CN109682557B - Method for evaluating bearing capacity test of pedestrian overpass railing structure - Google Patents

Method for evaluating bearing capacity test of pedestrian overpass railing structure Download PDF

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CN109682557B
CN109682557B CN201811467443.6A CN201811467443A CN109682557B CN 109682557 B CN109682557 B CN 109682557B CN 201811467443 A CN201811467443 A CN 201811467443A CN 109682557 B CN109682557 B CN 109682557B
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test
value
thrust
loading
displacement
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CN109682557A (en
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周明珲
周宏亮
杨扬
景飒
赵辉
张振华
孔祥民
关爱博
王灏
靳军
王光明
董健
陶水忠
李桐
扈莉
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Beijing Urban Road Maintenance And Management Center
Beijing Municipal Road and Bridge Co Ltd
Beijing Municipal Engineering Research Institute
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Beijing Urban Road Maintenance And Management Center
Beijing Municipal Road and Bridge Co Ltd
Beijing Municipal Engineering Research Institute
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01M5/0008—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of bridges
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01D—CONSTRUCTION OF BRIDGES, ELEVATED ROADWAYS OR VIADUCTS; ASSEMBLY OF BRIDGES
    • E01D19/00—Structural or constructional details of bridges
    • E01D19/10—Railings; Protectors against smoke or gases, e.g. of locomotives; Maintenance travellers; Fastening of pipes or cables to bridges
    • E01D19/103—Parapets, railings ; Guard barriers or road-bridges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
    • G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
    • G01M5/0058—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems of elongated objects, e.g. pipes, masts, towers or railways

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Abstract

A method for testing and evaluating the bearing capacity of a pedestrian overpass railing structure comprises the steps of collecting or measuring test parameters of the pedestrian overpass railing structure, determining the positions of test measuring points and test load, testing the bearing capacity of the pedestrian overpass railing structure, and testing and evaluating the test results. The invention adopts the principle of internal force equivalence, equivalently simulates the upright posts and the upright posts into spring elements according to the bending rigidity of the upright posts and the upright posts, equivalently simulates the handrail beams into elastic supporting beams for calculation, forms a new calculation model, establishes a test evaluation method for the bearing capacity of the pedestrian overpass handrail structure in the city, establishes a unified test method and a judgment standard in the aspects of test steps, sampling positions, sampling frequency and the like, perfects a rapid nondestructive detection method system of facilities, provides powerful data basis for detection evaluation and construction acceptance, is convenient for developing comprehensive general investigation and identification work on the overpass handrail structure, realizes accurate release of limited maintenance funds, and ensures that the facilities provide safe and reliable services.

Description

Method for evaluating bearing capacity test of pedestrian overpass railing structure
Technical Field
The invention relates to an evaluation method, in particular to a pedestrian overpass railing structure bearing capacity test evaluation method.
Background
The urban pedestrian overpass is used as one of urban traffic infrastructures, can effectively avoid conflicts generated when traffic flow and pedestrian flow planes are intersected, greatly improves traffic capacity, and reduces traffic accidents. Along with the development of urbanization, more and more cities begin to use a great amount of pedestrian overpass facilities to realize intersection pedestrian and vehicle shunting, alleviate the traffic pressure that increases day by day, and this creates city system of walking slowly promptly, provides infrastructure guarantee for green trip. The main body of the pedestrian overpass service object is a pedestrian, and besides the upper structure and the lower structure have enough bearing capacity, the railing of the pedestrian overpass is also one of the important components of the facility for providing functional service, and enough rigidity, strength and integrity must be provided to ensure the use safety of the pedestrian.
At present, no relevant specifications or standards are provided for a test verification and evaluation method for the bearing capacity of a railing structure to meet unified technical requirements, a conventional test method is a truncation test method, and an integral test method is gradually derived along with popularization of finite elements in recent years.
The truncation test method is to locally truncate and divide the handrail into linear meter sections, and the horizontal pushing resistance bearing capacity applied to the handrail is tested according to the horizontal load requirement. However, the method belongs to a damage test method, the secondary connection of the handrail exists after the test, the integrity and the attractiveness of the handrail are influenced, the secondary connection can also become a weak link of the handrail, and the test method is different from the actual use condition.
The integral test method is developed along with the progress of finite element calculation means in recent years, the method is to utilize finite element calculation software to carry out modeling, carry out load equivalent calculation according to horizontal load required by specifications, utilize a reaction frame device to apply single-point or multi-point acting force to a railing on site to test, and measure the related deformation of the railing structure at the same time.
