Damage identification method for cantilever beams based on the curvature of free end inclination influence line
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A technology of damage identification and influence lines, applied in elastic testing, testing of machine/structural components, instruments, etc.
Active Publication Date: 2021-04-02
XIANGTAN UNIV
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[0003]
The indicators of structural damage identification technology based on static parameters are mostly based on deflection, static strain, and support reaction force influence line indicators. With the advancement of inclination sensor technology, the change of structural inclination curve before and after damage is expected to be applied to Currently, there are few literature reports related to dip damage identification.
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Embodiment 1
[0087] Embodiment one: see Figure 7 , the span of the cantilever beam with equal cross-section is 100cm, and a unit is divided by 5cm, a total of 20 units and 21 measuring points (the numbers in the upper circle in the figure are the unit numbers, and the lower numbers are the measuring point numbers). The cross-sectional size of the plate is b×h=4.5cm×1.5cm, and the elastic modulus of the material is 2.7×10 3 MPa, Poisson's ratio is 0.37, density is 1200kg / m 3 .
[0088] The damage in the actual engineering structure, such as the generation of cracks, material corrosion or the reduction of elastic modulus, generally only causes a large change in the structural stiffness, but has little impact on the quality of the structure. Therefore, in the finite element calculation, it is assumed that the damage of the structural element only causes the decrease of the stiffness of the element, and does not cause the change of the mass of the element. Damage to elements is simulated b...
Embodiment 2
[0097] Embodiment two: see Figure 12 , the span of the variable-section cantilever beam is 100cm, and the division of units and nodes is the same as in Embodiment 1. The free end of the plate section size is b×h=4.5cm×1.5cm, and the fixed support end is b×h=22.5cm×3.0cm, The modulus of elasticity of the material is 2.7×10 3 MPa, Poisson's ratio is 0.37, density is 1200kg / m 3 .
[0098] The damage condition is the same as that in Embodiment 1.
[0099] The specific implementation steps are as follows:
[0100] Step 1: Apply a moving load of 1kN to obtain the influence line of the measured inclination angle of the free end measuring point 21 after the cantilever beam is damaged, respectively as follows Figure 13 .
[0101] Step 2: Calculate the curvature of the influence line of the dip angle after the damage of the beam structure, such as Figure 14 , the results show that there is an obvious peak at the unit 10, and it can be preliminarily judged that the unit 10 is da...
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Abstract
The invention discloses a cantilever beam damage identification method based on the curvature of a free end inclination angle influence line, which comprises the steps of applying a moving load to a damaged cantilever beam, and obtaining an actually measured inclination angle influence line of a free end measurement point; solving the curvature of the actually measured inclination angle influenceline after the beam structure is damaged; obtaining the rigidity of each position of the beam structure by dividing the load value by the curvature of the inclination angle influence line, and identifying a damage position through sudden change of a rigidity curve of the damaged state; eliminating the rigidity of the damaged position, and fitting the residual rigidity curve to obtain a rigidity curve of an undamaged state; and calculating the damage degree according to the rigidity curves of the damaged state and the undamaged state to obtain the structural rigidity of the damaged position. According to the method, the damage of the cantilever beam can be accurately positioned and quantified, the method is applied to damage assessment of the cantilever beam, and the application value of the curvature index of the inclination angle influence line in cantilever beam damage identification is verified through equal-section and variable-section cantilever beam calculating examples.
Description
technical field [0001] The invention relates to the technical field of non-destructive testing of beam structures, in particular to a damage identification method of a cantilever beam based on the curvature of a free end inclination influence line. Background technique [0002] In recent years, there are more and more old bridges in our country, and the problems are becoming more and more obvious. Many existing bridges can no longer meet the functional requirements, and safety accidents such as bridge breakage and collapse occur from time to time. Scholars in the field of civil engineering have gradually realized the importance of health monitoring and safety assessment of bridge structures, and have studied various damage identification technologies. . Structural damage identification is an important part of the bridge structural health monitoring system. At present, there are two main types of damage identification methods. One is the damage identification method based on...
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