Construction method of bridge vehicle-temperature coupling fatigue damage analysis model

Abstract

A construction method of a bridge vehicle-temperature coupling fatigue damage analysis model comprises the following steps: firstly, constructing a temperature stress course by using a temperature fatigue load model, and obtaining a vehicle fatigue stress course by using a vehicle load model, random traffic flow simulation or an actual measurement means; forming a mechanical mechanism by combining the bridge temperature and the vehicle stress, and performing nonlinear coupling of the bridge vehicle-temperature stress process by adopting a real-time sequential coupling method and considering the influence of the welding residual stress; fatigue damage under the temperature-vehicle coupling effect can be obtained by using a rain flow counting method and a linear cumulative damage theory; the model solves the problem that the temperature contribution is not included in the traditional fatigue damage analysis, and provides a technical basis for the long-life design of the bridge.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a method for constructing a bridge vehicle-temperature coupling fatigue damage analysis model. Background Art

[0002] Under actual operating conditions, bridge structures will inevitably be subjected to temperature loads. Existing studies have shown that temperature effects not only produce significant static effects, but also cause temperature fatigue effects. The coupling of temperature loads and vehicle loads will increase the fatigue load effect, increase the fatigue stress amplitude at the details, aggravate the fatigue cumulative damage at the details, and shorten the normal service life of the bridge structure. Therefore, it is of great engineering significance to conduct in-depth research on the temperature effects and structural behaviors of bridge structures in natural environments, construct a temperature fatigue load model, comprehensively consider the coupling effects of temperature and vehicles, and propose a vehicle-temperature coupling fatigue damage model and construction method. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for constructing a bridge vehicle-temperature fatigue stress coupling analysis model.

[0004] The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model provided by the present invention comprises the following steps:

[0005] (1) Constructing the thermal fatigue stress history

[0006] Based on the temperature fatigue load model T(y), the temperature stress history σ at different fatigue details is obtained T (y,t):

[0007]

[0008] In the formula, mod(·) is the symbol for the remainder calculation, t is any time within the design service life, the unit is hours, and the value is [0,24×N d ×365],N d is the design service life of the bridge, which is 100, 150 or 200, in years, E is the elastic modulus of the material, α is the thermal expansion coefficient of the material, and y is any position of the bridge section.

[0009] (2) Constructing vehicle load stress history

[0010] Construct vehicle load stress history σ according to measured traffic flow, random traffic flow model or single vehicle fatigue load model V (y,t).

[0011] (3) Constructing coupled vehicle-temperature stress history

[0012] Determine the temperature-vehicle coupling stress history σ as followsCoup (y,t):

[0013] In the formula, σ rs (y) is the welding residual stress at the fatigue detail position to be analyzed, ∧ is the mathematical logic calculation symbol.

[0014] (4) Determine vehicle-temperature coupled fatigue damage

[0015] The stress amplitude vector A at the y position is obtained by the rain flow counting method. st :

[0016] A st =(Δσ A1 (y), Δσ A2 (y),…,Δσ An (y))

[0017] In the formula, Δσ An (y) is the nth stress amplitude at position y, n is A st The number of elements in the vector, a positive integer.

[0018] The fatigue damage degree D(y) at position y is determined by the following formula:

[0019]

[0020] Where N n (y) is the stress amplitude of Δσ An (y) is the number of cycles corresponding to fatigue failure, C is the fatigue coefficient of steel, and its value is 11.5~12.6.

[0021] In the above step (1), the method for constructing the temperature fatigue load model T(y) comprises the following steps:

[0022] (1.1) Long-term monitoring of bridge temperature field

[0023] Temperature sensors are arranged vertically along the bridge to collect temperature. The collection interval is set to 1 to 20 minutes. The collected temperature value is recorded as T V (y).

[0024] (1.2) Construct the temperature stress history at various locations on the bridge

[0025] Take the acquisition time interval as the time interval and make the measured temperature gradient time history curve T V (y,t).

[0026] The temperature stress history σ at each position is obtained by the following formula TV (y,t);

[0027]

[0028] Where ρ is the temperature secondary bending moment influence coefficient, which is 0.8 to 1.5, A is the cross-sectional area of ​​the bridge, h is the height of the bridge section, which is a finite positive integer, I is the moment of inertia of the bridge section, and y is s is the vertical neutral axis position of the bridge section, and b(y) is the section thickness at the vertical y position of the bridge.

