CN112414649B - Simple beam/slab bridge effective prestress testing and evaluating method based on beam slab overturning - Google Patents
Simple beam/slab bridge effective prestress testing and evaluating method based on beam slab overturning Download PDFInfo
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
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- G—PHYSICS
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- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
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Abstract
A method for testing and evaluating effective prestress of simply supported beam/slab bridge based on beam-slab overturning belongs to the technical field of bridge engineering structure performance identification and evaluation. The method utilizes the characteristics of small dead weight and portability of the assembled simply supported beam/plate, turns over the simply supported prestressed concrete beam/plate through the hoisting equipment, analyzes test data in the states before and after turning over, and successfully filters out coupled constant load effect factors from the overall effect, thereby realizing accurate evaluation of the current effective prestress degree of the simply supported beam/plate. The method has the advantages of low cost, simple equipment, suitability for field application and the like, and is particularly suitable for quickly and accurately testing and evaluating the effective prestress of the assembled simply supported beam/slab bridge.
Description
Technical Field
The invention belongs to the technical field of bridge engineering performance identification and evaluation, and particularly relates to a method for testing and evaluating effective prestress of a simply supported beam/slab bridge based on beam slab overturning.
Background
For an in-service bridge without a pre-arranged prestress tension sensor, the service performance problems of insufficient structural crack resistance, rigidity degradation and the like can be caused by the occurrence of over-expected prestress loss caused by multiple factors such as concrete shrinkage creep, steel bar stress relaxation, anchoring end compression, force bar slippage, force bar and friction between the force bar and the periphery during service, the current effective prestress residual level of the bridge cannot be accurately mastered, and great uncertainty is brought to the subsequent technical disposal decision. The technical bottlenecks mainly exist in the following two points: in a prestressed beam/slab without an initial sensing device, due to the coupling effect of a dead load effect and a prestress effect, the magnitude and the distribution rule of the generated overrun prestress are difficult to obtain, so that great difficulty is brought to the evaluation of the operation safety of a bridge in a normal use limit state; and secondly, after crack and other defects occur in the normal operation period of the prestressed concrete simply supported beam/slab bridge serving for years, due to the influence of dual nonlinear effects of nonlinearity of concrete materials and change of geometric characteristics after section cracking, the generation of the overrun prestress loss is aggravated. However, the effect of prestress loss analysis based on the traditional linear elastic simulation analysis means and design method is lost, and effective prestress quantitative evaluation under the traditional means cannot be realized; the loss of the prestress is predicted by using a grey theory or the effective prestress is predicted by using an artificial neural network model, and the method can be carried out only by relying on a large amount of field measured data and combining laboratory test results; although an ideal test result can be obtained by the method combining the local damage technology and theoretical analysis and calculation, the technology belongs to a semi-destructive technology, and is large in workload, high in investment cost and not easy to popularize and apply.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a method for testing and evaluating the effective prestress of a simply supported beam/slab bridge based on beam-slab overturning, which can filter out the interference factor of the dead load effect, identify the prestress loss and the current effective prestress which cannot be predicted by the simply supported beam/slab bridge with in-service diseases, and is suitable for evaluating the current service performance (stress, rigidity and crack resistance) of the simply supported beam/slab bridge with in-service prestressed concrete with the existing cracking diseases.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for testing effective prestress of a simply supported beam/slab bridge based on beam-slab overturning comprises the following steps:
the method comprises the following steps: selecting the worst bridge span and the target beam/plate according to the appearance survey of the solid bridge and the disease state result, and recording the cracking characteristics of typical crack diseases;
step two: the longitudinal and transverse bridge direction relation between the target beam/plate and the adjacent beam/plate is removed, so that the structure is in a single beam/plate simply supported state, and a simply supported beam/plate is obtained;
step three: planing and milling an asphalt concrete wearing layer in the simply supported beam/slab bridge deck pavement, and reserving a cement concrete leveling layer and a bridge deck pavement reinforcing mesh;
step four: additionally arranging a strain sensor 1 or a deflection sensor 2 in the midspan region of the simply supported beam/plate after being planed and milled to obtain a corresponding strain or deflection parameter test value;
step five: defining the stress and deformation state of the exposed simply supported beam/plate as a pre-overturning state, and acquiring a strain or deflection parameter test value in the pre-overturning state through a data collector 3;
step six: the simple support beam/plate body is turned over after the simple support beam/plate is lifted by the hoisting equipment, the turned simple support beam/plate is restored to be in the original position, and the stress and deformation state of the beam/plate at the moment are defined to be in a turned state;
step seven: after the beam/plate is turned over and the structure is stable, the turned beam/plate is tested, and a strain or deflection parameter test value in a turned state is obtained through the data collector 3.
