CN102121858A - Tension test method for stay cable steel strand of partially cable-stayed bridge - Google Patents

Abstract

The invention provides a tension test method for a stay cable steel strand of a partially cable-stayed bridge. A steel strand of a certain length is fixed in the stay cable steel strand of the partially cable-stayed bridge, and the fundamental frequency and bending stiffness of the steel strand are tested, so that the tension of the stay cable steel strand can be calculated based on the cable free vibration computation theory considering the influence of bending stiffness according to the fundamental frequency, bending stiffness, length and quality parameters of the steel strand. By utilizing the test method, the high-precision tension test result of the steel strand can be obtained; and moreover, the test process is convenient, and the test method meets the requirement of tension test in the construction process and operation period of the stay cable steel strand of the partially cable-stayed bridge.

Description

Part cable-stayed bridge cable steel strand wires tension test method

Technical field

The present invention relates to a kind of tension test method of part cable-stayed bridge cable steel strand wires.

Background technology

Cable wire uses as a kind of tensional element, not only can give full play to the service efficiency of high-strength material, can make things convenient for the design and the construction of bridge simultaneously.Cable wire has been widely used in arch bridge, cable-stayed bridge and suspension bridge structure since 1883 use first in U.S. Brooklyn bridge.The part cable-stayed bridge is because the body of the tower cross section is less, and drag-line adopts and divides the form of fiber tube to pass bridge tower, and every branch fiber tube is worn an epoxy steel hinge line.The epoxy steel strand wires adopt the method construction of stretch-draw one by one, connect into integral body and put outer protective sleeve by cord clip after stretch-draw is finished.Therefore, the bending stiffness of this short drag-line and boundary condition are obvious to the influence of stayed structure fundamental frequency, and the tension force between each steel strand wires is very inhomogeneous.

Drag-line tension force (being commonly referred to Suo Li) is the important evidence of assessment bridge mechanics performance, accurately understands Suo Lishi and guarantees that bridge structure is safe in utilization and prolong the bridge prerequisite in serviceable life.At present, it is several that the Suo Li assay method of using always both at home and abroad mainly contains pressure transducer method, hydraulic jack method, vibration frequency method, magnetic flux method etc.The vibration frequency method is according to concerning between the Suo Li and the natural frequency of vibration, trying to achieve the method for tension force from the natural frequency of vibration (normally fundamental frequency) measured result.Adopt accurate vibro-pickup, record time-histories data obtain its natural frequency of vibration through filtering, amplification and spectrum analysis, and then reckoning obtain Suo Li under ambient vibration.Easy to operate, the low advantages such as being fit to daily detection that reaches of cost that this method has is a kind of Suo Li measuring technology that is most widely used at present.

Adopt vibration frequency method test Suo Li, should have clear and definite boundary condition, the rigidity of structure and mass parameter.And be to lean on the cord clip at two ends to bundle between the epoxy steel strand wires of part cable-stayed bridge cable, drag-line length is shorter relatively, can not ignore the influence of bending stiffness and edge-restraint condition to the natural frequency of vibration, but at present traditional method of testing all is difficult to accurate identification to the bending stiffness of drag-line steel strand wires, causes the precision of vibration frequency method test drag-line steel strand wires tension force not high.Therefore need the rational rope force test method of research, improve measuring accuracy, to satisfy the needs of actual engineering safety management.

Summary of the invention

Technical matters to be solved by this invention provides a kind of part cable-stayed bridge cable steel strand wires tension test method.For this reason, the present invention adopts the technical scheme of following artificial simulating boundary condition:

In part cable-stayed bridge cable steel strand wires, fix the steel strand wires of a segment length, by the fundamental frequency and the bending stiffness of testing this section steel strand wires, fundamental frequency, bending stiffness, length, mass parameter according to this section steel strand wires, according to the rope free vibration theory of computation of considering the bending stiffness influence, calculate the tension force of drag-line steel strand wires; The test process of described fundamental frequency may further comprise the steps:

(1), the steel strand wires of a segment length are fixed with buckstay its two ends as test section in the selected part cable-stayed bridge cable steel strand wires, make the two ends boundary condition of test section steel strand wires clear and definite;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of test section steel strand wires.

