Steel bridge deck u-rib vertical temperature gradient fatigue load model

Abstract

The vertical temperature gradient fatigue load model of steel bridge deck U-rib is shown as formula (1), which is a double-fold line type. According to the characteristics of closed section of steel bridge deck U-rib and the distribution of temperature field, the Latin hypercube sampling method and the damage equivalent principle are used to construct the vertical temperature gradient fatigue load model of bridge deck U-rib. The model takes into account the influence of U-rib height, realizes the calculation of temperature fatigue stress history at the details of steel bridge deck U-rib, and can be used for the fatigue design and evaluation of steel bridge deck U-rib for 100-200 years of design service life.

Description

Technical Field

[0001] The present 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 a steel bridge deck is located at the top of the beam section, a typical closed cross-section. Air convection within the cross-section is insufficient, and solar radiation can produce significant vertical nonlinear temperature gradients within the U-rib section. This vertical nonlinear temperature gradient generates longitudinal thermal fatigue stresses, contributing to the cumulative fatigue damage of the U-rib details. Therefore, to calculate thermal fatigue damage at the U-rib details within the design service life, it is necessary to deploy temperature sensors based on the temperature field distribution characteristics of the U-ribs in the bridge deck. Using long-term monitoring data of the U-rib temperature field, we conduct an in-depth study of the temperature effects and structural response of the U-ribs. Using the Latin hypercube sampling method and the fatigue damage equivalence principle, we construct a vertical thermal gradient fatigue load model for U-ribs in long-life steel bridge decks with design service lives 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 0.64H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U4 is the representative temperature value 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, 0.64H from the U-rib bottom plate 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: 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 long-term monitoring data of steel bridge deck U-ribs, adopts the Latin hypercube sampling method and the fatigue damage equivalence principle to construct a vertical temperature gradient fatigue load model for steel bridge deck U-ribs. The model is simple in form and can be used for fatigue resistance design and fatigue life assessment of steel bridge deck U-ribs 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 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 is the histogram of the measured temperature stress amplitude. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below with reference to 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 steel bridge deck U-rib vertical temperature gradient fatigue load model, 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 0.64H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U4 is the representative temperature value 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, 0.64H from the U-rib bottom plate 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 deck of Nanjing Yangtze River Bridge as an example, the U-rib type is as follows: Figure 1 As shown. In formula (1), the U rib height H U 0.28m, is 24.0℃, The corresponding U-rib vertical temperature gradient fatigue load model 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 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 temperature values ​​of the 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, is 22.0℃, The corresponding U-rib vertical temperature gradient fatigue load model is constructed according to this parameter. 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 temperature values ​​of the 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, is 26.0℃, The corresponding U-rib vertical temperature gradient fatigue load model is constructed according to this parameter. 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 Table 3. Figure 2 shown.

[0032] Table 3 Representative temperature values ​​of the 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 deck of the Nanjing Yangtze River Cable-stayed Bridge and long-term temperature field monitoring was carried out.

[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 represented by the vertical distance from the lower surface of the U-rib bottom plate as 0.0m, 0.08m, 0.18m, 0.23m and 0.28m. The sampling interval is 1 minute. The temperature history σ at the measuring point position of the U-rib under the action of 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 based on the simplified temperature stress formula, 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 steel, A is the cross-sectional area of ​​the U rib, I is the moment of inertia of the U rib cross-section, and 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 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 The equivalent fatigue stress was then calculated based on the temperature stress amplitude spectrum, and the result was 57.6 MPa.

[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 the following formula

[0045]

[0046] The equivalent thermal fatigue stress is 58.1 MPa. 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 steel bridge deck U-rib vertical temperature gradient fatigue load model, characterized by: The steel bridge deck U-rib vertical temperature gradient fatigue load model T 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 0.64H from the U-rib bottom plate U The temperature at the position is the representative value, in °C, T U4 is the representative temperature value 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, 0.64H from the U-rib bottom plate 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, 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: is 24.0℃, 20.6℃, H U It is 0.28m.

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