Vertical temperature gradient fatigue load model of flat steel box girder bridge

Abstract

The invention relates to a vertical temperature gradient fatigue load model of a flat steel box girder bridge, in particular to a bifold line form. The temperature sensors are arranged according to the temperature field distribution characteristics of the flat steel box girder, long-term temperature field monitoring is carried out, the temperature fatigue stress distribution characteristics of the flat steel box girder are analyzed by utilizing long-term monitoring data, and the temperature fatigue stress distribution characteristics of the flat steel box girder are analyzed based on a Latin hypercube sampling method and a damage equivalence principle. And a vertical temperature gradient fatigue load model of the flat steel box girder bridge with the designed service life within 200 years is established. The temperature gradient fatigue load model realizes the construction of the vertical temperature fatigue stress process of the flat steel box girder bridge, and can be used for the anti-fatigue design and evaluation of the long-life flat steel box girder bridge.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge engineering, and in particular relates to a vertical temperature gradient fatigue load model of a flat steel box girder bridge. Background Art

[0002] Flat steel box girder is a typical closed section type. Under the action of sunlight, the cross section of flat steel box girder will form a nonlinear vertical temperature gradient with periodic changes. Under the action of this nonlinear vertical temperature gradient, longitudinal temperature fatigue stress will be generated. Existing studies have shown that the coupling effect of temperature and vehicle load will significantly increase the fatigue damage of steel box girder bridge details, and the temperature-vehicle fatigue stress cannot be simply linearly decoupled during damage analysis. Therefore, it is necessary to reasonably arrange temperature sensors in the flat steel box girder, conduct long-term monitoring of the temperature field, and conduct in-depth research on the temperature effect and structural response of the flat steel box girder. Using the Latin hypercube sampling method and the damage equivalence principle, a vertical temperature gradient fatigue load model for long-life flat steel box girder bridges with a design service life of 100, 150 and 200 years is established. The temperature fatigue stress history is obtained, and it is sequentially coupled with the vehicle fatigue stress history to calculate the coupled fatigue damage. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a vertical temperature gradient fatigue load model for a flat steel box girder bridge.

[0004] The vertical temperature gradient fatigue load model T(y) of the above flat steel box girder bridge is shown in formula (1):

[0005]

[0006] Where y is the distance from the upper surface of the bottom plate, h is the height of the flat steel box girder, and β Gb1 (b), β Gb2 (b), β Gb3 (b), β GB1 (B), β GB2 (B), β(N d ) is an intermediate variable, T G1 is the representative value of the temperature at the top plate of the flat steel box girder bridge, in °C, T G2 is the representative value of the temperature at the distance of 0.7h from the bottom plate of the flat steel box girder transverse diaphragm, in °C, T G3 is the representative value of the temperature at the bottom plate, in °C, B is the bottom plate width of the flat wide steel box girder, b is the top plate width of the flat wide steel box girder, N d The design service life is in years, and the value is 100, 150 or 200 years. is the initial temperature value at the top plate of the flat steel box girder bridge, in °C. is the initial temperature of the flat steel box girder transverse diaphragm at a distance of 0.7h from the bottom plate, in °C. is the initial temperature at the bottom plate, in °C.

[0007] In the formula (1) of the present invention, The value is [11.4,12.2], the unit is ℃, The value of is [9.1,9.7], the unit is ℃, The value of is [5.3,5.7], the unit is ℃, the value of b is [25.00,50.00], the unit is m, and the value of B is [10.00,40.00], the unit is m.

[0008] In the formula (1) of the present invention, B, b, The values ​​of are: the best value for B is 31.30m, the best value for b is 42.10m, The best temperature is 11.8℃. The best temperature is 9.4℃. The best temperature is 5.5℃.

[0009] The beneficial effects of the present invention are as follows:

[0010] 1. The present invention uses the measured temperature field data of Nansha Bridge, adopts the Latin hypercube sampling method and the damage equivalence principle, and constructs a vertical temperature fatigue load model for flat steel box girder bridges. The model takes into account the influence of section height, top plate width and bottom plate width.

[0011] 2. The vertical temperature gradient fatigue load model of the flat steel box girder bridge constructed by the present invention is simple in form, and realizes the calculation of the temperature fatigue stress history of the flat steel box girder bridge with a design service life of 100 years, 150 years and 200 years, and can be used for the temperature-vehicle coupled fatigue analysis of the flat steel box girder bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a cross-sectional view of the flat steel box girder bridge of the Nansha Bridge in the present invention.

[0013] Figure 2 It is a distribution diagram of temperature representative values ​​in the vertical temperature fatigue load model of the present invention.

