CN101915650A - System and method for measuring deflection of bridge structure based on wireless tilt - Google Patents

Abstract

The invention discloses a system and method for measuring deflection of a bridge structure based on wireless tilt, belonging to the technical field of bridge structure measurement. The invention is characterized in that the system is jointly formed by two wireless tilt sensors, a wireless data unit and a personal computer (PC), wherein the wireless data unit is connected with the PC via a serial port; and each wireless tilt sensor is jointly formed by a micro electro mechanical system (MEMS) technology based tilt unit, a tilt acquisition unit, a wireless transceiving unit and an energy module. The method is characterized by building the bridge deflection curve formula in consideration of the joint action of the deal weight of the bridge structure and the external load, deriving the deflection formula to obtain the tilt formula, computing the unknown parameters according to the actually measured tilt and further obtaining the deflection. The invention overcomes the defects existing in the traditional wired measuring systems and methods, the system has the characteristics of high testing precision, good stability, strong real-time property, accurate computation, etc, and the method is suitable for measuring deflection of similar bridge structures and has good application prospect.

Description

Deflection of bridge structure measuring system and method based on wireless tilt

Technical field

The invention belongs to the bridge structure field of measuring technique, relate to a kind of bridge structure monitoring deflection metrology system and method that is suitable for being applied in based on the wireless tilt acquisition system, specifically a kind of wireless sensor technology that utilizes carries out the structure measurement of dip angle, calculates measuring system and the method that obtains the structural deflection value again.

Background technology

Bridge is an ingredient important in the Modern Traffic transportation network, and it is carried out safety monitoring is very necessary.In the past mostly bridge monitoring was to estimate, now along with science and technology development, increasing monitoring instrument is used for bridge monitoring.By analysis to the bridge monitoring data, can understand the past and present working condition of bridge structure, predict the situation that it is following, and amount of deflection is an important monitoring parameter.Amount of deflection is to judge bridge vertical rigidity, structural bearing capacity and the of paramount importance technical parameter of structural integrity, is the important indicator that rating bridge, unsafe bridge transformation and new bridge are checked and accepted.If deflection of bridge span has surpassed the design margin of regulation, bridge has the danger of collapsing at any time, jeopardizes the people's life security, causes huge property loss.Therefore, the measurement to deflection of bridge span is quite necessary.

The method of measuring deflection of bridge span in recent years has many, the robot measurement method is measured as adopting, communicating pipe the photoelectricity level gauging, utilize the precision positioning technology of GPS to measure, utilize displacement transducer to measure etc.In the said method, the robot measurement method is measured amount of deflection, have characteristics such as high intelligence, rapidity, wide range and high precision, but cost is than higher; Communicating pipe photoelectricity level gauging amount of deflection, though have very high precision, implementation process complexity, implementation cycle are long; And the precision positioning technology of GPS implements, and cost is also expensive.Adopt the measurement of dip angle deflection of bridge span not need the in-site measurement benchmark to reach and not influenced by daylight, rain, mist etc., measurement range is bigger, can realize one dimension/two-dimensional measurement.The obliquity sensor chip is a kind of integrated chip, and its inside has modulation-demodulation circuit, utilizes this circuit that the conversion of signals that collects is become voltage signal, with signal extraction, changes into actual angle value by microprocessing unit.And along with the development of sensing technology, wireless communication technology and MEMS technology, wireless sensor technology has begun to the structure monitoring infiltration and has become the focus of this respect research.

According to material mechanics principle, be example with freely-supported bridge Fig. 1, because the amount of deflection and the load of beam are linear, obey the Hookean elasticity law, coefficient is relevant with the characteristics such as rigidity of material.The deformation effect that each load causes on the beam is incoherent each other, satisfies superposition law.Therefore load can be decomposed, calculate the deflection deformation that causes under the situation of the independent effect of each load.

Do not having under the extraneous load condition, when only considering the loading of bridge self gravitation, load is evenly distributed in the length range of bridge, and establishing the load intensity is q (N/m), and overall length of bridge is l.Set up coordinate system, the equations of rotating angle that can try to achieve any point on the beam is,

$\mathrm{\θ}=w^{\′}=\frac{q}{24\mathrm{EI}}(l^3-{6\mathrm{lx}}^2+{4x}^3)---\left(1\right)$

EI is a constant, the bendind rigidity of expression beam, and E is the tension and compression elastic modulus, I is a moment of inertia.By formula 1 can be in the hope of the sag curve equation:

$w=\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-{2\mathrm{lx}}^2+x^3)---\left(2\right)$

Utilize above-mentioned fundamental formular, carry out transform operation and just can obtain deflection value.