In the second step, the longitudinal and transverse bridging connection to be released comprises: beam/slab wet joints, bridge deck continuous concrete and rebar constructions, hollow slab longitudinal hinge joint concrete and rebar constructions.
In the fourth step, the strain sensors 1 are symmetrically arranged at the midspan positions of the simply supported beam/slab bridge along the beam height, the number of the strain sensors is 5, and the strain sensors are sequentially marked as S from the top plate 4 to the bottom plate 5 1 、S 2 、S 3 、S 4 、S 5 The obtained strain parameter test values are sequentially recorded as epsilon 1 、ε 2 、ε 3 、ε 4 、ε 5 。
In the fourth step, the deflection sensors 2 are arranged at the intersections of the simply supported beam/slab bridge span middle top plate 4, the bottom plate 5, the left web center line 6 and the right web center line 7, the number of the deflection sensors is 4, and the deflection sensors are sequentially marked as N TL 、N TR 、N BL 、N BR And the obtained deflection parameter test value is recorded as delta TL 、δ TR 、δ BL 、δ BR 。
The invention also provides an evaluation method based on the beam-slab turnover-based simple supported beam/slab bridge effective prestress test method, which is characterized in that:
(1) The strain or deflection effect of the simply supported beam/slab before turning is the coupling effect under the combined action of the prestress and the gravity and is marked as S Front side (ii) a Wherein the effect of strain or deflection caused by the action of prestress is denoted S Preparation of The effect of strain or deflection caused by the action of gravity is denoted S Heavy load Since the strain and deflection effects caused by the prestress are opposite to those caused by the gravity, respectively, the strain or deflection effect S under the coupling effect of the prestress and the gravity is obtained in the pre-overturn state Front side ＝S Preparation of -S Heavy load ；
(2) The strain or deflection effect of the simply supported beam/plate after turning over is the coupling effect under the combined action of the prestress and the gravity and is marked as S Rear end (ii) a Wherein the effect of strain or deflection caused by the action of prestress is denoted S Preparation of The effect of strain or deflection caused by gravity is denoted S Heavy load Because the strain and deflection effects caused by the action of the prestress are respectively in the same direction as the strain and deflection effects caused by the action of the gravity, the strain or deflection effect S under the coupling effect of the prestress and the action of the gravity is realized in the state after the overturning Rear end ＝S Preparation of -S Heavy load ；
(3) From (1) and (2), the strain or deflection effect S under the action of prestress can be obtained Preparation of ＝(S Front side +S Rear end )/2。
(4) Evaluating the current effective prestress sigma of the target beam/plate based on the strain effect or the deflection effect under the prestress action pe 。
Wherein, in the state before the simply supported beam/plate is turned over, for the strain effect, the gravity action causes the bottom of the beam/plate to generate tensile strain, and the top of the beam/plate generates compressive strain; the prestress action causes the bottom of the beam/plate to generate compressive strain, and the top of the beam/plate to generate tensile strain; for the deflection effect, before the beam/plate is turned over, the beam/plate generates downward deflection under the action of gravity, and the beam/plate generates upward deflection under the action of prestress;
under the state of the simply supported beam/plate after being overturned, for the strain effect, the original bottom position of the beam/plate generates compressive strain under the action of gravity, and the original top position of the beam/plate generates tensile strain; the prestress action causes the original bottom position of the beam/plate to generate compressive strain, and the original top position of the beam/plate generates tensile strain; for the deflection effect, gravity acts to deflect the beam/plate downward, and prestressing acts to deflect the beam/plate downward.
