CN105223272A - A kind of method of Quick Measuring Hollow Slab Beam Bridge Transverse Distribution and quality vibrator - Google Patents

Abstract

The invention belongs to engineering structure detection technique field, be specifically related to a kind of method and quality vibrator of Quick Measuring prefabricated PC concrete hollow slab girder bridge Transverse Distribution, the method comprises: calculate each hollow slab girder vibration frequency mean value f; Determine the vertical exciting quality of the inertial mass vibrator being arranged on <i>j</iGreatT.Gr eaT.GT beam: measure vibrator with frequency f _j, amplitude A stable state exciting time each beam vertical motion speed time-domain signal; Determine the dynamic deflection maximal value y of each girder span middle section _ij; Calculate the Transverse Distribution η of No. i-th beam under exciting effect in j girder span _ij.The present invention adopts single-point to load, and influencing each other when avoiding multipoint excitation, has accurate, quick and economic advantage; Load mode transfers power to by static loading and loads, owing to there is clear and definite corresponding relation between maximum dynamic deflection and natural bow, test result of the present invention and theoretical method are more close, measure not by the restriction of under-clearance, test process is simple, quick, is convenient to resume traffic fast.

Description

A kind of method of Quick Measuring Hollow Slab Beam Bridge Transverse Distribution and quality vibrator

Technical field

The invention belongs to engineering structure detection technique field, be specifically related to a kind of method and quality vibrator of Quick Measuring prefabricated PC concrete hollow slab girder bridge Transverse Distribution.

Background technology

The essence of bridge lateral distribution coefficient is unit force when acting on certain sheet girder span middle section, and the size of the power that each beam is born respectively, it has reacted the lateral ties between each beam, contributes to determining that the least favorable load of bridge is arranged.In Design of Highway Bridge, usually extend that to be calculated as the peak load that certain root girder bears be the multiple that each axle is heavy.In the detecting appraisal of unit construction bridge girder construction, the mensuration of Transverse Distribution is also a very important job.

In existing Bridge Design specification, the general Transverse Distribution adopting transversely hinge to calculate prefabricated PC concrete hollow slab girder spanning middle section.The method supposition only transmits vertical shear in bonding crack (hinge seam) under vertical uniform load q, the concentrated force P acting on span centre is equivalent to the sinusoidal load of half-wave (after equivalence, loading characteristic meets the boundary condition of former stressing conditions, and equivalent forward and backward mid-span deflection is very close), solves the mid-span deflection obtaining each beam by force method.During actual computation, first calculate the cross section property of hollow slab girder, then direct according to stiffness parameters (wherein, I represents cross section bending resistance moment of inertia, I _trepresent cross section torsional moment inertia, b represents the width of every sheet beam, and L represents that calculating is across footpath), look into articulated slab load relieving system effect string and erect mark table, calculate Transverse Distribution.

The Transverse Distribution of prefabricated PC concrete hollow slab girder spanning middle section detects, and is all that the method loaded based on loaded vehicle measures.That is: loaded vehicle is carried on span centre most unfavorable combination, measures the mid-span deflection of each beam, and obtain Transverse Distribution with the amount of deflection of single beam divided by combined deflection.

Obviously, theoretical computing method clear principle, definite conception.But the measuring method of reality but has a tremendous difference with theoretical method.Be set up at load cloth, in fact loaded vehicle that adopts loads more, and load action on multiple points of multi-disc beam, and should be that single-point span centre loads in theory; On Method And Principle, the Transverse Distribution reflection of bridge be lateral ties between each beam, and integral bridge is a space structure, single-point is loaded with the contact being beneficial to and accurately analyzing between each beam, also the problem of lateral connection is more easily found, i.e. the local damage of location hinge seam when bridge machinery.And when multipoint excitation, influence each other between each load(ing) point, measured amount of deflection is different from theoretical method, and to survey be only the superposition amount of deflection under multiple concentrated force effect, be difficult to the lateral connection disease identifying bridge.In addition, in practical operation, before measurement, to loaded vehicle be got out, under bridge, set up support, displacement meter etc. is installed, workload is large, waste time and energy, and uneconomical.

