CN112348329A - Method for evaluating ultrahigh-strength prestressed anchor backing plate and spiral rib - Google Patents

Method for evaluating ultrahigh-strength prestressed anchor backing plate and spiral rib Download PDF

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CN112348329A
CN112348329A CN202011162095.9A CN202011162095A CN112348329A CN 112348329 A CN112348329 A CN 112348329A CN 202011162095 A CN202011162095 A CN 202011162095A CN 112348329 A CN112348329 A CN 112348329A
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test piece
backing plate
anchor backing
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CN112348329B (en
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胡所亭
苏永华
石龙
马林
班新林
牛斌
陈胜利
赵体波
葛凯
袁磊
王乐然
杨心怡
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China Academy of Railway Sciences Corp Ltd CARS
Railway Engineering Research Institute of CARS
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Abstract

The invention provides an evaluation method of an ultrahigh-strength prestressed anchor backing plate and a spiral rib, which comprises the following steps: s1, manufacturing a test piece; s2, mounting the test piece on a test pedestal; s3, calculating a standard value of the tensile resistance of the steel strand in the force transmission test of the anchor backing plate according to various numerical values of the test piece; s4, loading the test piece by using a press machine and recording test data; and S5, after the loading is finished, judging whether the data are qualified or not according to the loaded data. The invention relates to an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib, which is characterized in that the suspension and observation of each stage in the process are carried out, the crack width is read, whether a test piece meets the requirement of the normal use limit state of an anchoring area of a prestressed structure is verified, and the crack development and the crack width of concrete are mainly controlled; and after the loading force reaches 1.0, loading to destroy, and verifying the requirement of the limit state of the bearing capacity of the test piece, thereby judging that the bearing capacity can meet the use requirement and reserving sufficient safety margin.

