CN109635497B - Steel beam bridge service life and reliability analysis method based on nonlinear damage theory - Google Patents
Steel beam bridge service life and reliability analysis method based on nonlinear damage theory Download PDFInfo
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Abstract
The invention relates to a method for analyzing the service life and reliability of a steel beam bridge based on a nonlinear damage theory, which comprises the following steps: s1, modeling and stationing: modeling and distributing points according to each dangerous point and random point of the steel beam bridge, measuring frequency discrete samples of the distributed points, and measuring and calculating frequency discrete samples of distributed point indications; s2, calculating a structural damage factor of the steel beam bridge according to the indication frequency discrete sample; s3, calculating the structural damage amount and the damage safety value of the steel beam bridge according to the structural damage factor of the steel beam bridge; s4, calculating the dynamic load of the steel beam bridge to obtain the total stress of the steel beam bridge in a monitoring period; and S5, calculating the service life and the reliability of the steel beam bridge according to the total stress of the steel beam bridge.
Description
Technical Field
The invention belongs to the field of structural safety evaluation, and mainly relates to a method for analyzing the service life and reliability of a steel beam bridge based on a nonlinear damage theory.
Technical Field
The fatigue damage of the bridge mainly comes from alternating cyclic stress under the action of dynamic loads such as vehicles and wind, and the fatigue damage accumulation of the bridge structure and main components causes the degradation and safety reduction of the bridge structure. Since the material used for the bridge construction is not uniform and continuous, there are actually many tiny defects, which gradually develop, merge to form damages and gradually form macrocracks in the material under the influence of load and environmental factors as the service time is prolonged. On one hand, the damage affects the durability of the structure and shortens the service life of the bridge structure; on the other hand, the reduction of structural strength and rigidity can be caused, and potential safety hazards are buried for road operation.
Although a few existing bridges are provided with health monitoring systems to monitor the operation state in real time, the correlation degree of various monitoring data is low, the safety state of the bridges in operation is difficult to evaluate directly, and the bridges cannot be effectively maintained. In actual operation, the bridge and the running vehicle are a coupled system, and the response of the coupled system is influenced by environmental factors. At present, the engineering field researches the damage assessment of the bridge structure based on vibration by using a multi-mode method. However, the modality-like approach makes it difficult in practice to distinguish whether a change in the modality observation is due to structural damage or due to a change in the operating conditions or environmental factors. This is because the power observation response changes due to environmental factors (noise, temperature, humidity, etc.) and changes in the operating state even if the structural state is not degraded. The existing structure damage identification research based on probability is also aimed at load forms such as deterministic excitation, white noise, environmental excitation and the like, is very sensitive to the randomness of dynamic load parameters, and cannot effectively identify damage.
Because the bridge is subjected to dynamic loads such as vehicles, wind and the like and complex actions of multiple media in the environment in actual operation, quantitative research on the influence of the damage of the bridge under the discontinuous amplitude-variable cyclic stress on the long-term service life of the bridge is less at present. A small amount of bridge life quantitative research is only based on a linear damage theory, and the linear damage theory has inherent defects in the analysis and research of the discontinuous loading condition of the bridge, so that the quantitative analysis error of the bridge life is larger. And the traditional linear damage theory can not solve the problem of how to change the bridge damage and the residual service life after the load and the environment are changed.
Disclosure of Invention
The invention adopts a nondeterministic method based on the improved performance function structure damage identification, which is insensitive to the randomness of dynamic load parameters; meanwhile, the existing nonlinear damage theory is corrected according to the actual complex loading condition of the bridge, the service life of the bridge after discontinuous amplitude-variable loads such as vehicles, wind, rain and the like or accidental events is quantitatively analyzed, and the safe use reliability of the bridge is calculated. In order to achieve the purpose, the invention provides the following technical scheme:
a method for analyzing the service life and reliability of a steel beam bridge based on a nonlinear damage theory comprises the following steps:
s1, modeling and stationing: modeling and distributing points according to each dangerous point and random point of the steel beam bridge, measuring frequency discrete samples of the distributed points, and measuring and calculating frequency discrete samples of distributed point indications;
s2, calculating structural damage factors of the steel beam bridge according to the indication frequency discrete samples;
s3, calculating the structural damage amount and the damage safety value of the steel beam bridge according to the structural damage factor of the steel beam bridge;
s4, calculating the dynamic load of the steel beam bridge to obtain the total stress of the steel beam bridge in a monitoring period;
and S5, calculating the service life and the reliability of the steel beam bridge according to the total stress of the steel beam bridge.
