CN112507496B - Grid structure damage assessment method based on static load test - Google Patents

Grid structure damage assessment method based on static load test Download PDF

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CN112507496B
CN112507496B CN202110161565.8A CN202110161565A CN112507496B CN 112507496 B CN112507496 B CN 112507496B CN 202110161565 A CN202110161565 A CN 202110161565A CN 112507496 B CN112507496 B CN 112507496B
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damage
grid structure
test
static load
loading
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CN112507496A (en
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朋茜
赵�卓
杨秋伟
吕忠达
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Ningbo University of Technology
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Abstract

The invention discloses a grid structure damage assessment method based on static load test, and relates to the technical field of structure damage assessment. The invention does not need to know the size of the static load, has no limit on the loading position and the loading direction, and can carry out damage evaluation only by measuring the displacement data of each node. Numbering the degrees of freedom of all rod pieces of a grid structure and all end nodes of the rod pieces, establishing a finite element model of the grid structure, and obtaining a rigidity matrix; and carrying out a single-point loading test, calculating a damage vector, and evaluating the damage position and the severity degree according to the damage vector. By using the grid structure damage assessment method based on the static load test, the defects that the load size needs to be measured and strict requirements are imposed on the loading position and direction in the conventional method are overcome, and the experiment cost and time can be saved.