Description

Method for evaluating ultrahigh-strength prestressed anchor backing plate and spiral rib
Technical Field
The invention relates to the field of anchoring devices, in particular to an ultra-high-strength prestressed anchor backing plate and an evaluation method of spiral ribs.
Background
Permanent anchorage devices used in prestressed concrete, anchorage devices also called prestressed anchorage devices, are anchorage means used in post-tensioned structures or elements to maintain the tension of the tendon and to transmit it to the inside of the concrete. Anchors can be divided into two broad categories depending on the type of application: the anchoring tool comprises a tensioning end anchorage and a fixed end anchorage, wherein the tensioning end anchorage is arranged at the end part of the prestressed tendon and can always keep the prestressed tendon in an anchoring state in the tensioning process of the prestressed tendon. The fixed end anchorage is suitable for the condition that the stress of the member end layout is large or the end space is limited, and is a bond type anchorage which uses an extruder to press and bond an extrusion sleeve on a steel strand, is pre-embedded in concrete and arranged according to requirements, and is tensioned after the concrete is solidified to the designed strength.
The existing prestressed anchor backing plate and spiral rib evaluation method does not have an evaluation method aiming at ultrahigh strength, and an evaluation method is needed to fill the blank.
Disclosure of Invention
The invention provides an ultra-high strength prestressed anchor backing plate and an evaluation method of a spiral rib, aiming at solving the problem that the existing prestressed anchor backing plate and the evaluation method of the spiral rib in the prior art do not aim at ultra-high strength.
The invention provides an evaluation method of an ultrahigh-strength prestressed anchor backing plate and a spiral rib, which comprises the following steps:
s1, manufacturing a test piece;
s2, mounting the test piece on a test bed;
s3, calculating a standard tensile strength value F of the steel strand bundle in the anchor backing plate force transmission test according to the standard tensile strength value of the nominal steel strand of the test piece, the number of the steel strands corresponding to the test anchor backing plate and the nominal cross-sectional area of the single steel strandptk，FptkThe specific calculation formula of (2) is as follows:
Fptk＝fptk×n×Ap；
wherein f isptkIs the nominal tensile strength standard value of the steel strand, n is the number of the steel strands corresponding to the test anchor backing plate, ApThe nominal cross-sectional area of the single steel strand;
s4, loading the test piece by using a press machine and recording test data;
s5, after the loading is finished, if a, b and c are simultaneously met, judging that the product is qualified; otherwise, the product is unqualified; wherein
a. The loading reaches 0.5FptkAfter holding the load for 10min, no visible cracks appear in the concrete;
b. the loading reaches 0.8FptkAfter holding the load for 10min, the maximum crack width of the concrete is not more than 0.20mm
c. Loading to 1.0FptkIn time, no crack appears in the anchor backing plate and the ultimate load is tested
Figure BDA0002744682700000021
Wherein, FuFor testing the ultimate load value, fcu,kDesigning concrete cube compression strength standard value f for test piecec'uAnd maintaining the actually measured average value of the compressive strength of the cubic test piece under the same conditions during the test.
The invention relates to an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib, and as a preferred mode, the step S1 specifically comprises the following steps:
s11, removing rust on the inner and outer surfaces of the steel template and coating a release agent;
s12, binding a reinforcement cage, and placing the bound reinforcement cage into a steel template;
s13, installing spiral ribs and anchor backing plates in the reinforcement cage;
s14, pouring concrete into the steel template;
s15, performing watering curing on the concrete for 7 consecutive days;
s17, when the concrete strength reaches the design value of 60%, demoulding the test piece;
s18, waiting for the concrete strength of the test piece to reach the design value of 100%;
and S19, finishing the manufacturing of the test piece.
The invention relates to an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib, and as a preferred mode, the step S4 specifically comprises the following steps:
s41, loading the test piece from 0 to 0.5F by using a press machineptkHolding the lotus for 10 min;
s42, continuously using the press machine to load pressure on the test piece to 0.8FptkHolding the lotus for 10 min;
s43, continuing to load the test piece until the member is damaged, and recording the test limit load Fu。
The crack width is observed and read when the bearing capacity of the concrete reaches 1.0, so that the bearing capacity can be judged to meet the use requirement, and sufficient safety margin is reserved.
The invention relates to an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib, and test data comprise the occurrence, width and expansion conditions of cracks on the top surface and the side surface of a test piece and a limit load value F of the test piece as an optimal modeuCracking and deformation of the anchor backing plate and damage forms of the test piece.
As a preferred mode, the test piece comprises a concrete column, a spiral rib, a leveling layer, a guide pipe and an anchor device, wherein the guide pipe and the anchor device are cast in the concrete column, the guide pipe and the anchor device are coaxial, the anchor device is arranged at one end of the guide pipe, the anchor device is arranged at the end part of the concrete column, the leveling layer is arranged on the outer surface of the other end of the concrete column, the spiral rib is arranged on the outer side of the guide pipe and inside the concrete column, and the spiral rib and the guide pipe are coaxial.
The anchor backing plate and the spiral rib are force transmission parts for transmitting the force value of the steel strand of the prestressed concrete structure to the concrete structure, along with the integral improvement of the strength of the prestressed steel strand, the key is how to design the used anchor backing plate and the spiral rib and test and verify the stress performance of the anchor backing plate and the spiral rib, and the stress test needs to manufacture special anchor backing plates, spiral ribs and reinforced concrete components for carrying out the stress test because the anchor backing plate and the spiral rib are actually poured in the concrete structure to carry the stress.