The specific steps of the step S1 are as follows:
(1) Modeling and stationing: according to the steel beam bridge structure and the preliminary static load analysis, calculating each dangerous point on the main body structure and the key component of the steel beam bridge by using finite element analysis software or theory, then distributing points on each dangerous point and random points, and measuring the structural dynamic characteristics of the steel beam bridge;
(2) Measuring distributed point frequency discrete samples, wherein the dynamic excitation of the vehicle load to the steel beam bridge is a random load which is continuously distributed in time and continuously moved in space, the random load is dispersed, and the duration of each discrete random pulse is set as 1/t second; setting the length of the steel beam bridge to be L meters, limiting the speed to be V meters per second, and dispersing a vehicle passing through the bridge once into Lt/V random pulse loads; carrying out spectrum analysis on each 1/t second time micro-segment to obtain a spectrogram; extracting the first n frequency values of each micro-segment frequency spectrum according to the amplitude, wherein nLt/V frequency values of distributed points are acquired under the excitation of one-time bridge-crossing driving, and the frequency values I are obtained i As a point frequency primary discrete sample;
(3) The natural frequency of the steel beam bridge structure is reduced when the steel beam bridge structure is damaged, and the frequency spectrum shows the natural vibration characteristic of the structureIt remains unchanged under the geometrical and physical characteristics of no damage or damage and no development; frequency values appearing for multiple times in a discrete sample, namely frequency stable points, are insensitive to environmental parameters; weighted average is carried out on the frequencies indicating the structural damage condition in a discrete sample to obtain an indication frequency I C The method comprises the following steps:
in the formula k i N is the repeated probability of the frequency points, the distributed points are measured for a plurality of times in a cycle, discrete samples of the indicated frequency of the distributed points in the cycle are obtained, and the quantity is set as N C And (4) respectively.
In the step S2, the structural damage factor of the steel beam bridge is calculated according to the discrete sample of the indication frequency, and the specific steps are as follows:
setting I according to the distributed frequency discrete samples of the points Ci Frequency indicative of a state of structural damage in a time domain; let J C Indicating the frequency I for the distributed point in a cycle Ci Average value of (i), i.e.
To take the uncertainty of various media in the environment into account, set Q C Indicating the frequency I for the distributed point in a cycle Ci Standard deviation of (i), i.e.
Calculating structural damage factor P of steel beam bridge by using Gaussian function
Wherein f (x) is a Gaussian function, I 0 Frequency of structural damage-free status indications, J C As an indication of the mean frequency, Q C Is an indicationA frequency standard deviation; considering the effect of the environment multi-medium on the bridge, introducing a parameter lambda related to the elastic modulus E and the temperature T of the material, and correcting a Gaussian function into the following values:
in the formula E 0 ＝2.0×10 5 MPa，T 0 =298 ℃ (absolute temperature).
Wherein, the step S3 is used for calculating the structural damage quantity D of the steel beam bridge according to the structural damage factor of the steel beam bridge 0 And degree of injury safety R 0 The specific steps are as follows:
damage to steel beam bridge structure D 0 The method comprises the following steps:
D 0 ＝2P-1
safety degree R for damage to steel beam bridge structure 0 The method comprises the following steps:
R 0 ＝2-2P
wherein P is a structural damage factor of the steel beam bridge.
And S4, calculating the dynamic load of the steel beam bridge, including traffic load, wind load and rain load.
Wherein the traffic load is calculated by:
(1) Calculating the average traffic load F borne by the steel beam bridge in one period cars Then, then
In the formula (I), the compound is shown in the specification,
is the average vehicle weight;
is the average vehicle distance; the length of the steel beam bridge is L meters, the speed limit is V meters/second, g is a gravity constant, and the dynamic load coefficient of the vehicle is K d The calculation formula is as follows:
in the formula, the state divides the grade Q of the road surface into 1-8 grades, and the delta Q = Q-1; vehicle speed V,. DELTA.V = V-60km/h.
