A fatigue design method for a double-deck four-line railway steel truss girder cable-stayed bridge

Abstract

The present invention relates to a fatigue design method for a double-layer four-line railway steel truss girder cable-stayed bridge. The multi-line coefficients of different components of the cable-stayed bridge are obtained, and then the corresponding components are designed according to the multi-line coefficients of the components. Among them, the components include upper chord members, lower chord members, diagonal web members, vertical web members and stay cables. By obtaining the respective multi-line coefficients of different components such as upper chord members, lower chord members, diagonal web members, vertical web members and stay cables, and then designing the corresponding components according to the respective multi-line coefficients, compared with the unified values in the specifications, it can better reflect the fatigue characteristics of different components, enabling the fatigue design of different components to achieve a safety level close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some members can be optimized, or even the cross-section types of the components can be optimized, so as to achieve the purpose of saving costs, improving the economy of the steel girder, and facilitating construction.

Description

Technical Field

[0001] The invention relates to the technical field of double-layer four-track fatigue design, in particular to a fatigue design method for a double-layer four-track railway steel truss cable-stayed bridge. Background Art

[0002] In recent years, my country's railway industry has developed rapidly, and the number of long-span bridges across large rivers and high-level navigable rivers has increased. Building too many bridges on large rivers will have an adverse impact on the coastal ecology, landscape and overall planning. In order to save cross-river channel resources, multi-line railways are usually planned to be constructed using the same cross-river channel, and there are more and more cases where four-line railways share one cross-river channel. Four-line railway cable-stayed bridges can be arranged on the same layer (such as the Anqing Yangtze River Bridge of the Ning'an Railway, the Jiaojiang Bridge of the Hangzhou-Shaoxing-Taizhou Railway, and the Dongxin Ganjiang Bridge of the Nanchang Hub, etc.), or in a double-layer arrangement (such as the Chongqing Mingyuexia Yangtze River Bridge, etc.). When the same layer is used, trusses or box girders can be used, and when the double-layer arrangement is used, trusses are generally used. The choice of double-layer or flat-layer arrangement is usually determined by the two-strait relief project and connection conditions.

[0003] Moreover, the load of four-track railway bridges is heavy, which makes fatigue problems prominent. In addition, the fatigue design method of railway bridges adopts the method of "when checking the fatigue of the components of the main truss (or main beam) of a multi-track railway bridge, the fatigue load can be loaded as one line, acting on the most unfavorable position in the lateral direction, and multiplied by the multi-line coefficient γd". The value of γd takes different values ​​according to the number of lines. Article 4.3.2 of the "Code for Design of Steel Structures of Railway Bridges" (TB10091-2017) stipulates that the multi-line coefficient of four-track railways is: 2.15~2.30, the lower limit is all high-speed / intercity railways, the upper limit is all passenger and freight railways, and the middle part is interpolated. This coefficient does not distinguish between flat-deck and double-deck railways. For flat-deck railways, the load effect of four-line loading is consistent with the load effect characteristics of one line, so it is reasonable to adopt a unified load coefficient. However, for double-deck railways, especially for double-deck railway cable-stayed bridges, if a unified multi-line coefficient is selected for all stress conditions of all components of the cable-stayed bridge, it is not very applicable. Analysis shows that it is conservative, and the economic efficiency of the steel beams designed according to this indicator is biased. Summary of the invention

[0004] The purpose of the present invention is to provide a fatigue design method for a double-deck four-track railway steel truss cable-stayed bridge in view of the fatigue design of the prior art double-deck four-track railway cable-stayed bridge, in which a unified multi-line coefficient is selected for all stress conditions of all components of the cable-stayed bridge, and there is a problem of economic deviation of steel beams.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A fatigue design method for a double-deck four-track railway steel truss cable-stayed bridge obtains multi-line coefficients of different components of the cable-stayed bridge, and then designs corresponding components according to the multi-line coefficients of the components, wherein the components include an upper chord, a lower chord, a diagonal web member, a vertical web member and a stay cable.

[0007] In this scheme, the upper chord, lower chord, diagonal web, vertical web and cable are the main components of the cable-stayed bridge. By obtaining the corresponding multi-line coefficients of the upper chord, lower chord, diagonal web, vertical web and cable, and then designing the corresponding components according to the corresponding multi-line coefficients, the fatigue characteristics of different components can be better reflected compared to the unified values ​​in the specifications, so that the fatigue design of different components can achieve a safety level close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods can be optimized, and even the cross-sectional types of components can be optimized to achieve the purpose of saving costs, improving the economy of steel beams, and facilitating construction.