Summary of the invention

The present invention is directed to existing measuring method and differ comparatively large with theoretical method, time and effort consuming during mensuration, spends the problems such as larger, proposes a kind of method and quality vibrator of Quick Measuring Hollow Slab Beam Bridge Transverse Distribution.Technical scheme of the present invention is: a kind of method of Quick Measuring Hollow Slab Beam Bridge Transverse Distribution, and the method comprises the following steps:

Step one adopts ambient vibration advocate approach to test the vertical natural frequency f of single order obtaining each hollow slab girder ₁, f ₂f _nwith damping ratios ζ ₁, ζ ₂ζ _n, wherein n is hollow sheet number, calculates average frequency value f;

Step 2, requirement according to hollow slab girder maximum defluxion limit value, determine the vertical exciting quality of the inertial mass vibrator being arranged on jth beam:

In formula:

M _shakerepresent the moving-mass of vibrator,

ζ _jrepresent the damping ratios of jth beam,

M _jrepresent the gross mass of jth beam,

L represents that the calculating of beam is across footpath,

A represents the displacement amplitude of vibrator,

η _jrepresent the spaning middle section Transverse Distribution calculated value of jth beam (unit force acts in jth girder span simultaneously);

Step 3, above the span centre of jth beam, install inertial mass vibrator, in each girder span, fixing low frequency vibro-pickup is installed in position, measures vibrator with vibration frequency f _j, amplitude A stable state exciting time each beam span centre vertical motion speed time-domain signal;

Step 4, determine the dynamic deflection maximal value y of each girder span middle section _ij: in frequency domain, obtain displacement signal to rate signal integration, namely the dynamic deflection curve of bridge, dynamic deflection curve is got the average of the absolute value of maximum crest and trough, as the maximum dynamic deflection value y of No. i-th girder span middle section under exciting effect in j girder span _ij;

Step 5, calculate the spaning middle section Transverse Distribution η of No. i-th beam under exciting effect in j girder span _ij:

${\mathrm{\&eta;}}_{ij}=\frac{y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}}{\underset{i=1}{\overset{n}{\&Sigma;}}\left(y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}\right)}.$

A kind of inertial mass vibrator of the method for Quick Measuring Hollow Slab Beam Bridge Transverse Distribution, comprise: base plate, guide shaft and mass, guide shaft is right cylinder, be fixedly connected on base plate center, base plate be provided with fixed orifice and column, the upper surface of column is provided with caging bolt, guide shaft is set with helical compression spring, helical compression spring upper-end contact mass, mass is connected with guide shaft by linear bearing, then the top of guide shaft is provided with limiting plate by screw thread.

Described inertial mass vibrator, base plate is anchored on hollow slab girder by chemical bolt.

Described inertial mass vibrator, the vibration frequency of vibrator is regulated by the quality increasing and decreasing mass.

Described inertial mass vibrator, described mass is equal to the distance of uppermost limit plate and lowermost limit bolt.

The invention has the beneficial effects as follows: 1, accurate, than existing automobile Loading Method, this invention adopts single-point to load, influencing each other when avoiding multipoint excitation; Load mode transfers power to by static loading and loads, and owing to there is clear and definite corresponding relation between maximum dynamic deflection and natural bow, test result of the present invention and theoretical method are more close.

2, quick, the method arranges displacement meter without the need to proping under bridge in measuring process, and required vibrator and vibro-pickup are arranged on bridge floor, measures not by the restriction of under-clearance; Test process is simple, quick, is convenient to resume traffic fast.

3, economical, this invention only needs to install vibrator and vibro-pickup at bridge floor in measuring process, and do not need loaded vehicle to load, also arrange displacement meter without the need to proping under bridge, test process is simple, decreases spending that is artificial and apparatus, time saving and energy saving, saves fund.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of Fast Measurement bridge lateral distribution coefficient method of the present invention;

Fig. 2 is the structural representation of vibrator of the present invention;

In figure, 1, limiting plate, 2, circular mass, 3, bolt, 4, column, 5, chemical bolt, 6, linear bearing, 7, helical compression spring, 8, guide shaft, 9, base plate, 10, hollow slab girder.