Wherein the wind load is calculated by:
(1) Calculating the average wind load F borne by the steel beam bridge in one period wind Then F is wind ＝β·μ h ·μ s ·P wind ·A；
In the formula, beta is a wind vibration coefficient representing wind load pulsation excitation; mu.s h Is the wind pressure height variation coefficient; mu.s s Is the wind load body shape coefficient; p wind The basic wind pressure is obtained; a is the windward area;
for the wind vibration coefficient beta, the calculation formula is as follows:
wherein mu is a peak value-preserving factor; s is the change of bridge deflection caused by wind load, wherein S 1 Determining the mean value of the displacement, S, for the points laid 2 Measuring the mean square deviation of the displacement for the distributed points;
for basic wind pressure P wind The calculation formula is as follows:
P wind ＝k·U 2
wherein k is a constant; u is the wind speed.
Wherein the rain load is calculated by:
(1) Calculating the average rain load F borne by the steel beam bridge in one period rain Then F is rain ＝P rain A; in the formula, rain pressure P rain (ii) a A bridge deck area A; p is rain ＝g·ρ 1 H, where g is the gravitational constant, ρ 1 The density of the rainwater is shown, and h is the average water accumulation depth per unit area in heavy rains.
Wherein, the steel beam is calculated according to the traffic load, the wind load and the rain loadCalculating the total stress of the bridge structure, and calculating the equivalent stress amplitude sigma of the steel beam bridge under the action of multiple loads in a monitoring period E The value:
in the formula, k is a variable amplitude fatigue curve coefficient; sigma i The stress amplitude of the steel beam bridge in a certain period; n is i To correspond to sigma i And (3) the fatigue cycle times of the steel beam bridge loaded in one period during the stress amplitude.
The concrete steps of calculating the service life and the reliability of the steel beam bridge in the step S5 are as follows:
(1) Service life N of steel beam bridge f Comprises the following steps:
N fi ＝9.384·K·(1.01·σ 0 -σ i ) 1-A ·R i-1
(2) The use reliability R of the steel beam bridge is as follows:
in the formula, R i-1 The existing damage safety degree of the structure of the device at the beginning of a period; sigma i The structural stress amplitude under the action of multiple loads in one period; sigma 0 Is the fatigue limit; A. k is a constant; n is a radical of an alkyl radical i To correspond to sigma i And (3) the fatigue cycle times of the steel beam bridge loaded in one period during the stress amplitude.
Specifically, the total stress of the steel beam bridge structure in a monitoring period when the steel beam bridge is subjected to multi-medium action is calculated, the traffic load, the wind load and the rain load obtained through analysis are input into an existing model of finite element software for analysis, and the total stress (namely the fatigue stress amplitude) of the steel beam bridge structure is calculated according to a fourth strength theory. Equivalent stress amplitude sigma E Comprises the following steps:
in the formula, k is a variable amplitude fatigue curve coefficient; sigma i A certain periodic component stress amplitude; n is i To correspond to sigma i Number of cycles of the member during stress amplitude.
Specifically, regarding to the calculation of the service life and the reliability of the steel beam bridge, according to the actual situation that the steel beam bridge is subjected to the discontinuous amplitude load of vehicles, wind, rain and the like, the CHABOCHE nonlinear damage model dD = f (D, σ) dn which is the mainstream in the international world is corrected, and the following is applied:
(1) Service life N of steel beam bridge f Comprises the following steps:
N fi ＝9.384·K·(1.01·σ 0 -σ i ) 1-A ·R i-1
(2) The use reliability R of the steel beam bridge is as follows:
A. the K value is a material property. After the preliminary data is obtained by the fatigue test, the preliminary data is substituted into the formula, and the A and K values are obtained by performing function fitting by using software such as Origin and the like.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, the discontinuous effect of various actual complex loads and environmental media on the bridge is fully considered, and the corrected nonlinear damage model is used for carrying out relatively accurate quantitative analysis and reliability calculation on the service life of the bridge after normal operation or accidental events; the method of the invention does not interrupt and interfere traffic, and the damage identification and service life analysis result is closer to the real state of the bridge structure in the operation state.