The effect of the strain as described in the present invention,can reflect the total deformation characteristics of the current section, and the representative value is the main deformation characteristic parameter of the section, including the edge strain epsilon of the compression area 0 And cross-sectional curvature psi 0 According to the assumed principle of the flat section, the final strain of the beam section is in linear distribution, the strain distribution linear equation of the section is obtained, and the strain parameter test value epsilon is obtained by the strain sensor 1 1 、ε 2 、ε 3 、ε 4 、ε 5 The edge strain epsilon of the compression zone of the characteristic parameter of the cross section deformation is obtained by linear fitting 0 And cross-sectional curvature psi 0 Obtained by fitting a resulting linear equation in which the section curvature ψ 0 Defined as the tangent of the included straight line angle, i.e.. Psi 0 ＝tanθ；
The deflection effect of the invention can reflect the overall bending deformation characteristic of the current beam/plate, and the representative value is midspan deflection delta 0 The deflection parameter test value delta obtained by the deflection sensor 2 TL 、δ TR 、δ BL 、δ BR Obtained by solving the arithmetic mean, i.e. delta 0 ＝(δ TL +δ TR +δ BL +δ BR )/4。
Target Beam/slab Current effective Pre-stress σ pe The evaluation method of (1) comprises:
(1) Based on the strain effect under the prestress action, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
The beam section strain conforms to the assumption of a flat section, the final strain on the beam section is in linear distribution, and the main deformation characteristic parameter of the section is the edge strain epsilon of a compression zone 0 And cross-sectional curvature psi 0 Expressed as:
in the formula:
wherein epsilon 0 Is compression zone edge strain; psi 0 Is the section curvature; a. The p Area of prestressed reinforcement; e C Is the modulus of elasticity of concrete; y is p The distance from the resultant point of the prestressed steel bars in the tension area to the center of gravity axis of the converted section is calculated; alpha is alpha EP The ratio of the elastic modulus of the prestressed reinforcement to the elastic modulus of the concrete; n is the number of prestressed reinforcement; d is the converted cross-sectional area of the beam; b is Liang Huansuan cross-sectional area moment; i is converted beam section second moment; d n Is the beam net cross-sectional area; b is n Is Liang Jing cross-sectional area moment; i is n Is Liang Jing second moment of area; d s The area of the section of the prestressed reinforcement is shown; b is s The area moment of the prestressed reinforcement is obtained; i is s The second moment of the section of the prestressed reinforcement is;
wherein the strain effect represents the value of the cross-sectional compressive zone edge strain ε as previously described 0 And cross-sectional curvature psi 0 Measured value of strain parameter ε obtained by strain sensor 1 1 、ε 2 、ε 3 、ε 4 、ε 5 The strain straight line distribution equation obtained by linear fitting is obtained, so that the effective prestress sigma can be simultaneously solved pe And the resultant acting distance y of the prestressed reinforcement p ；
(2) Based on the deflection effect under the prestress action, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
Wherein, delta pe Is the bending value of the prestress effect; m pe The bending moment effect is caused by the effective prestress effect at any section x;
the bending moment effect is caused at any section x when unit force acts on the midspan; b is o Is the bending stiffness of the member; q is a prestress equivalent uniform load; l is the simply supported beam/plate span; EI is the section bending rigidity; f is the mid-span sag of the post-tensioned curve prestressed tendon; n is a radical of p The resultant force of the prestress is obtained; a is the cross-sectional area;
the effective prestress σ pe Solving by the equation:
compared with the prior art, the invention has the beneficial effects that:
(1) The method for testing and evaluating the effective prestress of the simply supported beam/slab bridge based on the beam-slab overturning is provided.
(2) The coupling effect of the constant-load effect and the prestress effect is overcome, coupling gravity effect factors are filtered through beam-slab overturning and technical evaluation, and the accurate evaluation of the current effective prestress degree of the simply supported beam/slab is realized.
(3) The method can be completed without depending on a large amount of field measured data and engineering tests, and has convenience and economy.
(4) The method is different from the traditional local damage technology detection and evaluation method, is suitable for on-site actual conditions, and has no damage to the bridge structure.
(5) The beam-slab overturning method can be used for prestressed concrete simply supported beams/slab bridges and is also suitable for other portable beam structures considering the existence of effective prestress.
Drawings
FIG. 1 is a schematic view of the test structure installation of the present invention.
Fig. 2 is a schematic diagram of a target single beam selection.
FIG. 3 is a schematic diagram of a strain sensor layout.
FIG. 4 is a schematic view of a deflection sensor layout; wherein (a) is a beam/plate overturning front deflection sensor layout schematic diagram, and (b) is a beam/plate overturning rear deflection sensor layout schematic diagram.
Fig. 5 is a schematic diagram of the strain test before the simple supported beam/plate is turned over.