Above-mentioned formula has only been considered the effect situation of bridge deadweight, obviously utilizes above-mentioned formula to carry out deflection metrology under the various states of bridge, because of not considering the external loads situation, measures inaccurate.

Summary of the invention

The invention provides deflection of bridge structure measuring system and the computational accuracy high deflection of bridge structure measuring method based on wireless tilt of a kind of easy-to-install based on wireless tilt.

Technical scheme of the present invention is as follows:

Measure wireless tilt sensor that amount of deflection adopted and acquisition system structure thereof as shown in Figure 2: a kind of deflection of bridge structure measuring system based on wireless tilt, comprise two wireless tilt sensor units, wireless data unit and computer unit, computer unit adopts serial mode to be connected with wireless data unit, and carries out radio communication with the wireless tilt sensor unit.Wherein the wireless tilt sensor unit comprises general inclination angle MEMS chip, inclination angle collecting unit, wireless transmit/receive units and energy module.Wireless data unit adopts the wireless universal module that has serial ports to realize; Computer unit comprises Calculation of Deflection unit and data display unit.Two wireless tilt sensor nodes are pre-loaded embedded capture program.

A kind of method of the deflection of bridge structure measuring system based on wireless tilt, at first measure the inclination data of bridge by the inclination angle collecting unit of wireless tilt sensor unit, the inclination data that the inclination angle collecting unit will be measured gained is converted to can carry out the data layout of serial communication and transfer to computer unit by wireless transmit/receive units, computer unit adopts the Calculation of Deflection formula to calculate amount of deflection, and the Calculation of Deflection formula is as follows:

With the freely-supported bridge is example, and wherein p is an external load, and q is the load intensity, and l is the beam total length, and EI is a constant, the bendind rigidity of expression beam, and E is the tension and compression elastic modulus, I is a moment of inertia.

Show as Fig. 1, can get by above-mentioned formula (1), (2):

${\mathrm{\θ}}_{\max }=\±\frac{{\mathrm{ql}}^3}{24\mathrm{EI}}---\left(3\right)$

$w_{\max }=w{|}_{x=\frac{l}{2}}=\frac{{5\mathrm{ql}}^4}{384\mathrm{EI}}$ (maximal value obtains at the mid point of beam) (4)

When only considering external load, the distortion amount of deflection of bridge is analyzed.External load generally is that the vehicle that travels on the bridge etc. applies, and is little with respect to the deflection deformation that is caused by the bridge deadweight.Say that with regard to freely-supported beam type bridge the amount of deflection of span centre is a key point.Therefore with model simplification, load concentration to span centre, is calculated.External load P acts on span centre, and promptly during x=1/2, the deflection deformation that is produced by external load is a formula 5,6:

$y=-\frac{\mathrm{px}}{12\mathrm{EI}}(\frac{{3l}^2}{4}-x^2),0\≤x\≤\frac{l}{2}---\left(5\right)$

$y=-\frac{\mathrm{px}}{12\mathrm{EI}}(x^3+\frac{{9l}^{2}x}{4}-{3\mathrm{lx}}^2-\frac{l^3}{4}),\frac{l}{2}\≤x\≤l---\left(6\right)$

By superposition principle, the sag curve that bridge deadweight and external load produce is formula (7), (8):

$y=-\frac{\mathrm{px}}{12\mathrm{EI}}(\frac{{3l}^2}{4}-x^2)-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-{2\mathrm{lx}}^2+x^3),$ Wherein $0\≤x\≤\frac{l}{2}---\left(7\right)$

$y=-\frac{p}{12\mathrm{EI}}(x^3+\frac{{9l}^{2}x}{4}-{3\mathrm{lx}}^2-\frac{l^3}{4})-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-{2\mathrm{lx}}^2+x^3),$ Wherein $\frac{l}{2}\≤x\≤l---\left(8\right)$

Maximal value is got at the place at span centre:

$y_{\max }=-\frac{l^3}{48\mathrm{EI}}(p+\frac{5\mathrm{ql}}{8})---\left(9\right)$