[0029] (1.3) Temperature stress amplitude cycle count

[0030] The temperature stress cycle is counted by the rain flow counting method, and the temperature stress amplitude vector B at each position of the cross section is obtained:

[0031] B=(Δσ B1 (y),Δσ B2 (y),…,Δσ Bna (y))

[0032] In the formula, Δσ Bna (y) is the nath measured stress amplitude at position y, na represents the number of elements in vector B and is a finite positive integer.

[0033] The Weibull function is fitted to the temperature stress amplitude vector at the typical position to obtain the corresponding temperature stress amplitude probability density curve f(g):

[0034]

[0035] Where: μ is the mean value of the temperature stress amplitude, σ is the variance of the temperature stress amplitude, and g is taken as [min(B)-max(B),2max(B)].

[0036] (1.4) Determine the total number of temperature stress cycle loadings

[0037] Determine the total number of total temperature stress cycle loading N corresponding to different design service life according to the following formula fs :

[0038] N fs =δ×N d ×365

[0039] Where δ is the stress cycle coefficient, ranging from 1 to 1.2, N d It is the design service life, with values ​​of 100, 150, and 200, in years.

[0040] (1.5) Temperature stress amplitude data sampling

[0041] Determine the number of layers N for stratified sampling La , N La Take N d , the upper limit of stratified sampling is xT , the lower limit is x B , x T Take 2max(B), x B Take min(B)-max(B), and determine the number of sampling times n of the pth layer under the service life according to the corresponding probability density function f(g) y :

[0042]

[0043] In the formula, the value of p is [1,N La ].

[0044] According to the uniform sampling method, the stress amplitude sampling result A is obtained. p :

[0045] A p =(σ p1 (y),σ p2 (y),...,σ pny (y))

[0046] In the formula, σ pny (y) is the nyth stress amplitude at position y, and ny is the number of elements in the vector, which is a finite positive integer.

[0047] The final stress amplitude sampling vector A y According to the following formula:

[0048]

[0049] (1.6) Determine the equivalent temperature stress amplitude

[0050] The equivalent thermal stress amplitude Δσ of the bridge is obtained as follows: eq :

[0051]

[0052] In the formula, is the vector A y The i-th element in , i is a positive integer.

[0053] (1.7) Constructing the thermal fatigue load model

[0054] The equivalent fatigue temperature T of the bridge is constructed as follows: eq :

[0055]

[0056] The equivalent fatigue temperature T is fitted by the least square method at typical locations. eq , establish the temperature fatigue load model T(y).

[0057] In the above step (2), the vehicle load stress history σ V (y,t) is obtained by direct monitoring.

[0058] In the above step (2), the vehicle load stress history σ V (y, t) is: The vehicle fatigue load model is input into the finite element analysis software to obtain the stress response line σ in (y,l), and construct the vehicle load stress history σ V (y,t):

[0059]

[0060] In the formula, t d is the intermediate variable, V D is the daily traffic volume in vehicles, v is the average vehicle speed on the bridge in m / h, and l is the span of the bridge.

[0061] In the above step (2), the vehicle load stress history σ V (y, t) is: The dynamic weighing data of the vehicle obtained by the load monitoring system is used to obtain the stress response line of each vehicle, a total of n vehicles, expressed as: σ re =(σ re,1 (y,l),σ re,2 (y,l),...,σ re,n (y,l)), and construct the vehicle load stress history σ by random sampling method V (y,t):

[0062]

[0063] In the formula, t d is the intermediate variable, V D is the daily traffic volume in vehicles, v is the average vehicle speed of the bridge in m / h, l is the span of the bridge, rand(j) is the jth randomly sampled vehicle load sample, 1≤j≤n.

[0064] Further preferably, the daily traffic volume V D The value range of is [500,4000], the unit is vehicle, and the value range of vehicle speed v is [50000,120000], the unit is m / h.

[0065] Further preferably, the V D 、The value of v is: V D It is 1000 vehicles and v is 55000m / h.

[0066] The beneficial effects of the present invention are as follows:

[0067] 1. The bridge vehicle-temperature fatigue stress coupling analysis model construction method proposed in the present invention comprehensively considers the influence of temperature and vehicle coupling on bridge fatigue damage, provides a new way for temperature vehicle coupling stress history analysis, and overcomes the deficiency of only considering vehicle load in traditional fatigue damage analysis.

