CN105865916A - Method for determining peak load of mortar or concrete members with cracks - Google Patents

Method for determining peak load of mortar or concrete members with cracks Download PDF

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CN105865916A
CN105865916A CN201610231190.7A CN201610231190A CN105865916A CN 105865916 A CN105865916 A CN 105865916A CN 201610231190 A CN201610231190 A CN 201610231190A CN 105865916 A CN105865916 A CN 105865916A
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max
peak load
specimen
crack
mortar
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CN105865916B (en
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管俊峰
胡晓智
姚贤华
白卫峰
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North China University of Water Resources and Electric Power
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North China University of Water Resources and Electric Power
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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
    • 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
    • G01N3/20—Investigating strength properties of solid materials by application of mechanical stress by applying steady bending forces

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Abstract

The invention belongs to the field of civil and water conservancy projects, and particularly relates to a method for determining peak load of mortar or concrete members with cracks. According to the method, peak load Pmax of different mortar or concrete members with the cracks or structural styles can be determined in an individualized mode by means of determined concrete material parameters including tensile strength ft and fracture toughness KIC. The method is simple in form and has enough accuracy.

Description

Determine the method with crack mortar or concrete component peak load
Technical field
The invention belongs to building and hydraulic engineering field, particularly relate to a kind of method of determining with crack mortar or concrete component peak load.
Background technology
The chief component of concrete component or structure is aggregate, sand and cement mortar etc., and therefore, concrete is not inherently homogeneous material, but typical heterogeneous body quasi-brittle material. Randomness, concreting condition and the curing condition etc. of aggregate distribution, all can produce a very large impact the result of the test of concrete component or structure. Therefore, adopt member or the structure of concrete for making, the discreteness of its result of the test is its build-in attribute.
For concrete component, the ratio of its aggregate size and sample dimensions generally 5 ~ 20 doubly. Because the ratio of concrete aggregate size and member or structure is relatively little, aggregate distribution is very large on its results of property impact. Such as building 8 concrete samples under similarity condition, result of the test may obtain 8 different peak loads. Current research can only qualitative explanation 8 test specimen results otherness or discreteness, and the discreteness of quantitatively determining concrete test result is technical problem urgently to be resolved hurrily.
Summary of the invention
For the problems referred to above, the present invention proposes a kind of personalizable and determines the method with crack mortar or concrete component peak load, and the method is by concrete material parameter (the hot strength f determiningt, fracture toughness KIC) come personalized determine the different mortars with crack or concrete component or structural shape peak load Pmax, the inventive method form is simple, has enough accuracy.
For solving above technical problem, the present invention is achieved through the following technical solutions:
Design a kind of method of determining with crack mortar or concrete component peak load, comprise the following steps:
One, according to test specimen type used, the equivalent fissure length a of different band crack member is determinede；aeCalculated by formula (1):
（1）
According to stress intensity factor handbook, determine the geometry affecting parameters Y (α) of different component.
According to three-point bending beam test specimen, then
(2a)
As L/W=2.5,
(2b)
As L/W=4,
(2c)
As L/W=8,
(2d)
According to compact tension specimen or wedge-splitting specimen, then
(3a)
(3b)。
Two, by known test specimen mortar or the concrete material parameter-hot strength f determiningtWith fracture toughness KICPut into elastic plastic theory formula (4), σ can be calculatedn(Pmax) value.
(4)
Three, for three-point bending beam test specimen, based on the σ trying to achieven(Pmax), by elastic plastic theory formula (5), by β, different values can be got, solve the personalized peak load P of test specimenmax：
(5)；
For compact tension specimen or wedge-splitting specimen, based on the σ trying to achieven(Pmax), by elastic plastic theory formula (6), by β, different values can be got, thus solve the personalized peak load P of test specimenmax：
(6)；
In various above, W1=W -a0；W2=W1- (β·dmax)；W3=W1 + (β·dmax); W is height of specimen, and L is piece lengths, and B is specimen thickness; PmaxFor peak load; a0For incipient crack length, β dmaxFor peak load PmaxThe fracture propagation amount at corresponding tip, incipient crack; dmaxFor mortar or aggregate maximum particle diameter. α is seam high ratio, i.e. incipient crack length a0Ratio with height of specimen W; A (α) is Specimen Shape affecting parameters, and different value is got to three-point bending beam and wedge-splitting specimen; σnFor considering the nominal stress of crack impact; β is the regulation coefficient of considering test specimen result discreteness, and β is not definite value, for accurate personalization solves each test specimen peak load, β can between 0.1 ~ 2.0 discrete value, as 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 ... 2.0; Y (α) is geometry affecting parameters.