Drawings
FIG. 1 is a flow chart of the present invention for predicting the service life and safety reliability of a steel beam bridge;
FIG. 2 shows the reliability data of the steel beam bridge under different equivalent stress amplitudes and different expected service life.
Detailed Description
The technical solutions of the present invention are further explained below with reference to the accompanying drawings and specific examples, it should be understood that the examples are only for illustrating the present invention and are not intended to limit the scope of the present invention, and after reading the present invention, various modifications of equivalent forms of the present invention by those skilled in the art are within the scope defined by the claims appended to the present application.
A method for analyzing the service life and reliability of a steel beam bridge based on a nonlinear damage theory comprises the following steps:
s1, modeling and stationing: modeling and distributing points according to each dangerous point and random point of the steel beam bridge, measuring frequency discrete samples of the distributed points, and measuring and calculating frequency discrete samples of the distributed points;
s2, calculating structural damage factors of the steel beam bridge according to the indication frequency discrete samples;
s3, calculating the structural damage amount and the damage safety value of the steel beam bridge according to the structural damage factor of the steel beam bridge;
s4, calculating the dynamic load of the steel beam bridge to obtain the total stress of the steel beam bridge in a monitoring period;
and S5, calculating the service life and the reliability of the steel beam bridge according to the total stress of the steel beam bridge.
The specific steps of step S1 are as follows:
(1) Modeling and point distribution: according to the steel beam bridge structure and the preliminary static load analysis, calculating each dangerous point on the main body structure and the key component of the steel beam bridge by using finite element analysis software or theory, then distributing points on each dangerous point and random points, and installing monitoring equipment to measure the structural dynamic characteristics of the steel beam bridge;
(2) Measuring distributed point frequency discrete samples, namely, the dynamic excitation of the vehicle load on the steel beam bridge is a random load which is continuously distributed in time and continuously moves in space, and dispersing the random load, wherein the duration of each discrete random pulse is set as 1/t second; if the length of the steel beam bridge is set to be L meters and the speed is limited to be V meters per second, dispersing a vehicle passing through the bridge for one time into Lt/V random pulse loads; carrying out spectrum analysis on each 1/t second time micro-segment to obtain a spectrogram; extracting the first n frequency values of each micro-segment frequency spectrum according to the amplitude value, wherein the frequency values of the distributed points acquired under the excitation of one-time bridge-crossing driving have nLt/V, and the frequency values I i As a single discrete sample of the spotted frequency;
(3) Measuring and calculating a distributed point indication frequency discrete sample, wherein the inherent frequency of the steel beam bridge structure is reduced when the steel beam bridge structure is damaged, and the frequency spectrum shows the natural vibration characteristic of the structure, and the natural vibration characteristic of the structure is kept unchanged under the geometric physical characteristic that the structure is not damaged or damaged and does not develop; frequency values appearing for multiple times in a discrete sample, namely frequency stable points, are insensitive to environmental parameters; weighted average is carried out on the frequencies indicating the structural damage condition in a discrete sample to obtain an indication frequency I C The method comprises the following steps:
in the formula k i N is the repeated probability of the frequency points, the distributed points are measured for a plurality of times in a cycle, discrete samples of the indicated frequency of the distributed points in the cycle are obtained, and the quantity is set as N C And (4) respectively.
In the step S2, the structural damage factor of the steel beam bridge is calculated according to the discrete sample of the indication frequency, and the specific steps are as follows:
setting I according to the distributed frequency discrete samples of the points Ci Frequency indicative of a state of structural damage in a time domain; let J C Indicating the frequency I for the distributed point in a cycle Ci Average value of (i), i.e.
To take the uncertain conditions of various media in the environment into consideration, Q is set C Indicating the frequency I of the distributed points in a cycle Ci Standard deviation of (i), i.e.
Calculating structural damage factor P of steel beam bridge by using Gaussian function
Wherein f (x) is a Gaussian function, I 0 Frequency of structural non-invasive state indications, J C Mean value of frequency of indications, Q C The standard deviation of the indicated frequency is; considering the effect of the environment multi-medium on the bridge, introducing a parameter lambda related to the elastic modulus E and the temperature T of the material, and correcting a Gaussian function into the following values:
in the formula E 0 ＝2.0×10 5 MPa，T 0 =298 ℃ (absolute temperature).