[0008] Preferably, when obtaining the multi-line coefficient of the upper chord, the multi-line coefficient of the axial force of the upper chord and the multi-line coefficient of the in-plane secondary bending moment are obtained, and the upper chord is designed according to the multi-line coefficient of the axial force of the upper chord and the multi-line coefficient of the in-plane secondary bending moment;

[0009] When obtaining the multi-line coefficient of the lower chord, the multi-line coefficient of the axial force of the lower chord and the multi-line coefficient of the in-plane secondary bending moment are obtained, and the lower chord is designed according to the multi-line coefficient of the axial force of the lower chord and the multi-line coefficient of the in-plane secondary bending moment.

[0010] The main fatigue characteristics of the upper and lower chords are reflected in the axial force and in-plane secondary bending moment, and the fatigue difference of the axial force and in-plane secondary bending moment of the lower chord is greater. By obtaining the multi-line coefficients of different internal force factors of axial force and in-plane secondary bending moment, the upper and lower chords can be designed to better reflect the fatigue characteristics of the upper and lower chords, so that the fatigue design of the upper and lower chords can achieve a safety degree close to the actual requirements, and the component design is more refined. It can also further optimize the structural dimensions of some upper and lower chords, and even optimize the cross-sectional types of the upper and lower chords.

[0011] Preferably, when obtaining the multi-linear coefficient of the diagonal web, the multi-linear coefficient of the axial force of the diagonal web, the multi-linear coefficient of the in-plane secondary bending moment and the multi-linear coefficient of the out-of-plane bending moment are obtained, and the diagonal web is designed based on the multi-linear coefficient of the axial force of the diagonal web, the multi-linear coefficient of the in-plane secondary bending moment and the multi-linear coefficient of the out-of-plane bending moment.

[0012] The main fatigue characteristics of the diagonal brace are reflected in the axial force, in-plane secondary bending moment and out-of-plane bending moment, and the fatigue characteristics of different internal force factors are very different. By obtaining the multi-line coefficients of different internal force factors such as axial force, in-plane secondary bending moment and out-of-plane bending moment, the diagonal brace can be designed to better reflect the fatigue characteristics of the diagonal brace, so that the fatigue design of the diagonal brace can achieve a safety degree close to the actual requirements, and the component design is more refined. It can also further optimize the structural size of the diagonal brace, and even optimize the cross-sectional type of the diagonal brace.

[0013] Preferably, when obtaining the multi-linear coefficient of the vertical web member, the multi-linear coefficient of the axial force of the vertical web member, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment are obtained, and the vertical web member is designed based on the multi-linear coefficient of the axial force of the vertical web member, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment.

[0014] The main fatigue characteristics of the vertical web members are reflected in the axial force, in-plane secondary bending moment and out-of-plane bending moment, and the fatigue characteristics of different internal force factors are very different. By obtaining the multi-line coefficients of different internal force factors such as axial force, in-plane secondary bending moment and out-of-plane bending moment, the vertical web members can be designed to better reflect the fatigue characteristics of the vertical web members, so that the fatigue design of the vertical web members can achieve a safety degree close to the actual requirements, and the component design is more refined. It can also further optimize the structural dimensions of the vertical web members, and even optimize the cross-sectional type of the vertical web members.

[0015] Preferably, when obtaining the multi-line coefficient of the inclined cable, the multi-line coefficient of the axial force of the inclined cable is obtained, and the inclined cable is designed according to the multi-line coefficient of the axial force of the inclined cable.

[0016] The main fatigue characteristics of the cable are reflected in the axial force. By obtaining the multi-line coefficient of the axial force of the cable, the fatigue characteristics of the cable can be reflected more directly, so that the fatigue design of the cable can achieve a safety level close to the actual requirements, and the component design is more refined. It can also reduce the consideration of other internal force factors of the cable.

[0017] Preferably, the components of the cable-stayed bridge are divided into components of the auxiliary span, components of the secondary side span and components of the middle span. When obtaining the multi-line coefficients of different components of the cable-stayed bridge, the multi-line coefficients of the components of the auxiliary span, the multi-line coefficients of the components of the secondary side span and the multi-line coefficients of the components of the middle span are obtained.

[0018] The fatigue characteristics of components at different longitudinal positions of the bridge may be different. The components of the cable-stayed bridge are divided into components of the auxiliary span, components of the secondary side span, and components of the middle span. The fatigue characteristics of the components of the cable-stayed bridge are better segmented, so that when designing components at different longitudinal positions of the bridge, the multi-line coefficients of the components at the corresponding positions can be used, so that the fatigue characteristics of the components at different positions can be better reflected, so that the fatigue design of different components at different positions can achieve a safety degree close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods at some positions can be further optimized, and even the cross-sectional types of the components can be optimized to achieve the purpose of saving costs, improving the economy of steel beams, and facilitating construction.