[0014] Figure 3 This is a schematic diagram of the measurement point arrangement for the flat steel box girder section of the Nansha Bridge.

[0015] Figure 4 This is the temperature history curve of the vertical measuring point of Nansha Bridge.

[0016] Figure 5 The histogram of temperature stress amplitude at fatigue details of bottom plate butt weld. DETAILED DESCRIPTION

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the present invention is not limited to the following embodiments.

[0018] Example 1

[0019] The present invention relates to a vertical temperature gradient fatigue load model for a flat steel box girder bridge, wherein the model T(y) is as shown in formula (1):

[0020]

[0021] Where y is the distance from the upper surface of the bottom plate, h is the height of the flat steel box girder, and β Gb1 (b), β Gb2 (b), β Gb3 (b), β GB1 (B), β GB2 (B), β(N d ) is an intermediate variable, T G1 is the representative value of the temperature at the top plate of the flat steel box girder bridge, in °C, T G2 is the representative value of the temperature at the distance of 0.7h from the bottom plate of the flat steel box girder transverse diaphragm, in °C, T G3 is the representative value of the temperature at the bottom plate, in °C, B is the bottom plate width of the flat wide steel box girder, b is the top plate width of the flat wide steel box girder, N d The design service life is in years, and the value is 100, 150 or 200 years. is the initial temperature value at the top plate of the flat steel box girder bridge, in °C. is the initial temperature of the flat steel box girder transverse diaphragm at a distance of 0.7h from the bottom plate, in °C. is the initial temperature at the bottom plate, in °C.

[0022] Taking the Nansha Bridge in Guangdong as an example, its cross-section is as follows: Figure 1 In formula (1), the top plate width b is 42.10m, the bottom plate width B is 31.30m, is 11.8℃, 9.4℃, The vertical temperature gradient fatigue load model of the flat steel box girder bridge is constructed according to this parameter. The temperature representative values ​​corresponding to 100 years, 150 years and 200 years are shown in Table 1. The vertical fatigue temperature representative values ​​of the flat steel box girder bridge are distributed as follows: Figure 2 shown.

[0023] Table 1 Representative values ​​of temperature for vertical temperature gradient fatigue load model of flat steel box girder bridge

[0024]

[0025] Example 2

[0026] The expression of the vertical temperature gradient fatigue load model of the flat steel box girder bridge involved in this embodiment is the same as that in Embodiment 1.

[0027] The flat steel box girder section of this embodiment has a bottom plate width B of 10.00m and a top plate width b of 25.00m. 11.4℃, 9.1℃, The vertical temperature gradient fatigue load model of the flat steel box girder bridge is constructed according to this parameter. The temperature representative values ​​at different heights corresponding to 100 years, 150 years and 200 years are shown in Table 2. The distribution of the fatigue temperature representative values ​​of the vertical temperature gradient fatigue load model of the flat steel box girder bridge is shown in Table 2. Figure 2 shown.

[0028] Table 2 Representative values ​​of temperature for vertical temperature gradient fatigue load model of flat steel box girder bridge

[0029]

[0030] Example 3

[0031] The expression of the vertical temperature gradient fatigue load model of the flat steel box girder bridge involved in this embodiment is the same as that in Embodiment 1, but the temperature representative value is different.

[0032] The flat steel box girder section of this embodiment has a bottom plate width B of 40.00m and a top plate width b of 50.00m. 12.2℃, 9.7℃, The corresponding vertical temperature gradient fatigue load model of the flat steel box girder bridge is constructed according to this parameter. The representative values ​​of temperature at different heights corresponding to 100 years, 150 years and 200 years are shown in Table 3. The distribution of representative values ​​of fatigue temperature at typical positions of the vertical temperature gradient fatigue load model of the flat steel box girder bridge is shown in Table 3. Figure 2 shown.

[0033] Table 3 Representative values ​​of temperature at different heights in the vertical temperature gradient fatigue load model of flat steel box girder bridge

[0034]

[0035] Test 1

[0036] In order to verify the effect of the vertical temperature gradient fatigue load model of the flat steel box girder bridge, sensors were arranged on the Nizhou Waterway Bridge of Nansha Bridge in Dongguan City, Guangdong Province, and the temperature field was monitored for a long time.

[0037] 1. Long-term monitoring instruments

[0038] The monitoring instrument is a 32-channel DH2002 temperature acquisition device produced in Taizhou, Jiangsu. The temperature acquisition software is the PHM long-term health monitoring software produced in Taizhou, Jiangsu. The temperature sensor is a three-wire Pt100 sensor.

