CN110082206B - Steel truss pedestrian overpass static load test evaluation method considering pin hole gap influence - Google Patents
Steel truss pedestrian overpass static load test evaluation method considering pin hole gap influence Download PDFInfo
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Abstract
The invention provides a steel truss considering the influence of pin hole clearanceA static load test evaluation method for a pedestrian overpass belongs to the technical field of bridge bearing capacity tests. The method comprises the following steps: firstly, eliminating the inelastic deformation of the steel trestle with partial loading capacity, then finding out the starting point of the elastic stage in the test process according to the displacement change value, and then using the loading capacity of the elastic stage to unload the check coefficient eta of the bridge effect change value caused by the loading capacity of the elastic stageVariation valueAnd evaluating the bearing capacity of the steel truss pedestrian overpass, wherein the change value of the bridge effect comprises a strain change value and a displacement change value. The method fully considers the structural characteristics of the steel truss pedestrian overpass, can evaluate the bearing capacity of the steel truss pedestrian overpass more effectively and objectively, reduces misjudgment, can be carried out after a test loading vehicle is adopted to carry out appropriate prepressing during the test, can reduce resource waste, improves the safety of the test, and can be widely applied to the field of evaluating the bearing capacity of the steel truss pedestrian overpass through a static load test.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of bridge bearing capacity tests, and particularly relates to a static load test evaluation method of a steel truss pedestrian overpass, which considers the influence of pin hole gaps.
[ background of the invention ]
In the field of urban bridge construction, in order to avoid conflict between traffic flow and pedestrian flow planes when the traffic flow and the pedestrian flow planes are intersected, ensure safe crossing of people, improve the speed of a vehicle and reduce traffic accidents, pedestrian overpasses are usually constructed in sections with large traffic flow and dense pedestrians, or on intersections, squares and railways. The pedestrian overpass comprises prestressed concrete pedestrian overpasses, steel box girder pedestrian overpasses, steel truss pedestrian overpasses and other structural forms. No matter which structure type of pedestrian overpass is adopted, after the erection of the pedestrian overpass is completed, whether the bearing capacity of the pedestrian overpass meets the design requirement or not is often evaluated through a static load test.
The current common practice of the static load test evaluation of the steel truss pedestrian overpass is as follows: the method comprises the following steps of: solving the internal force of the control section of the bridge according to the design load, taking the internal force as the basis of loading control of the static load test, and then loading the internal force of the bridge in a grading manner through vehicle load or other loads to meet the standard requirement so as to solve the theoretical loading value; secondly, data acquisition: at the beginning of the static load test, before loading, the stress value epsilon of the control section is read0Sum displacement value H0(ii) a Reading the stress value epsilon of the control section during first-stage loading1Sum displacement value H1(ii) a Reading the stress value epsilon of the control section during the ith-level loadingiSum displacement value Hi(ii) a Reading the stress value epsilon of the control section during the final Nth-level loadingNSum displacement value HN(ii) a After unloading, reading the stress value epsilon of the control sectionN-0Sum displacement value HN-0. Processing data: found through practical measurement values in the two ways: strain elastic value epsilonElastic value＝εN-εn-0(ii) a Value of displacement elasticity HElastic value＝HN-Hn-0(ii) a Residual strain value epsilonResidual value＝εN-0-ε0(ii) a Residual value of displacement HResidual value＝HN-0-H0(ii) a Further, the strain checking coefficient eta is obtainedStrain of＝εElastic value/εCalculated valueAnd a displacement check coefficient etaDisplacement of＝HElastic value/HCalculated value(wherein εCalculated valueAnd HCalculated valueCalculated values of the tested section strain and displacement under corresponding loading conditions) respectively,Relative residual strain SStrain of＝(εN-0-ε0)/(εN-ε0) Relative residual displacement SDisplacement of＝(HN-0-H0)/(HN-H0). Fourth static test evaluation: checking coefficient η by strainStrain ofAnd a displacement check coefficient etaDisplacement ofRelative residual strain SStrain ofAnd relative residual displacement SDisplacement ofTo evaluate the static load test. However, there are many disadvantages to this method for evaluating the bearing capacity of the steel truss pedestrian bridge: the structural characteristics of the steel truss pedestrian overpass are neglected, namely the connecting members of the steel truss pedestrian overpass are mainly Bailey beams, the finished product size and the design of the connecting members may have differences, so that gaps of different degrees often exist among the connecting members, the connecting members are generally connected through pins, and gaps also exist among the pins and the pin holes. The steel truss pedestrian overpass structure has large inelastic deformation, so that the actual measurement effect (strain and displacement) is often larger than the effect directly generated on the bridge structure due to vehicle load or other loads, especially the displacement, and the check coefficient eta is larger due to the fact that the actual measurement effect contains a large part of pin hole gap amount, and misjudgment is easily caused. The two structures have the characteristics of causing larger residual values of strain and displacement after unloading, thereby leading the relative residual strain SStrain ofAnd relative residual displacement SDisplacement ofToo large so that its value does not meet the specification requirements. Thirdly, in order to eliminate the pin hole clearance of structure itself and make bridge structures load efficiency coefficient satisfy the standard requirement, need more or heavier vehicle load, cause material, energy waste, neither economy nor safety.