Step S3 is carried out, wherein the structural damage quantity D of the steel beam bridge is calculated according to structural damage factors of the steel beam bridge 0 And degree of injury safety R 0 The method comprises the following specific steps:
damage to steel beam bridge structure D 0 The method comprises the following steps:
D 0 ＝2P-1
safety degree R for structural damage of steel beam bridge 0 The method comprises the following steps:
R 0 ＝2-2P
wherein P is a structural damage factor of the steel beam bridge.
And S4, calculating dynamic loads of the steel beam bridge, wherein the dynamic loads comprise traffic loads, wind loads and rain loads.
Wherein the traffic load is calculated by:
(1) Calculating the average traffic load F borne by the steel beam bridge in one period cars Then, then
In the formula (I), the compound is shown in the specification,
is the average vehicle weight;
is the average vehicle distance; the length of the steel beam bridge is L meters, the speed limit is V meters per second, g is a gravity constant, and the dynamic load coefficient of the vehicle is K d The calculation formula is as follows:
in the formula, the state divides the grade Q of the road surface into 1-8 grades, and the delta Q = Q-1; vehicle speed V,. Delta.v = V-60km/h.
Wherein the wind load is calculated by:
(1) Calculating the average wind load F borne by the steel beam bridge in one period wind Then F is wind ＝β·μ h ·μ s ·P wind ·A；
In the formula, beta is a wind vibration coefficient representing wind load pulsation excitation; mu.s h Is the wind pressure height variation coefficient; mu.s s Is the wind load form factor; p is wind The basic wind pressure is obtained; a is the windward area;
and for the wind vibration coefficient beta, the calculation formula is as follows:
wherein mu is a peak value-preserving factor; s is the change of bridge deflection caused by wind load, wherein S 1 Determining the mean value of the displacement, S, for the points laid 2 Measuring the mean square deviation of the displacement for the distributed points;
for basic wind pressure P wind The calculation formula is as follows:
P wind ＝k·U 2
wherein k is a constant; u is the wind speed.
Wherein the rain load is calculated by:
(1) Calculating the average rain load F suffered by the steel beam bridge in one period rain Then F is rain ＝P rain A; in the formula, rain pressure P rain (ii) a A bridge deck area A; p rain ＝g·ρ 1 H, where g is the gravitational constant, ρ 1 The density of the rainwater is shown, and h is the average water accumulation depth per unit area in heavy rains.
Wherein, the total stress of the steel beam bridge structure is calculated according to the traffic load, the wind load and the rain load, and the equivalent stress amplitude sigma of the steel beam bridge under the action of multiple loads in a monitoring period is calculated E The value:
in the formula, k is a variable amplitude fatigue curve coefficient; sigma i The stress amplitude of the steel beam bridge in a certain period; n is i To correspond to sigma i And the fatigue cycle times of the steel beam bridge under load in one period during the stress amplitude.
The concrete steps of calculating the service life and the reliability of the steel beam bridge in the step S5 are as follows:
(1) Service life N of steel beam bridge f Comprises the following steps:
N fi ＝9.384·K·(1.01·σ 0 -σ i ) 1-A ·R i-1
(2) The use reliability R of the steel beam bridge is as follows:
in the formula, R i-1 The existing damage safety degree of the structure of the device at the beginning of a period; sigma i The structural stress amplitude under the action of multiple loads in one period is shown; sigma 0 Is the fatigue limit; A. k is a constant; n is a radical of an alkyl radical i To correspond to sigma i And (3) the fatigue cycle times of the steel beam bridge loaded in one period during the stress amplitude.