The present invention has following positive useful technique effect:
(1) the present invention is by concrete material parameter-hot strength and fracture toughness, and the peak load of different test specimen structures personalized can be determined.
(2) by parameter beta dmaxConsider the fracture propagation amount that peak load is corresponding. From statistics angle beta=1.0, the mean value of measurable integrated member peak load; And get 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 as β ... 2.0, accurately personalization solves each test specimen peak load again.
Accompanying drawing explanation
Fig. 1 is external load P-displacement δ curve synoptic diagram (the peak load P that identical components is corresponding differentmax）；
When Fig. 2 is the peak load on average, aggregate schematic diagram (β=1.0 when considering result of the test mean value) is crossed in fracture propagation;
When Fig. 3 is the peak load of actual conditions personalization, aggregate schematic diagram (β=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 when peak load is determined in personalization is crossed in fracture propagation ... 2.0).
Detailed description of the invention
Below in conjunction with accompanying drawing, complete description is known to the technical scheme in the embodiment of the present invention. Some steps or method involved by following examples, if no special instructions, be the conventional method of this area, involved material if no special instructions, is commercially available material.
Embodiment 1 determines the method with crack mortar or concrete component peak load, comprises the following steps:
Build 4 of the concrete by three-point bending beam members of same size, the high ratio of identical seam, its sample dimensions L × B × W=320 × 40 × 80mm, wherein W is height of specimen, and B is specimen thickness, and L is test specimen effective length, and test specimen meets L/W=4. The identical a of its incipient crack length0 =24mm, i.e. a0/ W=0.3 is consistent. Its maximum aggregate size dmax=10 mm。W/dmax=8. Known this concrete material characteristic-hot strength ft=4.7MPa, fracture toughness KIC=1.3 MPa·m1/2。
According to test specimen type used, determine the equivalent fissure length a of different band crack membere。aeCan be calculated by formula (1). According to stress intensity factor handbook, the geometry affecting parameters Y (α) of different component or structural shape can be determined, three-point bending beam can be calculated by formula (2).
By the concrete material parameter-hot strength f of known this test specimen of determiningtWith fracture toughness KICPut into bullet formula (4), release σn(Pmax) value.
By formula (5), got different values by β, thus counter solve different test specimens personalized peak load Pmax. See Fig. 1, because coagulation great soil group quasi-brittle material self-characteristic determines, even the member of building same size same types, the peak load of each member is also not quite similar.
See Fig. 2, consider the mean value of the measurable integrated member peak load in β=1.0 from statistics angle.
See Fig. 3, consider the discreteness of result of the test, for the prediction of each test specimen peak load test value, then β=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 ... 2.0, β value is not definite value, and span size is relevant to material property discreteness.
See table 1, for the test specimen of 4 high ratios of the identical seam of same size of the present embodiment, its actual measurement peak load is not identical. Adopt the inventive method, the β of 4 test specimens gets respectively different value 0.9,1.1,0.8,0.7, and predicted value will be fine identical with 4 peak load test values respectively. β=1.0 can predicted entire 4 members mean value.
Four peak loads with crack member are determined in table 1 personalization
。
Embodiment 2 determines the method with crack mortar or concrete component peak load, comprises the following steps:
Build 4 of the concrete by three-point bending beam members of same size, the high ratio of identical seam, its sample dimensions L × B × W=320 × 40 × 80mm, wherein W is height of specimen, and B is specimen thickness, and L is test specimen effective length, and test specimen meets L/W=4. The identical a of its incipient crack length0 =32mm, i.e. a0/ W=0.4 is consistent. Its maximum aggregate size dmax=10 mm。W/dmax=8. Known this concrete material characteristic-hot strength ft=4.7MPa, fracture toughness KIC=1.3 MPa·m1/2。
According to test specimen type used, determine the equivalent fissure length a of different band crack membere。aeCan be calculated by formula (1). According to stress intensity factor handbook, the geometry affecting parameters Y (α) of different component or structural shape can be determined, three-point bending beam can be calculated by formula (2).
By the concrete material parameter-hot strength f of known this test specimen of determiningtWith fracture toughness KICPut into bullet formula (4), release σn(Pmax) value.
By formula (5), got different values by β, thus counter solve different test specimens personalized peak load Pmax. See Fig. 1, because coagulation great soil group quasi-brittle material self-characteristic determines, even the member of building same size same types, the peak load of each member is also not quite similar.
See Fig. 2, consider the mean value of the measurable integrated member peak load in β=1.0 from statistics angle.
See Fig. 3, consider the discreteness of result of the test, for the prediction of each test specimen peak load test value, then β=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 ... 2.0, β value is not definite value, and span size is relevant to material property discreteness.
