CN1201146A - Concrete-bridge fatigue detecting technology and instrument - Google Patents

Abstract

The present invention relates to a fatigue detection process for concrete bridge beam and its detection apparatus. It is characterized by that it uses ultra-sonic detector to detect fatigue microcrack produced by tensile stress along cross-bridge direction on the upper edge of the bridge beam to determine the fatigue life of said concrete bridge beam. By determining the ratio value Kv of wave propagating time in beam span and wave propagating time in beam end and determining value KN according to the regression curve formula the endurance failure degree and residual failure life of said bridge beam can be determined. Said invention can be matched with computer, possesses data storage system, and has the advantages of simple method and quick accurate detection, small volume and light weight, etc..

Description

Concrete-bridge fatigue detecting technology and detector

The present invention relates to a kind of concrete-bridge detection technique, be specifically related to a kind of detection technique and adopt the employed detector of this technology fatigue lifetime of concrete-bridge.

The composite architectural materials that reinforced concrete is formed starts from 1850s, China just begins to adopt this material bridge construction in the beginning of this century, these bridges and the concrete-bridge passing and the use in time of thereupon progressively building up later will progressively enter the aged stage.Under long-term operation mobile load effect, bridge structure can produce fatigue damage gradually, and when the damage of accumulating over a long period reached a certain limit value, bridge can take place by unexpected destruction, and this do not have the broken ring of fragility of obvious sign to constitute very big threat to traffic safety in advance.In general, the fatigue lifetime of concrete-bridge is about more than 80 years, because the transportation environment difference of bridge, the safety margin difference of different types of rridges, the fatigue damage of its concrete-bridge is also inequality, as untimely these bridges are detected, just might change or reinforce the bridge that some temporarily need not be changed, and cause waste; Simultaneously may not take engineering measure to cause the generation of security incident to some bridges that has produced serious fatigue damage yet.

At present in the world the fatigue damage of bridge being detected state-of-the-art method is to adopt Miner linear damage theory to estimate, as Britain bridge standard BS5400 etc.This method will be made appropriate estimation to historical operation situation, or on the concrete of runing concrete-bridge or reinforcing bar, stick the resistance strain gage test stress and compose and construction coefficient, with rain stream method test data is made analysis then, estimate the remanent fatigue life of bridge again with the Miner theory.Generally adopt though this method is a domestic and abroad bridge circle institute, it has following shortcoming, and at first, it will chisel beams of concrete, exposes reinforcing bar, so that stick resistance strain gage, this way can produce new detection damage to beam.Secondly, this method requires the appropriate historical operation situation of estimating, the space-time of crossing over owing to bridge is big, can't make this accurate estimation, and therefore, its result's accuracy is often controversial.The 3rd, this is a kind of theoretical method, and is not directly perceived, will do several stress spectrum observations round the clock toward contact, wastes time and energy.

The objective of the invention is to overcome the defective of above-mentioned prior art, a kind of directly perceived, accurate, quick, easy concrete-bridge fatigue detecting technology and detector of detecting is provided.

The objective of the invention is to realize by following technical proposal.It is to produce small fatigue crack to finish the fatigue lifetime of measuring this concrete-bridge by ultrasonic listening concrete-bridge upper limb along cross-bridges direction tension.Its method is: earlier the detector probe is placed the vertical side of beam-ends upper limb concrete, measure Mintrop wave with transmission beam method and pass the speed time, can survey one group of data; Again the detector detecting head is placed the vertical side of span centre upper limb concrete, measure another group data; Then according to formula: Determine travel-time and beam-ends wave propagation time ratio Kv with a slice girder span medium wave; Again with Kv substitution formula: F _h=10 ^{0.29 * [14.92+8.116Kv]}Obtain the concrete fatigue damage degree of beams of concrete span centre F _hThen according to the concrete fatigue damage degree of all kinds beam F _hWith span centre lower edge reinforcing bar fatigue damage degree F _gRelation, determine the remanent fatigue life of full beam.

The realization said method is finished by detector, and it mainly comprises receiver, transmitter, amplifier, A/D converter, shows energy device waveform output etc., it is characterized in that it is provided with data storage system and microcomputer interface.

The present invention changes traditional concrete-bridge fatigue life detecting method, by the fatigue crack that is invisible to the naked eye that is produced with upper limb concrete pulling stress in the ultrasonic listening bridge, field recognition concrete-bridge fatigue injury tolerance can be worked as and the remanent fatigue life of bridge can accurately be calculated, it has got rid of Effect of Environmental, and torture test through several ten million times, have solid experiment basis, this technology has been filled up the blank that goes up bridge fatigue detecting technology aspect both at home and abroad.Simple, quick, the realization easily of assay method of the present invention, the detector volume is little, and is in light weight, is particularly suitable for field work, can be widely used in the fatigue detecting of domestic and abroad bridge.

Fig. 1 measures sample point and regression curve graph of a relation for the present invention;

Fig. 2 is a detector principle schematic of the present invention.

The present invention is described in detail in detail below.