According to the method for evaluating the ultrahigh-strength prestressed anchor backing plate and the spiral reinforcement, disclosed by the invention, as an optimal mode, the concrete column is also internally provided with the longitudinal reinforcement and the stirrup, and the longitudinal reinforcement and the stirrup are connected in a net manner to form a reinforcement cage.
The invention has the following beneficial effects:
(1) pausing and observing each stage in the process, reading the crack width, verifying whether the test piece meets the requirement of the normal use limit state of the anchoring area of the prestressed structure, and mainly controlling the crack development and the crack width of the concrete;
(2) and after the loading force reaches 1.0, loading to destroy, and verifying the requirement of the limit state of the bearing capacity of the test piece, thereby judging that the bearing capacity can meet the use requirement and reserving sufficient safety margin.
Drawings
FIG. 1 is a flow chart of an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib;
FIG. 2 is a schematic sectional view of a test piece structure of an evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib;
FIG. 3 is a schematic plan view of a test piece structure of an evaluation method for an ultra-high-strength prestressed anchor backing plate and a spiral rib.
Reference numerals:
1. a concrete column; 2. a spiral rib; 3. leveling layer; 4. a conduit; 5. an anchorage device; 6. longitudinal reinforcing steel bars; 7. and (5) hooping.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Example 1
As shown in fig. 1, the method for evaluating the ultra-high strength prestressed anchor backing plate and the spiral bar comprises the following steps:
s1, manufacturing a test piece, removing rust on the inner surface and the outer surface of the steel template, and coating a release agent;
s2, binding a reinforcement cage, and placing the bound reinforcement cage into a steel template;
s3, installing spiral ribs 2 and anchor backing plates in the reinforcement cage;
s4, pouring concrete into the steel template;
s5, performing watering curing on the concrete for 7 consecutive days;
s6, when the concrete strength reaches the design value of 60%, demoulding the test piece;
s7, waiting for the concrete strength of the test piece to reach the design value of 100%;
s8, completing the manufacture of the test piece;
s9, mounting the test piece on a test bed;
s10, according to the testStandard value F of tensile strength of steel strand bundle in force transmission test of anchor backing plate calculated by using nominal tensile strength standard value of steel strand, number of steel strands corresponding to test anchor backing plate and nominal cross-sectional area of single steel strandptk，FptkThe specific calculation formula of (2) is as follows:
Fptk＝fptk×n×Ap；
wherein f isptkIs the nominal tensile strength standard value of the steel strand, n is the number of the steel strands corresponding to the test anchor backing plate, ApThe nominal cross-sectional area of the single steel strand;
s11, loading the test piece from 0 to 0.5F by using a press machineptkHolding the lotus for 10 min;
s12, continuously using the press machine to load pressure on the test piece to 0.8FptkHolding the lotus for 10 min;
s13, continuing to load the test piece until the member is damaged, and recording the test limit load Fu。
S14, after the loading is finished, if a, b and c are simultaneously met, judging that the product is qualified; otherwise, the product is unqualified; wherein
a. The loading reaches 0.5FptkAfter holding the load for 10min, no visible cracks appear in the concrete;
b. the loading reaches 0.8FptkAfter holding the load for 10min, the maximum crack width of the concrete is not more than 0.20mm
c. Loading to 1.0FptkIn time, no crack appears in the anchor backing plate and the ultimate load is tested
Figure BDA0002744682700000061
Wherein, FuFor testing the ultimate load value, fcu,kDesigning concrete cube compression strength standard value f for test piecec'uAnd maintaining the actually measured average value of the compressive strength of the cubic test piece under the same conditions during the test.
During the test, a concrete structure test piece is firstly manufactured, the concrete strength is C50 grade (or according to the actual concrete strength) commonly used for the railway prestressed concrete structure, and the common steel bar is HRB400 grade. After the test piece is manufactured according to the requirements, the concrete curing time needs to meet at least 15 days, and a loading test can be developed after the strength and the elastic modulus of the concrete meet the design requirements.
And eccentricity is avoided during loading, and the uniform stress of the pressed end face of the concrete member is ensured. The loading speed is not more than 100 MPa/min.
As shown in fig. 2 ~ 3, the test piece includes concrete column 1, spiral muscle 2, screed-coat 3, the pipe 4 of pouring in concrete column 1, ground tackle 5, longitudinal reinforcement 6 and stirrup 7, pipe 4 and ground tackle 5 are coaxial, ground tackle 5 sets up in the one end of pipe 4, ground tackle 5 sets up in the tip of concrete column 1, screed-coat 3 sets up in the other end surface of concrete column 1, spiral muscle 2 sets up in the pipe 4 outside, inside the concrete column 1, spiral muscle 2 is coaxial with pipe 4, longitudinal reinforcement 6 and 7 netted connections of stirrup are the steel reinforcement cage.
As the specifications of the anchorage devices used in the railway prestressed concrete engineering are more than 1-27 holes, the test method provides for selecting representative 9-hole, 15-hole, 19-hole and 23-hole specifications to be matched with an anchor backing plate and a spiral rib to carry out system verification. The size is selected mainly according to the center distance value of the adopted anchorage device when the anchorage device of each specification is actually used by the railway prestressed concrete structure, and the height is 2 times of the width. The dimensions of the specification test pieces are as follows:
Figure BDA0002744682700000071
wherein A is the width and H is the height. The specification of the cubic test block is 150 multiplied by 150mm, 8 groups are reserved, 3 pieces of each group are maintained along with the beam, and the strength is tested so as to judge the strength of the concrete test piece.
The stirrups 7 are uniformly arranged along the height direction of the concrete member, the diameter of each stirrup 7 is 16mm, and the distance between the stirrups 7 ensures that the hooping rate of the member is 100-110 kg/m 3. The diameters of the 4 longitudinal steel bars 6 are all 12 mm. The thickness of the concrete protective layer of the stirrup 7 is not less than 15 mm.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims (6)