Embodiment

Embodiment 1: composition graphs 1-Fig. 2, a kind of method for rapidly testing of prefabricated PC concrete hollow slab girder bridge Transverse Distribution, its central principle adopts less dynamic load stable state exciting to replace traditional loaded vehicle static loading, going out maximum static deflection by testing the maximum dynamic deflection inverse of hollow slab girder spaning middle section obtained, finally obtaining Transverse Distribution according to the Transverse Distribution computing formula of classics again.

The method comprises the following steps:

Step one, the test of employing ambient vibration advocate approach obtain the vertical natural frequency f of single order of each hollow slab girder ₁, f ₂f _nwith damping ratios ζ ₁, ζ ₂ζ _n, calculate average frequency value f;

Step 2, requirement according to hollow slab girder maximum defluxion limit value, determine the vertical exciting quality of the inertial mass vibrator being arranged on jth beam:

In formula:

M _shakerepresent the moving-mass of vibrator,

ζ _jrepresent the damping ratios of jth beam,

M _jrepresent the gross mass of jth beam,

L represents that the calculating of beam is across footpath,

A represents the displacement amplitude of vibrator,

η _jrepresent the spaning middle section Transverse Distribution calculated value of jth beam (unit force acts in jth girder span simultaneously).

Step 3, in jth girder span above fixing inertial mass vibrator is installed, in each girder span, fixing low frequency vibro-pickup is installed in position, measures vibrator with frequency f _j, amplitude A stable state exciting time each beam span centre vertical motion speed time-domain signal.

Step 4, determine the dynamic deflection maximal value y of each girder span middle section _ij: in frequency domain, obtain displacement signal to rate signal integration, namely the dynamic deflection curve of bridge, dynamic deflection curve is got the average of the absolute value of maximum crest and trough, as the maximum dynamic deflection value y of No. i-th girder span middle section under exciting effect in j girder span _ij;

Step 5, calculate the spaning middle section Transverse Distribution η of No. i-th beam under exciting effect in j girder span _ij:

${\mathrm{\&eta;}}_{ij}=\frac{y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}}{\underset{i=1}{\overset{n}{\&Sigma;}}\left(y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}\right)}$

A kind of inertial mass vibrator of a kind of method for Quick Measuring Hollow Slab Beam Bridge Transverse Distribution, comprise, base plate, guide shaft and mass, guide shaft is right cylinder, is fixedly connected on base plate center, base plate is provided with fixed orifice and column, the upper surface of column is provided with caging bolt, it is characterized in that: guide shaft is set with helical compression spring, helical compression spring upper-end contact mass, mass is connected with guide shaft by linear bearing, then the top of guide shaft is provided with limiting plate by screw thread.

Base plate is anchored on hollow slab girder by chemical bolt, and the frequency of vibrator is regulated by the quality increasing and decreasing mass, and described mass is equal to the distance of uppermost limit plate and lowermost limit bolt.

Wherein, classical Transverse Distribution computing formula is when unit force acts on position in j girder span, and the natural bow in each girder span is designated as u _st.Then the Transverse Distribution of No. i-th girder span middle section is:

${\mathrm{\&eta;}}_{ij}=\frac{u_{st}}{\underset{i=1}{\overset{n}{\&Sigma;}}{u}_{st}}$

The Transverse Distribution of dynamic action underbeam calculates

1. the modal mass of hollow slab girder single-degree of freedom vibration model:

Get:

Can obtain:

m＝0.5M

2. the differential equation of motion of hollow slab girder one degree of freedom modeling under extraneous Simple Harmonic Load effect

$m\stackrel{\&CenterDot;\&CenterDot;}{u}+c\stackrel{\&CenterDot;}{u}+ku=P_{0}sin\mathrm{\&omega;}t$

Starting condition:

$u{|}_{t=0}=0,\stackrel{\&CenterDot;}{u}{|}_{t=0}=\stackrel{\&CenterDot;}{u}\left(0\right)$

In formula: c=2m ω ζ;

M represents modal mass, and ζ represents damping ratio, and ω represents exciting circular frequency, ω _nrepresent the inherent circular frequency of beam, P ₀represent exciting force.

