CN109738099B - OFDR-based steel truss structure axisymmetric spherical node stress monitoring method - Google Patents
OFDR-based steel truss structure axisymmetric spherical node stress monitoring method Download PDFInfo
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- CN109738099B CN109738099B CN201910004493.9A CN201910004493A CN109738099B CN 109738099 B CN109738099 B CN 109738099B CN 201910004493 A CN201910004493 A CN 201910004493A CN 109738099 B CN109738099 B CN 109738099B
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 20
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 19
- 239000010959 steel Substances 0.000 title claims abstract description 19
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000002168 optical frequency-domain reflectometry Methods 0.000 title claims description 10
- 239000013307 optical fiber Substances 0.000 claims abstract description 48
- 239000003365 glass fiber Substances 0.000 claims abstract description 16
- 239000003822 epoxy resin Substances 0.000 claims abstract description 8
- 229920000647 polyepoxide Polymers 0.000 claims abstract description 8
- 239000002390 adhesive tape Substances 0.000 claims abstract description 7
- 238000011160 research Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
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Abstract
The invention provides an OFDR (optical fiber field-oriented DR) -based steel truss structure axisymmetric spherical node stress monitoring method, and belongs to the technical field of optical fiber sensing. The method is characterized in that a plurality of distributed optical fiber sensing tapes are pasted on the surface of an axisymmetric ball node along the warp direction and the weft direction to form a main stress distributed monitoring network of the surface of the ball node. The invention adopts the glass fiber narrow band and the tough epoxy resin to package the distributed optical fiber, and the packaged sensor adhesive tape has narrow width and good flexibility and is suitable for being pasted on the surface of a ball. The stress monitoring method for the axisymmetric ball node can realize real-time online distributed monitoring of the surface stress of the ball node, and has important significance for correcting a calculation formula of the bearing capacity of the ball node and researching the actual working state.
Description
Technical Field
The invention discloses an OFDR-based steel truss structure axisymmetric spherical node stress monitoring method, relates to the technical field of optical fiber sensing, and discloses a real-time online distributed monitoring method for spherical node stress.
Background
The steel net frame structure has been widely used in venues and facilities such as convention and exhibition centers, gymnasiums, cultural entertainment and the like due to large span, light weight and beautiful appearance. However, the increasingly complex structural forms, while bringing continuous innovation to the architectural concepts and structural designs, also make the grid structure face unprecedented risks and challenges. In fact, the steel mesh frame structure can bear three-dimensional stress and space action, the ball joint plays a crucial role, and once the joint fails, the force transmission path can be changed, the structure system can be locally damaged, and even the whole system can be continuously damaged. At present, a great result has been achieved in the research on the bearing capacity and the stress performance of the ball joint, but the following problems generally exist: (1) the research on the bearing capacity of the welded ball joint is usually considered in a uniaxial stress state, but in practical engineering, the ball joint is generally subjected to space stress, and the research on the influence of mutual influence among rod pieces on the bearing capacity of the ball joint is less in a multidirectional stress state; (2) different insights exist on the ball joint compression failure mechanism, and related experimental verification is lacked; (3) for the experimental research of the spherical joint, strain gauges and other point sensors are commonly adopted, the distribution of the spherical stress field in a stressed state is difficult to obtain, the monitoring efficiency is low, and the arrangement of measuring points is complicated.
The distributed optical fiber sensing technology based on Optical Frequency Domain Reflectometry (OFDR) has been widely applied to strain monitoring of structures such as concrete, steel bars, pipelines and the like due to high spatial resolution (minimum 1mm) and high precision (± 1 μ ∈). The optical fiber is a sensing element and a transmission element in the self-measuring range, and the common single-mode optical fiber can meet the requirement and can continuously measure the structural information to be measured on the path covered by the whole optical fiber. The characteristic plays an important role in researching the surface stress field distribution of the spherical joint in a space stress state.
Disclosure of Invention
Aiming at the defects of the monitoring method, the invention provides an OFDR-based steel truss structure axisymmetric spherical node stress monitoring method. The method is simple and easy to implement, high in precision and low in cost, is suitable for monitoring the surface stress of the axisymmetric ball joint in any form of the steel mesh frame structure, and has important significance for correcting a ball joint bearing capacity calculation formula and researching the actual working state.