Fig. 6 is a schematic diagram of the strain test after the simple beam/plate is flipped.
FIG. 7 is a schematic diagram of a deflection test before turning of a simply supported beam/plate
Fig. 8 is a schematic diagram of the deflection test after the simple supported beam/plate is turned over.
FIG. 9 is a linear plot of cross-sectional strain as a result of a linear fit of the strain measurements.
FIG. 10 is a schematic diagram of strain and deflection changes before the simply supported beam/slab is overturned; wherein, the graphs (a), (b) and (c) are respectively the cross-section strain graphs under the action of gravity, prestress and the coupling of the gravity and the prestress, wherein (+) (plus) represents compression, (-) represents tension, the upper part is the beam top, and the lower part is the beam bottom; the figures (d), (e) and (f) are respectively the deflection deformation schematic diagrams under the action of gravity, prestress and the coupling of the gravity and the prestress.
FIG. 11 is a schematic diagram of the strain and deflection changes of a simply supported beam/slab after being overturned; wherein, the graphs (a), (b) and (c) are respectively the section strain graphs under the gravity, the prestress and the coupling action of the gravity and the prestress, (+) represents the compression, (-) represents the tension, the upper part is the beam top, and the lower part is the beam bottom; the figures (d), (e) and (f) are respectively the deflection deformation schematic diagrams under the action of gravity, prestress and the coupling of the gravity and the prestress.
The notation in the figures:
1-a strain sensor; 2. a deflection sensor; 3. a data acquisition unit; 4. a top plate; 5. a base plate; 6. a left web centerline; 7. the center line of the right web plate.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to the drawings and examples.
Example one
The invention can complete the effective prestress evaluation of the prestressed concrete hollow simply supported beam bridge by analyzing and calculating the strain test values before and after the simply supported beam/plate is turned, and the specific embodiment is shown as follows.
Firstly, a method for testing effective prestress of a simply supported beam/slab bridge based on beam-slab overturning is introduced, and referring to fig. 1, the method comprises the following steps:
the method comprises the following steps: according to the appearance survey of the solid bridge and the disease state result, the bridge span with the worst performance and the target beam/plate are selected, and the cracking characteristics of the typical crack disease are recorded, as shown in fig. 2.
Step two: and (3) removing the longitudinal and transverse bridge-direction relations of the beam/plate wet joint of the target beam/plate and the adjacent beam/plate, the bridge deck continuous concrete and steel bar structure, the hollow plate longitudinal hinge joint concrete and steel bar structure and the like, so that the structure is in a single beam/plate simply supported state, and obtaining the simply supported beam/plate.
Step three: and planning and milling an asphalt concrete wearing layer in the pavement of the simply supported beam/slab bridge deck, and reserving a cement concrete leveling layer and a bridge deck pavement steel mesh.
Step four: referring to fig. 3, the strain sensors 1 are symmetrically arranged at the middle positions of the planned simply supported beam/slab bridge span along the beam height, the number of the strain sensors is 5, and the strain sensors are sequentially marked as S from the top plate 4 to the bottom plate 5 1 、S 2 、S 3 、S 4 、S 5 And the obtained strain parameter test values are sequentially recorded as epsilon 1 、ε 2 、ε 3 、ε 4 、ε 5 。
Step five: on the basis of the exposed simply supported beam/plate, the stress and deformation state of the beam/plate at the moment is defined as the state before overturning, and the strain parameter test value in the state before overturning is obtained through the data collector 3, as shown in fig. 5.
Step six: and the simple support beam/plate body is turned over after the simple support beam/plate is lifted by the hoisting equipment, the turned simple support beam/plate is restored to be in the original position, and the stress and deformation state of the beam/plate at the moment is defined to be the turned state.
Step seven: after the beam/plate is turned over and the structure is stabilized, a test is performed on the turned beam/plate, and a strain parameter test value in a turned state is obtained through the data collector 3, as shown in fig. 6.
The evaluation method based on the test method comprises the following steps:
(1) Before the simply supported hollow beam is turned over, the strain effect caused by the action of gravity is opposite to the strain effect caused by the action of prestress. The gravity causes the bottom of the beam/plate to generate tensile strain, and the top of the beam to generate compressive strain; the prestressing causes compressive strain at the bottom of the beam and tensile strain at the top of the beam, as shown in fig. 10 (a), (b), and (c).