[ summary of the invention ]
The invention aims to: aiming at the existing problems, the method for evaluating the static load test of the steel truss pedestrian overpass considering the influence of the pin hole clearance is provided, the structural characteristics of the steel truss pedestrian overpass are fully considered, the bearing capacity of the steel truss pedestrian overpass can be evaluated more effectively and objectively, misjudgment is reduced, and the method can be widely applied to the field of evaluating the bearing capacity of the steel truss pedestrian overpass through the static load test.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a steel truss pedestrian bridge static load test evaluation method considering pin hole gap influence comprises the following steps: firstly, eliminating the inelastic deformation of the steel trestle with partial loading capacity, then finding out the starting point of the elastic stage in the test process according to the displacement change value, and then using the loading capacity of the elastic stage to unload the check coefficient eta of the bridge effect change value caused by the loading capacity of the elastic stageVariation valueAnd evaluating the bearing capacity of the steel truss pedestrian overpass, wherein the change value of the bridge effect comprises a strain change value and a displacement change value.
In the invention, further, the method comprises the following steps:
establishing a finite element numerical model of a steel trestle according to relevant data of a steel truss manway overpass to be tested, and formulating a static load test scheme;
secondly, embedding sensors at key positions of the steel truss pedestrian overpass, namely a maximum positive bending moment section in a main span and a maximum negative bending moment section at a main span fulcrum position, carrying out field grading loading, reading bridge effect values under each grade of loading conditions, namely a strain change value and a displacement change value, and finding out a starting point of an elastic stage in the test process according to the displacement change value;
thirdly, unloading twice after the bridge structure is stable in the full-load state, unloading the loading capacity in the elastic stage for the first time, unloading all the residual loads for the second time, and reading the strain change value and the displacement change value of the bridge under each stage of unloading working condition;
fourthly, arranging analysis data, and checking coefficients eta of bridge effect change values, namely strain change values and displacement change values, caused by loading amount in unloading elastic phaseVariation valueThe bearing capacity of the steel truss pedestrian bridge is evaluated.
In the invention, further, the field grading loading in the step (2) is carried out according to the total test load and the load increment in a grading way, and the grading number is not less than 5; reading strain value epsilon of the control section during the ith-level loadingiSum displacement value Hi(ii) a Reading strain value epsilon of the control section during the i +1 level loadingi+1Sum displacement value Hi+1(ii) a The theoretical calculation bit under the loading condition of the stage is assumedShift change value of Δ HTheoretical valueIf there is Δ HMeasured value＝Hi+1-Hi≤△HTheoretical valueAnd considering the ith level as the starting point of the elastic deformation of the structure.
In the invention, further, the field unloading in the step (3) is carried out in two stages, the first stage unloading is carried out to the starting point of the elastic stage, the second stage unloading is completed to all the residual loads, and the strain change value and the displacement change value of the bridge under each stage of unloading working condition are read.
In the invention, further, in the step (3), the check coefficient eta of the strain change value caused by the loading amount in the elastic stage is unloadedValue of change of strainAnd a check coefficient η of the displacement variation valueValue of change in displacementThe method is determined by the following formula:
ηvalue of change of strain＝△εVariation value/△εTheoretical value
ηValue of change in displacement＝△HVariation value/△HTheoretical value
In the formula, Delta epsilonVariation value＝ε-1-ε+n，△HVariation value＝H-1-H+n；
ε-1、H-1Respectively testing the strain change value and the displacement change value of the bridge effect of the section under the first-stage unloading working condition; epsilon+n、H+nTesting the strain change value and the displacement change value of the bridge effect of the section under the full-load condition, namely under the final loading working condition; delta epsilonTheoretical value、△HTheoretical valueRespectively are theoretical calculated values of strain and displacement change caused by the loading amount in the unloading elastic stage in the test process.