In order to explain the technical effects of the present invention, the present invention takes Xiamen sea cang bridge as an analysis object. The mansion sea cang bridge is a three-span continuous full-floating steel box girder suspension bridge with two-way six lanes, has the function of a city bridge, has the total length of about 6000 meters, is a suspension main bridge with the length of 1108 meters, has the main span of 648 meters, has the bridge deck width of 36.6 meters, has the design traffic capacity of 50000 vehicles per day, has the driving speed of 80 kilometers per hour, moves earth in 1997 and completes the traffic in 1999. The steel box girder is made of Q345 steel, and the net height between the steel box girder and the sea surface is 55 meters. The bridge is provided with a double tower with the height of 140 meters, two main cables are erected, and the main cables and the steel box girder are pulled by the suspension rods. The climate of the area is mild, the rainfall is abundant, the annual average wind speed is about 3.4 m/s, and the climate is the marine climate of subtropical monsoon. In 2017, the sea cang bridge is monitored in a segmented and centralized manner in 5-10 months, and the detection is carried out for six time periods every 24 multiplied by 7 hours.
As shown in FIG. 1, the method for analyzing the service life and reliability of the steel beam bridge based on the nonlinear damage theory mainly comprises the following steps:
and modeling and distributing points according to the finite element preliminary analysis of the sea cang bridge structure and the load so as to monitor and obtain discrete samples of the distribution point indication frequency of the steel beam bridge. And calculating a frequency discrete sample of the distribution points of the steel beam bridge to obtain a structural damage factor P value (0.50139).
Calculating the structural damage D of the steel beam bridge by a formula 0 Value (0.278%) and structural damage safety factor R 0 Value (99.722%).
And calculating the traffic load. The average vehicle distance S of all the vehicles passing through the steel beam bridge in the peak period time period in each period is obtained by monitoring the traffic flow, and the average S is taken for multiple times to obtain 58.374 meters; the average weight m of all the automobiles passing through the steel beam bridge in each period is 4.217 tons according to detection. Substituting the relevant parameters into a formula of the vehicle dynamic load coefficient Kd, which is as follows:
K d ＝(1.026+0.236×1)×(1.022+0.0076×20)×[1+0.52·exp(-4.217/5.47)]
calculating to obtain K d The value was 1.838. The above parameters are substituted into the traffic load formula,
the average traffic load of the steel girder bridge in the peak period is 1442kN.
The wind load is calculated. Measuring and calculating distributed point measuring displacement average value S by displacement monitoring sensor 1 Mean square error of displacement S 2 The wind vibration retention factor mu is 2.08. Substituting the formula, and calculating the wind vibration coefficient beta to be 1.741. At the wind speed by a wind speed and direction sensorThe average wind speed U of the larger data monitored in a certain period of 10 months is 6.796 m/s, and relevant parameters are substituted into a formula, wherein the formula comprises the following components:
P wind ＝0.613×6.796 2
F wind ＝1.741×1.22×1.08×28.312×16195；
calculating to obtain the wind load F of the steel beam bridge wind Was 1051.8kN.
The rain load is calculated. When monitoring raining by an instrument, the average water accumulation depth h of the unit area of the bridge is 2.73mm, the rainwater density is set to be 1kg/m < 3 >, and the average rain load of the bridge during raining is calculated as follows:
F rain ＝g·ρ·h·A＝9.8N/kg×1kg/m 3 ×0.00273m×40553m 2
calculating to obtain the rain load F rain Is 1.085kN. Therefore, the influence of rain load on the bridge with smooth drainage is little, and the total stress can not be counted.
According to the fourth strength theory, the analyzed traffic load, wind load and rain load are input into an existing model of finite element analysis software for calculation, and the fatigue stress amplitude (namely total stress) sigma of the model is 54.203MPa. Calculating the 5-10 month equivalent stress amplitude sigma of the data monitored in all 6 time periods E Is 37.525MPa.
The fatigue cycle is calculated by the number of passing vehicles; if the vehicle runs without the vehicle due to severe weather such as storm and the like, the fatigue cycle frequency is calculated according to the self-vibration frequency of the bridge. The average value of the natural vibration frequency of the steel beam bridge is calculated to be 2.13HZ.