The strain effect of the simply supported beam/plate in the state before turning is the coupling effect under the combined action of the prestress and the gravity and is recorded as S Front side (ii) a Wherein the effect of the strain caused by the action of the prestress is denoted S Preparation of The effect of the strain caused by the action of gravity is denoted S Heavy load Then in the pre-roll-over state, the strain effect S under the coupling effect of the prestress and the gravity Front side ＝S Preparation of -S Heavy load 。
(2) After the simply supported hollow beam is turned over, the strain effect caused by the action of gravity and the strain effect caused by the action of prestress are in the same direction. The gravity causes the original bottom position of the beam/plate to generate compressive strain, and the original top position of the beam/plate to generate tensile strain. The prestressing force causes compressive strain at the original bottom of the beam/plate and tensile strain at the original top of the beam/plate, as shown in fig. 11 (a), (b), and (c).
The strain effect of the simply supported beam/plate in the turned state is the coupling effect under the combined action of the prestress and the gravity and is recorded as S Rear end (ii) a Wherein the effect of the strain caused by the action of the prestress is denoted S Preparation of The effect of the strain caused by the action of gravity is denoted S Heavy load Then, in the turned-over state, the strain effect S under the coupling effect of the prestress and the gravity Rear end ＝S Preparation of -S Heavy load ；
(3) From (1) and (2), the strain effect S under the action of prestress can be obtained Preparation of ＝(S Front side +S Rear end )/2。
(4) In the above steps, the strain effect can reflect the total deformation characteristics of the current cross section, and the representative value is the main deformation characteristic parameter of the cross section, including the edge strain epsilon of the stressed region 0 And cross-sectional curvature psi 0 According to the assumed principle of flat section, the final strain of the beam section is linearly distributed, and the strain parameter measured value epsilon obtained by the strain sensor 1 is used as the linear equation of the strain distribution of the section 1 、ε 2 、ε 3 、ε 4 、ε 5 Obtained by linear fitting, compression zone edge strain ε 0 And cross-sectional curvature psi 0 Obtained by fitting a resulting linear equation in which the section curvature ψ 0 Defined as the tangent of the included straight line angle, i.e.
As shown in fig. 9.
(5) Based on the strain effect under the action of the prestress, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
The beam section strain conforms to the assumption of a flat section, the final strain on the beam section is in linear distribution, and the main deformation characteristic parameter of the section is the edge strain epsilon of a compression zone 0 And cross-sectional curvature psi 0 Expressed as:
in the formula:
wherein epsilon 0 Is the compressive zone edge strain; psi 0 Is the section curvature; a. The p Area of prestressed reinforcement; e C Is the modulus of elasticity of concrete; y is p The distance from the resultant point of the prestressed steel bars in the tension area to the center of gravity axis of the converted section is calculated; alpha is alpha EP The ratio of the elastic modulus of the prestressed reinforcement to the elastic modulus of the concrete; n is the number of prestressed steel bars; d is the converted cross-sectional area of the beam; b is Liang Huansuan cross-sectional area moment; i is converted beam section second moment; d n Is the beam net cross-sectional area; b is n Is Liang Jing cross-sectional area moment; i is n Is Liang Jing second moment of area; d s The area of the section of the prestressed reinforcement is shown; b is s Being prestressed reinforcementsArea moment; i is s The second moment of the section of the prestressed reinforcement is;
obtaining the edge strain ε of the compression zone according to the method 0 And cross-sectional curvature psi 0 Then, the effective prestress sigma can be solved simultaneously pe And the resultant acting distance y of the prestressed reinforcement p And finishing the evaluation of the effective prestress of the prestressed concrete hollow simply-supported beam bridge.
Example two
The invention can complete the effective prestress evaluation of the prestressed concrete hollow simply supported beam bridge by analyzing and calculating the deflection test values before and after the simple supported beam/plate is overturned, and the specific embodiment is shown as follows.
Firstly, a method for testing effective prestress of a simply supported beam/slab bridge based on beam-slab overturning is introduced, and referring to fig. 1, the method comprises the following steps:
the method comprises the following steps: according to the appearance survey of the solid bridge and the disease state result, the bridge span with the worst performance and the target beam/plate are selected, and the cracking characteristics of the typical crack disease are recorded, as shown in fig. 2.