In the invention, further, the relevant data of the trestle to be tested in the step (1) comprise a design drawing, an completion drawing, a construction record, an supervision log, completion data, existing maintenance and repair data, historical bridge detection test data, reinforcement and repair data, and an apparent condition and a surrounding environment condition inspected on site by the trestle.
In order to solve the unscientific, unsafe and uneconomical method of the existing evaluation method of the static load test of the steel truss pedestrian overpass, the inventor establishes the evaluation method of the static load test of the steel truss pedestrian overpass considering the influence of pin hole gaps, and evaluates the static load test of the steel truss pedestrian overpass according to the check coefficient of the change value of the effect (stress and displacement). The method fully considers the structural characteristics of the steel truss pedestrian overpass, namely the connecting members of the steel truss pedestrian overpass are mainly Bailey beams, the sizes and the designs of finished products of the connecting members are possibly different, so that gaps of different degrees often exist among the members, the members are generally connected through pins, gaps also exist among the pins and the pin holes, and only after the pin hole gaps of the structure are eliminated, the structure can enter an elastic stress stage, and the static load test of the structure can be better evaluated.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
the method fully considers the structural characteristics of the steel trestle, namely: the connecting components of the steel truss pedestrian overpass are mainly Bailey beams, the sizes and the designs of the finished products of the connecting components are possibly different, so that gaps with different degrees often exist among the components, the components are generally connected through pins, gaps also exist among the pins and the pin holes, the steel truss pedestrian overpass structure has large inelastic deformation caused by the above steps, the actual measurement effect (strain and displacement) is often larger than the effect directly generated on the bridge structure due to vehicle load or other loads, particularly the displacement, and the verification coefficient eta is larger due to the fact that the steel truss pedestrian overpass structure contains a large part of pin hole gap, and misjudgment is easily caused. The method eliminates the inelastic deformation of the steel trestle by partial loading capacity, finds out the starting point of the elastic stage in the test process according to the displacement change value, and then uses the check coefficient eta of the bridge effect change value caused by the loading capacity in the elastic stage to unloadVariation valueThe bearing capacity of the steel truss pedestrian bridge is evaluated, so that the calibration coefficient eta is more accurate, and misjudgment is reduced.
The method of the invention considers the characteristics of the structure per se, so that the relative residual strain S is obtainedStrain ofOr relative residual displacement SDisplacement ofCan meet the standard requirement.
In order to eliminate the inelastic deformation of the structure and enable the load efficiency coefficient of the bridge structure to meet the standard requirement, the conventional evaluation method needs more or heavier vehicle loads, wastes materials and energy and is neither economical nor safe. The method can be carried out after the test loading vehicle is properly pre-pressed, so that the resource waste can be reduced, and the test safety can be improved.
[ description of the drawings ]
FIG. 1 is an elevation view of a steel truss pedestrian bridge in an example of use;
FIG. 2 is a cross-sectional view of a steel truss pedestrian bridge in an application example;
FIG. 3 is a finite element model diagram of a steel truss pedestrian overpass in an application example.
[ detailed description ] embodiments
In order that the invention may be more clearly expressed, the invention will now be further described by way of specific examples.
1. The technical problem is as follows: strain check coefficient eta calculated by existing methodStrain ofAnd a displacement check coefficient etaDisplacement ofRelative residual strain SStrain ofAnd relative residual displacement SDisplacement ofThe static load test of the steel truss pedestrian overpass is evaluated, the structural characteristics of the steel truss pedestrian overpass are ignored, namely the connecting members of the steel truss pedestrian overpass are mainly Bailey beams, the finished product size and the design of the connecting members are possibly different, so that gaps of different degrees often exist among the members, the members are generally connected through pins, and gaps also exist among the pins and the pin holes. The steel truss pedestrian overpass structure has large inelastic deformation, so that the actual measurement effect (strain and displacement) is often larger than the effect directly generated on the bridge structure due to vehicle load or other loads, especially the displacement (which contains a large part of pin hole gap amount), further the calibration coefficient eta is large, and misjudgment is easily caused; and the residual values of strain and displacement after unloading are large, thereby leading the relative residual strain SStrain ofAnd relative residual displacement SDisplacement ofIt is big partially, in order to eliminate the pinhole clearance of structure itself and make bridge structures load efficiency coefficient satisfy the standard requirement, need more or heavier vehicle load, cause material, energy extravagant, neither economic, also safe.
