Based on cable anchorage zone, implant the method that strain transducer is realized Suo Li on-line measurement
Technical field
The present invention relates to engineering survey field, particularly a kind of method that realizes Suo Li on-line measurement based on cable anchorage zone implantation strain transducer.
Background technology
The drag-line of cable-stayed bridge is the core component of bridge, have the title of lifeline, due to structure design, environmental corrosion, the reasons such as fatigue accumulation, cable is unavoidable there is damage in various degree and deteriorated, line style due to bridge, internal force distributes, the decline of load and cable itself, lost efficacy and even the structural safety of integral bridge all can embody a concentrated expression of on cable stressed, for ease of grasping structural safety and the operational regime of cable self and full-bridge, timely discovery accident tendency, prevent that sudden accident from occurring, to cable force carry out on-line real time monitoring become one very important and there is the work of bright prospects.
Existing cable force measurement method is mainly divided into additional detection part, inner detection part two class methods of implanting.
Additional detection part method comprises pressure transducer method, method of oscillatory frequency, magnetoelasticity method etc.Wherein, in pressure transducer method, because force bearing ring and sensor all bear the continuous pressure of cable, forever without the chance of recovering, very easily cause bearing ring and sensor thereof tired, so serviceable life is limited; Method of oscillatory frequency is because measurement result is subject to a plurality of Boundary Condition Effects such as length, density, sag of cable self, and the boundary condition of cable in anchorage zone often has larger uncertainty, causes result of calculation widely different; Magnetoelasticity rule, because the magnetic parameter of coil is affected by the tension force of cable not only, is also subject to the impact of cable self material, cable protective materials, be more subject to the impact of environment temperature, humidity, so measuring accuracy is lower.
The inner detection part method of implanting, owing to making sensor and cable fusion in aggregates, makes cable possess the ability from perception Suo Li, so claim again intelligent cable technology.Composite reinforcing (strain transducer) method is as the Typical Representative of intelligent cable technology, although there is many marked improvements and advantage, but still exist, wait improvements: in cable twisting process, composite reinforcing need twisting together with single steel wire, bear very large shearing force effect, more easily cause the destruction of composite reinforcing structure, sensing element, increase site technique and implement difficulty, time and effort consuming, the actual normal operation strain value of cable rope body part is in 4000 μ ε left and right, and the steady strain operation interval of existing fiber strain sensor is only below 3500 μ ε, simultaneously, for cable force monitoring system, not only need to monitor the cable force of normal work stage, the more important thing is, must carry out continuous stability monitoring to the abnormal Suo Li in bridge and line structure generation slight damage situation, and once bridge structure morphs or the interior part steel wire of cable ruptures, cable strain meeting increases greatly, cable range of strain is well beyond the strain working range of existing strain sensing technology, so the strain measurement interval of cable rope body part is well beyond the operation interval of existing strain sensor, if overwork, not only can affect the strain transport properties of the interior sensing element of composite reinforcing and compound substance bonding interface, and affect the precision of final cable force measurement and reliably and with long-term, stability, even cause sensing element to destroy.
The above, must seek Suo Li reliable measurements in a kind of applicable various situations eventually, and technique realizes comparatively simple cable force measuring method.
Summary of the invention
In view of this, the invention provides a kind of method that realizes Suo Li on-line measurement based on cable anchorage zone implantation strain transducer, by be implanted into the strain transducer that length is less than anchorage zone axial length in anchorage zone, record the strain value corresponding with cable tension, by corresponding relation, realize the on-line measurement to cable force, solved that existing implanted method measuring accuracy is poor, the problem of poor work stability.
The object of this invention is to provide a kind of method that realizes Suo Li on-line measurement based on cable anchorage zone implantation strain transducer, comprise the following steps:
1) according to the quantity of cable steel wire in the size of anchorage zone, anchorage zone, determine the implantation position for the treatment of of implanted strain transducer, its implantation position should guarantee parallel with the direction of cable steel wire in anchorage zone;
2) according to step 1) in treat the situation of implantation position, determine the size of strain transducer, and prefabricated flexible barcode structural strain sensor, the tail end extension line of reserved sufficient length;
3) after the steel wire pier nose link in cable cabling process finishes, before anchor head casting link, the strain transducer of flexible barcode structure is implanted to cable anchorage zone according to pre-implantation position;
4) the signal extension line of strain transducer is drawn from wire sub-panel preformed hole;
5) fill with anchor after strain transducer position is fixed, add stabilizing agent and also carry out hot setting, make strain transducer and anchoring filling agent close contact be consolidated into one;
6) fill with anchor and complete, treat that anchor head casting carries out annealing in process to anchor head after solidifying;
7) utilize the value of thrust in the super stretching process of cable to demarcate strain transducer data, set up the output strain of strain sensor and the relation of cable force, by measuring the STRESS VARIATION of the strain sensor element in anchorage zone, realize the measurement to cable force.