At present, methods and specifications for detecting, evaluating and maintaining a pedestrian overpass structure mainly aim at evaluating and maintaining the overall bearing capacity and technical conditions of a main body structure at the upper part and the lower part of the overpass, and effective local evaluation is difficult to be made in the aspects of test and evaluation of the connection quality and the bearing capacity of a railing structural part. The lack of uniform and perfect test evaluation methods in the industry and the lack of uniform test methods and judgment standards in the aspects of test steps, sampling positions, sampling frequencies and the like causes the judgment results to be only individualized and not representative, cannot cover the evaluation of the whole structure, and is not suitable for large-scale regular census of the railing structure.
Disclosure of Invention
The invention aims to provide a test evaluation method for the bearing capacity of a pedestrian bridge railing structure, and aims to solve the technical problems that secondary connection influences the overall use safety of the railing and the test method is different from the actual use condition in a cut-off test method and also solve the problems that the analysis accuracy degree of the overall test method is too dependent on analysts, the equivalent standard is not uniform or the equivalent is unreasonable and a uniform and complete test evaluation method is not available.
In order to achieve the purpose, the invention adopts the following technical scheme:
a test evaluation method for the bearing capacity of a pedestrian overpass railing structure comprises the following evaluation steps:
step one, collect or measure pedestrian overpass railing structure's test parameter, include:
step A, material strength of the structure:
when the data is available:
taking a delivery quality certificate and an entrance inspection qualified report of the material, and taking a standard value of the material strength;
when no data can be checked: intercepting a detection test piece on the structural member to perform a material strength test, and taking the minimum value of the test strength;
step B, geometric parameters of the structure:
pedestrian bridge railing structure includes vertical pole setting between horizontal handrail, vertical stand and the stand:
the two adjacent expansion joint spaces of the handrail: the length of the handrail structure between two adjacent temperature control seams is defined by the temperature control seams of the handrail;
the type and size of the cross-section of the handrail;
the type of cross-section, the size of the cross-section, the height of the uprights and the average spacing between two adjacent uprights
The section type, the section size and the height of the vertical rods and the average distance between two adjacent vertical rods;
step two, determining the position of a test point and the test load:
step A: position of test station:
selecting a position where horizontal thrust can generate disadvantage on the handrail structure as a test point; in the loading range, the number of test points is not less than 3 and not more than 5, and the width of the loading range is not more than 1.0 m;
step B, determining a test load, namely an equivalent thrust and deformation relation:
calculating the relation between equivalent thrust and deformation according to the material strength of the step A and the geometric parameters of the step B in the step I, and determining the control values of the thrust and the deformation loaded in the test; during calculation, according to an internal force equivalent principle, the vertical rods and the upright columns are equivalently simulated into spring elements according to the bending rigidity of the vertical rods and the upright columns for calculation, and the handrails are equivalently used as elastic supporting beams to form a calculation model;
step three: testing the bearing capacity of the pedestrian overpass railing structure:
step A: carrying out a loading test on the railing structure by using the platform bridge railing bearing capacity nondestructive testing device according to a designed loading mode, wherein the loading mode is as follows:
when the equivalent thrust value is used as a control value for loading, measuring a corresponding displacement value, and comparing the measured data of a measuring point with a calculated value in the loading process;
when the equivalent displacement value is taken as a control value for loading, measuring a corresponding thrust value, and comparing the measured data of a measuring point with a calculated value in the loading process;
and B: starting a detection device to load a measuring point:
equally dividing the maximum test load into not less than 5 grades; before formal loading test, the test structure is preloaded, and the preloaded load is loaded in a grading way according to grade I-2: loading the structure step by step during formal loading, and then unloading to zero step by step or at one time; the loading duration is determined according to the time required for the structural deformation to reach stability;
step four: test results and evaluation:
step A: and (3) outputting a test result:
inputting the geometric parameters of the structure in the first step before the test, and obtaining a thrust-displacement calculated value curve by a detection device according to a finite element calculation mode;
during the step-by-step loading process of the detection device, the detection device observes and stores data of thrust and displacement in real time, and after test data are processed, the detection device draws a relation curve of a thrust-displacement measured value and compares the relation curve with a thrust-displacement calculated value curve;
and B: and (3) evaluating test results:
when the equivalent thrust value is used as a control value for loading, a 'thrust X-displacement Y' curve is output, the actually measured displacement value is compared with the calculated displacement value, the judgment is unqualified when the actually measured displacement value is equal to or exceeds the calculated value, and the judgment is qualified when the actually measured displacement value is smaller than the calculated value;
when the equivalent displacement value is used as a control value for loading, a 'displacement X-thrust Y' curve is output, the actually measured thrust value is compared with the calculated thrust value, the judgment that the measured thrust value is equal to or exceeds the calculated thrust value is qualified, and the judgment that the measured thrust value is smaller than the calculated value is unqualified.