2. Design idea
The invention relates to a static load test evaluation method of a steel truss pedestrian bridge, which considers the influence of pin hole gaps, and evaluates a static load test according to a check coefficient of a bridge effect (stress and displacement) change value in a static load test project.
The method comprises the following steps of: and calculating the internal force of the control section of the bridge according to the design load, wherein the internal force is used as a basis for loading the control bending moment in the static load test, and then the internal force is loaded to the bridge in a grading manner through vehicle loads or other loads to meet the standard requirement, so that the theoretical loading value is calculated.
Secondly, determining the starting point of the elastic phase: embedding sensors at key positions of the steel trestle, namely the midspan maximum positive bending moment section and the main span fulcrum maximum negative bending moment section, reading a stress value epsilon of a control section before loading when a static load test is started0Sum displacement value H0(ii) a Reading the stress value epsilon of the control section during first-stage loading1Sum displacement value H1(ii) a Reading the stress value epsilon of the control section during the ith-level loadingiSum displacement value Hi(ii) a Reading the stress value epsilon of the control section during the i +1 level loadingi+1Sum displacement value Hi+1(ii) a When the last level, namely the Nth level is loaded and the bridge structure is stable in a full-load state, reading the stress value epsilon of the control sectionNSum displacement value HN. The required grading number is not lower than 5, and the stress value epsilon and the displacement value H of each loading stage of the control section are respectively read. And found by actual measurement: displacement variation value Δ HMeasured value＝Hi+1-Hi(ii) a If there is Δ HMeasured value≤△HTheoretical value(△HTheoretical valueTheoretically calculating the displacement change value under the corresponding loading working condition), the ith grade is considered as the starting point of the elastic stage.
Thirdly, unloading data acquisition: after the bridge structure is stable in the full-load state, reading the stress value epsilon of the control sectionnSum displacement value HnUnloading twice, the loading amount in the elastic stage of the first unloading, reading the stress value epsilon of the control section-1Sum displacement value H-1Unloading all residual loads for the second time, and reading the stress value epsilon of the control section-2Sum displacement value H-2；
Fourth, data processing: found through practical measurement values in the two ways: value of change in strain Δ εMeasured value＝ε-1-ε+nChange in displacement value Δ HMeasured value＝H-1-H+n(ii) a Calculating a strain change value verification coefficient eta caused by loading amount in an unloading elastic stageValue of change of strainAnd a check coefficient η of the displacement variation valueValue of change in displacement。
ηValue of change of strain＝△εVariation value/△εTheoretical value
ηValue of change in displacement＝△HVariation value/△HTheoretical value
In the formula, Delta epsilonMeasured value＝ε-1-ε+n；△HMeasured value＝H-1-H+n；△εTheoretical value、△HTheoretical valueRespectively are theoretical calculated values of strain and displacement change under corresponding unloading working conditions.
Fifthly, static load test evaluation: checking coefficient eta of strain variation value caused by elastic stage unloading amountValue of change of strainAnd a calibration coefficient eta of the displacement variation valueDisplacement to positionThe bearing capacity of the steel truss pedestrian bridge is evaluated.
3. Procedure for the preparation of the
Establishing a finite element numerical model of a steel truss pedestrian overpass according to design data and the like, and formulating a static load test scheme; the relevant data of the steel truss pedestrian bridge to be tested comprises a design drawing, a completion drawing, a construction record, a supervision log, completion data, existing maintenance data, data of a bridge historical detection test, data of reinforcement and maintenance, and apparent conditions and surrounding environment conditions inspected in the field of the steel trestle; the step is carried out by adopting the existing technical specification, is not the focus of the research of the invention, and therefore, the step is not explained herein.
Embedding sensors at key positions (the maximum positive bending moment section in the main span, the maximum negative bending moment section at the main span fulcrum position and the like) of the steel truss pedestrian overpass by using a test scheme, carrying out field graded loading, reading bridge effect (strain and displacement) values under each grade of loading working conditions, and finding out a starting point of an elastic stage in the test process according to a displacement change value;
thirdly, after the bridge structure is stable in the full-load state, unloading twice, unloading the loading capacity in the elastic stage once, unloading all the residual loads twice, and reading the bridge effect (strain and displacement) value under each stage of unloading working condition;
fourthly, arranging analysis data, and using the loading amount in the unloading elastic stage to cause the check coefficient eta of the change value of the bridge effect (strain and displacement)Variation valueThe bearing capacity of the steel truss pedestrian bridge is evaluated.