Order

Differentiate is carried out in formula (7), (8) gets the inclination angle equation,

$y^{\′}=({3x}^2-\frac{{3l}^2}{4})a+({6\mathrm{lx}}^2-l^3-{4x}^3)b$ Wherein $0\≤x\≤\frac{l}{2}---\left(10\right)$

$y^{\′}=(-{3x}^2-\frac{{9l}^2}{4}+6\mathrm{lx})a+(-l^3{+6\mathrm{lx}}^2-{4x}^3)b$ Wherein $\frac{l}{2}\≤x\≤l---\left(11\right)$

Both sides are laid the wireless tilt sensor node respectively in spanning, record 2 inclination angle value.Substitution formula (10), (11), i.e. the equations of rotating angle of span centre both sides, the value that obtains unknown quantity a, b is substitution formula (7), (8) again, thereby obtain the deflection equation of both sides in the spanning, and said method is measured amount of deflection and is called two-point method.Can utilize least square method from this method, expand to multimetering.

The invention has the beneficial effects as follows that the sensor chip of selecting for use based on the MEMS technology comes induced signal.Wireless data unit has been reserved serial ports.MEMS chip, inclination data collection and wireless transmit/receive units form the wireless tilt sensor.Wireless data unit and computing machine link and finish the reception of inclination data.Only need to measure 2 angles and just can extrapolate deflection value.Algorithm computation that computer program utilization the present invention proposes and demonstration amount of deflection.

Calculation of Deflection method and wireless tilt sensor measuring system based on the present invention's proposition, wireless sensor node is easy to assembling and disassembling, save lays the expense of lead and saves the set-up time, and calculates characteristics such as amount of deflection is accurate and determined its wide prospect and practical value.

Description of drawings

Fig. 1 is a freely-supported bridge mechanical model synoptic diagram of the present invention.

Fig. 2 is the deflection metrology system based on the wireless tilt sensor of the present invention.

Fig. 3 is the sag curve under the different loading environments.

Fig. 4 is a wireless tilt sensor construction synoptic diagram of the present invention.

Embodiment

Be described in detail specific embodiments of the invention below in conjunction with technical scheme and accompanying drawing.

Wireless tilt sensor construction of the present invention as shown in Figure 4.The measurement of dip angle unit selects for use the sensor chip based on the MEMS technology to come induced signal, the inclination angle collecting unit is responsible for the inclination data of MEMS chip induction is sent to radio receiving transmitting module with the serial ports pattern, radio receiving transmitting module adopts the wireless universal module that has serial ports to realize, energy module adopts the general lithium battery in market, Ni-MH battery or solar cell to realize.Two wireless tilt sensor nodes are pre-loaded embedded program, the algorithm routine of amount of deflection is calculated at the above-mentioned inclination angle of operation on the computing machine.

Calculating the amount of deflection algorithm implements as follows:

P is an external load, and q is the load intensity, and l is the beam total length, and EI is a constant, the bendind rigidity of expression beam, and E is the tension and compression elastic modulus, I is a moment of inertia, order

By superposition principle, the sag curve that bridge deadweight and external load produce is a formula 7,8:

$y=-\frac{\mathrm{px}}{12\mathrm{EI}}(\frac{{3l}^2}{4}-x^2)-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-{2\mathrm{lx}}^2+x^3),0\≤x\≤\frac{l}{2}---\left(7\right)$

$y=-\frac{p}{12\mathrm{EI}}(x^3+\frac{{9l}^{2}x}{4}-{3\mathrm{lx}}^2-\frac{l^3}{4})-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-{2\mathrm{lx}}^2+x^3),\frac{l}{2}\≤x\≤l---\left(8\right)$

Maximal value is got at the place at span centre:

$y_{\max }=-\frac{l^3}{48\mathrm{EI}}(p+\frac{5\mathrm{ql}}{8})---\left(9\right)$

Formula 7,8 is carried out differentiate gets the inclination angle equation:

$y^{\′}=({3x}^2-\frac{{3l}^2}{4})a+({6\mathrm{lx}}^2-l^3-{4x}^3)b,0\≤x\≤\frac{l}{2}---\left(10\right)$

$y^{\′}=(-{3x}^2-\frac{{9l}^2}{4}+6\mathrm{lx})a+(-l^3{+6\mathrm{lx}}^2-{4x}^3)b,\frac{l}{2}\≤x\≤l---\left(11\right)$