The method for calculating the reliability R of the safe use of the steel beam bridge under the existing damage, various dynamic load effects and the future design service life comprises the following steps:
in the formula, σ i The average stress amplitude of the component in one period is the bridge; n is i The number of load cycles of the steel beam bridge in one period is counted; r is 0 Safety degree of initial damage (99.722%)。
Calculating the service life N of the steel beam bridge under the action of existing damage and various dynamic loads f The calculation method comprises the following steps:
N fi ＝682.13·(58.58×10 6 -σ i ) 0.9698 ·R i-1
referring to fig. 2, fig. 2 shows reliability data of the steel beam bridge under different equivalent stress amplitudes and different expected service lives, under the condition that initial damage and annual average traffic flow are consistent, the reliability data of the different equivalent stress amplitudes under different expected service lives are different in change, under the same expected service life, the larger the equivalent stress amplitude is, the faster the reliability is reduced, and under the same equivalent stress amplitude, the reliability is reduced nonlinearly along with the increase of the expected service life.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A method for analyzing the service life and reliability of a steel beam bridge based on a nonlinear damage theory is characterized by comprising the following steps of: the method comprises the following steps:
s1, modeling and stationing: modeling and distributing points according to each dangerous point and random point of the steel beam bridge, measuring frequency discrete samples of the distributed points, and measuring and calculating frequency discrete samples of distributed point indications;
s2, calculating a structural damage factor of the steel beam bridge according to the indication frequency discrete sample;
s3, calculating the structural damage amount and the damage safety value of the steel beam bridge according to the structural damage factor of the steel beam bridge;
s4, calculating the dynamic load of the steel beam bridge to obtain the total stress of the steel beam bridge in a monitoring period;
and S5, calculating the service life and the reliability of the steel beam bridge according to the total stress of the steel beam bridge.
2. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as recited in claim 1, wherein: the specific steps of step S1 are as follows:
(1) Modeling and point distribution: according to the steel beam bridge structure and the preliminary static load analysis, calculating each dangerous point on the main body structure and the key component of the steel beam bridge by using finite element analysis software or theory, then distributing points on each dangerous point and random points, and measuring the structural dynamic characteristics of the steel beam bridge;
(2) Measuring distributed point frequency discrete samples, wherein the dynamic excitation of the vehicle load to the steel beam bridge is a random load which is continuously distributed in time and continuously moved in space, the random load is dispersed, and the duration of each discrete random pulse is set as 1/t second; if the length of the steel beam bridge is set to be L meters and the speed is limited to be V meters per second, dispersing a vehicle passing through the bridge for one time into Lt/V random pulse loads; carrying out spectrum analysis on each 1/t second time micro-segment to obtain a spectrogram; extracting the first n frequency values of each micro-segment frequency spectrum according to the amplitude, wherein nLt/V frequency values of distributed points are acquired under the excitation of one-time bridge-crossing driving, and the frequency values I are obtained i As a single discrete sample of the spotted frequency;
(3) Measuring and calculating a distributed point indication frequency discrete sample, wherein the inherent frequency of the steel beam bridge structure is reduced when the steel beam bridge structure is damaged, and the frequency spectrum shows the natural vibration characteristic of the structure, and the natural vibration characteristic of the structure is kept unchanged under the geometric physical characteristic that the structure is not damaged or damaged and does not develop; frequency values appearing for multiple times in a discrete sample, namely frequency stable points, are insensitive to environmental parameters; weighted average is carried out on the frequencies indicating the structural damage condition in a discrete sample to obtain an indication frequency I C The method comprises the following steps:
in the formula k i N is the repeated probability of the frequency points, the distributed points are measured for a plurality of times in a cycle, discrete samples of the indicated frequency of the distributed points in the cycle are obtained, and the quantity is set as N C And (4) respectively.
3. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 2, wherein: in the step S2, the structural damage factor of the steel beam bridge is calculated according to the discrete sample of the indication frequency, and the concrete steps are as follows:
according to the distributed point index frequency discrete sample, setting I Ci Frequency indicative of a state of structural damage in a time domain; let J C Indicating the frequency I of the distributed points in a cycle Ci Average value of (i), i.e.
To take the uncertainty of various media in the environment into account, set Q C Indicating the frequency I for the distributed point in a cycle Ci Standard deviation of (2), i.e.
