CN102495134A - Truss structure damage positioning method based on added mass - Google Patents

Abstract

The invention discloses a truss structure damage positioning method based on an added mass, and belongs to the technical field of structure monitoring. The truss structure damage positioning method is characterized in that: the damages to rod pieces of a truss are located by using a method for arranging and testing the rod pieces one by one through a mass block and a sensor. The bending stiffness of the rod pieces of the truss is required to be smaller than the axial rigidity; a response under partial excitation mainly reflects rod piece information; and the damage positions of the rod pieces are judged by comparing the positions of mass-added rod piece frequency response peak values. According to the method, the shortcomings that the truss structure is insensitive to partial damages and the damage positioning of the rod pieces is difficult to perform are overcome; and the method has the characteristics of simple actual operation, low cost, accurate identification and the like, and is good in application prospect.

Description

Truss-frame structure damage positioning method based on additional mass

Technical field

The invention belongs to the quality structure monitoring technical field, relate to a kind of method that is suitable for being applied in truss-frame structure damage location, specifically through relatively encouraging lower frequency peak value of response position to judge the method for member bar injury in the part each rod member behind the additional mass.

Background technology

Monitoring structural health conditions (SHM) is the research focus in the civil engineering work, and monitoring, early warning and man-rate that damage is identified as structure provide reliable theoretical foundation, are the most important theories foundations of monitoring structural health conditions.The truss-frame structure reasonable stress, computational analysis is simple, easy construction, adaptability is strong, is one of very important version of field of civil engineering.Truss-frame structure often is made up of hundreds of rod member, and the variation of each rod member or damage are all very little to the multidate information influence of whole truss-frame structure.Mode is the most basic multidate information of structure; So based on mode particularly the identification of frequency information be widely used in the damage identification of civil structure; Yet the several often rank of the mode that can identify in actual engineering mode; And insensitive to the damage of part, generally these data volumes also are not enough to accurately discern all whole component damages of truss-frame structure.(Damage Location Vector is DLV) through the definite position of damaging rod member of the svd of flexibility difference before and after the damage to damage location vector.Virtual deformation method (Virtual Distortion Method; VDM) utilize the thought of the quick weight analysis of its structure; Utilize the damage of virtual deformation model configuration, set up objective function, know damage through the mode of optimizing structure by the squared-distance of actual measurement time domain response and theoretical model response.Yet no matter be based on frequency, DLV or VDM method, all need on truss-frame structure, arrange more sensor, this makes it receive certain restriction in actual application in engineering.

Summary of the invention

The technical matters that the present invention will solve provides a kind of truss-frame structure damage positioning method based on additional mass simple to operate.

Truss is made up of a large amount of rod members, and the rod member that rod member length is identical with the cross section is divided into one type.To the quality together of additional phase on one type of rod member; The mode that adopts moving mass piece and sensor is carried out local dynamic test and analysis behind the additional mass one by one to this type rod member; And all frequency domain responses that will obtain are drawn on the figure position of comparison rod member frequency domain response peak value.Because the length of these rod members, cross section and additional identical in quality are so the peak of these rod member frequency domain responses should be very approaching.If some pairing position of rod member peak value less than or the corresponding frequency of average peak that squinted, that just shows that this rod member has damaged, thus the position of rod member is damaged in the location.Concrete scheme is following:

A kind of truss-frame structure damage positioning method based on additional mass, additional mass in the middle of the rod member of truss-frame structure; Mass can and be bolted on the rod member through anchor clamps; Transducer arrangements is in the centre position of rod member, and type of sensor selection dynamic strain sheet or acceleration transducer etc. can.Utilize hand hammer to knock the rod member centre position, the response of survey sensor, and calculated frequency response, the pairing frequency of main peak of frequency response has directly embodied the rigidity of rod member, and the big more rigidity of frequency is big more.Moving mass piece and sensor adopt the mode of rod member test one by one, the frequency response of all rod members of measurements and calculations truss to the centre position of other rod members of truss then;

$m=\frac{12\mathrm{EI}}{{\mathrm{\π}}^2{l}^3{f}_m}---\left(2\right)$

Wherein m be additional mass, anchor clamps and bolt quality and, E is the rod member elastic modulus, moment of inertia is I, l is a rod member length, f _mBe the desired rod member frequency that reaches.

The invention has the beneficial effects as follows the characteristics of utilizing truss-frame structure rod member light weight rigidity; Can reduce the thought of frequency through additional mass; Only utilize a quality and a sensor; To carrying out local dynamic test and analysis behind the additional mass on each rod member, judge the position of damage rod member then through the peak value of more similar rod member frequency domain response, overcome the deficiency of truss integral monitoring method.Experimentation cost of the present invention is cheap, and is easy to operate, implement easily, and data processing method is simple, has broad application prospects and practical value.

Description of drawings

Fig. 1 is the method at the present invention's additional mass in the middle of rod member.

Fig. 2 a is the front elevation of additional mass web member partial enlarged drawing

Fig. 2 b is the side view of additional mass web member partial enlarged drawing

Fig. 3 introduces transducer arrangements and energisation mode.

Fig. 4 three strides the truss synoptic diagram

The not frequency response of rod member 11 (rod member d) during additional mass of Fig. 5.