[0019] Preferably, the components of the secondary side span are divided into components of the first side span and components of the second side span from the secondary side span, and the multi-line coefficients of the components of the secondary side span are obtained, and the multi-line coefficients of the components of the first side span and the multi-line coefficients of the components of the second side span are obtained.

[0020] After research, it was found that the fatigue condition of the components of the secondary side span has a turning point in the secondary side span. The components of the secondary side span are divided into the components of the first side span and the components of the second side span from the secondary side span to obtain the multi-line coefficients of the components at the corresponding positions, so that the fatigue characteristics of the components at different positions can be better reflected, and the fatigue design of different components at different positions can achieve a safety level close to the actual requirements, and the component design is more refined.

[0021] Preferably, the multi-line coefficients of the components at the beam ends of the cable-stayed bridge are obtained, the multi-line coefficients of the components at the auxiliary piers of the cable-stayed bridge are obtained, the multi-line coefficients of the components in the secondary side spans of the cable-stayed bridge are obtained, the multi-line coefficients of the components at the bridge towers of the cable-stayed bridge are obtained, and the multi-line coefficients of the components in the middle spans of the cable-stayed bridge are obtained;

[0022] The multi-line coefficients of the components of the auxiliary span of the cable-stayed bridge are obtained by interpolating the multi-line coefficients of the components at the beam ends of the cable-stayed bridge and the multi-line coefficients of the components at the auxiliary piers of the cable-stayed bridge; the multi-line coefficients of the components of the first side span of the cable-stayed bridge are obtained by interpolating the multi-line coefficients of the components at the auxiliary piers of the cable-stayed bridge and the multi-line coefficients of the components in the secondary side span of the cable-stayed bridge; the multi-line coefficients of the components of the second side span of the cable-stayed bridge are obtained by interpolating the multi-line coefficients of the components in the secondary side span of the cable-stayed bridge and the multi-line coefficients of the components at the bridge towers of the cable-stayed bridge; the multi-line coefficients of the components of the middle span of the cable-stayed bridge are obtained by interpolating the multi-line coefficients of the components at the bridge towers of the cable-stayed bridge and the multi-line coefficients of the components in the middle span of the cable-stayed bridge.

[0023] After research, it was found that the fatigue conditions of the same components of the auxiliary span, the first side span, the second side span and the middle span were linearly distributed along the longitudinal direction of the bridge in their respective regions. By obtaining the multi-line coefficients of the components at both ends of each region and then obtaining the multi-line coefficients of the components in the corresponding region by interpolation, the fatigue conditions of the components in the corresponding region can be better reflected. It can also avoid the use of an exhaustive method that would make it impossible to implement.

[0024] Preferably, the double-deck four-track railway steel truss cable-stayed bridge comprises an upper deck system and a lower deck system, wherein the upper deck system is located directly above the lower deck system, two railways are arranged on the upper deck system, and two railways are arranged on the lower deck system, the upper deck system has the same width as the lower deck system, and the two railways of the upper deck system are located directly above the two railways of the lower deck system;

[0025] When all railways are high-speed railways or intercity railways, the polyline coefficients corresponding to the stresses of the beam ends, auxiliary piers, mid-spans of the secondary side spans, bridge towers and mid-span components of the cable-stayed bridge are as follows:

[0026]

[0027]

[0028] When all railways are passenger and freight railways, the polyline coefficients corresponding to the stresses of the beam ends, auxiliary piers, mid-span of the secondary side span, bridge towers and mid-span of the cable-stayed bridge are as follows:

[0029]

[0030] When the double-deck four-track railway steel truss cable-stayed bridge adopts the above structure, the polyline coefficients of the corresponding forces of the corresponding components in the corresponding area can be directly obtained by interpolation based on the polyline coefficients of the forces of the components at the end positions of the above area, so that the corresponding components in the corresponding area can be quickly designed.

[0031] Preferably, the degree of damage under various train encounter conditions is studied through the train encounter probability and the multi-line coefficient calculation expression is obtained, and by analyzing the stress characteristics of the double-deck four-track railway steel truss, the load effect and the lateral distribution coefficient under the action of each line train are studied, and then the multi-line coefficient of the component is obtained according to the multi-line coefficient calculation expression of the train encounter probability, the load effect and the lateral distribution coefficient.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. The fatigue design method of the double-deck four-track railway steel truss cable-stayed bridge described in the present invention, the upper chord, lower chord, diagonal web, vertical web and inclined cable are the main components of the steel truss cable-stayed bridge. By obtaining the multi-line coefficients corresponding to the different components of the upper chord, lower chord, diagonal web, vertical web and inclined cable, and then designing the corresponding components according to the corresponding multi-line coefficients, compared with the standardized unified value, it can better reflect the fatigue characteristics of different components, so that the fatigue design of different components can achieve a safety degree close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods can be optimized, and even the cross-sectional type of the components can be optimized, so as to achieve the purpose of saving cost, improving the economy of steel beams, and facilitating construction.