In the first step, the detection test piece is intercepted by a representative secondary stress member;
the secondary stress member is a stress member in the structure except the primary stress member;
the main stress components are armrests and upright posts.
In the second step, the positions of the measuring points are one or more of the following:
the position of the most adverse effect value of the internal force generated under different test loading conditions;
the position where the most adverse effect value of deformation is generated under different test loading conditions;
detecting positions of the whole structure, which do not meet requirements or have questions;
detecting positions which do not meet requirements or are in question by a single component;
the position with serious defect degree of the whole structure;
locations where single component defects are severe.
And in the third step, the loading duration time of the steel bar structure is 15-30 min, and the loading duration time of the steel structure is not less than lOmin.
And C, suspending loading and searching for reasons when one of the following conditions occurs in the test of the step three, and continuing the test after confirming the structure and the personnel safety:
the actually measured equivalent thrust value or displacement value reaches or exceeds a thrust or displacement calculated value under the action of a control load;
cracks appear in the structure in the loading process, or the development width of the existing cracks of a small number of structures is larger than the allowable crack width;
the rule of actually measured integral structure variation is greatly different from the calculation result;
the structure makes an abnormal sound.
In the fourth step, under the action of load, buckling failure or fracture failure is not allowed to occur on any part of the whole structure or the single component; after unloading, the deformation displacement is stable, and when the relative residual displacement value of the measuring point is greater than 20% of the maximum displacement, the bearing capacity of the railing structure is evaluated as not meeting the requirement; the calculation formula of the relative residual displacement value of the measuring point is as follows: Δ S/S is less than or equal to 20%, where Δ S is the residual displacement and S is the maximum displacement.
In the step B of the second step, an internal force equivalence principle is adopted, the vertical rods and the vertical columns are equivalently simulated into spring elements according to the bending rigidity of the vertical rods and the vertical columns, the handrail beams are equivalently simulated into elastic supporting beams for calculation, and a new calculation model is formed;
the field measurement and calculation of the geometric parameters of the railings comprises the following steps:
length L of railing unitrCalculating the lateral inertia moment I of the handrail according to the characteristics of the cross sectionr；
Measuring the height H of the vertical rodpDistance between vertical poles SpCalculating the transverse bridge direction inertia moment I of the vertical rod according to the characteristics of the cross sectionp(ii) a If the handrail is provided with the reinforced upright post, the height H of the upright post needs to be measuredsDistance between vertical poles Ss(ii) a Calculating the transverse bridge direction inertia moment I of the upright post according to the characteristics of the cross sections；
Based on an integral test method, adopting an internal force equivalence principle, equivalently simulating the handrail upright posts and the upright posts as spring elements according to the bending rigidity of the handrail upright posts and the upright posts, equivalently converting the handrail beams into elastic supporting beams for calculation, and forming a new calculation model;
the parameter calculation method of the calculation model comprises the following steps:
s1, the equivalent spring stiffness of the spring element is as follows:
Figure RE-GDA0001991739330000041
in the formula:
k-equivalent spring stiffness per linear meter in the test range;
Kp-equivalent spring stiffness per linear meter of upright within the test range;
Ksequivalent spring stiffness per linear meter of upright column in test range, and K when no reinforcing upright column is arrangeds＝0；
Sp-the spacing of the uprights within the test range;
Ssspacing of columns within the test range, S without reinforcing columnss＝Sp；
Hp，HsThe height from the welding points of the upright rods and the upright columns to the center of the handrail in the test range;
Ip，Is-moment of inertia of the uprights, within the test range;
Ep、Es-modulus of elasticity of the railing post, post;
the structure is replaced by a beam with rigidity K as elastic support, and the rigidity value of the beam body is ErIrCharacteristic coefficient of
Figure RE-GDA0001991739330000051
Alpha l is the converted length, wherein l is the distance between the side load and the nearest expansion joint of the handrail;
s2, calculating the internal force and deformation of the standard load:
A. calculating the internal force effect of the upright under the condition of equal rigidity, converting the rigidity ratio of the reinforced upright to the upright into the rigidity of the upright,
determining the number of vertical rods in the calculation range:
nj＝np+(Is/Ip)ns
in the formula:
nj-the number of equivalent uprights in the test range;
ns-number of uprights in the test range;
np-number of uprights in the test range;
B. displacement of handrail under action of standard horizontal uniform loaduCalculated as follows:
Figure RE-GDA0001991739330000052
wherein:
Figure RE-GDA0001991739330000053
solving foru＝y
S3, testing the equivalent thrust target displacement value:
the experimental equivalent target horizontal displacement value is determined according to the following formula:
'P＝γe u
in the formula:
'P-testing the target horizontal displacement value resulting from the equivalent thrust;
u-horizontal displacement values generated by the action of the equispaced loads q;
γe-conversion factor of the concentration, gammae＝1.232；
S4, calculating the effect of the equivalent concentrated load of the test:
when in equivalent loading, only test loading force is available in the whole range of the whole handrail, and the loading force P isiThe force is applied in the form of multi-point equidistant concentrated force:
A. concentration force PiWhen the alpha l is more than or equal to 2.75 from the action point to two sides, the calculation is carried out according to the following formula:
Figure RE-GDA0001991739330000061
wherein:
Figure RE-GDA0001991739330000062
B. concentration force PiWhen the acting point meets the condition that alpha l is less than 2.75 to one side, calculating according to an initial parameter formula:
Figure RE-GDA0001991739330000063
wherein:
Figure RE-GDA0001991739330000064
solving forP＝y
Obtaining the relation between the equivalent thrust and the deformation;
s5, determination of test parameters:
when in useP≈'PWhen the positive deviation and the negative deviation are less than 5 percent, calculating a thrust value to obtain the test equivalent loading thrust; test horizontal displacement judgment valueeCalculated according to the following formula:
e＝γt P
in the formula:
e-a test horizontal displacement decision value;
Ptest thrust Σ PiResulting horizontal displacement valueP；
γtDetermination of the correction coefficient of displacement, gamma, by experimentt＝0.7；
Therefore, the loading thrust P of the equivalent test of the railing system under the condition of equivalent internal force can be determinediAnd test horizontal displacement judgment valueeAnd determining the thrust force and deformation control values of the test loading.
Compared with the prior art, the invention has the following characteristics and beneficial effects:
the invention is based on an integral test method, adopts an internal force equivalence principle, enables the handrail upright post and the upright post to be equivalent to a spring element according to the bending rigidity of the handrail upright post and the upright post, and enables the handrail to be equivalent to an elastic supporting beam, and establishes a simplified handrail calculation method to replace finite element calculation by a method of calculating a parameter equation and combining polynomial fitting coefficients, so as to obtain the relation between equivalent loaded thrust and deformation.
The invention establishes a test evaluation method for the bearing capacity of the urban pedestrian overpass railing structure based on an integral test method, establishes a unified test method and a judgment standard in the aspects of test steps, sampling positions, sampling frequency and the like, perfects a rapid nondestructive detection method system of facilities, can provide powerful data basis for detection evaluation and construction acceptance, is convenient for carrying out comprehensive general survey and identification work on the overpass railing structure, is beneficial to a management and maintenance unit to know the technical condition of the railing structure in time, finds potential safety hazards, makes reasonable maintenance countermeasures, realizes accurate release of limited maintenance funds, and ensures that the facilities provide safe and reliable services.
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The present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is a schematic flow diagram of an equivalent principle of the present invention.
Detailed Description
Example (b):
a test evaluation method for the bearing capacity of a pedestrian overpass railing structure comprises the following evaluation steps:
step one, collecting test parameters of a pedestrian overpass railing structure, wherein the test parameters are comprehensively determined by combining the field investigation condition of a bridge and the feasibility of field detection implementation, and the method specifically comprises the following steps:
step A, material strength of the structure:
when the data is available:
taking a delivery quality certificate and an entrance inspection qualified report of the material, and taking a standard value of the material strength;
when no data can be checked: intercepting a detection test piece on the structural member to perform a material strength test, and taking the minimum value of the test strength;
in the first step, the detection test piece is intercepted by a representative secondary stress member;
the secondary stress member is a stress member in the structure except the primary stress member;
the main stress components are armrests and upright posts.
Step B, geometric parameters of the structure:
pedestrian bridge railing structure includes vertical pole setting between horizontal handrail, vertical stand and the stand:
the two adjacent expansion joint spaces of the handrail: the length of the handrail structure between two adjacent temperature control seams is defined by the temperature control seams of the handrail;
the type and size of the cross-section of the handrail;
the section type, the section size and the height of the upright post and the average distance between two adjacent upright posts;
the section type, the section size and the height of the vertical rods and the average distance between two adjacent vertical rods;
it is also desirable to record structural member defects and durability.
Step two, determining the position of a test point and the test load:
step A: position of test station:
selecting a position where horizontal thrust can generate disadvantage on the handrail structure as a test point; in the loading range, the number of test measuring points is not less than 3 and not more than 5, the width of the loading range is not more than 1.0m, the arrangement of the measuring points is convenient for instrument installation and reading observation, and the safety of personnel, instruments and equipment is guaranteed;
the measuring point positions are one or more of the following:
the position of the most adverse effect value of the internal force generated under different test loading conditions;
the position where the most adverse effect value of deformation is generated under different test loading conditions;
detecting positions of the whole structure, which do not meet requirements or have questions;
detecting positions which do not meet requirements or are in question by a single component;
the position with serious defect degree of the whole structure;
locations where single component defects are severe.