To further illustrate how the invention may be carried out, reference is made to the following examples of use which are made to the above-described steps.
Examples of the applications
The total length of the steel truss pedestrian overpass is 68.98m, the full width of the bridge deck is 4.10m, and the steel truss pedestrian overpass is orthogonal by 90 degrees. The main bridge has four spans, and the spans are combined: 16.17m +2 x 18.40m +13.07m, the main bridge adopts an aluminum alloy truss, and the step ladder is an aluminum alloy structural slab ladder way. The lower structure of the main body is a pier and a bearing platform with a T-shaped steel structure, and the foundation is a bored pile foundation. The lower part of the step ladder is provided with a T-shaped pier and a bearing platform, and the foundation is a bored pile foundation. The bridge deck pavement adopts an aluminum alloy bridge deck slab, and the bridge is provided with an anti-skidding wear-resistant coating. The bridge floor guardrail adopts double-layer rubber reinforced plastic toughened glass guardrail, and the main bridge is respectively provided with a left rail and a right rail. The drainage system on the bridge is provided with 4 drainage holes, and the left and right sides of the bridge heads on the two sides are respectively 1. The elevation and section views of the steel truss pedestrian bridge are shown in figures 1 and 2. The test is to be carried out to determine the bearing capacity, and the control section and the corresponding working condition are determined by finite element analysis, as shown in fig. 3.
For the assembly type Bailey beam steel truss pedestrian overpass, the assembling between the Bailey beams adopts pin connection, and gaps generally exist between pins and pin holes for convenient installation. After the structure is loaded, the Bailey beams generate relative displacement due to pin hole gaps, and the deflection of the staggered holes of the structure is caused. Theoretically, the pin hole gap can be eliminated to a large extent through repeated large-load prepressing, but under the common load test condition, the repeated prepressing is difficult to realize, and meanwhile, the prepressing with excessive weight is also an unsafe practice during the test. Therefore, the static load test is only carried out after the test loading block is properly pre-pressed.
The No. 2 span is selected as a static load test span, and the table 1 and the table 2 are respectively a displacement measured value and a theoretical calculated value, and a strain measured value and a theoretical calculated value under corresponding working conditions.
Calculating the check coefficient eta of the average value of the strain of the working condition 1+5 according to a conventional methodStrain of0.995 in 199-19)/181, and a check coefficient eta of the displacement average valueDisplacement of1.144 maximum relative residual strain SStrain of18/135 ═ 13.3% and maximum relative residual displacement SDisplacement of1.79/7.74 ═ 23.2% (1 station);
the method according to the invention: the solving steps are as follows
Determining a starting point of an elastic stage
Delta H under working condition 1+3Measured value＝(H3-H2)Variation value＝(7.14-5.62)>△HTheoretical value(H3-H2)Theoretical valueThe result is (4.48-2.99), which shows that the structure has no inelastic deformation in the working condition; similarly, working condition 1+4 is calculated: delta HMeasured in fact＝(H4-H3)Variation value＝(8.53-7.14)<△HTheoretical value＝(H4-H3)Theoretical valueAnd (5.98-4.48), indicating that the working condition 3 is the starting point of the elastic phase. The bearing capacity of the steel trestle can be evaluated according to the check coefficient of the effect (strain, displacement) change value caused by the loading capacity of the unloading elastic stage (namely the loading capacity of the unloading working condition 3-5).
The method is shown in the formula etaVariation value＝△SVariation value/△STheoretical valueAnd calculating a check coefficient for determining the change value of the effect (strain and displacement) in the static load test.
Calibration coefficient eta of strain variation valueValue of change of strain＝(135-199)/(109-181)＝0.889，
Calibration coefficient eta of displacement variation valueValue of change in displacement＝(7.15-10.01)/(4.48-7.47)＝0.957。
From the calculation results, it can be known that: the conventional method ignores the structural characteristics of the steel truss pedestrian overpass, namely the connection of the steel truss pedestrian overpassThere are numerous connecting members, typically joined by pins, with varying degrees of clearance between the members and also between the pins and pin holes. The steel truss pedestrian overpass structure has large inelastic deformation, so that the actual measurement effect (strain and displacement) is often larger than the effect directly generated on the bridge structure due to vehicle load or other loads, especially the displacement (which contains a large part of inelastic deformation values), and further the calculated strain check coefficient eta is causedStrain of(0.995) and a displacement check coefficient etaDisplacement of(1.144) is large, and does not meet the requirement that the check coefficient is less than 1 in the road and bridge load test regulation (JTG/T J21-01-2015), thus easily causing misjudgment. The method of the invention is based on the check coefficient of the effect (internal force, displacement) change value (the check coefficient eta of the strain change value)Value of change of strain0.889, the check coefficient η of the displacement variation valueValue of change in displacement0.957) to evaluate the static load test of the steel truss pedestrian overpass is more scientific.