[0034] 2. The fatigue design method of the double-deck four-track railway steel truss cable-stayed bridge of the present invention divides the components of the cable-stayed bridge into components of the auxiliary span, components of the first side span, components of the second side span and components of the middle span, and different components consider their corresponding internal force factors, and subdivide the multi-line coefficients corresponding to different regions, different components and different internal force types. Compared with the single value of the specification, it can better reflect the fatigue characteristics of the components, so that the fatigue design of different components can achieve a similar safety degree and the component design is more refined. On this basis, the structural dimensions of some rods can be optimized, and even the cross-sectional type of the components can be optimized to achieve the purpose of saving cost and facilitating construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of the regional distribution of the double-deck four-track railway steel truss cable-stayed bridge described in Example 1;

[0036] Figure 2 yes Figure 1 Enlarged schematic diagram of the middle circle;

[0037] Figure 3 is a schematic cross-sectional view of the double-deck four-track railway steel truss cable-stayed bridge described in Example 1;

[0038] Figure 4 It is a multi-line coefficient broken line diagram of components in different areas.

[0039] Icons: 1-upper chord; 2-lower chord; 3-diagonal web member; 4-vertical web member; 5-cable-stayed cable; 6-auxiliary span; 7-secondary side span; 71-first side span; 72-second side span; 8-middle span; 91-beam end; 92-auxiliary pier; 93-bridge tower; 101-upper deck system; 102-lower deck system; 103-railway. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] Example 1

[0043] This embodiment provides a fatigue design method for a double-deck four-track railway steel truss cable-stayed bridge. Figure 1-3 As shown, the polylinear coefficients of different components of the cable-stayed bridge are obtained, and then the corresponding components are designed according to the polylinear coefficients of the components, wherein the components include an upper chord 1, a lower chord 2, a diagonal web member 3, a vertical web member 4 and a stay cable 5.

[0044] In recent years, there are more and more steel bridges larger than double tracks in railway construction. According to actual needs and scientific research results, the double-track coefficient regulations are expanded to form multi-track coefficients. For fatigue inspection of multi-track railway steel bridges, the influence of the simultaneous action of multiple trains should be considered. The study of multi-track coefficients includes studying the probability of multi-track trains meeting on the bridge in different combinations and the calculation of damage when trains meet on the bridge. In the analysis, it is assumed that the operation of trains on each line is independent of each other. Through probability analysis and damage calculation, the multi-track coefficient is obtained by combining various situations. Studies have shown that the multi-track coefficient is mainly affected by the length and speed of the operating train. The longer the train length and the lower the speed, and the shorter the train length and the higher the speed, resulting in a large number of operations, the probability of multi-track trains meeting will increase, and thus the multi-track coefficient will also be larger.

[0045] In this scheme, the damage degree under various train encounter conditions is studied through the train encounter probability, and the multi-line coefficient calculation expression is obtained. The load effect and lateral distribution coefficient under the action of each line train are studied by analyzing the force characteristics of the double-deck four-track railway steel truss, and then the multi-line coefficient of the component is obtained according to the multi-line coefficient calculation expression of the train encounter probability, the load effect and the lateral distribution coefficient. The train encounter probability is the theoretical basis for determining the multi-line coefficient, which aims to study the damage degree under various train encounter conditions and obtain the multi-line coefficient calculation expression; the load effect and lateral distribution coefficient under the action of each line train are studied by analyzing the force characteristics of the double-deck four-track railway steel truss, and the multi-line coefficient value is determined. Therefore, the train encounter probability, train load effect, and lateral distribution coefficient are the principles for formulating the above multi-line coefficient. Based on the above principles, after a large number of analysis and calculations of the double-deck four-track steel truss cable-stayed bridge, the multi-line coefficient values ​​of each component are obtained, and they are distinguished according to the two situations of running passenger dedicated lines and passenger and freight co-lines. It is an existing technology to obtain multi-line coefficients based on the probability of train encounter, train load effect, and lateral distribution coefficient. It is also an existing technology to design bridges accordingly based on the multi-line coefficients.