Step B, determining a test load, namely an equivalent thrust and deformation relation:
and C, calculating the relation between equivalent thrust and deformation according to the material strength of the step A and the geometric parameters of the step B in the step I, and determining the control values of the thrust and the deformation of the test loading. During calculation, according to the principle of internal force equivalence, the vertical rods and the upright columns are equivalently simulated into spring elements according to the bending stiffness of the vertical rods and the upright columns, the vertical rods and the upright columns are calculated, the handrail is equivalently an elastic supporting beam, and a calculation model is formed.
Referring to fig. 1, in step B of step two, the cross-sectional dimensions of the balustrade handrail, the vertical rods and the vertical columns are measured on site according to the actual situation of the overpass balustrade, and the following physical quantities are calculated:
length L of railing unitrCalculating the lateral inertia moment I of the handrail according to the characteristics of the cross sectionr；
Measuring the height H of the vertical rodpDistance between vertical poles SpCalculating the transverse bridge direction inertia moment I of the vertical rod according to the characteristics of the cross sectionp(ii) a If the handrail is provided with the reinforced upright post, the height H of the upright post needs to be measuredsDistance between vertical poles Ss(ii) a Calculating the transverse bridge direction inertia moment I of the upright post according to the characteristics of the cross sections。
The parameter calculation method comprises the following steps:
based on an integral test method, by adopting an internal force equivalence principle, the handrail upright post and the upright post are equivalently simulated into a spring element according to the bending rigidity of the handrail upright post and the upright post, and the handrail beam is equivalently converted into an elastic supporting beam for calculation. A new computational model is formed.
S1, the equivalent spring stiffness of the spring element is as follows:
Figure RE-GDA0001991739330000091
in the formula:
k-equivalent spring stiffness per linear meter in the test range;
Kp-equivalent spring stiffness per linear meter of upright within the test range;
Ksequivalent spring stiffness per linear meter of upright column in test range, and K when no reinforcing upright column is arrangeds＝0；
Sp-the spacing of the uprights within the test range;
Ssspacing of columns within the test range, S without reinforcing columnss＝Sp；
Hp，HsThe height from the welding points of the upright rods and the upright columns to the center of the handrail in the test range;
Ip，Is-moment of inertia of the uprights, within the test range;
Ep、Esmodulus of elasticity of the railing uprights, posts.
The structure is replaced by a beam with rigidity K as elastic support, and the rigidity value of the beam body is ErIrCharacteristic coefficient of
Figure RE-GDA0001991739330000092
And alpha l is the converted length, wherein l is the distance between the side load and the nearest expansion joint of the handrail.
S2, calculating the internal force and deformation of the standard load:
A. calculating the vertical rod internal force effect under the condition of equal rigidity, converting the rigidity ratio of the reinforced vertical rods to the vertical rod rigidity, and determining the number of the vertical rods in the calculation range:
nj＝np+(Is/Ip)ns
in the formula:
nj-the number of equivalent uprights in the test range;
ns-number of uprights in the test range;
npthe number of uprights in the test range.
B. Displacement of handrail under action of standard horizontal uniform loaduCalculating by using an initial parameter formula according to the following formula:
Figure RE-GDA0001991739330000101
wherein:
Figure RE-GDA0001991739330000102
solving foru＝y
S3, testing the equivalent thrust target displacement value:
in order to avoid too concentrated test loads, a range, typically set at 1.0m, is recommended. And the multipoint concentrated force is synchronously loaded, so that the local damage to the structure is avoided. On the structure with the reinforced upright post, the loading center position is preferably selected to be the center of the reinforced upright post. The loading points are preferably loaded by 3-5 points, and the loading intervals of the loading points are preferably equal. The experimental equivalent target horizontal displacement value is determined according to the following formula:
'P＝γe u
in the formula:
'P-testing the target horizontal displacement value resulting from the equivalent thrust;
u-horizontal displacement values generated by the action of the equispaced loads q;
γe-conversion factor of the concentration, gammae＝1.232。
S4, calculating the effect of the equivalent concentrated load of the test:
when in equivalent loading, only test loading force is available in the whole range of the whole handrail, and the loading force P isiApplication is usually in the form of a multi-point equally spaced concentrated force.
A. Concentration force PiWhen the alpha l is more than or equal to 2.75 from the action point to two sides, the calculation is carried out according to the following formula:
Figure RE-GDA0001991739330000103
wherein:
Figure RE-GDA0001991739330000104
B. concentration force PiWhen the acting point meets the condition that alpha l is less than 2.75 to one side, calculating according to an initial parameter formula:
Figure RE-GDA0001991739330000105
wherein:
Figure RE-GDA0001991739330000106
solving forP＝y
And obtaining the relation between the equivalent thrust and the deformation.