Force-bearing situation according to bridge, concrete-bridge is under the effect of operation mobile load, the upper limb concrete can produce compressive stress in the bridge axes direction, because the cause of Poisson's ratio, the upper limb concrete produces tension along the cross-bridges direction, though this tension is less, behind direct action, can not produce appreciable impact, but under prolonged and repeated effect, this tension will cause small fatigue crack to bridge, this small fatigue crack is hidden in beams of concrete inside, and naked eyes can't be observed.Though the tested object of normal concrete ultrasound measuring instrument also is a concrete, their purpose is the degree of depth of concrete intensity of mensuration or obvious crackle etc., and this method obviously is not enough to the accuracy of test.Therefore, must measure the small fatigue crack of bridge to estimate the extent of damage of bridge accurately.Concrete-bridge fatigue detecting technology is invented based on this principle, and the detected object of detector is exactly thisly to be present in atomic little crackle in the concrete in a large number by what fatigue caused.It produces small fatigue crack to measure the fatigue lifetime of this concrete-bridge by upper limb in the ultrasonic listening concrete-bridge along cross-bridges direction tension.Its method is: when measuring bridge with the concrete-bridge fatigue detector, transmitting probe and acceptance probe are placed the vertical side of beam-ends upper limb concrete, measure Mintrop wave with transmission beam method and pass fast time T _i', get 10 data for one group, i.e. i=1,2,3 ... 10; Then probe is placed the vertical side of span centre upper limb concrete, measure another group data T _i", i=1,2,3 ... 10.Order $\mathrm{Kv}=\left[\underset{i=1}{\overset{10}{\mathrm{\Σ}}}{T_i}^{\′\′}\right]/\left[\underset{i=1}{\overset{10}{\mathrm{\Σ}}}{T_i}^{\′}\right]----\left(1\right)$ Parameter K v is one of key index.Because under the operation load action, beam-ends upper limb concrete does not almost have stress to produce, and the stressed maximum of span centre concrete, the fatigue damage difference at this two place is very big, so Kv＞1, and the beam Kv of only talented input utilization just can equal 1.The influence of environment, carbonization of concrete, check surfaces etc. all can influence the velocity of propagation of sound wave.The present invention adopts is ratio K v with the wave propagation time of wave propagation time in a slice girder span and beam-ends, so it has got rid of Effect of Environmental.

With Kv substitution following formula

F _h=10 ^{0.29 * [14.92+8.116Kv]}(2) can calculate the concrete fatigue damage degree of beams of concrete span centre F _h, it is worth at 0.95F _h～1.05F _hBetween; Use the bridge theory again, calculate the injury tolerance of reinforcing bar and the remanent fatigue life of this sheet beam.

Formula (2) is a beams of concrete fatigue damage degree, by beams of concrete fatigue damage curve

1gK _N=-14.92+8.116Kv (3) gets for introducing parameter 0.29 pusher.Formula (3) is in 3,388 ten thousand torture tests, and test data is tried to achieve the relation of sample point and regression curve such as Fig. 1 with the homing method arrangement.

Formula (3) is the intermediate value curve of sample cluster, therefore, also gets the average of test data when the real bridge of test, suc as formula (1).

The concrete-bridge fatigue detector is the improvement of being done on existing ultrasonoscope basis, as shown in Figure 2, it comprises two probes, A/D conversion equipment, amplifier, scanning markers, oscillography follower, counting display circuit, be characterized in that it is provided with data storage system, and connect with computing machine, be convenient to preserve the data that record from the field and carry out Computer Analysis.

Claims (3)

1. concrete-bridge fatigue detecting technology is characterized in that it surveys small fatigue crack that upper limb in the concrete-bridge produced along cross-bridges direction tension to measure the fatigue lifetime of this concrete-bridge by ultrasound wave behaviour.It is made up of the following step:

1〉earlier the detector detecting head is placed the vertical side of beam-ends upper limb concrete, measure the Mintrop wave travel-time, can measure one group of n data with transmission beam method;

2〉again the detector detecting head is placed the vertical side of girder span upper limb concrete, measure n data of another group;

3〉according to formula: $\mathrm{Kv}=\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{T_1}^{\′\′}\right]/\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{T_i}^{\′}\right]$

Wherein: T _i" and T _i, ' be respectively span centre and beam-ends wave propagation time, Kv is with the travel-time of a slice girder span medium wave and beam-ends wave propagation time ratio;

4〉with the following formula .F of Kv substitution _h=10 ^{0.29 * [14.92+5.116Kv]}

F in the formula _hBe the concrete fatigue damage degree of beams of concrete span centre, it is worth at 0.95F _h～1.05F _hBetween;

5〉according to the Kv value, the fatigue damage degree and the remanent fatigue life of evaluation bridge.

2, concrete-bridge fatigue detector as claimed in claim 1 mainly comprises receiver, transmitter, amplifier, A/D converter, waveform output etc., it is characterized in that it is provided with data storage system and microcomputer interface.

3, concrete-bridge fatigue detector according to claim 1 is characterized in that formula

Middle n is 10.

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