[0046] In this scheme, the upper chord 1, the lower chord 2, the diagonal brace 3, the vertical brace 4 and the inclined cable 5 are the main components of the steel truss cable-stayed bridge. By obtaining the corresponding multi-line coefficients of the upper chord 1, the lower chord 2, the diagonal brace 3, the vertical brace 4 and the inclined cable 5, and then designing the corresponding components according to the corresponding multi-line coefficients, compared with the unified values ​​in the specifications, the fatigue characteristics of different components can be better reflected, so that the fatigue design of different components can achieve a safety degree close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods can be optimized, and even the cross-sectional type of the components can be optimized to achieve the purpose of saving costs, improving the economy of steel beams, and facilitating construction.

[0047] In this embodiment, different components can be distinguished by multi-line coefficients according to the type of internal force, where the chord considers the axial force and in-plane secondary bending moment effects, the web considers the axial force, in-plane secondary bending moment, and out-of-plane bending moment effects, and the cable only considers the axial force effect. The upper chord 1 has a significantly increased local secondary bending moment effect due to the support effect of its cables. In addition to the upper chord 1, the lower chord 2, the diagonal web 3, the vertical web 4 and the inclined cable 5, the crossbeam is also the main component of the steel truss cable-stayed bridge, but the crossbeam is a local load-bearing component, and its calculation method can be the same as the calculation method of the multi-line coefficient of the double-track bridge, and it is not necessary to design it in the multi-line coefficient method in this scheme.

[0048] In this embodiment, the main fatigue characteristics of the upper chord 1 and the lower chord 2 are reflected in the axial force and the in-plane secondary bending moment, and the fatigue difference of the axial force and the in-plane secondary bending moment of the lower chord 2 is greater. By obtaining the multi-line coefficients of different internal force factors of the axial force and the in-plane secondary bending moment, the upper chord 1 and the lower chord 2 are designed, which can better reflect the fatigue characteristics of the upper chord 1 and the lower chord 2, so that the fatigue design of the upper chord 1 and the lower chord 2 can achieve a safety degree close to the actual requirements, and the component design is more refined. It can also further optimize the structural dimensions of some of the upper chords 1 and the lower chord 2, and even optimize the cross-sectional types of the upper chords 1 and the lower chord 2.

[0049] Specifically, when obtaining the polylinear coefficient of the upper chord 1, the polylinear coefficient of the axial force of the upper chord 1 and the polylinear coefficient of the in-plane secondary bending moment can be obtained, and the upper chord 1 can be designed according to the polylinear coefficient of the axial force of the upper chord 1 and the polylinear coefficient of the in-plane secondary bending moment.

[0050] When obtaining the polylinear coefficient of the lower chord 2, the polylinear coefficient of the axial force of the lower chord 2 and the polylinear coefficient of the in-plane secondary bending moment are obtained, and the lower chord 2 is designed according to the polylinear coefficient of the axial force of the lower chord 2 and the polylinear coefficient of the in-plane secondary bending moment.

[0051] In this embodiment, the main fatigue characteristics of the diagonal brace 3 are reflected in the axial force, the in-plane secondary bending moment and the out-of-plane bending moment, and the fatigue characteristics of different internal force factors are greatly different. By obtaining the multi-line coefficients of different internal force factors such as the axial force, the in-plane secondary bending moment and the out-of-plane bending moment, the diagonal brace 3 is designed, which can better reflect the fatigue characteristics of the diagonal brace 3, so that the fatigue design of the diagonal brace 3 can achieve a safety degree close to that actually required, and the component design is more refined. It can also further optimize the structural dimensions of the diagonal brace 3, and even optimize the cross-sectional type of the diagonal brace 3.

[0052] Specifically, when obtaining the multi-linear coefficient of the diagonal member 3, the multi-linear coefficient of the axial force of the diagonal member 3, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment can be obtained, and the diagonal member 3 can be designed according to the multi-linear coefficient of the axial force of the diagonal member 3, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment.

[0053] In this embodiment, the main fatigue characteristics of the vertical web member 4 are reflected in the axial force, the in-plane secondary bending moment and the out-of-plane bending moment, and the fatigue characteristics of different internal force factors are greatly different. By obtaining the multi-line coefficients of different internal force factors such as the axial force, the in-plane secondary bending moment and the out-of-plane bending moment, the vertical web member 4 is designed, which can better reflect the fatigue characteristics of the vertical web member 4, so that the fatigue design of the vertical web member 4 can achieve a safety degree close to the actual requirements, and the component design is more refined. It can also further optimize the structural dimensions of the vertical web member 4, and even optimize the cross-sectional type of the vertical web member 4.