Description

Grid structure damage assessment method based on static load test
Technical Field
The invention belongs to the technical field of structural damage assessment, and particularly relates to a grid structure damage assessment method based on a static load test.
Background
The grid structure is widely applied to large-span roofs, ocean platforms, steel structure bridges and tower crane systems, and damage conditions can inevitably occur in the structure due to the influence of adverse factors such as fatigue accumulation, environmental corrosion, weld joint expansion and looseness of metal materials, and serious safety accidents such as structural collapse can be caused when the damage is serious. Therefore, whether the net rack structure is damaged or not, and the position and the severity of the damage must be evaluated in time, and corresponding maintenance and reinforcement measures can be taken. Among the various proposed damage assessment methods, the method for assessing damage based on displacement data obtained from a structure static load test has high practical value. The existing damage assessment method based on the static test requires that the size of the known static load, the position of a loading point and the loading direction are strictly required, so that the large-area popularization and application of the damage assessment method based on the static test are greatly limited. A new damage assessment method which does not need to know the size of the static load and has no limit on the loading position and direction is urgently needed, so that the test cost and time are effectively saved, and a reliable damage assessment result is obtained.
Disclosure of Invention
In view of this, the invention provides a grid structure damage assessment method based on a static load test, and the method does not need to know the size of a static load, has no limitation on the loading position and direction, and can carry out damage assessment only by measuring displacement data of each node.
In order to achieve the purpose, the invention adopts the following technical scheme: a grid structure damage assessment method based on static load test comprises the following steps:
numbering all rod pieces of the grid structure, numbering the degrees of freedom of all end nodes of the rod pieces, listing a relation table of the rod piece numbers and the degrees of freedom, and establishing a finite element model of the grid structure by using finite element software so as to obtain a rigidity matrix K of the structure; carrying out at least two single-point loading tests on the grid structure; calculating a damage index vector from the single point loading test
Figure 866070DEST_PATH_IMAGE001
(ii) a According to the damage index vector
Figure 988747DEST_PATH_IMAGE001
Evaluating the position of the damaged rod piece; according to the factor of the degree of damage
Figure 177337DEST_PATH_IMAGE003
To determine the severity of the rod damage.
Furthermore, in the single-point loading test, the position and direction of a loading point and the magnitude of a load value are randomly selected, so that each node generates displacement data, the displacement data of each node is recorded, and the displacement data are sequentially arranged to form a vector
Figure 35703DEST_PATH_IMAGE004
。
Further, the damage index vector calculation formula is as follows,
Figure 758808DEST_PATH_IMAGE005
whereinnThe number of single point loading tests;
said
Figure 573181DEST_PATH_IMAGE006
This gives: computing
Figure 238386DEST_PATH_IMAGE007
Let us order
Figure 770999DEST_PATH_IMAGE008
The data of the middle corresponding single point loading freedom degree is zero, and each element in the obtained vector is respectively obtained by taking an absolute value
Figure 517369DEST_PATH_IMAGE006
。
Further, the position of the damaged rod piece is evaluated according to the damage index vector, specifically according to the following:
and determining the number corresponding to the degree of freedom with the absolute value remarkably larger than 0 in the damage index vector, determining the number of the damaged rod piece according to the relation table of the rod piece number and the degree of freedom number, and determining the position of the damaged rod piece.
Factor of degree of injury
Figure 717406DEST_PATH_IMAGE003
And (3) calculating: selecting the test far away from the damaged rod piece from two or more single-point loading tests to calculate the damage degree, and calculating the damage degree according to the test corresponding to the selected test
Figure 304245DEST_PATH_IMAGE008
The damage degree factor is calculated by the following formula:
Figure 325420DEST_PATH_IMAGE009
，
wherein
Figure 655907DEST_PATH_IMAGE010
Finger-shaped
Figure 444872DEST_PATH_IMAGE008
The element with the largest absolute value in the group,tthe number of the damaged rod pieces is numbered,
Figure 687765DEST_PATH_IMAGE011
unit rigidity matrix corresponding to finger damage rod pieceK t To (1) asThe number of the row vectors is,
Figure 991708DEST_PATH_IMAGE012
the displacement vectors obtained in the selected trial.
According to the technical scheme, compared with the prior art, the invention has the following beneficial effects:
the invention does not need to know the static load size and has no limit on the loading position and direction, thereby avoiding the defects that the prior method needs to measure the load size and has strict requirements on the loading position and direction, and saving the experiment cost and time.
Drawings
The drawings needed in the embodiments of the present invention will be briefly described below with reference to the drawings in the embodiments of the present invention, it is obvious that the drawings in the following description are only for more clearly illustrating the embodiments of the present invention or technical solutions in the prior art, and the embodiments of the present invention will be described below for the embodiments or the prior art.