See table 2, for the test specimen of 4 high ratios of the identical seam of same size of the present embodiment, its actual measurement peak load is not identical. Adopt the inventive method, the β of 4 test specimens gets respectively different value 1.6,0.9,1.1,1.3, and predicted value will be fine identical with 4 peak load test values respectively. β=1.0 can predicted entire 4 members mean value.
Four peak loads with crack member are determined in table 2 personalization
。
Embodiment 3 determines the method with crack mortar or concrete component peak load, comprises the following steps:
Build 4 of the concrete by three-point bending beam members of same size, the high ratio of identical seam, its sample dimensions L × B × W=400 × 100 × 100 mm, wherein W is height of specimen, and B is specimen thickness, and L is test specimen effective length, and test specimen meets L/W=4. The identical a of its incipient crack length0 =40mm, i.e. a0/ W=0.4 is consistent. Its maximum aggregate size dmax=20 mm。W/dmax=5. Known this concrete material characteristic-hot strength ft=4.7MPa, fracture toughness KIC=2.2 MPa·m1/2。
According to test specimen type used, determine the equivalent fissure length a of different band crack membere。aeCan be calculated by formula (1). According to stress intensity factor handbook, the geometry affecting parameters Y (α) of different component or structural shape can be determined, three-point bending beam can be calculated by formula (2).
By the concrete material parameter-hot strength f of known this test specimen of determiningtWith fracture toughness KICPut into bullet formula (4), release σn(Pmax) value.
By formula (5), got different values by β, thus counter solve different test specimens personalized peak load Pmax. See Fig. 1, because coagulation great soil group quasi-brittle material self-characteristic determines, even the member of building same size same types, the peak load of each member is also not quite similar.
See Fig. 2, consider the mean value of the measurable integrated member peak load in β=1.0 from statistics angle.
See Fig. 3, consider the discreteness of result of the test, for the prediction of each test specimen peak load test value, then β=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 ... 2.0, β value is not definite value, and span size is relevant to material property discreteness.
See table 3, for the test specimen of 4 high ratios of the identical seam of same size of the present embodiment, its actual measurement peak load is not identical. Adopt the inventive method, the β of 4 test specimens gets respectively different value 0.9,1.2,0.95,1.0, and predicted value will be fine identical with 4 peak load test values respectively. β=1.0 can predicted entire 4 members mean value.
Four peak loads with crack member are determined in table 3 personalization
。
Embodiment 4 determines the method with crack mortar or concrete component peak load, comprises the following steps:
Build 5 of the concrete by three-point bending beam members of same size, the high ratio of identical seam, its sample dimensions L × B × W=400 × 100 × 100 mm, wherein W is height of specimen, and B is specimen thickness, and L is test specimen effective length, and test specimen meets L/W=4. The identical a of its incipient crack length0 =50mm, i.e. a0/ W=0.5 is consistent. Its maximum aggregate size dmax=20 mm。W/dmax=5. Known this concrete material characteristic-hot strength ft=4.7MPa, fracture toughness KIC=2.2 MPa·m1/2。
According to test specimen type used, determine the equivalent fissure length a of different band crack membere。aeCan be calculated by formula (1). According to stress intensity factor handbook, the geometry affecting parameters Y (α) of different component or structural shape can be determined, three-point bending beam can be calculated by formula (2).
By the concrete material parameter-hot strength f of known this test specimen of determiningtWith fracture toughness KICPut into bullet formula (4), release σn(Pmax) value.
By formula (5), got different values by β, thus counter solve different test specimens personalized peak load Pmax. See Fig. 1, because coagulation great soil group quasi-brittle material self-characteristic determines, even the member of building same size same types, the peak load of each member is also not quite similar.
See Fig. 2, consider the mean value of the measurable integrated member peak load in β=1.0 from statistics angle.
See Fig. 3, consider the discreteness of result of the test, for the prediction of each test specimen peak load test value, then β=0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8 ... 2.0, β value is not definite value, and span size is relevant to material property discreteness.
See table 4, for the test specimen of 5 high ratios of the identical seam of same size of the present embodiment, its actual measurement peak load is not identical. Adopt the inventive method, the β of 5 test specimens gets respectively different value 0.55,0.85,1.0,1.1,1.4, and predicted value will be fine identical with 5 peak load test values respectively. β=1.0 can predicted entire 5 members mean value.
Four peak loads with crack member are determined in table 4 personalization
。
To the above-mentioned explanation of disclosed embodiment; those skilled in the art are realized or use the present invention; but obviously described embodiment is only the schematic part detailed description of the invention of the present invention; and be not used to limit scope of the present invention; the equivalent variations that any those skilled in the art makes under not departing from the prerequisite of design of the present invention and principle and amendment, all should belong to the scope of protection of the invention.