[0068] 2. The present invention can be used to evaluate the fatigue life of bridges in service, providing a basis for improving relevant design specifications for different bridge structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is the construction process of the present invention.

[0070] Figure 2 Schematic diagram of the temperature-vehicle stress coupling method.

[0071] Figure 3 It is a schematic diagram of the three-dimensional structure of the highway composite plate girder bridge.

[0072] Figure 4 It is the thermal fatigue load model of highway composite beam bridge.

[0073] Figure 5 is the temperature stress history of highway composite beam bridge.

[0074] Figure 6 is the stress history of vehicle load on highway composite beam bridge.

[0075] Figure 7 Vehicle-temperature coupled stress history of highway composite beam bridge.

[0076] Figure 8 This is a schematic diagram of the three-dimensional structure of a highway steel box girder bridge.

[0077] Fig. 9 It is the thermal fatigue load model of highway steel box girder bridge.

[0078] Fig.10 This is the coupled stress history at the butt weld details of the bottom plate of a highway steel box girder bridge.

[0079] Fig.11 This is the coupled stress history at the butt weld details of the highway steel box girder bridge top plate. DETAILED DESCRIPTION

[0080] The present invention is further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to these embodiments.

[0081] Example 1

[0082] like Figure 1 As shown, the present invention relates to a method for constructing a bridge vehicle-temperature coupling fatigue damage analysis model, which consists of the following steps:

[0083] (1) Constructing the thermal fatigue stress history

[0084] Based on the temperature fatigue load model T(y), the temperature stress history σ at different fatigue details is obtained T (y,t):

[0085]

[0086] In the formula, mod(·) is the symbol for the remainder calculation, t is any time within the design service life, the unit is hours, and the value is [0,24×N d ×365],N d is the design service life of the bridge, which is 100, 150 or 200, in years, E is the elastic modulus of the material, α is the thermal expansion coefficient of the material, and y is any position of the bridge section.

[0087] The construction method of the temperature fatigue load model T(y) consists of the following steps:

[0088] (1.1) Long-term monitoring of bridge temperature field

[0089] Temperature sensors are arranged vertically along the bridge to collect temperature. The collection interval is set to 1 to 20 minutes. The collected temperature value is recorded as T V (y).

[0090] (1.2) Construct the temperature stress history at various locations on the bridge

[0091] Take the acquisition time interval as the time interval and make the measured temperature gradient time history curve T V (y,t).

[0092] The temperature stress history σ at each position is obtained by the following formula TV (y,t);

[0093]

[0094] Where ρ is the temperature secondary bending moment influence coefficient, which is 0.8 to 1.5, A is the cross-sectional area of ​​the bridge, h is the height of the bridge section, which is a finite positive integer, I is the moment of inertia of the bridge section, and y is s is the vertical neutral axis position of the bridge section, and b(y) is the section thickness at the vertical y position of the bridge.

[0095] (1.3) Temperature stress amplitude cycle count

[0096] The temperature stress cycle is counted by the rain flow counting method, and the temperature stress amplitude vector B at each position of the cross section is obtained:

[0097] B=(Δσ B1 (y),Δσ B2(y),…,Δσ Bna (y))

[0098] In the formula, Δσ Bna (y) is the nath measured stress amplitude at position y, na represents the number of elements in vector B and is a finite positive integer.

[0099] The Weibull function is fitted to the temperature stress amplitude vector at the typical position to obtain the corresponding temperature stress amplitude probability density curve f(g):

[0100]

[0101] Where: μ is the mean value of the temperature stress amplitude, σ is the variance of the temperature stress amplitude, and g is taken as [min(B)-max(B),2max(B)].

[0102] (1.4) Determine the total number of temperature stress cycle loadings

[0103] Determine the total number of total temperature stress cycle loading N corresponding to different design service life according to the following formula fs :

[0104] N fs =δ×N d ×365

[0105] Wherein, δ is the stress cycle coefficient, which is 1 to 1.2. In this embodiment, it is 1.1. d It is the design service life, with values ​​of 100, 150, and 200, in years.

[0106] (1.5) Temperature stress amplitude data sampling

[0107] Determine the number of layers N for stratified sampling La , N La Take N d , the upper limit of stratified sampling is x T , the lower limit is x B , x T Take 2max(B), x B Take min(B)-max(B), and determine the number of sampling times n of the pth layer under the service life according to the corresponding probability density function f(g) y :

[0108]

[0109] In the formula, the value of p is [1,N La ].