Gained knowledge by mathematical computations and structural dynamic, can obtain:

$u_t=u_c+u_p=e^{-{\mathrm{\&zeta;\&omega;}}_{n}t}(A{\mathrm{cos\&omega;}}_{D}t+B{\mathrm{sin\&omega;}}_{D}t)+Csin\mathrm{\&omega;}t+Dcos\mathrm{\&omega;}t$

In formula:

U _crepresent transient response;

U _prepresent homeostatic reaction;

$C=u_{st}\frac{1-{\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)}^2}{{\&lsqb;1-{\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)\&rsqb;}^2},$ $u_{st}=\frac{P_0}{k}$ Represent that beam is at static(al) p ₀amount of deflection under effect;

$D=u_{st}\frac{-2\mathrm{\&zeta;}\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)}{{\&lsqb;1-{\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_n}\right)\&rsqb;}^2};$

ζ represents the damping ratios of beam;

represent the damping vibrition circular frequency of beam;

ω _nrepresent the undamped oscillation circular frequency of beam;

ω represents exciting circular frequency.

The present invention utilizes the amplitude under homeostatic reaction to carry out the calculating of Transverse Distribution.

Only consider homeostatic reaction below:

u _t＝Csinωt+Dcosωt

Amplitude can be obtained by mathematical computations

$u_0=\frac{u_{st}}{\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{f}{f_i}\right)\&rsqb;}^2}}$

In formula:

F represents excited frequency;

F _irepresent the natural frequency of i beam.

When exciting force is with frequency f effect j beam, both form resonance.Due to the lateral ties of each beam, every sheet beam is all subject to the exciting force effect of frequency f.The steady-state amplitude y of No. i-th beam _ijfor:

$y_{ij}=\frac{u_{si}}{\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{f}{f_i}\right)\&rsqb;}^2}}$

In formula: u _sirepresent the natural bow of No. i-th beam.

Then:

$u_{st}=y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{f}{f_i}\right)\&rsqb;}^2}$

When masterpiece is used in j beam, the spaning middle section Transverse Distribution of No. i-th beam is:

${\mathrm{\&eta;}}_{ij}=\frac{y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}}{\underset{i=1}{\overset{n}{\&Sigma;}}\left(y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}\right)}$

Especially, if the natural frequency of vibration of each beam is equal with damping ratio, then above formula is reduced to:

${\mathrm{\&eta;}}_{ij}=\frac{y_{ij}}{\underset{i=1}{\overset{n}{\&Sigma;}}{y}_{ij}}$

Obviously, when each beam natural frequency of vibration is equal, the ratio of its spaning middle section Transverse Distribution equals the ratio of each beam steady-state amplitude.

Inertial mass vibrator design procedure

1. design excited frequency: in order to reach the effect of resonance, excited frequency should be got equal with each beam natural frequency of vibration.The difference of actual bridge each beam is very little, and natural frequency is substantially equal, and a large amount of detection example also demonstrates this point.On this basis, the present invention gets the excited frequency f of mean value as vibrator of each girder natural frequency of vibration.

2. exciting quality is designed: according to " highway reinforced concrete and prestressed concrete bridge contain design specifications " regulation, reinforced concrete and prestressed concrete beam bridge span centre maximum defluxion must not more than L/600.

Calculated by the spaning middle section Transverse Distribution of dynamic action underbeam and know:

$u_0=\frac{u_{st}}{\sqrt{{\&lsqb;1-{\left(\frac{f}{f_n}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{f}{f_n}\right)\&rsqb;}^2}}$

Then:

$\frac{u_0}{u_{st}}=\frac{1}{\sqrt{{\&lsqb;1-{\left(\frac{f}{f_n}\right)}^2\&rsqb;}^2+{\&lsqb;2\mathrm{\&zeta;}\left(\frac{f}{f_n}\right)\&rsqb;}^2}}$

Above formula indicates the corresponding relation of the amount of deflection under Static behavior and the amplitude under dynamic action, and namely dynamic magnification factor is relevant with excited frequency, the natural frequency of vibration and damping ratio.