Fig. 1 is a grid structure for illustrating the implementation and effect of the present invention for structural damage identification. The basic parameters are as follows: the cross section of the rod member is
Figure 47257DEST_PATH_IMAGE013
Cross-sectional area of the hollow square tube
Figure 753045DEST_PATH_IMAGE014
Modulus of elasticity
Figure 166840DEST_PATH_IMAGE015
Density of
Figure 895762DEST_PATH_IMAGE016
(ii) a The existing structure was simulated by assuming 20% loss in elastic modulus for the 5 th rod piece;
FIG. 2 is a schematic diagram of a unit degree of freedom;
figure 3 the drawing is a schematic diagram of the structural static loading.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a grid structure damage assessment method based on a static load test.
For the grid structure shown in fig. 1, the steps of identifying structural damage by using the method of the invention are as follows:
(1) firstly, numbering all rod pieces of a grid structure, numbering the degrees of freedom of all end nodes of the rod pieces at the same time, listing a relation table (table 1) of the rod piece numbers and the degrees of freedom numbers as shown in fig. 1, and establishing a finite element model of the grid structure by using finite element software so as to obtain a rigidity matrix K of the structure;
Figure 568052DEST_PATH_IMAGE017
(2) and (5) carrying out static load test on the structure.
And in practical situations, the displacement values of the node positions of the rod pieces under the action of loading force are directly obtained by structural loading. In this embodiment, the finite element method is used to perform analog loading on the grid structure, and the damaged rod is assumed to be rod No. 10, and the damage degree is 20%.
For the first single-point loading test, the loading point locating the rod-taking member 2iThe load value of the end (node 2) is vertically downward, the load is 5kN, the displacement of each node obtained by testing is recorded and sequentially arranged to form a vector as shown in figure 3
Figure 377613DEST_PATH_IMAGE018
As shown in column 2 of table 2;
(3) and carrying out a second single-point loading test on the grid structure, wherein the loading point only needs to be far away from the first loading position, namely, the distance between the loading point and the first single-point loading displacement is at least one rod piece. The loading point locating the rod-taking member 4iThe load value direction of the end (node 4) is vertical downward, the load is 3kN, the displacement of each node obtained by testing is recorded and is sequentially arranged to form a vector
Figure 149260DEST_PATH_IMAGE019
As shown in column 3 of table 2;
(4) calculating damage index vector
Figure 444107DEST_PATH_IMAGE020
. Said
Figure 592191DEST_PATH_IMAGE021
This gives: first of all, calculate
Figure 272571DEST_PATH_IMAGE022
Let us order
Figure 464387DEST_PATH_IMAGE023
The data corresponding to the first single point loading freedom degree is zero, and then the absolute value of each element in the obtained vector is respectively obtained
Figure 230218DEST_PATH_IMAGE021
As shown in column 6 of table 2; said
Figure 181993DEST_PATH_IMAGE024
This gives: first of all, calculate
Figure 467612DEST_PATH_IMAGE025
Let us order
Figure 846641DEST_PATH_IMAGE026
The data of the position corresponding to the degree of freedom of the second single-point loading is zero, and then the absolute value of each element in the obtained vector is respectively taken to obtain the vector
Figure 886053DEST_PATH_IMAGE024
As shown in column 7 of table 2. Calculating damage index vector
Figure 641520DEST_PATH_IMAGE001
See table 2, column 8.
Figure 234175DEST_PATH_IMAGE027
(5) And evaluating the position of the damaged rod piece. According to the obtained damage index vector
Figure 331575DEST_PATH_IMAGE001
The position of the damaged rod piece is evaluated according to the following specific criteria: firstly, determining a damage index vector
Figure 806419DEST_PATH_IMAGE001
The absolute value of the middle element is obviously larger than the number corresponding to the degree of freedom of 0, and then the number of the damaged rod piece is determined according to the relation table of the rod piece number and the degree of freedom number, so that the position of the damaged rod piece can be determined. In this example, the results in column 8 of Table 2 show that the damage indicator vector
Figure 614844DEST_PATH_IMAGE001
The degree of freedom numbers with the absolute value of the middle element being significantly greater than 0 are 21 and 23 respectively, and then according to the relationship between the rod number and the degree of freedom number in table 1, the damaged rod can be determinedIn the position of the rod 10;
(6) the severity of the rod damage was assessed. Calculating a damage degree factor
Figure 327585DEST_PATH_IMAGE003
Firstly, selecting the 1 st test (namely the loading node 2 is farther from the damaged rod piece 10) with the loading point farther from the damaged rod piece from two single-point loading tests, and loading the corresponding 1 st test
Figure 48416DEST_PATH_IMAGE028
The damage degree factor is calculated by the following formula:
Figure 26867DEST_PATH_IMAGE009
，
wherein
Figure 124136DEST_PATH_IMAGE010
Finger-shaped
Figure 956963DEST_PATH_IMAGE008
The element with the largest absolute value in the group,tthe number of the damaged rod pieces is numbered,
Figure 160280DEST_PATH_IMAGE029
unit rigidity matrix corresponding to finger damage rod pieceK t To (1) asThe number of the row vectors is,
Figure 812979DEST_PATH_IMAGE012
get
Figure 448359DEST_PATH_IMAGE030
The calculated result is a damage factor
Figure 886425DEST_PATH_IMAGE031
Consistent with the assumptions.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (5)