[0039] 2. Temperature measurement point arrangement

[0040] like Figure 3 As shown in the figure, temperature measuring points are arranged on the top plate, diaphragm and bottom plate of the flat steel box girder. The positions of the temperature measuring points are expressed as 0.00m, 0.26m, 0.55m, 0.91m, 1.71m, 2.38m, 3.34m and 3.78m in vertical distance from the lower surface of the top plate of the flat steel box girder. The collection interval is 1 minute, and the temperature gradient history curve is obtained as shown in the figure below. Figure 4 shown.

[0041] 3. Analysis of the effect of vertical temperature gradient fatigue load model

[0042] The stress history curves at different heights are calculated according to the simplified formula of temperature stress, where the stress is:

[0043]

[0044] In the formula, σ c (y) is the pavement stress, σ s (y) is the cross-sectional stress of the steel box girder, E s is the elastic modulus of steel, α s is the thermal expansion coefficient of steel, E c is the elastic modulus of the pavement material, α c is the thermal expansion coefficient of the pavement material, A s is the cross-sectional area of ​​the flat steel box girder, A c is the cross-sectional area of ​​the pavement layer, I c is the moment of inertia of the flat steel box girder section, I c is the moment of inertia of the pavement section, γ is the structural system coefficient, M so 、N so 、M co 、M so is an intermediate variable. In this experiment, E s 2.06×105MPa, α s 1.1×10 -5 ℃ -1 , E c 3.45×10 4 MPa, α c 1.1×10 -5 ℃ -1 .

[0045] Taking the bottom plate butt weld of a flat steel box girder bridge as an example, the temperature stress is calculated based on the temperature monitoring data and the temperature stress history is constructed. The temperature stress amplitude cycle counting is performed using the rain flow counting method to obtain the temperature stress amplitude histogram at the fatigue details of the bottom plate butt weld, as shown in Figure 2. Figure 5 As shown. Then, the equivalent fatigue stress σ is calculated based on the temperature stress amplitude histogram. e (y) is calculated and the result is 19.8MPa.

[0046] The vertical temperature gradient fatigue load model of the flat steel box girder bridge constructs the temperature stress history and performs temperature stress amplitude analysis. Among them, the top plate width b is 42.1m, the bottom plate width B is 31.3m, y=0, and the design service life N d For 100 years, the equivalent stress σ is obtained according to the following formula eq (y):

[0047]

[0048] Where, E is the elastic modulus of steel, α is the thermal expansion coefficient of steel. In this embodiment, E is 2.06×10 5 MPa, α is 1.1×10 -5 ℃ -1 .

[0049] The equivalent temperature fatigue stress is 12.0 MPa, which shows that the established vertical temperature gradient fatigue load model of flat steel box girder bridge has good applicability and can be used for vertical temperature or temperature-vehicle coupling fatigue damage assessment of flat steel box girder bridge.

Claims

1. A vertical temperature gradient fatigue load model for a flat steel box girder bridge, characterized in that The model T(y) is shown in formula (1): Where y is the distance from the upper surface of the bottom plate, h is the height of the flat steel box girder, and β Gb1 (b), β Gb2 (b), β Gb3 (b), β GB1 (B), β GB2 (B), β(N d ) is an intermediate variable, T G1 is the representative value of the temperature at the top plate of the flat steel box girder bridge, in °C, T G2 is the representative value of the temperature at the distance of 0.7h from the bottom plate of the flat steel box girder transverse diaphragm, in °C, T G3 is the representative value of the temperature at the bottom plate, in °C, B is the bottom plate width of the flat wide steel box girder, b is the top plate width of the flat wide steel box girder, N d The design service life is in years, and the value is 100, 150 or 200 years. is the initial temperature value at the top plate of the flat steel box girder bridge, in °C. is the initial temperature of the flat steel box girder transverse diaphragm at a distance of 0.7h from the bottom plate, in °C. is the initial temperature at the bottom plate, in °C.

2. The vertical temperature gradient fatigue load model of the flat steel box girder bridge according to claim 1 is characterized in that: In formula (1), The value is [11.4,12.2], the unit is ℃, The value of is [9.1,9.7], the unit is ℃, The value of is [5.3,5.7], the unit is ℃, the value of b is [25.00,50.00], the unit is m, and the value of B is [10.00,40.00], the unit is m.

3. The vertical temperature gradient fatigue load model of the flat steel box girder bridge according to claim 1 is characterized in that: In formula (1), B, b, The values ​​of are: B is 31.30m, b is 42.10m, is 11.8℃, 9.4℃, It is 5.5℃.

Images