S5, determination of test parameters:
when in useP≈'PAnd (the positive deviation and the negative deviation are less than 5%), calculating a thrust value, namely the test equivalent loading thrust. Test horizontal displacement judgment valueeCalculated according to the following formula:
e＝γt P
in the formula:
e-a test horizontal displacement decision value;
Ptest thrust Σ PiResulting horizontal displacement valueP；
γtDetermination of the correction coefficient of displacement, gamma, by experimentt＝0.7。
Therefore, the loading thrust P of the equivalent test of the railing system under the condition of equivalent internal force can be determinediAnd test horizontal displacement judgment valueeAnd determining the thrust force and deformation control values of the test loading.
Step three: testing the bearing capacity of the pedestrian overpass railing structure:
step A: the platform bridge railing bearing capacity nondestructive testing device is used for carrying out loading test on the railing structure according to the designed loading mode,
the loading modes are as follows:
when the equivalent thrust value is used as a control value for loading, measuring a corresponding displacement value, and comparing the measured data of a measuring point with a calculated value in the loading process;
and when the equivalent displacement value is taken as a control value for loading, measuring the corresponding thrust value, and comparing the measured data of the measuring point with the calculated value in the loading process.
And B: starting a detection device to load a measuring point:
equally dividing the maximum test load into not less than 5 grades; before formal loading test, the test structure is preloaded, and the preloaded load is loaded in a grading way according to grade I-2: loading the structure step by step during formal loading, and then unloading to zero step by step or at one time; the duration of loading is determined by the time required for the structural deformation to reach stability.
The loading duration time of the steel bar structure is 15min-30min, and the loading duration time of the steel structure is not less than lOmin.
And C, suspending loading and searching for reasons when one of the following conditions occurs in the test of the step three, and continuing the test after confirming the structure and the personnel safety:
the actually measured equivalent thrust value or displacement value reaches or exceeds a thrust or displacement calculated value under the action of a control load;
cracks appear in the structure in the loading process, or the development width of the existing cracks of a small number of structures is larger than the allowable crack width;
the rule of actually measured integral structure variation is greatly different from the calculation result;
the structure makes an abnormal sound.
Step four: test results and evaluation:
step A: and (3) outputting a test result:
during the step-by-step loading process of the detection device, the detection device observes and stores thrust and displacement data in real time, after test data are processed, the detection device draws a relation curve of a thrust-displacement measured value and compares the relation curve with a thrust-displacement calculated value curve, wherein the thrust-displacement calculated value curve is a curve obtained in a finite element calculation mode;
and B: and (3) evaluating test results:
when the equivalent thrust value is used as a control value for loading, a 'thrust X-displacement Y' curve is output, the actually measured displacement value is compared with the calculated displacement value, the judgment is unqualified when the actually measured displacement value is equal to or exceeds the calculated value, and the judgment is qualified when the actually measured displacement value is smaller than the calculated value;
when the equivalent displacement value is used as a control value for loading, a 'displacement X-thrust Y' curve is output, the actually measured thrust value is compared with the calculated thrust value, the judgment that the measured thrust value is equal to or exceeds the calculated thrust value is qualified, and the judgment that the measured thrust value is smaller than the calculated value is unqualified.
In the fourth step, under the action of load, buckling failure or fracture failure is not allowed to occur on any part of the whole structure or the single component; after unloading, the deformation displacement is stable, and when the relative residual displacement value of the measuring point is greater than 20% of the maximum displacement, the bearing capacity of the railing structure is evaluated as not meeting the requirement; the calculation formula of the relative residual displacement value of the measuring point is as follows: Δ S/S is less than or equal to 20%, where Δ S is the residual displacement and S is the maximum displacement.