TABLE 1 summary of the 2# Cross-A section Displacement test results in Condition 1 (unit: mm)
TABLE 2 summary of 2# Cross A section Strain test results (Unit:. mu. epsilon.) under Condition 1
The above description is intended to describe in detail the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the claims of the present invention, and all equivalent changes and modifications made within the technical spirit of the present invention should fall within the scope of the claims of the present invention.
Claims (3)
1. A static load test evaluation method for a steel truss pedestrian overpass considering the influence of pin hole gaps is characterized by comprising the following steps: firstly, eliminating the inelastic deformation of the steel trestle with partial loading capacity, then finding out the starting point of the elastic stage in the test process according to the displacement change value, and then using the loading capacity of the elastic stage to unload the check coefficient eta of the bridge effect change value caused by the loading capacity of the elastic stageVariation valueEvaluating the bearing capacity of the steel truss pedestrian overpass, wherein the change value of the bridge effect comprises a strain change value and a displacement change value; the method comprises the following steps:
establishing a finite element numerical model of a steel trestle according to relevant data of a steel truss manway overpass to be tested, and formulating a static load test scheme;
secondly, embedding sensors at key positions of the steel truss pedestrian overpass, namely a maximum positive bending moment section in a main span and a maximum negative bending moment section at a main span fulcrum position, carrying out field grading loading, reading bridge effect values under each grade of loading conditions, namely a strain change value and a displacement change value, and finding out a starting point of an elastic stage in the test process according to the displacement change value;
thirdly, unloading twice after the bridge structure is stable in the full-load state, unloading the loading capacity in the elastic stage for the first time, unloading all the residual loads for the second time, and reading the strain change value and the displacement change value of the bridge under each stage of unloading working condition;
fourthly, arranging analysis data, and checking coefficients eta of bridge effect change values, namely strain change values and displacement change values, caused by loading amount in unloading elastic phaseVariation valueThe bearing capacity of the steel truss pedestrian bridge is evaluated;
the field grading loading in the step (2) is carried out according to the total test load and the load increment in a grading way, and the grading number is not lower than 5 grades; first, theiReading strain value epsilon of control section during stage loadingiSum displacement value Hi(ii) a First, theiReading strain value epsilon of the control section during +1 level loadingi+1Sum displacement value Hi+1(ii) a The theoretical calculation displacement change value is assumed to be delta H under the loading working condition of the stageTheoretical valueIf there is Δ HMeasured value=Hi+1-Hi≤△HTheoretical valueThen it is considered as the firstiThe stage is a starting point of structure elastic deformation; checking coefficient eta of strain change value caused by loading amount in unloading elastic stage in step (4)Value of change of strainAnd a check coefficient η of the displacement variation valueValue of change in displacementThe method is determined by the following formula:
ηvalue of change of strain=△εVariation value/△εTheoretical value
ηValue of change in displacement=△HVariation value/△HTheoretical value
In the formula, Delta epsilonVariation value=ε-1-ε+n，△HVariation value=H-1-H+n；
ε-1、H-1Respectively testing the strain change value and the displacement change value of the bridge effect of the section under the first-stage unloading working condition; epsilon+n、H+nTesting the strain change value and the displacement change value of the bridge effect of the section under the full-load condition, namely under the final loading working condition; delta epsilonTheoretical value、△HTheoretical valueRespectively are theoretical calculated values of strain and displacement change caused by the loading amount in the unloading elastic stage in the test process.
2. The evaluation method according to claim 1, characterized in that: and (4) in the step (3), the field unloading is carried out in two stages, the first stage unloads to the starting point of the elastic stage, the second stage unloads all residual loads, and the strain change value and the displacement change value of the bridge under each stage of unloading working condition are read.
3. The evaluation method according to claim 1, characterized in that: relevant data of the trestle to be tested in the step (1) comprise a design drawing, a completion drawing, a construction record, an supervision log, completion data, existing data of maintenance and repair, data of a bridge historical detection test, data of reinforcement and repair, and apparent conditions and surrounding environment conditions inspected in the field of the trestle.
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