In the bridge machinery of reality, the natural frequency of each beam can be recorded, make excited frequency equal natural frequency, i.e. f=f _i:

$\frac{u_0}{u_{st}}=\frac{1}{2\mathrm{\&zeta;}}$

For inertial mass vibrator:

P ₀=k _shakea=4m _shakeπ ²f ²a

In formula, A represents amplitude.

Jth beam for the effect of inertial mass vibrator:

$P_j=u_{st}k=8{\mathrm{\&pi;}}^2{\mathrm{\&zeta;u}}_0{\mathrm{mf}}_j^2={\mathrm{\&eta;}}_j{P}_0$

In formula, P _jrepresent the exciting force suffered by jth beam; η _jrepresent the Transverse Distribution of jth beam.

There is f=f again _j, then:

According to specification, ζ=1% ~ 5% is got to rc beam bridge, u ₀≤ L/600.For jth beam, for meeting amount of deflection requirement, the value of exciting quality is:

Do not measuring Transverse Distribution η _jbefore, first exciting quality can be estimated with theoretical value.

3. equivalent stiffness is determined:

Embodiment 2: composition graphs 1-Fig. 2, certain prefabricated PC concrete freely-supported bridge span of hollow slabs footpath 20m, superstructure is made up of 7 pieces of cored slabs, the wide b=1.25m of individual plates.According to design data, obtain the cross section property parameter of beam: bending resistance moment of inertia I=1.391 × 10 ⁶cm ⁴; Torsional moment inertia I _t=2.37 × 10 ⁶cm ⁴; Every linear meter(lin.m.) girder deadweight 11.2kN/m.Now intend surveying load action when the 4th beam, the Transverse Distribution of each beam.

First, designing quality vibrator.

1, excited frequency is designed

For reaching resonance effect, the free running frequency of excited frequency Ying Yuliang is identical.

$f=\frac{\mathrm{\&pi;}}{2L^2}\sqrt{\frac{EI}{m_c}}=1.42Hz$

2, exciting quality is designed

According to design data, can in the hope of stiffness parameters:

$\mathrm{\&gamma;}=5.8\frac{I}{I_T}{\left(\frac{b}{L}\right)}^2=0.0133$

According to linear interpolation, look into articulated slab load relieving system effect string and erect mark table, obtain load action when the 4th beam, the spaning middle section transverse distributing influence lines of each beam erects scale value, calculates Transverse Distribution as follows:

Obviously, the Transverse Distribution η of the 4th beam ₄=0.161, get ζ _j=2%, A=0.05m is then:

M _shakeget 1000kg.

3, equivalent stiffness is calculated

Then, Site Detection is carried out.

Step one, at the span centre position of every sheet beam axis, DH610V type electromagnetic type speed pickup is installed,

The sensor of the 4th beam can depart from span centre (but still being positioned on axis) slightly, so that the installation of vibrator.First, the test of ambient vibration advocate approach is adopted to obtain the vertical natural frequency f of single order of each hollow slab girder ₁, f ₂f _nwith damping ratios ζ ₁, ζ ₂ζ _n, calculate average frequency value f.

Step 2, determine the vertical exciting quality of inertial mass vibrator.Quality due to estimation is by supposition ζ _jto calculate with the f of theory and get, not accurate enough.Now vibrator has designed, and rigidity is certain, for reaching resonance, can increase and decrease qualitatively at original exciting.If the vibrator vibration frequency recorded is comparatively large, the exciting quality of vibrator can be reduced, otherwise, then increase certain exciting quality.The exciting quality of increase and decrease by vibration frequency inverse, equal the mean value f of each beam actual measurement natural frequency until the frequency measured value of quality vibrator till.