The technical scheme of the invention is as follows:
a steel truss structure axisymmetric spherical node stress monitoring method based on OFDR comprises the following steps:
adhering a plurality of distributed optical fiber sensing tapes on the surface of the ball joint along the warp direction and the weft direction, and sequentially connecting the adjacent distributed optical fiber sensing tapes; because the spherical joint is axisymmetric, the shear stress of a plane which is taken by each point of the spherical surface by taking the measuring direction as the outer normal direction is zero, namely the measured warp strain and weft strain are main strains, and the main stress value of the point is obtained according to the main stress formulas (1) and (2).
Wherein σ1And σ2Represents the surface principal stress (MPa) of the ball joint; epsilon1And ε2Represents the spherical node surface principal strain (mu epsilon); e represents the elastic modulus (MPa) of the steel material used for the ball joint; and v represents the Poisson's ratio of steel used by the ball joint.
The distributed optical fiber sensing adhesive tape comprises a glass fiber narrow band, a distributed optical fiber and an optical fiber loose tube; the glass fiber narrow band is divided into an upper layer and a lower layer which are the same in length and width, and tough epoxy resin is uniformly coated on the opposite surfaces of the upper layer and the lower layer so as to be suitable for surface adhesion of the ball joint;
the distributed optical fiber is embedded between two layers of glass fiber narrow bands and is ensured to be positioned on the axial line of the glass fiber narrow bands;
the optical fiber loose tube is sleeved on the lead ends at two sides of the distributed optical fiber.
The distributed optical fiber sensing adhesive tape is adhered to the surface of the ball joint by epoxy resin, so that the distributed optical fiber sensing adhesive tape and the ball joint are ensured to be deformed and coordinated.
The invention has the beneficial effects that:
(1) the distributed optical fiber is a transmission element and a sensing element, can realize real-time online monitoring of the surface stress of the spherical node, has high spatial resolution (1mm) and high precision (+/-1 mu epsilon), and can realize three-dimensional distributed monitoring of the surface stress of the spherical node.
(2) The invention adopts the glass fiber narrow band and the tough epoxy resin to package the distributed optical fiber, and the packaged sensor adhesive tape has narrow width and good flexibility and is suitable for being pasted on the surface of a ball.
Drawings
Fig. 1 is a schematic structural diagram of a ball joint stress monitoring method of the present invention.
Fig. 2 is a schematic structural diagram of the distributed optical fiber sensing tape of the present invention.
FIG. 3 is a cross-sectional view of a distributed optical fiber sensing tape of the present invention.
In the figure: 1, a ball node; 2, a distributed optical fiber sensing adhesive tape; 3 a glass fiber tape; 4, a distributed optical fiber; 5, loosening the sleeve of the optical fiber; 6 epoxy resin.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings that illustrate specific embodiments of the invention.
As shown in fig. 1, an embodiment of the present invention provides a method for monitoring an axisymmetric spherical joint stress of a steel lattice structure based on OFDR, where the method is implemented as follows: 14 distributed optical fiber sensing tapes 2 are pasted on the surface of the ball joint 1 at equal intervals along the warp direction and the weft direction respectively, adjacent optical fibers 4 are sequentially connected, a heat-shrinkable tube is adopted at the welding position of the optical fibers 4 for reinforcement, and the rest parts are protected by optical fiber loose tubes 5. The terminal of the optical fiber 4 is connected to an optical frequency domain reflectometer for data acquisition. Because the spherical joint 1 is axisymmetric, the shear stress of a plane taken by each point of the spherical surface by taking the measuring direction as the outer normal direction is zero, namely the measured warp strain and weft strain are main strains, and the main stress value of the point can be obtained according to the main stress formulas (1) and (2). The measurement method has high spatial resolution, so that the reconstruction of the main stress field on the surface of the ball node 1 can be realized.