Claims (4)

1. A test evaluation method for the bearing capacity of a pedestrian overpass railing structure is characterized by comprising the following evaluation steps:
step one, collect or measure pedestrian overpass railing structure's test parameter, include:
step A, material strength of the structure:
when the data is available:
taking a delivery quality certificate and an entrance inspection qualified report of the material, and taking a standard value of the material strength;
when no data can be checked: intercepting a detection test piece on the structural member to perform a material strength test, and taking the minimum value of the test strength;
step B, geometric parameters of the structure:
pedestrian bridge railing structure includes vertical pole setting between horizontal handrail, vertical stand and the stand:
the two adjacent expansion joint spaces of the handrail: the length of the handrail structure between two adjacent temperature control seams is defined by the temperature control seams of the handrail;
the type and size of the cross-section of the handrail;
the type of cross-section, the size of the cross-section, the height of the uprights and the average spacing between two adjacent uprights
The section type, the section size and the height of the vertical rods and the average distance between two adjacent vertical rods;
step two, determining the position of a test point and the test load:
step A: position of test station:
selecting positions where horizontal thrust can generate disadvantages on the handrail structure as test measuring points, wherein in a loading range, the number of the test measuring points is not less than 3, not more than 5, and the width of the loading range is not more than 1.0 m;
step B, determining a test load, namely an equivalent thrust and deformation relation:
calculating the relation between equivalent thrust and deformation according to the material strength of the step A and the geometric parameters of the step B in the step I, and determining the control values of the thrust and the deformation loaded in the test; during calculation, according to an internal force equivalent principle, the vertical rods and the upright columns are equivalently simulated into spring elements according to the bending rigidity of the vertical rods and the upright columns for calculation, and the handrails are equivalently used as elastic supporting beams to form a calculation model;
step three: testing the bearing capacity of the pedestrian overpass railing structure:
step A: carrying out a loading test on the railing structure by using the platform bridge railing bearing capacity nondestructive testing device according to a designed loading mode, wherein the loading mode is as follows:
when the equivalent thrust value is used as a control value for loading, measuring a corresponding displacement value, and comparing the measured data of a measuring point with a calculated value in the loading process;
when the equivalent displacement value is taken as a control value for loading, measuring a corresponding thrust value, and comparing the measured data of a measuring point with a calculated value in the loading process;
and B: starting a detection device to load a measuring point:
equally dividing the maximum test load into not less than 5 grades; before formal loading test, the test structure is preloaded, and the preloaded load is loaded in a grading way according to grade I-2: loading the structure step by step during formal loading, and then unloading to zero step by step or at one time; the loading duration is determined according to the time required for the structural deformation to reach stability;
step four: test results and evaluation:
step A: and (3) outputting a test result:
inputting the geometric parameters of the structure in the first step before the test, and obtaining a thrust-displacement calculated value curve by a detection device according to a finite element calculation mode;
during the step-by-step loading process of the detection device, the detection device observes and stores data of thrust and displacement in real time, and after test data are processed, the detection device draws a relation curve of a thrust-displacement measured value and compares the relation curve with a thrust-displacement calculated value curve;
and B: and (3) evaluating test results:
when the equivalent thrust value is used as a control value for loading, a 'thrust X-displacement Y' curve is output, the actually measured displacement value is compared with the calculated displacement value, the judgment is unqualified when the actually measured displacement value is equal to or exceeds the calculated value, and the judgment is qualified when the actually measured displacement value is smaller than the calculated value; when the equivalent displacement value is used as a control value for loading, a 'displacement X-thrust Y' curve is output, the actually measured thrust value is compared with the calculated thrust value, the judgment that the measured thrust value is equal to or exceeds the calculated thrust value is qualified, and the judgment that the measured thrust value is smaller than the calculated value is unqualified; in the first step, the detection test piece is intercepted by a representative secondary stress member;
the secondary stress member is a stress member in the structure except the primary stress member;
the main stress components are armrests and upright posts;
in the second step, the positions of the measuring points are one or more of the following:
the position of the most adverse effect value of the internal force generated under different test loading conditions;
the position where the most adverse effect value of deformation is generated under different test loading conditions;
detecting positions of the whole structure, which do not meet requirements or have questions;
detecting positions which do not meet requirements or are in question by a single component;
the position with serious defect degree of the whole structure;
locations where single component defects are severe;
and in the third step, the loading duration time of the steel bar structure is 15min-30min, and the loading duration time of the steel structure is not less than l0 min.
2. The test assessment method for the bearing capacity of the pedestrian overpass railing structure according to claim 1, characterized in that:
and C, suspending loading and searching for reasons when one of the following conditions occurs in the test of the step three, and continuing the test after confirming the structure and the personnel safety:
the actually measured equivalent thrust value or displacement value reaches or exceeds a thrust or displacement calculated value under the action of a control load; cracks appear in the structure in the loading process, or the development width of the existing cracks of a small number of structures is larger than the allowable crack width;
the rule of actually measured integral structure variation is greatly different from the calculation result;
the structure makes an abnormal sound.
3. The test assessment method for the bearing capacity of the pedestrian overpass railing structure according to claim 1, characterized in that:
in the fourth step, under the action of load, buckling failure or fracture failure is not allowed to occur on any part of the whole structure or the single component; after unloading, the deformation displacement is stable, and when the relative residual displacement value of the measuring point is greater than 20% of the maximum displacement, the bearing capacity of the railing structure is evaluated as not meeting the requirement; the calculation formula of the relative residual displacement value of the measuring point is as follows: Δ S/S is less than or equal to 20%, where Δ S is the residual displacement and S is the maximum displacement.
