Vertical temperature gradient fatigue load model for U rib of steel bridge deck

Abstract

A vertical temperature gradient fatigue load model of a U-shaped rib of a steel bridge deck slab is shown as a formula (1) and is in a double-broken-line type. A bridge deck slab U-rib vertical temperature gradient fatigue load model is constructed by adopting a Latin hypercube sampling method and a damage equivalence principle according to steel bridge deck slab U-rib closed section characteristics and temperature field distribution characteristics. According to the model, the influence of the height of the U rib is taken into account, temperature fatigue stress process calculation of details of the U rib of the steel bridge deck is achieved, and the model can be used for anti-fatigue design and evaluation of 100-200-year design and service life of the U rib of the steel bridge deck.

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 U-rib of a steel bridge deck. Background Art

[0002] The U-rib of the steel bridge deck is located at the top of the beam section. It is a typical closed section type. The air convection inside the section is insufficient. Under the action of solar radiation, the U-rib section will produce a significant vertical nonlinear temperature gradient. Under the action of the vertical nonlinear temperature gradient, longitudinal temperature fatigue stress will be generated, which will contribute to the cumulative fatigue damage of the U-rib details. Therefore, in order to calculate the temperature fatigue damage at the U-rib details within the design service life, it is necessary to arrange temperature sensors according to the temperature field distribution characteristics of the U-rib of the bridge deck. Using the long-term monitoring data of the U-rib temperature field, the temperature effect and structural response of the U-rib are deeply studied. The Latin hypercube sampling method and the fatigue damage equivalence principle are used to construct a vertical temperature gradient fatigue load model for the U-rib of a long-life steel bridge deck with a design service life of 100, 150 and 200 years. 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 U-ribs of steel bridge decks.

[0004] The steel bridge deck U-rib vertical temperature gradient fatigue load model T provided by the present invention U (y) is:

[0005]

[0006] Where y is the vertical distance from the U-rib bottom plate, H U is the U rib height, in m, T U1 The distance from the U rib bottom plate H U The temperature at the position is the representative value, in °C, T U2 0.8H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U3 The distance from the U-rib bottom plate is 0.64H U The temperature at the position is the representative value, in °C, T U4 is the representative value of the temperature at the bottom plate of the U rib, in °C. The distance from the U rib bottom plate H U The initial temperature value at position, in °C, 0.8H from the U-rib bottom plate U The initial temperature value at position, in °C, The distance from the U-rib bottom plate is 0.64H U The initial temperature value at position, in °C, is the initial temperature value of the U-rib bottom plate, in °C, Nd is the design service life, in years, with a value of 100, 150 or 200 years, β N (N d ), β H (H U ) is an intermediate variable.

[0007] More preferably, the The value is [22.0,26.0], the unit is ℃, The value is [18.0,24.0], the unit is ℃, H U The value range is [0.20,0.40], and the unit is m.

[0008] More preferably, the H U The value of is: 24.0℃, 20.6℃, H U It is 0.28m.

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

[0010] The present invention utilizes the long-term monitoring data of the U-rib of steel bridge deck, adopts the Latin hypercube sampling method and the fatigue damage equivalence principle to construct a vertical temperature gradient fatigue load model of the U-rib of steel bridge deck. The model is simple in form and can be used for the fatigue resistance design and fatigue life assessment of the U-rib of steel bridge deck with a design service life of up to 200 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the three-dimensional structure of the U-rib of the steel bridge deck.

[0012] Figure 2 This is the temperature representative value distribution diagram of the vertical temperature gradient fatigue load model of the U-rib of the steel bridge deck.

[0013] Figure 3 This is the layout diagram of the vertical temperature measurement points of the U-rib of the steel bridge deck.

[0014] Figure 4 It is the temperature history curve at the U-rib measuring point under the action of temperature load.

[0015] Figure 5 It is the histogram of the measured temperature stress amplitude. DETAILED DESCRIPTION

[0016] 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.

[0017] Example 1

[0018] The present invention relates to a vertical temperature gradient fatigue load model for U-ribs of steel bridge decks. The model T U (y) is:

[0019]

[0020] Where y is the vertical distance from the U-rib bottom plate, H U is the U rib height, in m, T U1 The distance from the U rib bottom plate H U The temperature at the position is the representative value, in °C, T U2 0.8H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U3 The distance from the U-rib bottom plate is 0.64H U The temperature at the position is the representative value, in °C, T U4 is the representative value of the temperature at the bottom plate of the U rib, in °C. The distance from the U rib bottom plate H U The initial temperature value at position, in °C, 0.8H from the U-rib bottom plate U The initial temperature value at position, in °C, The distance from the U-rib bottom plate is 0.64H U The initial temperature value at position, in °C, is the initial temperature value of the U-rib bottom plate, in °C, N d is the design service life, in years, with a value of 100, 150 or 200 years, β N (N d ), β H (H U ) is an intermediate variable.

[0021] Taking the U-rib of the steel bridge deck of Nanjing Yangtze River Bridge as an example, the U-rib type is as follows: Figure 1 In formula (1), the U rib height H U 0.28m, 24.0℃, The corresponding U-rib vertical temperature gradient fatigue load model is constructed according to this parameter, and the temperature representative values ​​corresponding to 100 years, 150 years, and 200 years are shown in Table 1. The temperature representative value distribution of the U-rib vertical temperature gradient fatigue load model is shown in Table 1. Figure 2 shown.