[0054] Specifically, when obtaining the multi-linear coefficient of the vertical web member 4, the multi-linear coefficient of the axial force, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment of the vertical web member 4 can be obtained, and the vertical web member 4 can be designed according to the multi-linear coefficient of the axial force, the multi-linear coefficient of the in-plane secondary bending moment, and the multi-linear coefficient of the out-of-plane bending moment of the vertical web member 4.

[0055] In this embodiment, the main fatigue characteristics of the inclined cable 5 are reflected in the axial force. By obtaining the multi-line coefficient of the axial force of the inclined cable 5, the fatigue characteristics of the inclined cable 5 can be more directly reflected, so that the fatigue design of the inclined cable 5 can achieve a safety degree close to the actual requirements, and the component design is more refined. And it can reduce the consideration of other internal force factors of the inclined cable 5. Specifically, when obtaining the multi-line coefficient of the inclined cable 5, the multi-line coefficient of the axial force of the inclined cable 5 can be obtained, and the inclined cable 5 can be designed according to the multi-line coefficient of the axial force of the inclined cable 5.

[0056] In addition, the multi-line coefficients of components in different areas can be determined by dividing the cable-stayed bridge into different areas according to its stress characteristics. Figure 1 and Figure 4As shown, the fatigue characteristics of components at different longitudinal positions of the bridge may be different. The components of the cable-stayed bridge are divided into components of the auxiliary span 6, components of the secondary side span 7 and components of the middle span 8. The fatigue characteristics of the components of the cable-stayed bridge are better segmented, so that when designing components at different longitudinal positions of the bridge, the multi-line coefficients of the components at the corresponding positions can be used, so that the fatigue characteristics of the components at different positions can be better reflected, so that the fatigue design of different components at different positions can achieve a safety degree close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods at some positions can be further optimized, and even the cross-sectional type of the components can be optimized to achieve the purpose of saving cost, improving the economy of steel beams, and facilitating construction. Specifically, the components of the cable-stayed bridge can be divided into components of the auxiliary span 6, components of the secondary side span 7 and components of the middle span 8. When obtaining the multi-line coefficients of different components of the cable-stayed bridge, the multi-line coefficients of the components of the auxiliary span 6, the multi-line coefficients of the components of the secondary side span 7 and the multi-line coefficients of the components of the middle span 8 are obtained.

[0057] like Figure 4 As shown in the figure, after research, the fatigue condition of the components of the secondary span 7 has a turning point in the secondary span 7. The components of the secondary span 7 are divided into the components of the first span 71 and the components of the second span 72 from the secondary span 7 to obtain the multi-line coefficients of the components at the corresponding positions, so that the fatigue characteristics of the components at different positions can be better reflected, so that the fatigue design of different components at different positions can achieve a safety degree close to the actual requirements, and the component design is more refined. The cable-stayed bridge is divided into three major areas along the longitudinal direction: the auxiliary span, the first span 71, the second span 72, and the middle span. Each area uses the beam end, the auxiliary pier, the middle span of the secondary span, the main tower, and the middle span of the middle span as the control nodes to form a broken line or straight line multi-line coefficient distribution curve, and the multi-line coefficients of the components between the control points are interpolated. After research, it is found that the fatigue conditions of the same components of auxiliary span 6, first side span 71, second side span 72 and middle span 8 are linearly distributed along the longitudinal direction of the bridge in their respective regions. By obtaining the multi-line coefficients of the components at both ends of each region and then obtaining the multi-line coefficients of the components in the corresponding region by interpolation, the fatigue conditions of the components in the corresponding region can be better reflected. It can also avoid the use of an exhaustive method that makes it impossible to implement.

[0058] Specifically, first obtain the multi-line coefficient of the component at the beam end 91 of the cable-stayed bridge, obtain the multi-line coefficient of the component at the auxiliary pier 92 of the cable-stayed bridge, obtain the multi-line coefficient of the component in the secondary side span 7 of the cable-stayed bridge, obtain the multi-line coefficient of the component at the bridge tower 93 of the cable-stayed bridge, and obtain the multi-line coefficient of the component in the middle span 8 of the cable-stayed bridge;