Further, in step 3) in, before burying underground, roughening treatment is carried out in the surface of strain transducer, make its surface there is frictional resistance, be convenient to combine closely with anchoring filling agent;
Further, described strain transducer profile is cylindrical or conical list structure, and inner sensing element is arranged on the axial location place of list structure;
Further, in step 3) in, described strain transducer treat that implantation position is parallel or approximate parallel near the contiguous cable steel wire of ,Qie Yu anchorage zone, the center axial location of wire sub-panel, and center or approximate center position in adjacent wires axis institute region;
Further, described strain sensor can be fiber grating, optical fiber F-P, resistance strain gage or indium steel wire.
The invention has the beneficial effects as follows:
1. the internal strain of cable anchorage zone has larger decay compared with the strain of cable rope body, owing to measuring Suo Li without measuring absolute strain, and only need set up the linear relationship of strain and cable tension, so by being implanted into strain transducer in anchorage zone, can set up the relation of anchorage zone strain and cable tension equally, and realize the on-line measurement to Suo Li by measuring anchorage zone strain, method of the present invention is passed through at anchorage zone implanted sensor, the large strain measurement of cable rope body is converted into small strain measures, to improve strain measurement scope in the situation that not increasing additional mechanics throw-over gear, meet cable and measure requirement,
2. the present invention is by being prefabricated into strain transducer flexible barcode structure, between cable steel wire in anchor head, fix and cast in cable anchor head, form the mode of a stressed integral body with anchor head, solve strain sensor in anchor head labyrinth and the problem that is difficult to survive in cable manufacture process, and improve the accuracy of strain measurement;
3. the present invention draws sensor lead, protect by anchorage zone tail end before anchor head casting, to reduce length of lead-out wire, reduces technology difficulty, and reduces costs;
4. the present invention is by adding stabilizing agent in anchoring material, after anchor head casting is solidified, anchor head being carried out to annealing in process, the stability of raising anchor head, realizes the stressed measurement accurately and reliably of anchor head.
Other advantages of the present invention, target, to set forth in the following description to a certain extent with feature, and based on will be apparent to those skilled in the art to investigating below, or can be instructed from the practice of the present invention to a certain extent.Target of the present invention and other advantages can be realized and be obtained by instructions and claims below.
Accompanying drawing explanation
In order to make the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the present invention is described in further detail, wherein:
Fig. 1 is anchorage zone structure diagrammatic cross-section;
Fig. 2 is the strain trend map of cable steel wire in anchorage zone;
Fig. 3 is the encapsulating structure schematic diagram of strain transducer;
Fig. 4 is that strain transducer is implanted the position view behind anchorage zone;
Fig. 5 is that Fig. 4 is along A to schematic diagram.
Embodiment
Hereinafter with reference to accompanying drawing, the preferred embodiments of the present invention are described in detail.Should be appreciated that preferred embodiment is only for the present invention is described, rather than in order to limit the scope of the invention.
1-cable steel wire; 2-anchoring filling agent; 3-anchor cup; 4-wire sub-panel; 5-strain transducer, 6-strain sensor, 7-strain signal output line.
As shown in Figure 1 and Figure 2, known according to mechanical analysis, in anchorage zone, the strain of cable steel wire is the trend of exponential damping, so by being implanted into strain transducer in anchorage zone, the small strain that just the large strain measurement of cable rope body can be converted into cable anchorage zone is measured, and reduces costs and realize difficulty.
The present invention adopts fiber grating as strain sensor 6, fiber-optic grating sensor (OpticalFiber Bragg Grating, OFBG) be a kind of sensitive element of function admirable, can respond to extraneous small strain variation by the movement of bragg reflection wavelength and realize the on-line measurement to structural stress, it not only has the rugged surroundings of not being afraid of, be not subject to ambient noise interference, anti-electromagnetic interference (EMI), collect sensing and be transmitted as all over the body, simple structure, the feature such as easy to use, but also have, can carry out high precision absolute measurement to the strain of structure, the advantage of quasi-distributed digital measurement.But because bare optical fibers and bare optical gratings is very thin especially, external diameter is about 125 μ m, and principal ingredient is SiO
2so fragile especially, especially its shearing resistance poor ability, therefore directly using it as sensor, cannot be competent at the extensive style construction of various engineerings, need to encapsulate or micro-processing it, the basic meaning of fiber-optic grating sensor encapsulation makes to utilize high performance material and dexterous version, researchs and develops and can meet the actual test of structure needs, the relatively simple and reliable Intelligence sensor of its installation technics of while.
As shown in Figure 3; the strain transducer 5 that the present invention adopts is also a kind of encapsulating structure of fiber-optic grating sensor; comprise capillary metal tube, fiber grating, transmission cable, adhesive etc.; in order to prevent that optical fiber is by external impacts; be encapsulated into the inside of capillary metal tube; the Main Function of adhesive makes capillary metal tube and fiber grating be bonded together fully; assurance fiber grating is experienced the structural strain that anchorage zone is come via the transmission of capillary metal tube exactly, fiber grating is played a very good protection simultaneously.That the profile of strain transducer can be made is cylindrical, conical or other forms of list structure, and inner strain sensor is arranged on the axial location place of list structure.