[0110] According to the uniform sampling method, the stress amplitude sampling result A is obtained. p :

[0111] A p =(σ p1 (y),σ p2 (y),...,σ pny (y))

[0112] In the formula, σ pny (y) is the nyth stress amplitude at position y, and ny is the number of elements in the vector, which is a finite positive integer.

[0113] The final stress amplitude sampling vector A y According to the following formula:

[0114]

[0115] (1.6) Determine the equivalent temperature stress amplitude

[0116] The equivalent thermal stress amplitude Δσ of the bridge is obtained as follows: eq :

[0117]

[0118] In the formula, is the vector A y The i-th element in , i is a positive integer.

[0119] (1.7) Constructing the thermal fatigue load model

[0120] The equivalent fatigue temperature T of the bridge is constructed as follows: eq :

[0121]

[0122] The equivalent fatigue temperature T is fitted by the least square method at typical locations. eq , establish the temperature fatigue load model T(y).

[0123] (2) Constructing vehicle load stress history

[0124] The vehicle load stress history σ can be constructed according to the measured traffic flow, random traffic flow model or single vehicle fatigue load model V (y,t).

[0125] The vehicle fatigue load model specified in the "JTG D64-2015 Highway Steel Structure Bridge Design Code" is used to input the finite element analysis software to obtain the stress response line σ in (y,l), and construct the vehicle load stress history σ V (y,t):

[0126]

[0127] Where, td is the intermediate variable, V D is the daily traffic volume, in units of vehicles, v is the average vehicle speed of the bridge, in units of m / h, and l is the span of the bridge. In this embodiment, the daily traffic volume V D The value of is 1000 vehicles, and the vehicle speed v is 55000m / h.

[0128] (3) Constructing coupled vehicle-temperature stress history

[0129] like Figure 2 As shown, the temperature-vehicle coupling stress history σ is determined by the following formula Coup (y,t):

[0130]

[0131] Where: rs (y) is the welding residual stress at the fatigue detail position to be analyzed, ∧ is a mathematical logic calculation symbol, and, in this embodiment, σ rs (y) is 120 MPa.

[0132] (4) Obtain vehicle-temperature coupled fatigue damage

[0133] The stress amplitude vector A at the y position is obtained by the rain flow counting method. st :

[0134] A st =(Δσ A1 (y), Δσ A2 (y),…,Δσ An (y))

[0135] In the formula, Δσ An (y) is the nth stress amplitude at position y, n is A st The number of elements in the vector, a positive integer.

[0136] The fatigue damage degree D(y) at a typical position is obtained by the following formula:

[0137]

[0138] Where N n (y) is the stress amplitude Δσ at position y n (y) is the number of cycles corresponding to fatigue failure, C is the fatigue coefficient of steel, and its value is 12.01.

[0139] Example 2

[0140] The construction method of the bridge vehicle-temperature coupling fatigue damage analysis model of this embodiment consists of the following steps:

[0141] (1) Constructing the thermal fatigue stress history

[0142] This step is the same as in Example 1.

[0143] (2) Constructing vehicle load stress history

[0144] The vehicle load stress history σ in this step V (y, t) is directly monitored. In this embodiment, the daily traffic volume V D The value of is 500 vehicles, and the average vehicle speed v is 50000m / h.

[0145] (3) Constructing coupled vehicle-temperature stress history

[0146] This step is the same as in Example 1.

[0147] (4) Obtain vehicle-temperature coupled fatigue damage

[0148] This step is the same as in Example 1, where C is the steel fatigue coefficient, which is 11.5. The construction of the bridge vehicle-temperature coupling fatigue damage analysis model is completed.

[0149] Example 3

[0150] The construction method of the bridge vehicle-temperature coupling fatigue damage analysis model of this embodiment consists of the following steps:

[0151] (1) Constructing the thermal fatigue stress history

[0152] This step is the same as in Example 1.

[0153] (2) Constructing vehicle load stress history

[0154] The vehicle load stress history σ in this step V (y, t) is: The dynamic weighing data of the vehicle obtained by the load monitoring system is used to obtain the stress response line of each vehicle. There are n vehicles in total, expressed as: σ re =(σ re,1 (y,l),σ re,2 (y,l),...,σ re,n (y,l)), and construct the vehicle load stress history σ by random sampling method V (y,t):

[0155]

[0156] In the formula, t d is the intermediate variable, V Dis the daily traffic volume, in units of vehicles, v is the average vehicle speed of the bridge, in units of m / h, l is the span of the bridge, and rand(j) is the jth random sampling vehicle load sample, 1≤j≤n. In this embodiment, the daily traffic volume V D The value of is 4000 vehicles, and the average vehicle speed v is 120000m / h.