1. An evaluation method of an ultra-high strength prestressed anchor backing plate and a spiral rib is characterized in that: the method comprises the following steps:
s1, manufacturing a test piece;
s2, mounting the test piece on a test pedestal;
s3, calculating a standard tensile strength value F of the steel strand bundle in the anchor backing plate force transmission test according to the standard tensile strength value of the nominal steel strand of the test piece, the number of the steel strands corresponding to the test anchor backing plate and the nominal cross-sectional area of the single steel strandptk，FptkThe specific calculation formula of (2) is as follows:
Fptk＝fptk×n×Ap；
wherein f isptkIs the nominal tensile strength standard value of the steel strand, n is the number of the steel strands corresponding to the test anchor backing plate, ApThe nominal cross-sectional area of the single steel strand;
s4, loading the test piece by using a press machine and recording test data;
s5, after the loading is finished, if a, b and c are simultaneously met, judging that the product is qualified; otherwise, the product is unqualified; wherein
a. The loading reaches 0.5FptkAfter holding the load for 10min, no visible cracks appear in the concrete;
b. the loading reaches 0.8FptkAfter holding the load for 10min, the maximum crack width of the concrete is not more than 0.20mm
c. Loading to 1.0FptkIn time, no crack appears in the anchor backing plate and the ultimate load is tested
Figure FDA0002744682690000011
Wherein, FuFor testing the ultimate load value, fcu,kDesign concrete cube compressive strength standard value, f 'for test piece'cuActual measured average value of compressive strength of cubic test piece maintained under same conditions during test。
2. The method for evaluating an ultra-high strength prestressed anchor backing plate and a spiral bar according to claim 1, wherein: the step S1 specifically includes:
s11, removing rust on the inner and outer surfaces of the steel template and coating a release agent;
s12, binding a reinforcement cage, and placing the bound reinforcement cage into the steel template;
s13, installing a spiral rib (2) and an anchor backing plate in the reinforcement cage;
s14, pouring concrete into the steel formwork;
s15, performing watering curing on the concrete for 7 consecutive days;
s17, when the strength of the concrete reaches 60% of the design value, demoulding the test piece;
s18, waiting for the concrete strength of the test piece to reach the design value of 100%;
and S19, finishing the manufacturing of the test piece.
3. The method for evaluating an ultra-high strength prestressed anchor backing plate and a spiral bar according to claim 1, wherein: the step S4 specifically includes:
s41, loading the test piece from 0 to 0.5F by using the pressptkHolding the lotus for 10 min;
s42, continuously using the press machine to load pressure on the test piece to 0.8FptkHolding the lotus for 10 min;
s43, continuing to load the test piece until the member is damaged, and recording the test limit load Fu。
4. The method for evaluating an ultra-high strength prestressed anchor backing plate and a spiral bar according to claim 1, wherein: the test data comprises the occurrence, width and expansion conditions of cracks on the top surface and the side surface of the test piece and the limit load value F of the test pieceuCracking and deformation of the anchor backing plate and damage forms of the test piece.
5. The method for evaluating an ultra-high strength prestressed anchor backing plate and a spiral bar according to claim 1, wherein: the test piece comprises a concrete column (1), a spiral rib (2), a leveling layer (3), a guide pipe (4) and an anchorage device (5), wherein the guide pipe (4) and the anchorage device (5) are poured in the concrete column (1), the guide pipe (4) and the anchorage device (5) are coaxial, the anchorage device (5) is arranged at one end of the guide pipe (4), the anchorage device (5) is arranged at the end part of the concrete column (1), the leveling layer (3) is arranged on the outer surface of the other end of the concrete column (1), the spiral rib (2) is arranged on the outer side of the guide pipe (4) and inside the concrete column (1), and the spiral rib (2) is coaxial with the guide pipe (4).
6. The method for evaluating an ultra-high strength prestressed anchor backing plate and a spiral reinforcement according to claim 5, wherein: the concrete column (1) is also internally provided with longitudinal steel bars (6) and stirrups (7), and the longitudinal steel bars (6) and the stirrups (7) are connected in a net mode to form a steel reinforcement cage.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2615047C1 (en) * 2015-11-02 2017-04-03 федеральное государственное бюджетное образовательное учреждение высшего образования "Самарский государственный технический университет" Evaluation method for fire-resistance of reinforced concrete column of building
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Publication number Priority date Publication date Assignee Title
RU2615047C1 (en) * 2015-11-02 2017-04-03 федеральное государственное бюджетное образовательное учреждение высшего образования "Самарский государственный технический университет" Evaluation method for fire-resistance of reinforced concrete column of building
RU2678780C1 (en) * 2018-02-26 2019-02-01 федеральное государственное бюджетное образовательное учреждение высшего образования "Самарский государственный технический университет" Method for determining fire resistance of reinforced concrete column of round section

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