Step 3, inertial mass vibrator is fixed on the 4th beam bridge floor span centre position, together with base plate chemical anchor bolts are anchored at beam body.Low frequency vibro-pickup is arranged on each girder span centre position.Vibrator in the 4th girder span with frequency f ₄, amplitude 0.05m carries out exciting, the vertical motion speed time-domain signal of each beam during record exciting.The amplitude of vibrator is controlled by bolt and limiting plate, and both are very convenient in the adjustment of short transverse.Excited frequency coordinates control by metronome.

Step 4, determine the dynamic deflection maximal value y of each girder span middle section _i4: in frequency domain, displacement signal is obtained to rate signal integration, the i.e. dynamic deflection curve of bridge, dynamic deflection curve is got the average of the absolute value of maximum crest and trough, as the maximum dynamic deflection value y of No. i-th girder span middle section under exciting effect in the 4th girder span _i4.

Step 5, calculate the spaning middle section Transverse Distribution η of No. i-th beam under exciting effect effect in the 4th girder span _i4:

${\mathrm{\&eta;}}_{i4}=\frac{y_{i4}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}}{\underset{i=1}{\overset{n}{\&Sigma;}}\left(y_{i4}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}\right)}.$

Claims (5)

1. a method for Quick Measuring Hollow Slab Beam Bridge Transverse Distribution, is characterized in that: the method comprises the following steps:

Step one, the test of employing ambient vibration advocate approach obtain the vertical natural frequency f of single order of each hollow slab girder ₁, f ₂f _nwith damping ratios ζ ₁, ζ ₂ζ _n, wherein n is hollow sheet number, calculates average frequency value f;

Step 2, requirement according to hollow slab girder maximum defluxion limit value, determine the vertical exciting quality of the inertial mass vibrator being arranged on jth beam:

In formula:

M _shakerepresent the moving-mass of vibrator,

ζ _jrepresent the damping ratios of jth beam,

M _jrepresent the gross mass of jth beam,

L represents that the calculating of beam is across footpath,

A represents the displacement amplitude of vibrator,

η _jrepresent the spaning middle section of jth beam (unit force acts in jth girder span simultaneously) laterally

Distribution coefficient calculated value;

Step 3, above the span centre of jth beam, install inertial mass vibrator, in each girder span, fixing low frequency vibro-pickup is installed in position, measures vibrator with frequency f _j, amplitude A stable state exciting time each beam span centre vertical motion speed time-domain signal;

Step 4, determine the dynamic deflection maximal value y of each girder span middle section _ij: in frequency domain, obtain displacement signal to rate signal integration, namely the dynamic deflection curve of bridge, dynamic deflection curve is got the average of the absolute value of maximum crest and trough, as the maximum dynamic deflection value y of No. i-th girder span middle section under exciting effect in j girder span _ij;

Step 5, calculate the spaning middle section Transverse Distribution η of No. i-th beam under exciting effect in j girder span _ij:

${\mathrm{\&eta;}}_{ij}=\frac{y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}}{\underset{i=1}{\overset{n}{\&Sigma;}}\left(y_{ij}\sqrt{{\&lsqb;1-{\left(\frac{f}{f_i}\right)}^2\&rsqb;}^2+{\&lsqb;2{\mathrm{\&zeta;}}_i\left(\frac{f}{f_i}\right)\&rsqb;}^2}\right)}.$

2. the inertial mass vibrator for right 1, comprise, base plate, guide shaft and mass, guide shaft is right cylinder, is fixedly connected on base plate center, base plate is provided with fixed orifice and column, the upper surface of column is provided with caging bolt, it is characterized in that: guide shaft is set with helical compression spring, helical compression spring upper-end contact mass, mass is connected with guide shaft by linear bearing, then the top of guide shaft is provided with limiting plate by screw thread.

3. inertial mass vibrator according to claim 2, is characterized in that: base plate is anchored on hollow slab girder by chemical bolt.

4. inertial mass vibrator according to claim 2, is characterized in that: the vibration frequency of vibrator is regulated by the quality increasing and decreasing mass.

5. inertial mass vibrator according to claim 2, is characterized in that: described mass is equal to the distance of uppermost limit plate and lowermost limit bolt.