4. The test assessment method for the bearing capacity of the pedestrian overpass railing structure according to claim 1, characterized in that:
in the step B of the second step, an internal force equivalence principle is adopted, the vertical rods and the vertical columns are equivalently simulated into spring elements according to the bending rigidity of the vertical rods and the vertical columns, the handrail beams are equivalently simulated into elastic supporting beams for calculation, and a new calculation model is formed;
the field measurement and calculation of the geometric parameters of the railings comprises the following steps:
length L of railing unitrCalculating the lateral inertia moment I of the handrail according to the characteristics of the cross sectionr；
Measuring the height H of the vertical rodpDistance between vertical poles SpCalculating the transverse bridge direction inertia moment I of the vertical rod according to the characteristics of the cross sectionp(ii) a If the handrail is provided with the reinforced upright post, the height H of the upright post needs to be measuredsDistance between vertical poles Ss(ii) a Calculating the transverse bridge direction inertia moment I of the upright post according to the characteristics of the cross sections；
Based on an integral test method, adopting an internal force equivalence principle, equivalently simulating the handrail upright post and the upright post as spring elements according to the bending rigidity of the handrail upright post and the upright post, equivalently converting the handrail beam into an elastic supporting beam for calculation, and forming a new calculation model;
the parameter calculation method of the calculation model comprises the following steps:
s1, the equivalent spring stiffness of the spring element is as follows:
Figure FDA0002686799670000041
in the formula:
k-equivalent spring stiffness per linear meter in the test range;
Kp-equivalent spring stiffness per linear meter of upright within the test range;
Ksequivalent spring stiffness per linear meter of upright column in test range, and K when no reinforcing upright column is arrangeds＝0；
Sp-the spacing of the uprights within the test range;
Ssspacing of columns within the test range, S without reinforcing columnss＝Sp；
Hp，HsThe height from the welding point of the upright rod to the center of the handrail in the test range and the height from the welding point of the upright rod to the center of the handrail in the test range;
Ip，Is-moment of inertia of the uprights in the test range, moment of inertia of the uprights in the test range;
Ep，Es-the modulus of elasticity of the uprights, of the uprights;
the structure is replaced by a beam with rigidity K as elastic support, and the rigidity value of the beam body is ErIrCharacteristic coefficient of
Figure FDA0002686799670000042
Alpha l is the converted length, wherein l is the distance between the side load and the nearest expansion joint of the handrail;
s2, calculating the internal force and deformation of the standard load:
A. calculating the vertical rod internal force effect under the condition of equal rigidity, converting the rigidity ratio of the reinforced vertical rods to the vertical rods into the vertical rod rigidity, and determining the number of the vertical rods in the calculation range:
nj＝np+(Is/Ip)ns
in the formula:
nj-the number of equivalent uprights in the test range;
ns-number of uprights in the test range;
np-number of uprights in the test range;
B. displacement of handrail under action of standard horizontal uniform loaduCalculated as follows:
Figure FDA0002686799670000051
wherein:
Figure FDA0002686799670000052
solving foru＝y
S3, testing the equivalent thrust target displacement value:
the experimental equivalent target horizontal displacement value is determined according to the following formula:
'P＝γe u
in the formula:
'P-testing the target horizontal displacement value resulting from the equivalent thrust;
u-horizontal displacement values generated by the action of the equispaced loads q;
γe-conversion factor of the concentration, gammae＝1.232；
S4, calculating the effect of the equivalent concentrated load of the test:
when in equivalent loading, only test loading force is available in the whole range of the whole handrail, and the loading force P isiThe force is applied in the form of multi-point equidistant concentrated force:
A. concentration force PiWhen the alpha l is more than or equal to 2.75 from the action point to two sides, the calculation is carried out according to the following formula:
Figure FDA0002686799670000053
wherein:
Figure FDA0002686799670000054
B. concentration force PiWhen the acting point meets the condition that alpha l is less than 2.75 to one side, calculating according to an initial parameter formula:
Figure FDA0002686799670000055
wherein:
Figure FDA0002686799670000061
solving forP＝y
Obtaining the relation between the equivalent thrust and the deformation;
s5, determination of test parameters:
when in useP≈'PWhen the positive deviation and the negative deviation are less than 5 percent, calculating a thrust value to obtain the test equivalent loading thrust; test horizontal displacement judgment valueeCalculated according to the following formula:
e＝γt P
in the formula:
e-a test horizontal displacement decision value;
Ptest thrust Σ PiResulting horizontal displacement valueP；
γtDetermination of the correction coefficient of displacement, gamma, by experimentt＝0.7；
Therefore, the loading thrust P of the equivalent test of the railing system under the condition of equivalent internal force can be determinediAnd test horizontal displacement judgment valueeAnd determining the thrust force and deformation control values of the test loading.
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