On the basis of adopting above technical scheme, can take further scheme:

(1), choose one section steel strand wires that tension force is known, its sectional area, material are identical with described test section steel strand wires, and its two ends are fixed with buckstay, regular length is identical with described test section steel strand wires;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of this section steel strand wires;

(3), go out the bending stiffness of these tension force known segment steel strand wires, and with its bending stiffness as part cable-stayed bridge cable test section steel strand wires according to known tension force condition inverse.

Adopt technical scheme of the present invention, can obtain high-precision steel strand wires tension test result, and test process is convenient, satisfy the tension test needs during part cable-stayed bridge cable steel strand wires work progress and the operation.

Description of drawings

The structural representation of the border stationary installation that Fig. 1 is adopted in test for the present invention.

Embodiment

Method of testing provided by the present invention utilizes one section steel strand wires in the part cable-stayed bridge cable steel strand wires as the test section steel strand wires, test the fundamental frequency and the bending stiffness of this section steel strand wires, fundamental frequency, bending stiffness, length, mass parameter according to this section steel strand wires, according to the rope free vibration theory of computation of considering the bending stiffness influence, calculate the tension force of part cable-stayed bridge cable steel strand wires; The test process of described fundamental frequency may further comprise the steps:

(1), the steel strand wires of any segment length fix the two ends of test section steel strand wires as the test section steel strand wires by the method that connects rigid body between the two ends in the selected part cable-stayed bridge cable steel strand wires;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of test section steel strand wires.

Described bending stiffness test process may further comprise the steps:

(1), choose the steel strand wires of one section no tension force effect, be that the border is fixed to its two ends with the people, its length, sectional area and material are identical with described test section steel strand wires;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of this section steel strand wires;

(3), go out the bending stiffness of test section steel strand wires according to known tension force condition (as zero tension force time) inverse.

With reference to Fig. 1, present embodiment adopts following apparatus fixing to the two ends 11,12 of test section steel strand wires 1.

This device comprises strip rigid body 2 and steel strand connector 31,32, and described steel strand connector 31,32 is fixed on the strip rigid body 2 and is respectively applied for the two ends of test section steel strand wires and is connected, so that test section steel strand wires two ends are fixed.

Strip rigid body 2 can adopt girder steel, drawing reference numeral 4 is a vibration transducer, it adopts acceleration transducer, the DH301 type condenser type three-dimensional sensor of producing such as Dong Hua Electronic Instruments Plant, and gather and analyze with DH5901 hand-held Dynamic Signal measuring and analysing meter 5.Calculate the tension force T of steel strand wires from frequency measured value f according to the computational length l between steel strand wires two restrained boundaries, cross section parameter (linear mass m, cross section bendind rigidity EI and sectional area A).

Calculate the tension force T of steel strand wires from frequency measured value f according to the computational length l between steel strand wires two restrained boundaries, cross section parameter (linear mass m, cross section bendind rigidity EI and sectional area A).

Set forth the theory of computation of calculating tension force according to frequency below.

The steel strand wires Free Vibration Equations of considering the bending stiffness influence is:

$\mathrm{EI}\frac{{\∂}^{4}w}{\∂x^4}-T\frac{{\∂}^{2}w}{\∂x^2}+m\frac{{\∂}^{2}w}{\∂t^2}=0---\left(1\right)$

In the formula, w is the lateral vibration displacement of steel strand wires, and EI is a bending stiffness, and promptly elastic modulus E and cross sectional moment of inertia I's is long-pending, and T is a tension force, and m is the linear mass of suspension rod.Here, suppose that the vibration of suspension rod is a small deformation, the variation of tension force can be ignored in the vibration processes.