[0157] (3) Constructing coupled vehicle-temperature stress history

[0158] This step is the same as in Example 1.

[0159] (4) Obtain vehicle-temperature coupled fatigue damage

[0160] This step is the same as that in Example 1, where C is the steel fatigue coefficient, which is 12.6. The construction of the bridge vehicle-temperature coupling fatigue damage analysis model is completed.

[0161] In order to verify the beneficial effects of the present invention, the method for constructing the bridge vehicle-temperature coupling fatigue damage analysis model of Example 1 of the present invention is adopted to perform vehicle-temperature coupling fatigue damage analysis on the fatigue details of the bolts of a highway composite steel plate girder bridge, and the details of the top plate butt welds and bottom plate butt welds of a highway steel box girder bridge.

[0162] Example 1

[0163] A vehicle-temperature coupled fatigue damage analysis was conducted on a highway composite steel plate girder bridge. The coupled damage effect at the fatigue details of the bolts was analyzed. The three-dimensional structure of the composite girder bridge is shown in the figure below. Figure 3 The specific construction method is as follows:

[0164] (1) Constructing the thermal fatigue stress history

[0165] Based on the thermal fatigue load model of composite beam bridge, the thermal stress history σ at the fatigue detail of the stud is obtained T (y,t):

[0166]

[0167] In the formula, mod(·) is the symbol for the remainder calculation, t is any time within the design service life, the unit is hour, and the value range is [0,876000], N d is the design service life of the bridge, which is 100 years in this embodiment, E is the elastic modulus of the material, α is the thermal expansion coefficient of the material, and E is 2.06×10 5 MPa, α is 1.1×10 -5 ℃ -1, y is any position of the bridge section, T(y) is the temperature fatigue load model, and the method for constructing the temperature fatigue load model is the same as that in Example 1. The specific temperature fatigue load model is as follows:

[0168]

[0169] Where y is the position of any bridge section, h is the height of the composite plate beam, and h s is the height of the steel plate beam, h c is the height of the combined layer, T c0 is the representative value of the temperature at the top plate of the composite plate-beam section, in °C, T c1 h is the distance between the composite plate beam section and the top plate c The representative value of the temperature at the position, in °C, T c2 The distance between the composite plate beam section and the top plate is 0.7h s The representative value of the temperature at the position, in °C, T c3 is the representative value of the temperature at the bottom of the composite plate-beam section, in °C, β T (h), β T (b), β T (B), β T (k) is the intermediate variable, b is the bottom plate width of the composite plate beam, in m, B is the top plate width of the composite plate beam, in m, k is the number of I-beams in the composite plate beam, T1 0 is the initial temperature value at the top plate of the composite plate-beam section, in °C. h is the distance between the composite plate beam section and the top plate c Initial temperature value at position, in °C, T3 0 The distance between the composite plate beam section and the top plate is 0.7h s The initial temperature value at the position, in °C, is the initial temperature of the bottom plate of the composite plate-beam section, in °C, N d The service life is 100, 150 or 200, in years.

[0170] The temperature fatigue load model constructed is as follows Figure 4 As shown, Take 4.8℃, and the representative values ​​of the temperature at the typical position are shown in Table 1. The temperature at the typical position is used for difference calculation at other positions.

[0171] Temperature stress history Figure 5 shown.

[0172] Table 1 Representative values ​​of temperature at typical locations of thermal fatigue load model of composite steel plate girder bridge

[0173]

[0174] (2) Constructing vehicle load stress history

[0175] Based on the vehicle fatigue load model specified in the specification, the loading response line σ is obtained by inputting the finite element analysis software. in (y,l), and construct the vehicle load stress history σ V (y,t):

[0176]

[0177] Where V D is the daily traffic volume. In this example, the daily traffic volume is 1000 vehicles, 1500 vehicles and 2000 vehicles for analysis and comparison. v is the average vehicle speed of the bridge, which is 55000m / h in this example. td is the intermediate variable. l is the span of the bridge, which is 30m in this example. The constructed vehicle load stress history is as follows: Figure 6 shown.