[0022] Table 1 Representative values ​​of temperature for U-rib vertical temperature gradient fatigue load model

[0023]

[0024] Example 2

[0025] The U-rib vertical temperature gradient fatigue load model involved in this embodiment is the same as that in Embodiment 1, but the temperature representative value is different.

[0026] The U-rib type of the steel bridge deck in this embodiment is as follows Figure 1 As shown. Its U rib height H U 0.20m, 22.0℃, The corresponding U-rib vertical temperature gradient fatigue load model is constructed according to this parameter, and the temperature representative values ​​corresponding to 100 years, 150 years, and 200 years are shown in Table 2. The temperature representative value distribution of the U-rib vertical temperature gradient fatigue load model is shown in Table 2. Figure 2 shown.

[0027] Table 2 Representative values ​​of temperature for U-rib vertical temperature gradient fatigue load model

[0028]

[0029] Example 3

[0030] The U-rib vertical temperature gradient fatigue load model involved in this embodiment is the same as that in Embodiment 1, but the temperature representative value is different.

[0031] The U-rib type of the steel bridge deck in this embodiment is as follows Figure 1 As shown. Its U rib height H U 0.40m, 26.0℃, is 24.0℃. According to this parameter, the corresponding U-rib vertical temperature gradient fatigue load model is constructed, and the temperature representative values ​​corresponding to 100 years, 150 years, and 200 years are shown in Table 3. The temperature representative value distribution of the U-rib vertical temperature gradient fatigue load model is shown in Figure 2 shown.

[0032] Table 3 Representative values ​​of temperature for U-rib vertical temperature gradient fatigue load model

[0033]

[0034] Test 1

[0035] In order to verify the effect of the U-rib vertical temperature gradient fatigue load model, sensors were arranged on the U-ribs of the steel bridge deck of the Nanjing Yangtze River cable-stayed Bridge and the long-term temperature field was monitored.

[0036] 1. Long-term monitoring instruments

[0037] The monitoring instrument is a 64-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.

[0038] 2. Temperature measurement point arrangement

[0039] like Figure 3 As shown in the figure, temperature measuring points are arranged on the top plate, web plate and bottom plate of the U-rib. The positions of the temperature measuring points are expressed as 0.0m, 0.08m, 0.18m, 0.23m and 0.28m in vertical distance from the lower surface of the bottom plate of the U-rib. The collection interval is 1 minute. The temperature history σ at the measuring point position of the U-rib under the temperature load te (y,t), such as Figure 4 shown.

[0040] 3. Analysis of the effect of U-rib vertical temperature gradient fatigue load model

[0041] The stress history curves at different heights are calculated according to the simplified formula of temperature stress, where the stress history of the U-rib section σ te (y,t) is:

[0042] Where: E s is the elastic modulus of steel, α s is the thermal expansion coefficient of the steel, A is the cross-sectional area of ​​the U rib, I is the moment of inertia of the U rib cross section, in this case E s 206GPa, α s 1.1×10 -5 ℃ -1 .

[0043] Taking the fillet weld details of the U-rib and top plate connection of the steel bridge deck as an example, the temperature stress is calculated based on the temperature measurement monitoring data and the temperature stress history σ is constructed. te (y, t), the temperature stress amplitude cycle count is performed using the rain flow counting method to obtain the temperature stress amplitude histogram, such as Figure 5 Then, the equivalent fatigue stress was calculated based on the temperature stress amplitude spectrum, and the result was 57.6MPa.

[0044] Based on the U-rib vertical temperature gradient fatigue load model, the temperature stress history is constructed and the temperature stress amplitude analysis is performed. U is 0.28m, y is 0.28m, and the design service life is N d For 100 years, substitute into the following formula

[0045]

[0046] The equivalent temperature fatigue stress is 58.1MPa. The difference between the two is very small, indicating that the established U-rib vertical temperature gradient fatigue load model has good applicability.

Claims

1. A vertical temperature gradient fatigue load model for U-rib of steel bridge deck, characterized by: The vertical temperature gradient fatigue load model T of the U-rib of the steel bridge deck U (y) is: Where y is the vertical distance from the U-rib bottom plate, H U is the U rib height, in m, T U1 The distance from the U rib bottom plate H U The temperature at the position is the representative value, in °C, T U2 0.8H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U3 The distance from the U-rib bottom plate is 0.64H U The temperature at the position is the representative value, in °C, T U4 is the representative value of the temperature at the bottom plate of the U rib, in °C. The distance from the U rib bottom plate H U The initial temperature value at position, in °C, 0.8H from the U-rib bottom plate U The initial temperature value at position, in °C, The distance from the U-rib bottom plate is 0.64H U The initial temperature value at position, in °C, is the initial temperature value of the U-rib bottom plate, in °C, N d is the design service life, in years, with a value of 100, 150 or 200 years, β N (N d ), β H (H U ) is an intermediate variable.

2. The U-rib vertical temperature gradient fatigue load model according to claim 1 is characterized in that: In formula (1), The value is [22.0,26.0], the unit is ℃, The value is [18.0,24.0], the unit is ℃, H U The value range is [0.20,0.40], and the unit is m.

3. The U-rib vertical temperature gradient fatigue load model according to claim 1 is characterized in that: In formula (1), H U The value of is: 24.0℃, 20.6℃, H U It is 0.28m.

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