The frequency response of rod member 11 when Fig. 6 is additional mass m=0.2kg (rod member d).

The frequency response of 11 bars when Fig. 7 is additional mass m=0.2kg

Fig. 8 is the damage factor of 11 rod members of truss-frame structure.

Fig. 9 is the frequency response behind the damage truss member additional mass.

Among the figure: 1 rod member; 2 masses; 3 web members; 4 rod member nodes; 5 anchor clamps; 6 bolts; 6 masses; 7 sensors; 8 hand hammers; 9 rod member a; 10 rod member b; 11 rod member c; 12 rod member d; 13 rod member e; 14 rod member f; 15 rod member g; 16 rod member h; 17 rod member i; 18 rod member j; 19 rod member k.

Embodiment

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

So that three to stride truss be that example is introduced this embodiment among Fig. 4, the rod member numbering is seen Fig. 4, the identical 1m that is of each rod member length, and the external diameter of rod member is 5cm, and thickness is 3mm, and elastic modulus E is 2 * 10 ¹¹, density is 7.83 * 10 ¹¹Kg/m ³, the node quality is 0.5kg.Mass 2 is selected iron block for use, and two anchor clamps 5 are clamped rod member through bolt 6, then mass 2 is utilized through being bolted on the web member.

When on rod member, during additional mass (being m=0), directly not applying vertical unit pulse in the centre of rod member 12 (rod member d), the frequency response of corresponding mid point is Fig. 5, because rod member rigidity is in light weight, its frequency domain response peak value institute respective frequencies is very high, is 5914Hz.According to sampling thheorem, for can this frequency of accurate recognition, require SF at least more than 12000Hz, this requirement to sensor and data acquisition equipment is all very high, in actual engineering be do not allow readily accessible.

The span centre rigidity of rod member is 48EI/l ³, wherein the rod member elastic modulus is E, and moment of inertia is I, and rod member length is l.If the span centre additional mass is m, ignore the quality of rod member, then the frequencies omega of rod member can be released the approximate expression formula (2) of additional mass so thus by formula (1) approximate treatment.Additional quality m is the quality summation of mass, anchor clamps and bolt.The SF of general actual engineering expects that then the frequency of rod member can be at f about 1000Hz _mAbout=400Hz, can calculate the additional mass m month by formula (2) is 0.187kg.At the middle additional mass m=0.2kg of rod member 4, utilize truss-frame structure to calculate frequency response and see Fig. 6 so, its peak value institute respective frequencies is 378Hz.

$\mathrm{\ω}=\sqrt{\frac{48\mathrm{EI}}{m{l}^3}}---\left(1\right)$

$m=\frac{12\mathrm{EI}}{{\mathrm{\π}}^2{l}^3{f}_m}---\left(2\right)$

M=0.2kg is arranged on all 11 rod members of truss; And the frequency response of calculating corresponding rod member mid point, seeing Fig. 7, can find out because the length of each rod member is consistent with sectional dimension; The peak of its frequency response is very approaching behind the additional phase homogenous quantities, all about 380Hz.

When damage took place truss, the rigidity of establishing rod member 11 (rod member d) and rod member 17 (rod member i) reduction respectively was 40% and 70% of former bar, and damage factor is seen Fig. 8.Each corresponding rod member frequency response is Fig. 9 after the additional mass m=0.2kg so; The peak value of rod member 11 (rod member d) respective frequencies response is 242.6Hz; The frequency that 17 (rod member i) are corresponding is 320.1Hz; And other rod members are about 380Hz, can judge very clearly that damage has taken place for rod member 11 (rod member d) and 17 (rod member i), and the damage that bar 4 takes place is bigger.

To sum up, utilize the light characteristics of truss member, additional certain mass improves the local characteristics of rod member in the centre of rod member, adopts the position that can judge member bar injury through the mode of all rod member frequency response peak values relatively.

Claims (3)

1. the truss-frame structure damage positioning method based on additional mass is characterized in that, in the middle of the rod member of truss-frame structure, according to formula (2) additional mass, near mass, arranges a sensor; The middle part of adopting hand hammer to knock rod member, the response under the measure local excitation, and the frequency response of calculating rod member; Moving mass piece and sensor adopt the mode of rod member test one by one, the frequency response of all rod members of measurements and calculations truss to the centre position of other rod members of truss then; The rod member that the cross section is identical with length is as one type of rod member; Combined Ration than this type rod member additional mass after the peak value of frequency response; The pairing frequency in peak-peak position has embodied the rigidity of rod member; If certain rod member peak less than or the corresponding frequency of average peak that squinted, show that this rod member has damaged, thereby the position of rod member is damaged in the location;

$m=\frac{12\mathrm{EI}}{{\mathrm{\π}}^2{l}^3{f}_m}---\left(2\right)$

The quality of m additional mass wherein, E is the rod member elastic modulus, and moment of inertia is I, and l is a rod member length, f _mBe the desired rod member frequency that reaches.

2. the truss-frame structure damage positioning method based on additional mass is characterized in that, sensor is selected dynamic strain sheet or acceleration transducer.

3. the truss-frame structure damage positioning method based on additional mass is characterized in that mass is selected iron block for use.

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