1. A grid structure damage assessment method based on static load test is characterized by comprising the following steps:
numbering all rod pieces of the grid structure, numbering the degrees of freedom of all end nodes of the rod pieces, listing a relation table of the rod piece numbers and the degrees of freedom, and establishing a finite element model of the grid structure by using finite element software so as to obtain a rigidity matrix K of the structure;
carrying out at least two single-point loading tests on the grid structure;
calculating a damage index vector from the single point loading test
Figure DEST_PATH_IMAGE001
；
According to the damage index vector
Figure 54093DEST_PATH_IMAGE001
Evaluating the position of the damaged rod piece;
according to the factor of the degree of damage
Figure DEST_PATH_IMAGE002
Determining the severity of the damage to the rod;
factor of degree of injury
Figure 498850DEST_PATH_IMAGE002
And (3) calculating: selecting the test far away from the damaged rod piece from two or more single-point loading tests to calculate the damage degree, and calculating the damage degree according to the test corresponding to the selected test
Figure DEST_PATH_IMAGE003
The damage degree factor is calculated by the following formula:
Figure DEST_PATH_IMAGE004
；
wherein
Figure DEST_PATH_IMAGE005
Finger-shaped
Figure 758055DEST_PATH_IMAGE003
The element with the largest absolute value in the group,tthe number of the damaged rod pieces is numbered,
Figure DEST_PATH_IMAGE006
unit rigidity matrix corresponding to finger damage rod pieceK t To (1) asThe number of the row vectors is,
Figure DEST_PATH_IMAGE007
the displacement vectors obtained in the selected trial.
2. The grid structure damage assessment method based on static load test as claimed in claim 1, wherein the single point loading test, the position and direction of the loading point and the magnitude of the loading value are arbitrarily selected, so that each node generates displacement data, the displacement data of each node is recorded, and the displacement data are sequentially arranged to form a vector
Figure DEST_PATH_IMAGE008
。
3. The grid structure damage assessment method based on static load test according to claim 1, wherein the damage index vector is calculated as follows,
Figure DEST_PATH_IMAGE009
whereinnThe number of single point loading trials is the number of single point loading trials,
Figure DEST_PATH_IMAGE010
is a damage index subvector.
4. The grid structure damage assessment method based on static load test as claimed in claim 3, wherein the damage index sub-vector
Figure 750413DEST_PATH_IMAGE010
This gives: calculating pseudo nodal forces
Figure DEST_PATH_IMAGE011
Let us order
Figure 946908DEST_PATH_IMAGE003
The data of the middle corresponding single point loading freedom degree is zero, and each element in the obtained vector is respectively obtained by taking an absolute value
Figure 793641DEST_PATH_IMAGE010
。
5. The grid structure damage assessment method based on static load test according to claim 3 or 4, characterized in that, the grid structure damage assessment method is based on the damage index vector
Figure 286065DEST_PATH_IMAGE001
Evaluating the position of the damaged rod member according to the following specific steps:
determining damage index vector
Figure 280566DEST_PATH_IMAGE001
And determining the number of the damaged rod piece according to the relation table of the rod piece number and the degree of freedom number, and determining the position of the damaged rod piece.
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US20040251067A1 (en) * 2000-01-10 2004-12-16 Government Of The U.S.A As Represented By The Adm. Of The U.S. Environmental Protection Agency Hydraulic hybrid vehicle with integrated hydraulic drive module and four-wheel-drive, and method of operation thereof
CN111608315A (en) * 2020-06-08 2020-09-01 百安力钢结构应用科技有限公司 Fire-resistant composite floor slab and fire resistance testing method thereof

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US20040251067A1 (en) * 2000-01-10 2004-12-16 Government Of The U.S.A As Represented By The Adm. Of The U.S. Environmental Protection Agency Hydraulic hybrid vehicle with integrated hydraulic drive module and four-wheel-drive, and method of operation thereof
CN111608315A (en) * 2020-06-08 2020-09-01 百安力钢结构应用科技有限公司 Fire-resistant composite floor slab and fire resistance testing method thereof

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