[0059] Then, the multi-line coefficients of the components at the beam end 91 of the cable-stayed bridge and the multi-line coefficients of the components at the auxiliary pier 92 of the cable-stayed bridge are interpolated to obtain the multi-line coefficients of the components at the auxiliary span 6 of the cable-stayed bridge; the multi-line coefficients of the components at the auxiliary pier 92 of the cable-stayed bridge and the multi-line coefficients of the components in the secondary span 7 of the cable-stayed bridge are interpolated to obtain the multi-line coefficients of the components at the second span 72 of the cable-stayed bridge; the multi-line coefficients of the components at the bridge tower 93 of the cable-stayed bridge and the multi-line coefficients of the components in the middle span 8 of the cable-stayed bridge are interpolated to obtain the multi-line coefficients of the components at the middle span 8 of the cable-stayed bridge. Reference Figure 4 , γ 1 is the multi-line coefficient of a component at the beam end 91 of the cable-stayed bridge, γ 2 is the multi-line coefficient of the member at the auxiliary pier 92 of the cable-stayed bridge, γ 3 is the multi-line coefficient of the member in the 7th span of the secondary side span of the cable-stayed bridge, γ 4 is the multi-line coefficient of the member at tower 93 of the cable-stayed bridge, γ 5 is the multi-line coefficient of the components in the middle span 8 of the cable-stayed bridge. According to the above two γ 1 , two γ 2 , two γ 3 , two γ 4 and a γ 5 The multi-line coefficients of the component with a total of 9 control points form a broken line multi-line coefficient distribution curve, and then the multi-line coefficients of the component in the area are obtained by interpolating the multi-line coefficients of the component at the two control points corresponding to each area. 1 and γ 2 The interpolated value is used to obtain the multi-line coefficient of this component of the auxiliary span 6 of the cable-stayed bridge.

[0060] In this embodiment, the railway line with the maximum live load of the next / last railway can also be used as the single-line fatigue load, and the different internal force effects of specific components can be obtained. The corresponding fatigue load system and reduction factor are multiplied according to the specification, and the comprehensive fatigue stress is obtained after combination as the fatigue design value.

[0061] In this embodiment, a specific multi-line coefficient of a double-deck four-track railway steel truss cable-stayed bridge structure is provided. The double-deck four-track railway steel truss cable-stayed bridge includes 101 and a lower deck system 102, such as Figure 3As shown, the upper bridge deck system 101 is located directly above the lower bridge deck system 102, two railways 103 are arranged on the upper bridge deck system 101, and two railways 103 are arranged on the lower bridge deck system 102. The width of the upper bridge deck system 101 is consistent with that of the lower bridge deck system 102, and the two railways 103 of the upper bridge deck system 101 are located directly above the two railways 103 of the lower bridge deck system 102;

[0062] When all railways 103 are high-speed railways or intercity railways, the polyline coefficients corresponding to the stresses of the components of the beam end 91, the auxiliary pier 92, the middle span of the secondary side span 7, the bridge tower 93 and the middle span 8 of the cable-stayed bridge are as follows:

[0063]

[0064] ; In the above table, the multi-line coefficient of the axial force of the upper chord at the beam end is 2.15, the multi-line coefficient of the axial force of the lower chord at the beam end is 2.15, and the multi-line coefficient of the axial force of the diagonal web at the beam end is 1.80; the multi-line coefficient of the in-plane secondary bending moment of the lower chord at the beam end is 1.50; the in-plane secondary bending moment of the diagonal web at the beam end is 1.60; the in-plane secondary bending moment of the diagonal web in the secondary side span is 1.80; and so on, the multi-line coefficients of different control points, different components, and different internal forces can be obtained.

[0065] When all railways 103 are passenger and freight co-line railways, the polyline coefficients corresponding to the stresses of the components of the beam end 91, auxiliary pier 92, the middle span of the secondary side span 7, the bridge tower 93 and the middle span 8 of the cable-stayed bridge are as follows:

[0066]

[0067] , this table is read in the same way as the table above.

[0068] When the double-deck four-track railway steel truss cable-stayed bridge adopts the above structure, the polyline coefficients of the corresponding forces of the corresponding components in the corresponding area can be directly obtained by interpolation based on the polyline coefficients of the forces of the components at the end positions of the above area, so that the corresponding components in the corresponding area can be quickly designed.

[0069] This embodiment subdivides the multi-line coefficients corresponding to different regions, different components, and different internal force types according to the stress characteristics of the double-deck four-track railway steel truss cable-stayed bridge. Compared with the single value in the specification, it can better reflect the fatigue characteristics of different components in different regions, so that the fatigue design of different components can achieve a safety degree close to the actual requirements, and the component design is more refined. On this basis, the structural dimensions of some rods can be optimized, and even the cross-sectional types of components can be optimized to achieve the purpose of saving costs and facilitating construction.

[0070] In this embodiment, taking the relatively controlled diagonal web member as an example, the I-shaped cross section cannot meet the fatigue design requirements by adopting the standard value, so a box-shaped cross section with a larger cross-sectional area needs to be adopted. The fatigue stress amplitude corresponding to the box-shaped member is lower than that of the I-shaped member, so the cross-sectional size of the box-shaped member needs to be further increased, resulting in an increase in the size of the corresponding node plate and the size of the corresponding bolt group, causing further waste. However, by adopting the fatigue design method of the double-deck four-track railway steel truss cable-stayed bridge of the present invention, an I-shaped member can be used as the diagonal web member, which saves investment and facilitates construction and later maintenance work.

