 河海大学 | A method of quickly determining prefabricated cracked concrete beam fatigue life |
| CN113075060A (en) * | 2021-04-01 | 2021-07-06 | 中国石油天然气集团有限公司 | Interface crack II type shearing dynamic stress intensity factor testing system and method |
| CN113218789A (en) * | 2021-04-13 | 2021-08-06 | 同济大学 | Reinforced concrete beam post-crack fatigue performance testing system and method |
| CN113218754A (en) * | 2021-04-23 | 2021-08-06 | 河海大学 | Device and method for testing deflection of precast crack concrete specimen |
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