[0178] (3) Constructing coupled vehicle-temperature stress history

[0179] Determine the temperature-vehicle coupling stress history σ according to formula (2): Coup (y,t)

[0180]

[0181] Where: rs (y) is the welding residual stress at the fatigue detail position to be analyzed, which is 120MPa, ^ is a mathematical logic calculation symbol, and the coupled vehicle-temperature stress history established in this example is as follows: Figure 7 shown.

[0182] (4) Obtain vehicle-temperature coupled fatigue damage

[0183] According to the temperature-vehicle coupling stress history determined in step (3), the vehicle-temperature coupling fatigue stress spectrum is obtained by the rain flow counting method, and the stress amplitude vector A at the y position is obtained. st :

[0184] A st =(Δσ A1 (y), Δσ A2 (y),…,Δσ An (y))

[0185] In the formula, Δσ An (y) is the nth stress amplitude at position y, n is A st The number of elements in the vector, a positive integer.

[0186] The fatigue damage degree D(y) at position y is obtained by the following formula:

[0187]

[0188] Where N n (y) is the stress amplitude of Δσ n (y) is the number of cycles corresponding to fatigue failure, and C is the fatigue coefficient of steel, which is 12.01 in this example.

[0189] The fatigue damage of the bolt fatigue details of the highway composite steel plate girder bridge constructed above under different daily traffic volumes within the 100-year design service life is shown in Table 2.

[0190] Table 2 Coupled fatigue assessment results of highway composite steel plate girder bridge

[0191]

[0192] The above analysis results show that the damage contribution of temperature fatigue can reach up to about 14.1%, which is much higher than the fatigue damage caused by vehicle load alone, which fully demonstrates the necessity of constructing this analysis model.

[0193] Example 2

[0194] The vehicle-temperature coupled fatigue damage analysis of Shenyang Houdingxiang Viaduct is shown in the following three-dimensional schematic diagram: Figure 8 The specific construction method is as follows:

[0195] (1) Constructing the thermal fatigue stress history

[0196] Based on the thermal fatigue load model of steel box girder bridge, the thermal stress history σ at the details of the top plate butt weld and the bottom plate butt weld is obtained. T (y,t):

[0197]

[0198] In the formula, mod(·) is the symbol for the remainder calculation, t is any time within the design service life, the unit is hour, and the value range is [0,876000], N d is the design service life of the bridge, which is 100 years in this example, E is the elastic modulus of the material, α is the thermal expansion coefficient of the material, and the E value of steel is 2.06×10 5 MPa, α is 1.1×10 -5 ℃ -1 , y is any position of the bridge section, such as Fig. 9 As shown, T(y) is the temperature fatigue load model. The method for constructing the temperature fatigue load model is the same as that in Example 1. The specific temperature fatigue load model is as follows:

[0199]

[0200] In the formula, y is the height of the position to be calculated, h is the section height, TG1 is the representative value of the temperature at the top plate, T G2 is the representative value of the temperature at the distance h / 4 from the top plate to the web, T G3 is the representative value of the temperature at the bottom plate, B is the width of the top plate, b is the width of the bottom plate, k is the number of chambers, β TG (B), β TG (b), β TG (h), β TG (k) intermediate variables, is the initial temperature value at the top plate, in °C, is the initial temperature value of the web at a distance of h / 4 from the top plate, in °C. is the initial temperature value at the bottom plate, in °C, N d It is the design service life, and its value is 100, 150 or 200, in years.

[0201] The beam height h is selected as 3.0m, the top plate width B is selected as 18.0m, the bottom plate width b is selected as 11.25m, and the number of box chambers k of the steel box girder bridge with flange plates is selected as 3. The value of is 14.5℃, The value is 9.4℃, and the design service life is 100 years. The representative temperature values ​​at typical locations are shown in Table 3. The temperature values ​​at other locations are calculated using the linear difference of the representative temperature values.

[0202] Table 3 Representative values ​​of temperature at typical locations of thermal fatigue load model for steel box girder bridges

[0203]

[0204] (2) Constructing vehicle load stress history

[0205] Based on the vehicle fatigue load model specified in the specification, the loading response line σ is obtained by inputting the finite element analysis software. in (y,l), and construct the vehicle load stress history σ V (y,t):

[0206]

[0207] Where V D is the daily traffic volume, in this case the values ​​are 1000, 1500 and 2000 vehicles, v is the average vehicle speed of the bridge, in this case the value is 55000m / h, td is the intermediate variable, l is the span of the bridge, in this case it is 80m.