Step two: and (3) removing the longitudinal and transverse bridge-direction relations of the beam/plate wet joint of the target beam/plate and the adjacent beam/plate, the bridge deck continuous concrete and steel bar structure, the hollow plate longitudinal hinge joint concrete and steel bar structure and the like, so that the structure is in a single beam/plate simply supported state, and obtaining the simply supported beam/plate.
Step three: and planning and milling an asphalt concrete wearing layer in the pavement of the simply supported beam/slab bridge deck, and reserving a cement concrete leveling layer and a bridge deck pavement reinforcing mesh.
Step four: referring to fig. 4, the deflection sensors 2 are arranged at the intersections of the top plate 4 and the bottom plate 5 of the simply supported beam/slab bridge span, the left web central line 6 and the right web central line 7, the number of the deflection sensors is 4, and the number of the deflection sensors is sequentially marked as N TL 、N TR 、N BL 、N BR And the obtained deflection parameter test value is recorded as delta TL 、δ TR 、δ BL 、δ BR The specific layout can be as shown in fig. 4 (a) and (b).
Step five: on the basis of the exposed simply supported beam/plate, the stress and deformation state of the beam/plate at the moment is defined as a pre-overturn state, and a deflection parameter test value in the pre-overturn state is obtained through the data collector 3, as shown in fig. 7.
Step six: and the simple support beam/plate body is turned over after the simple support beam/plate is lifted by the hoisting equipment, the turned simple support beam/plate is restored to be in the original position, and the stress and deformation state of the beam/plate at the moment is defined to be the turned state.
Step seven: after the beam/board is turned over and the structure is stable, a test is performed on the turned beam/board, and a deflection parameter test value in a turned state is obtained through the data collector 3, as shown in fig. 8.
The evaluation method based on the test method comprises the following steps:
(1) Before the simply supported hollow beam is turned over, the deflection caused by the action of gravity is opposite to the deflection caused by the action of prestress. The gravity causes the beam/plate to deflect downwards, and the prestressing causes the beam/plate to deflect upwards, as shown in fig. 10 (d), (e), (f).
The deflection effect of the simply supported beam/plate before turning over is the coupling effect under the combined action of the prestress and the gravity and is marked as S Front side (ii) a Wherein the deflection state caused by the prestress action is marked as S Preparation of The deflection state caused by gravity is denoted as S Heavy load In the pre-overturn state, the deflection state S under the coupling effect of the prestress and the gravity Front side ＝S Preparing -S Heavy load 。
(2) After the simply supported hollow beam is turned over, the deflection caused by the action of gravity and the deflection caused by the action of prestress are in the same direction. The gravity acts to deflect the beam/slab downward and the prestressing acts to deflect the beam/slab downward as shown in fig. 11 (d), (e), (f).
The deflection effect of the simply supported beam/plate in the turned state is the coupling effect under the combined action of the prestress and the gravity and is marked as S Rear end (ii) a Wherein the deflection state caused by the prestress action is marked as S Preparing The deflection state caused by gravity is denoted as S Heavy load In the turned-over state, the deflection state S under the coupling effect of the prestress and the gravity Rear end ＝S Preparation of -S Heavy load ；
(3) The flexibility effect S under the action of prestress can be obtained from (1) and (2) Preparation of ＝(S Front part +S Rear end )/2。
(4) In the steps, the deflection effect can reflect the overall bending deformation characteristic of the current beam/plate, and the representative value is midspan deflection delta 0 The deflection parameter test value delta obtained by the deflection sensor 2 TL 、δ TR 、δ BL 、δ BR Obtained by solving the arithmetic mean, i.e. delta 0 ＝(δ TL +δ TR +δ BL +δ BR )/4。
(5) Based on the deflection effect under the action of the prestress, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
Wherein, delta pe Is the bending value of the prestress effect; m is a group of pe The bending moment effect is caused by the effective prestress effect at any section x;
the bending moment effect is caused at any section x when unit force acts on the midspan; b is o The bending rigidity of the component is obtained; q is a prestress equivalent uniform load; l is the simply supported beam/plate span; EI is the section bending rigidity; f is the mid-span sag of the post-tensioning curve prestressed tendon; n is a radical of p The resultant force of the prestress is obtained; a is the cross-sectional area;
the effective prestress σ pe Solving by the equation:
according to the invention, the effective prestress of the prestressed concrete hollow simply-supported girder bridge is evaluated.