In addition, strain transducer 5 also can adopt FRP-OFBG muscle, fibre reinforced plastics (FRP) muscle is to take fiber as reinforcing material, take resin as matrix material, and admixture assistant, through drawing moulding and the necessary formed a kind of advanced composite material (ACM) of surface treatment, there is high-strength light, antifatigue, corrosion-resistant, easily processing, material mechanical performance is the advantages such as linearity, due to the easy machine-shaping of FRP muscle, in the process of preparation FRP muscle, OFBG is imbedded in centre position at muscle along its length, make FRP-OFBG muscle, this kind of structure has the sensing feature of excellent mechanical performances and decay resistance and the Fibre Optical Sensor of FRP muscle concurrently, overcome Fibre Optical Sensor fragile, the shortcoming of difficult arrangement, greatly improved the permanance of Fibre Optical Sensor.
The method that realizes Suo Li on-line measurement based on cable anchorage zone implantation strain transducer of the present invention, comprises the following steps:
1) according to the quantity of cable steel wire in the size of anchorage zone, anchorage zone, determine the implantation position for the treatment of of strain transducer 5, its implantation position should guarantee parallel with the direction of cable steel wire 1 in anchorage zone; The length of strain transducer 5 is less than the axial length of anchorage zone, and the diameter of strain transducer 5 is less than the spacing between adjacent cable steel wire 1;
2) according to step 1) in treat the situation of implantation position, determine the size of strain transducer, and prefabricated flexible barcode structural strain sensor, the tail end extension line of reserved sufficient length;
3) after the steel wire pier nose link in cable cabling process finishes, before anchor head casting link, the strain transducer of flexible barcode structure is implanted to cable anchorage zone according to pre-implantation position; The implantation position for the treatment of of strain transducer should be near the center of wire sub-panel, and on the horizontal section of anchorage zone, strain transducer is parallel or approximate parallel with near the cable steel wire axial location of anchorage zone, and center or approximate center position in adjacent wires axis institute region.As shown in Figure 4, Figure 5, adopt this kind of layout mainly based on following consideration: because steel wire in anchorage zone becomes vertebra shape, to distribute, in anchorage zone, steel wire is more close to cross-section center position, anchorage zone, more be similar to parastate, so in order to guarantee the linear feature of strain transfer, and in order to guarantee sensor construction stability, strain transducer must be planted between the steel wire of cross-section center position; Arrange and make the center of the position of strain transducer in anchorage zone like this, because the center of anchorage zone is the most concentrated region of stress, strain transducer is arranged in to this region, can makes the sensing element of strain transducer inside accurately predict the maximum stress scope of cable; Strain transducer is arranged in to the center between adjacent cable steel wire, makes the stressed more even of strain sensor, reduce error;
4) the signal extension line of strain transducer is drawn from wire sub-panel preformed hole;
5) fill with anchor after strain transducer position is fixed, add stabilizing agent and also carry out hot setting, make strain transducer and anchoring filling agent close contact be consolidated into one.
6) fill with anchor and complete, treat that anchor head casting carries out annealing in process to anchor head after solidifying;
7) utilize the value of thrust in the super stretching process of cable to demarcate strain transducer data, set up the output strain of strain sensor and the relation of cable force, by measuring the STRESS VARIATION of the strain sensor element in anchorage zone, realize the measurement to cable force.
It should be noted that in step 3) in, before burying underground, also roughening treatment should be carried out in the surface of strain transducer, make its surface there is frictional resistance, be convenient to combine closely with anchoring filling agent.
Measuring method of the present invention, by being implanted into strain transducer in anchorage zone, is converted into small strain by the large strain measurement of cable rope body and measures, and has reduced cost and has realized difficulty; Solved the survive problem of strain sensor in anchor head labyrinth simultaneously; Because anchorage zone is positioned at the tail end of cable, so can reduce to greatest extent DOL Data Output Line length at anchorage zone implanted sensor, not only reduced technology difficulty, and reduced cost.
Application example:
Buttress shaft shape implantable sensor parameter: resolution < 0.5 μ ε, operating temperature range-30 ℃~+ 80 ℃, range 0~3500 μ ε.Test apparatus: fiber grating network analyzer, the super tensioning system of cable.
According to above-mentioned steps, carry out actual cable test, stretched three reciprocal test findings back and forth as shown in Figure 6.As seen from the figure, fiber bragg grating center wavelength becomes good linear replicated relation with cable tension, and the linearity reaches more than 0.99, proves that the intelligent cable scheme based on anchorage zone strain measurement is feasible.
Finally explanation is, above embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is had been described in detail with reference to preferred embodiment, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement technical scheme of the present invention, and not departing from aim and the scope of the technical program, it all should be encompassed in the middle of claim scope of the present invention.