Both sides are laid the wireless tilt sensor node respectively in spanning, record 2 inclination angle value.Substitution (10) or (11) formula, i.e. the equations of rotating angle of span centre both sides, the value that obtains unknown quantity a, b is substitution formula (7), (8) again, thereby obtain the deflection equation of both sides in the spanning.Can utilize least square method from this method, expand to multimetering.For system of the present invention and algorithm, be to have carried out experiment test on the simple span bridge beam model of 1.44m in length, the wireless tilt sensor is put on the bridge model and powers on then, monitor channel, the computing machine that links to each other with wireless data unit constitutes network.Wireless tilt sensor acquisition data send to computing machine by serial ports with the data that receive by wireless data unit, and computer program reads serial data, after the data processing, show sag curve.Under beam self evenly load effect situation, deflection of bridge span is measured, load 1kg, 2kg, 3kg counterweight in the span centre position of beam, record corresponding deflection of bridge span with the two-point method that proposes respectively.Sag curve under the different loading environments as shown in Figure 3.Use laser displacement gauge to record corresponding amount of deflection simultaneously, the amount of deflection that records with two-point method compares, and is as shown in table 1.A is a two-point method, and B is the laser displacement gauge method.The corresponding amount of deflection that laser displacement gauge is recorded is as approximate true value.

Contrast of table 1 deflection metrology and analysis

A is the wireless tilt method, and B is the laser displacement gauge method.

As can be seen from the above experimental data, the amount of deflection of using the wireless tilt sensor to record has degree of accuracy preferably.In unloaded and loading experiment, the relative error that records amount of deflection is all less than 3%.Can verify deflection metrology system and algorithm validity that the present invention proposes.

Claims (3)

1. deflection of bridge structure measuring system based on wireless tilt, it is characterized in that, should comprise two wireless tilt sensor units, wireless data unit and computer unit based on deflection of bridge structure measuring system of wireless tilt, computer unit adopts serial mode to be connected with wireless data unit, and carries out radio communication with the wireless tilt sensor unit; Wherein the wireless tilt sensor unit comprises general inclination angle MEMS chip, inclination angle collecting unit, wireless transmit/receive units and energy module; Wireless data unit adopts the wireless universal module that has serial ports; Computer unit comprises Calculation of Deflection unit and data display unit.

2. the deflection of bridge structure measuring system based on wireless tilt according to claim 1 is characterized in that: energy module adopts lithium battery, Ni-MH battery or solar cell.

3. use the method for claim 1 or 2 described deflection of bridge structure measuring systems based on wireless tilt, it is characterized in that:

The sag curve that bridge deadweight and external load produce is

$y=-\frac{\mathrm{px}}{12\mathrm{EI}}(\frac{3l^2}{4}-x^2)-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-2l{x}^2+x^3),$ Wherein $0\≤x\≤\frac{l}{2}---\left(7\right)$

$y=-\frac{p}{12\mathrm{EI}}(x^3+\frac{9l^{2}x}{4}-3l{x}^2-\frac{l^3}{4})-\frac{\mathrm{qx}}{24\mathrm{EI}}(l^3-2l{x}^2+x^3),$ Wherein $\frac{l}{2}\≤x\≤l---\left(8\right)$

Order

Differentiate gets the inclination angle equation

$y^{\′}=(3x^2-\frac{3l^2}{4})a+(6l{x}^2-l^3-4x^3)b$ Wherein $0\≤x\≤\frac{l}{2}---\left(10\right)$

$y^{\′}=(-3x^2-\frac{9l^2}{4}+6\mathrm{lx})a+(-l^3+6l{x}^2-4x^3)b$ Wherein $\frac{l}{2}\≤x\≤l---\left(11\right)$

Both sides are laid the wireless tilt sensor node respectively in spanning, record 2 inclination angle value, substitution formula (10), (11), and the value that obtains unknown quantity a, b is substitution formula (7), (8) again, thereby obtain the deflection equation of both sides in the spanning; From this method, utilize least square method, expand to multimetering;

Wherein p is an external load, and q is the load intensity, and l is the beam total length, and EI is a constant, the bendind rigidity of expression beam, and E is the tension and compression elastic modulus, I is a moment of inertia.

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