Calculating structural damage factor P of steel beam bridge by using Gaussian function
Wherein f (x) is a Gaussian function, I 0 Frequency of structural damage-free status indications, J C Mean value of frequency of indications, Q C The standard deviation of the indicated frequency is; the action of the environment multi-medium on the bridge is considered, parameters lambda related to the elastic modulus E and the temperature T of the material are introduced, and a Gaussian function is corrected to be as follows:
in the formula E 0 ＝2.0×10 5 MPa，T 0 =298 ℃ (absolute temperature).
4. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 3, wherein: s3, calculating structural damage quantity D of the steel beam bridge according to structural damage factors of the steel beam bridge 0 And degree of injury safety R 0 The method comprises the following specific steps:
damage to steel beam bridge structure D 0 The method comprises the following steps:
D 0 ＝2P-1
safety degree R for structural damage of steel beam bridge 0 The method comprises the following steps:
R 0 ＝2-2P
wherein P is a structural damage factor of the steel beam bridge.
5. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 4, wherein: and S4, calculating the dynamic loads of the steel beam bridge, including traffic load, wind load and rain load.
6. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as recited in claim 5, wherein: the traffic load is calculated by the steps of:
(1) Calculating the average traffic load F borne by the steel beam bridge in one period cars Then, then
In the formula (I), the compound is shown in the specification,
is the average vehicle weight;
is the average vehicle distance; the length of the steel beam bridge is L meters, the speed limit is V meters/second, g is a gravity constant, and the dynamic load coefficient of the vehicle is K d The calculation formula is as follows:
in the formula, the country divides the grade Q of the road surface into 1-8 grades, and delta Q = Q-1; vehicle speed V,. Delta.v = V-60km/h.
7. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 6, wherein: the wind load is calculated by the following steps:
(1) Calculating the average wind load F borne by the steel beam bridge in one period wind Then F is wind ＝β·μ h ·μ s ·P wind ·A；
In the formula, beta is a wind vibration coefficient representing wind load pulsation excitation; mu.s h Is the wind pressure height variation coefficient; mu.s s Is the wind load body shape coefficient; p wind The basic wind pressure is obtained; a is the windward area;
and for the wind vibration coefficient beta, the calculation formula is as follows:
wherein mu is a peak value-preserving factor; s is the change of bridge deflection caused by wind load, wherein S 1 Determining the mean value of the displacement, S, for the points laid 2 Measuring the mean square deviation of the displacement for the distributed points;
for basic wind pressure P wind The calculation formula is as follows:
P wind ＝k·U 2
wherein k is a constant; u is the wind speed.
8. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 7, wherein: the rain load is calculated by the following steps:
(1) Calculating the average rain load F borne by the steel beam bridge in one period rain Then F is rain ＝P rain ·A；In the formula, rain pressure P rain (ii) a A bridge deck area A; p is rain ＝g·ρ 1 H, where g is the gravitational constant, ρ 1 The density of the rainwater is shown, and h is the average water accumulation depth per unit area in heavy rains.
9. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as recited in claim 8, wherein: calculating the total stress of the steel beam bridge structure according to the traffic load, the wind load and the rain load, and calculating the equivalent stress amplitude sigma of the steel beam bridge under the action of multiple loads in a monitoring period E The value:
in the formula, k is a variable amplitude fatigue curve coefficient; sigma i The stress amplitude of the steel beam bridge in a certain period; n is a radical of an alkyl radical i To correspond to sigma i And (3) the fatigue cycle times of the steel beam bridge loaded in one period during the stress amplitude.
10. The method for analyzing the service life and the reliability of the steel beam bridge based on the nonlinear damage theory as claimed in claim 9, wherein: s5, calculating the service life and the reliability of the steel beam bridge comprises the following specific steps:
(1) Service life N of steel beam bridge f Comprises the following steps:
N fi ＝9.384·K·(1.01·σ 0 -σ i ) 1-A ·R i-1
(2) The use reliability R of the steel beam bridge is as follows:
in the formula, R i-1 The existing damage safety degree of the structure of the device at the beginning of a period; sigma i The structural stress amplitude under the action of multiple loads in one period; sigma 0 Is the fatigue limit; A. k is a constant; n is a radical of an alkyl radical i To correspond to sigma i And (3) the fatigue cycle times of the steel beam bridge loaded in one period during the stress amplitude.
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