[0208] (3) Constructing coupled vehicle-temperature stress history

[0209] Determine the temperature-vehicle coupling stress history σ according to formula (2): Coup (y,t):

[0210]

[0211] σ rs (y) is the welding residual stress at the fatigue detail position to be analyzed, which is 120MPa. ∧ is the mathematical logic calculation symbol "and". The vehicle-temperature stress history of the top plate and bottom plate butt weld coupled is established as follows: Fig.10 and Fig.11 shown.

[0212] (4) Obtain vehicle-temperature coupled fatigue damage

[0213] According to the temperature-vehicle coupling stress history determined in step (3), the vehicle-temperature coupling fatigue stress spectrum is obtained by the rain flow counting method, and the stress amplitude vector A at the y position is obtained. st :

[0214] A st =(Δσ A1 (y), Δσ A2 (y),…,Δσ An (y))

[0215] In the formula, Δσ An (y) is the nth stress amplitude at position y, n is A st The number of elements in the vector, a positive integer.

[0216] The fatigue damage degree D(:) at position y is obtained by the following formula:

[0217]

[0218] Where D(y) is the fatigue detail damage degree, N n (y) is the stress amplitude of Δσ n (y) is the number of cycles corresponding to fatigue failure, and C is the fatigue coefficient of steel, which is 12.01 in this example.

[0219] The fatigue damage of the fatigue details of the butt welds between the top and bottom plates of the above-mentioned highway steel box girder bridge under different daily traffic volumes within the design service life of 100 years, considering the coupling effect of temperature fatigue load and not considering the effect of temperature, are shown in Tables 4 and 5.

[0220] Table 4 Coupled fatigue assessment of butt weld details of highway steel box girder bridge bottom plate

[0221]

[0222] Table 5 Coupled fatigue assessment of butt weld details on top slab of highway steel box girder bridge

[0223]

[0224] The above analysis results show that the temperature load has an obvious effect on the increase of fatigue damage. Under the coupling effect of temperature and vehicle, the fatigue damage will also increase by more than 7%. When the daily traffic volume of vehicle fatigue load is less than 1,000 vehicles, the contribution of temperature fatigue load to coupled fatigue damage can reach more than 10%. Therefore, the fatigue damage increment caused by temperature-vehicle coupled fatigue should not be ignored. The proposed method for constructing the bridge vehicle-temperature coupled fatigue damage analysis model has a high application value.

Claims

1. A method for constructing a bridge vehicle-temperature coupling fatigue damage analysis model, characterized in that It consists of the following steps: (1) Constructing the thermal fatigue stress history Based on the temperature fatigue load model T(y), the temperature stress history σ at different fatigue details is obtained T (y,t): In the formula, mod(·) is the symbol for the remainder calculation, t is any time within the design service life, the unit is hours, and the value is [0,24×N d ×365],N d is the design service life of the bridge, which is 100, 150 or 200, in years, E is the elastic modulus of the material, α is the thermal expansion coefficient of the material, and y is any position of the bridge section; (2) Constructing vehicle load stress history Construct vehicle load stress history σ according to measured traffic flow, random traffic flow model or single vehicle fatigue load model V (y,t); (3) Constructing coupled vehicle-temperature stress history Determine the temperature-vehicle coupling stress history σ as follows Coup (y,t): In the formula, σ rs (y) is the welding residual stress at the fatigue detail position to be analyzed, ∧ is a mathematical logic calculation symbol; (4) Determine vehicle-temperature coupled fatigue damage The stress amplitude vector A at the y position is obtained by the rain flow counting method. st : A st =(Ds A1 (y), Ds A2 (y),…,Ds An (y)) In the formula, Δσ An (y) is the nth stress amplitude at the y position, n is the number of elements in the Ast vector, which is a positive integer; The fatigue damage degree D(y) at position y is determined by the following formula: Where N n (y) is the stress amplitude of Δσ An (y) is the number of cycles corresponding to fatigue failure, C is the fatigue coefficient of steel, and its value is 11.5~12.

6.

2. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 1 is characterized in that: In step (1), the method for constructing the temperature fatigue load model T(y) comprises the following steps: (1.1) Long-term monitoring of bridge temperature field Temperature sensors are arranged vertically along the bridge to collect temperature. The collection interval is set to 1 to 20 minutes. The collected temperature value is recorded as T V (y); (1.2) Construct the temperature stress history at various locations on the bridge Take the acquisition time interval as the time interval and make the measured temperature gradient time history curve T V (y,t), The temperature stress history σ at each position is obtained by the following formula TV (y,t): Where ρ is the temperature secondary bending moment influence coefficient, which is 0.8 to 1.5, A is the cross-sectional area of ​​the bridge, h is the height of the bridge section, which is a finite positive integer, I is the moment of inertia of the bridge section, and y is s is the vertical neutral axis position of the bridge section, b(y) is the section thickness at the vertical y position of the bridge; (1.3) Temperature stress amplitude cycle count The temperature stress cycle is counted by the rain flow counting method, and the temperature stress amplitude vector B at each position of the cross section is obtained: B=(Ds) B1 (y),Ds B2 (y),…,Ds Bna (y)) In the formula, Δσ Bna (y) is the nth measured stress amplitude at position y, na represents the number of elements in vector B and is a finite positive integer; The Weibull function is fitted to the temperature stress amplitude vector at the typical position to obtain the corresponding temperature stress amplitude probability density curve f(g): Where: μ is the mean value of the temperature stress amplitude, σ is the variance of the temperature stress amplitude, and g is taken as [min(B)-max(B),2max(B)]; (1.4) Determine the total number of temperature stress cycle loadings Determine the total number of total temperature stress cycle loading N corresponding to different design service life according to the following formula fs : N fs =δ×N d ×365 Where δ is the stress cycle coefficient, ranging from 1 to 1.2, N d is the design service life, with values ​​of 100, 150, and 200, in years; (1.5) Temperature stress amplitude data sampling Determine the number of layers N for stratified sampling La , N La Take N d , the upper limit of stratified sampling is x T , the lower limit is x B , x T Take 2max(B), x B Take min(B)-max(B), and determine the number of sampling times n of the pth layer under the service life according to the corresponding probability density function f(g) y : In the formula, the value of p is [1,N La ]; According to the uniform sampling method, the stress amplitude sampling result A is obtained p : A p =(s p1 (y),s p2 (y),...,s pny (y)) In the formula, σ pny (y) is the nyth stress amplitude at position y, ny is the number of elements in the vector, which is a finite positive integer; The final stress amplitude sampling vector A y According to the following formula: (1.6) Determine the equivalent temperature stress amplitude The equivalent thermal stress amplitude Δσ of the bridge is obtained by the following formula: eq : In the formula, is the vector A y The i-th element in , i is a finite positive integer; (1.7) Constructing the thermal fatigue load model The equivalent fatigue temperature T of the bridge is constructed as follows: eq : The equivalent fatigue temperature T is fitted by the least square method at typical locations. eq , establish the temperature fatigue load model T(y).

3. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 1, characterized in that: In step (2), the vehicle load stress history σ V (y,t) is obtained by direct monitoring.

4. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 1 is characterized in that In step (2), the vehicle load stress history σ V (y, t) is: The vehicle fatigue load model is input into the finite element analysis software to obtain the stress response line σ in (y,l), and construct the vehicle load stress history σ V (y,t): In the formula, td is the intermediate variable, V D is the daily traffic volume in vehicles, v is the average vehicle speed on the bridge in m / h, and l is the span of the bridge.

5. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 1 is characterized in that In step (2), the vehicle load stress history σ V (y, t) is: The dynamic weighing data of the vehicle obtained by the load monitoring system is used to obtain the stress response line of each vehicle, a total of n vehicles, expressed as: σ re =(σ re,1 (y,l),σ re,2 (y,l),...,σ re,n (y,l)), and construct the vehicle load stress history σ by random sampling method V (y,t): In the formula, td is the intermediate variable, V D is the daily traffic volume in vehicles, v is the average vehicle speed of the bridge in m / h, l is the span of the bridge, rand(j) is the jth randomly sampled vehicle load sample, 1≤j≤n.

6. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 4 is characterized in that: The daily traffic volume V D The value range of is [500,4000], the unit is vehicle, and the value range of vehicle speed v is [50000,120000], the unit is m / h.

7. The method for constructing a bridge vehicle-temperature coupled fatigue damage analysis model according to claim 4, characterized in that: The V D 、The value of v is: V D It is 1000 vehicles and v is 55000m / h.

Images