The natural frequency of vibration of steel strand wires can obtain according to equation (1) untrivialo solution condition, and the natural frequency of vibration of the i vibration shape is:

$f_i^2=\frac{{\mathrm{\π}}^2\mathrm{EI}}{4{\mathrm{ml}}^4}{(i-\frac{\mathrm{\φ}}{\mathrm{\π}})}^4+\frac{T}{4{\mathrm{ml}}^2}{(i-\frac{\mathrm{\φ}}{\mathrm{\π}})}^2---\left(2\right)$

In the formula,

$\tan \mathrm{\φ}=-\frac{2\mathrm{\ω}}{T}\sqrt{\mathrm{mEI}}---\left(3\right)$

Wherein ω is a circular frequency.

Fix one zero steel strand wires under the tension force condition, the test vibration frequency, through type (2) obtains bending stiffness EI, and substitution formula again (2) can obtain the steel strand wires tension force of any stressing conditions lower part cable-stayed bridge cable.

In order to verify the validity of the inventive method and device, in the detection of Hangzhou part cable-stayed bridge cable, verify, choose several drag-lines and measure.For easy to operate, choosing one section steel strand wires, its two ends are fixed with device shown in Figure 1 near the girder side, measure the length of canned paragraph.Adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of steel strand wires.The bending stiffness of tested steel twisted wire then, steel strand wires according to identical material, sectional area and length, identical fixed form being adopted at its two ends, measure the fundamental frequency of steel strand wires under ambient vibration under zero tension state, is the zero contrary bending stiffness that calculates steel strand wires according to tension force.Like this, be under the known prerequisite, adopt the vibration frequency method to obtain tension force according to formula (2) by the fundamental frequency of steel strand wires at steel strand wires boundary condition and bending stiffness.

Drag-line to a root portion cable-stayed bridge carries out cable force measurement, chooses any steel strand wires of drag-line, its tension calibration value T=129.0kN, actual measurement vibration frequency f=228.44Hz, the tension force T that adopts method of the present invention to calculate ^*=130.2kN is with the ratio delta of calibration value ^*=1.01; Tension force T by the string theory reckoning of not considering bending stiffness ₀=171.02kN is with the ratio delta of calibration value ₀=1.33.This shows that algorithm of the present invention is compared traditional string theory and calculated that the tension force that obtains is more accurate.

According to identical method of testing, detected the tension force of other 6 steel strand wires again respectively, list in table 1.As can be known from the table data, adopt method of testing of the present invention, 3 groups of tension test precision are arranged about 100%, all the other precision are also all above 90%, and traditional string theory test result is average bigger by about 30% than calibration value.Hence one can see that, and the tension force result who uses method of testing of the present invention and device to obtain has higher precision.

Table 1 drag-line steel strand wires tension test precision

Claims (2)

1. part cable-stayed bridge cable steel strand wires tension test method is characterized in that it utilizes the tension force of the method part of detecting cable-stayed bridge cable steel strand wires on manual simulation border:

Described method is fixed the steel strand wires of a segment length in part cable-stayed bridge cable steel strand wires, by the fundamental frequency and the bending stiffness of testing this section steel strand wires, fundamental frequency, bending stiffness, length, mass parameter according to this section steel strand wires, according to the rope free vibration theory of computation of considering the bending stiffness influence, calculate the tension force of part cable-stayed bridge cable steel strand wires; The test process of described fundamental frequency may further comprise the steps:

(1), the steel strand wires of a segment length are fixed with buckstay its two ends as test section in the selected part cable-stayed bridge cable steel strand wires, make the two ends boundary condition of test section steel strand wires clear and definite;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of test section steel strand wires.

2. part cable-stayed bridge cable steel strand wires tension test method as claimed in claim 1 is characterized in that described bending stiffness test process may further comprise the steps:

(1), choose one section steel strand wires that tension force is known, its sectional area, material are identical with described test section steel strand wires, and its two ends are fixed with buckstay, regular length is identical with described test section steel strand wires;

(2), adopt acceleration transducer and supporting Acquisition Instrument to measure the fundamental frequency of this section steel strand wires;

(3), go out the bending stiffness of these tension force known segment steel strand wires, and with its bending stiffness as part cable-stayed bridge cable test section steel strand wires according to known tension force condition inverse.

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