The embodiments of the present invention described herein are not intended to be all limiting, and any modifications, equivalent alterations and the like, which are made by those skilled in the art, are intended to be included within the scope of the present invention, all of which are within the spirit and scope of the inventive concept.
Claims (3)
1. The evaluation method of the method for testing the effective prestress of the simply supported beam/slab bridge based on the beam-slab overturning is characterized by comprising the following steps of:
the method comprises the following steps: selecting the bridge span and the target beam/plate which are the worst according to the appearance survey of the solid bridge and the disease state result, and recording the cracking characteristics of typical crack diseases;
step two: the longitudinal and transverse bridge-direction connection between the target beam/plate and the adjacent beam/plate is removed, so that the structure is in a single-beam/plate simply-supported state, and a simply-supported beam/plate is obtained;
step three: planing and milling an asphalt concrete wearing layer in the simply supported beam/slab bridge deck pavement, and reserving a cement concrete leveling layer and a bridge deck pavement reinforcing mesh;
step four: distributing a strain sensor (1) or a deflection sensor (2) in a midspan region of the simply supported beam/plate after planing and milling to obtain a corresponding strain or deflection parameter test value; wherein, the strain sensors (1) are symmetrically arranged at the midspan positions of the simply supported beam/slab bridge along the beam height, the number of the strain sensors is 5, and the strain sensors are sequentially marked as S from the top plate (4) to the bottom plate (5) 1 、S 2 、S 3 、S 4 、S 5 And the obtained strain parameter test values are sequentially recorded as epsilon 1 、ε 2 、ε 3 、ε 4 、ε 5 (ii) a The deflection sensors (2) are arranged at the intersections of the simply supported beam/slab bridge span middle top plate (4), the bottom plate (5), the left web central line (6) and the right web central line (7), the number of the deflection sensors is 4, and the deflection sensors are sequentially marked as N TL 、N TR 、N BL 、N BR And the obtained deflection parameter test value is recorded as delta TL 、δ TR 、δ BL 、δ BR ；
Step five: defining the stress and deformation state of the simply supported beam/plate as the state before overturning on the basis of the simply supported beam/plate after planing and milling, and acquiring a strain or deflection parameter test value in the state before overturning through a data collector (3);
step six: the simple support beam/plate body is turned over after the simple support beam/plate is lifted through the hoisting equipment, the turned simple support beam/plate body is restored to be in the original position, and the stress and deformation state of the simple support beam/plate are defined to be in the turned state;
step seven: after the simple supporting beam/plate is turned over and reaches the stable structure, carrying out test testing on the turned simple supporting beam/plate, and acquiring a strain or deflection parameter test value in a turned state through a data collector (3);
wherein:
(1) The strain or deflection effect of the simply supported beam/slab before turning is the coupling effect under the combined action of the prestress and the gravity and is marked as S Front side (ii) a Wherein the effect of strain or deflection caused by the action of prestress is denoted S Preparing The effect of strain or deflection caused by the action of gravity is denoted S Heavy load Since the strain and deflection effects caused by the action of the prestress are respectively opposite to the strain and deflection effects caused by the action of the gravity, the strain or deflection effect S under the coupling effect of the prestress and the gravity is realized in the state before the overturning Front side ＝S Preparing -S Heavy load ；
(2) The strain or deflection effect of the simply supported beam/plate after turning over is the coupling effect under the combined action of the prestress and the gravity and is marked as S Rear end (ii) a Wherein the effect of strain or deflection caused by the action of prestress is denoted S Preparing The effect of strain or deflection caused by the action of gravity is denoted S Heavy load Because the strain and deflection effects caused by the action of the prestress are respectively in the same direction as the strain and deflection effects caused by the action of the gravity, the strain or deflection effect S under the coupling effect of the prestress and the action of the gravity is realized in the state after the overturning Rear end ＝S Preparing +S Heavy load ；
(3) From (1) and (2), the strain or deflection effect S under the action of prestress can be obtained Preparation of ＝(S Front side +S Rear end )/2；
Wherein:
(31) The strain effect can reflect the total deformation characteristics of the current section, and the representative value is the main deformation characteristic parameter of the section and comprises the edge strain epsilon of the compression area 0 And cross-sectional curvature psi 0 According to the assumed principle of a flat section, the final strain of the beam section is linearly distributed, and the strain distribution linear equation of the section and a strain parameter test value epsilon obtained by a strain sensor (1) 1 、ε 2 、ε 3 、ε 4 、ε 5 Linear fitting results in compression zone edge strain ε 0 And cross-sectional curvature psi 0 Obtained by fitting the obtained straight-line equation in which the cross-sectional curvature ψ 0 Defined as the tangent of the included straight line angle, i.e.. Psi 0 ＝tanθ；
(32) The deflection effect can reflect the overall bending deformation characteristic of the current beam/plate, and the representative value is midspan deflection delta 0 The deflection parameter test value delta obtained by the deflection sensor (2) TL 、δ TR 、δ BL 、δ BR Obtained by solving the arithmetic mean, i.e. delta 0 ＝(δ TL +δ TR +δ BL +δ BR )/4；
(41) Based on the strain effect under the action of the prestress, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
The beam section strain conforms to the assumption of a flat section, the final strain on the beam section is in linear distribution, and the main deformation characteristic parameter of the section is the edge strain epsilon of a compression zone 0 And cross-sectional curvature psi 0 Expressed as:
in the formula:
wherein epsilon 0 Is the compressive zone edge strain; psi 0 To cut offA surface curvature; a. The p Area of prestressed reinforcement; e C Is the modulus of elasticity of concrete; y is p The distance from the resultant point of the prestressed steel bars in the tension area to the center of gravity axis of the converted section is calculated; alpha is alpha EP The ratio of the elastic modulus of the prestressed reinforcement to the elastic modulus of the concrete; n is the number of prestressed reinforcement; d is the converted cross-sectional area of the beam; b is Liang Huansuan cross-sectional area moment; i is converted beam section second moment; d n Is the beam net cross-sectional area; b is n Is Liang Jing cross-sectional area moment; i is n Liang Jing second moment of area; d s The area of the section of the prestressed reinforcement is shown; b is s The area moment of the prestressed reinforcement is obtained; i is s The second moment of the section of the prestressed reinforcement is;
obtaining the edge strain epsilon of the compression zone 0 And cross-sectional curvature psi 0 Then, the effective prestress sigma is solved simultaneously pe And the resultant acting distance y of the prestressed reinforcement p ；
(42) Based on the deflection effect under the action of the prestress, the current effective prestress sigma of the target beam/plate is evaluated by the following method pe ：
Wherein, delta pe Is the bending value of the pre-stress effect; m pe The bending moment effect is caused by the effective prestress effect at any section x;
the bending moment effect is caused at any section x when unit force acts on the midspan; b is o Is the bending stiffness of the member; q is a prestress equivalent uniform load; l is the simply supported beam/plate span; EI is the section bending rigidity; f is the mid-span sag of the post-tensioned curve prestressed tendon; n is a radical of hydrogen p The resultant force of the prestress is obtained; a is the cross-sectional area;
the effective prestress σ pe The solution is given by:
2. the method for evaluating the effective prestress test method of the simply supported beam/slab bridge based on the beam-slab overturning as claimed in claim 1, wherein in the second step, the longitudinal and transverse bridge-direction relation to be released comprises: beam/slab wet joints, bridge deck continuous concrete and rebar constructions, hollow slab longitudinal hinge joint concrete and rebar constructions.
3. The method for evaluating the effective prestress test method of the simply supported beam/plate bridge based on the beam-plate overturning as claimed in claim 1, wherein:
(1) In the state before the simply supported beam/plate is turned over, for the strain effect, the bottom of the beam/plate generates tensile strain under the action of gravity, and the top of the beam/plate generates compressive strain; the prestress action causes the bottom of the beam/plate to generate compressive strain, and the top of the beam/plate to generate tensile strain; for the deflection effect, before the beam/plate is turned over, the beam/plate generates downward deflection under the action of gravity, and generates upward deflection under the action of prestress;
(2) In the state after the simply supported beam/plate is turned over, for the strain effect, the gravity action enables the original bottom position of the beam/plate to generate the compressive strain, and the original top position of the beam/plate generates the tensile strain; the prestress action causes the original bottom position of the beam/plate to generate compressive strain, and the original top position of the beam/plate generates tensile strain; for the deflection effect, gravity acts to deflect the beam/plate downward, and prestressing acts to deflect the beam/plate downward.
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| CN113283130B (en) * | 2021-04-21 | 2022-04-15 | 中国铁路设计集团有限公司 | Method for monitoring dynamic deflection of standard beam of 32 meters of high-speed railway based on strain mode |
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