Claims (7)

1. determine the method with crack mortar or concrete component peak load, it is characterized in that, comprise the following steps:
(1) according to test specimen type used, the equivalent fissure length a of different band crack member is determinede；aeCalculated by formula (1):
（1）
In formula, a0For incipient crack length; α is seam high ratio, i.e. incipient crack length a0Ratio with height of specimen W; A (α) is Specimen Shape affecting parameters, and different value is got to three-point bending beam and wedge-splitting specimen; Y (α) is geometry affecting parameters;
(2) by known test specimen mortar or concrete material parameter---the hot strength f determiningtWith fracture toughness KICPut into elastic plastic theory formula (4), σ can be calculatedn(Pmax) value:
(4)
In formula, PmaxFor peak load; σnFor considering the nominal stress of crack impact;
(3) based on the σ trying to achieven(Pmax), by elastic plastic theory formula, got different values by β, solve the corresponding personalized peak load P of test specimenmax; β is the regulation coefficient of considering test specimen result discreteness.
2. determine the method with crack mortar or concrete component peak load according to claim 1, it is characterized in that: in described step (1), according to stress intensity factor handbook, determine the geometry affecting parameters Y (α) of different component according to a conventional method.
3. determine the method with crack mortar or concrete component peak load according to claim 1, it is characterized in that: in described step (1), according to three-point bending beam test specimen, then
(2a)；
As L/W=2.5,
(2b)；
As L/W=4,
(2c)；
As L/W=8,
(2d)；
In formula, L is piece lengths, and W is height of specimen.
4. determine the method with crack mortar or concrete component peak load according to claim 1, it is characterized in that: in described step (1), according to compact tension specimen or wedge-splitting specimen, then
(3a)
(3b)。
5. determine the method with crack mortar or concrete component peak load according to claim 1, it is characterized in that:
In described step (3), for three-point bending beam test specimen, based on the σ trying to achieven(Pmax), by elastic plastic theory formula (5), by β, different values can be got, solve the personalized peak load P of test specimenmax：
(5)
In formula, W1=W -a0；W2=W1 - (β·dmax)；W3=W1 + (β·dmax); W is height of specimen, and L is piece lengths, and B is specimen thickness; PmaxFor peak load; a0For incipient crack length, β dmaxFor peak load PmaxThe fracture propagation amount at corresponding tip, incipient crack; dmaxFor mortar or aggregate maximum particle diameter.
6. determine the method with crack mortar or concrete component peak load according to claim 1, it is characterized in that:
In described step (3), for compact tension specimen or wedge-splitting specimen, based on the σ trying to achieven(Pmax), by elastic plastic theory formula (6), by β, different values can be got, thus solve the personalized peak load P of test specimenmax：
(6)
In formula, W1=W -a0；W2=W1 - (β·dmax)；W3=W1 + (β·dmax); W is height of specimen, and L is piece lengths, and B is specimen thickness; PmaxFor peak load; a0For incipient crack length, β dmaxFor peak load PmaxThe fracture propagation amount at corresponding tip, incipient crack; dmaxFor mortar or aggregate maximum particle diameter.
7. according to claim 5 or 6, determine the method with crack mortar or concrete component peak load, it is characterized in that: described β is in 0.1 ~ 2.0 value.
CN201610231190.7A 2016-04-14 2016-04-14 The method with crack mortar or concrete component peak load of determination Active CN105865916B (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112326429A (en) * 2020-10-30 2021-02-05 安徽新力电业科技咨询有限责任公司 Method for determining plane strain fracture toughness of steel
CN114577564A (en) * 2022-02-11 2022-06-03 中国电建集团西北勘测设计研究院有限公司 Method for loading cracks of prefabricated mortar test piece by three-point bending
CN114970093A (en) * 2022-04-15 2022-08-30 华北水利水电大学 Construction and application of concrete material strength and fracture toughness compatibility regulation and control model

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112326429A (en) * 2020-10-30 2021-02-05 安徽新力电业科技咨询有限责任公司 Method for determining plane strain fracture toughness of steel
CN114577564A (en) * 2022-02-11 2022-06-03 中国电建集团西北勘测设计研究院有限公司 Method for loading cracks of prefabricated mortar test piece by three-point bending
CN114577564B (en) * 2022-02-11 2023-02-10 中国电建集团西北勘测设计研究院有限公司 Method for prefabricating cracks of mortar test piece by three-point bending loading
CN114970093A (en) * 2022-04-15 2022-08-30 华北水利水电大学 Construction and application of concrete material strength and fracture toughness compatibility regulation and control model

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