Wherein σ1And σ2Represents the surface principal stress (MPa) of the ball joint; epsilon1And ε2Represents the spherical node surface principal strain (mu epsilon); e represents the elastic modulus (MPa) of the steel material used for the ball joint; v represents the poisson's ratio of the steel used for the ball joint. As shown in fig. 2 and fig. 3, preferably, the distributed optical fiber sensing tape 2 includes a glass fiber narrow band 3, a distributed optical fiber 4 and a fiber loose tube 5; the width of the glass fiber narrow band 3 is 15mm, the thickness is 1mm, the glass fiber narrow band is divided into an upper layer and a lower layer, and high-toughness epoxy resin 6 is uniformly coated on the opposite surfaces of the two layers; the distributed optical fiber 4 is a common single-mode optical fiber with the diameter of 250 mu m, is embedded between two layers of glass fiber narrow bands 3 and is ensured to be positioned on the axial line of the glass fiber narrow bands 3; the optical fiber loose tube 5 is sleeved on the lead ends at two sides of the distributed optical fiber 4 to protect the optical fiber.
The above description is a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and all persons skilled in the art should be able to cover the technical solutions of the present invention and the concepts of the present invention by equivalent substitutions or changes within the scope of the present invention.
Claims (2)
1. A steel truss structure axisymmetric spherical node stress monitoring method based on OFDR is characterized by comprising the following steps:
adhering a plurality of distributed optical fiber sensing tapes on the surface of the ball joint along the warp direction and the weft direction, and sequentially connecting the adjacent distributed optical fiber sensing tapes; because the spherical joint is axisymmetric, the shear stress of a plane which is taken by each point of the spherical surface by taking the measuring direction as the outer normal direction is zero, namely the measured warp strain and weft strain are main strains, and the main stress value of the point is obtained according to main stress formulas (1) and (2):
wherein σ1And σ2The surface principal stress of the spherical node is expressed in MPa; epsilon1And ε2Represents the principal strain of the surface of the spherical node, mu epsilon; e represents the elastic modulus, MPa, of the steel used for the ball joint; v represents the Poisson's ratio of steel used by the ball joint;
the distributed optical fiber sensing adhesive tape comprises a glass fiber narrow band, a distributed optical fiber and an optical fiber loose tube; the glass fiber narrow band is divided into an upper layer and a lower layer which are the same in length and width, and tough epoxy resin is uniformly coated on the opposite surfaces of the upper layer and the lower layer so as to be suitable for surface adhesion of the ball joint;
the distributed optical fiber is embedded between two layers of glass fiber narrow bands and is ensured to be positioned on the axial line of the glass fiber narrow bands;
the optical fiber loose tube is sleeved on the lead ends at two sides of the distributed optical fiber.
2. The method for monitoring the stress of the axisymmetric spherical node of the steel truss structure based on OFDR as claimed in claim 1, wherein said distributed optical fiber sensing tape is adhered to the surface of the spherical node by epoxy resin, so as to ensure the deformation coordination between the distributed optical fiber sensing tape and the spherical node.
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| CN111808543B (en) * | 2020-06-24 | 2021-08-10 | 浙江大学 | Structural deformation monitoring adhesive tape based on friction electricity generation |
| CN115290315A (en) * | 2022-10-08 | 2022-11-04 | 安徽中亚钢结构工程有限公司 | Device and method for testing mechanical properties of grid structure support of clinker silo |
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| CN102818665B (en) * | 2012-08-28 | 2014-08-20 | 中国矿业大学 | Device and method for integrated collection of stress and displacement of surrounding rocks |
| KR101726024B1 (en) * | 2014-04-30 | 2017-04-12 | 성균관대학교산학협력단 | Force sensor using optical fiber and cathether using the same |
| CN105259184B (en) * | 2015-11-24 | 2018-10-16 | 大连大学 | Tunnel vault distributed optical fiber sensing device and its construction technology and monitoring method |
| CN105547539B (en) * | 2016-03-01 | 2018-01-30 | 中国地震局地壳应力研究所 | Stress direction measuring system and method based on longitude and latitude strain line |
| CN108871638B (en) * | 2018-04-25 | 2020-04-28 | 中国工程物理研究院化工材料研究所 | Optical fiber measuring device and monitoring method for residual stress of material |
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