[0071] Although this method still adopts the method of single-line loading × multi-line coefficient, the multi-line coefficient is subdivided according to the structural stress characteristics, the region where the component is located, the component type, and the internal force type. For specific components, different internal force components are combined and valued according to the corresponding multi-line coefficient to evaluate their fatigue performance.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fatigue design method for a double - layer four - line railway steel truss girder cable - stayed bridge, characterized in that, the multi - line coefficients of different components of the cable - stayed bridge are obtained, and then the corresponding components are designed according to the multi - line coefficients of the components, where the components include the upper chord (1), the lower chord (2), the diagonal web member (3), the vertical web member (4) and the stay cable (5); when obtaining the multi - line coefficient of the upper chord (1), the multi - line coefficient of the axial force of the upper chord (1) and the multi - line coefficient of the in - plane secondary moment are obtained, and the upper chord (1) is designed according to the multi - line coefficient of the axial force of the upper chord (1) and the multi - line coefficient of the in - plane secondary moment; when obtaining the multi - line coefficient of the lower chord (2), the multi - line coefficient of the axial force of the lower chord (2) and the multi - line coefficient of the in - plane secondary moment are obtained, and the lower chord (2) is designed according to the multi - line coefficient of the axial force of the lower chord (2) and the multi - line coefficient of the in - plane secondary moment; when obtaining the multi - line coefficient of the diagonal web member (3), the multi - line coefficient of the axial force of the diagonal web member (3), the multi - line coefficient of the in - plane secondary moment and the multi - line coefficient of the out - of - plane moment are obtained, and the diagonal web member (3) is designed according to the multi - line coefficient of the axial force of the diagonal web member (3), the multi - line coefficient of the in - plane secondary moment and the multi - line coefficient of the out - of - plane moment; when obtaining the multi - line coefficient of the vertical web member (4), the multi - line coefficient of the axial force of the vertical web member (4), the multi - line coefficient of the in - plane secondary moment and the multi - line coefficient of the out - of - plane moment are obtained, and the vertical web member (4) is designed according to the multi - line coefficient of the axial force of the vertical web member (4), the multi - line coefficient of the in - plane secondary moment and the multi - line coefficient of the out - of - plane moment; when obtaining the multi - line coefficient of the stay cable (5), the multi - line coefficient of the axial force of the stay cable (5) is obtained, and the stay cable (5) is designed according to the multi - line coefficient of the axial force of the stay cable (5).

2. The fatigue design method for a double - layer four - line railway steel truss girder cable - stayed bridge according to claim 1, characterized in that, the components of the cable - stayed bridge are divided into the components of the auxiliary span (6), the components of the secondary side span (7) and the components of the main span (8). When obtaining the multi - line coefficients of different components of the cable - stayed bridge, the multi - line coefficients of the components of the auxiliary span (6), the multi - line coefficients of the components of the secondary side span (7) and the multi - line coefficients of the components of the main span (8) are obtained.

3. The fatigue design method for a double - layer four - line railway steel truss girder cable - stayed bridge according to claim 2, characterized in that, the components of the secondary side span (7) are divided into the components of the first secondary side span (71) and the components of the second secondary side span (72) from the mid - span of the secondary side span (7). When obtaining the multi - line coefficients of the components of the secondary side span (7), the multi - line coefficients of the components of the first secondary side span (71) and the multi - line coefficients of the components of the second secondary side span (72) are obtained.

4. The fatigue design method for a double - layer four - line railway steel truss girder cable - stayed bridge according to claim 3, characterized in that, the multi - line coefficients of the components at the beam end (91) of the cable - stayed bridge are obtained, the multi - line coefficients of the components at the auxiliary pier (92) of the cable - stayed bridge are obtained, the multi - line coefficients of the components at the mid - span of the secondary side span (7) of the cable - stayed bridge are obtained, the multi - line coefficients of the components at the bridge tower (93) of the cable - stayed bridge are obtained, and the multi - line coefficients of the components at the mid - span of the main span (8) of the cable - stayed bridge are obtained; The multi-line coefficient of the components of the auxiliary span (6) of the cable-stayed bridge is obtained by taking the interpolation value according to the multi-line coefficients of the components at the beam end (91) of the cable-stayed bridge and the multi-line coefficients of the components at the auxiliary pier (92) of the cable-stayed bridge; the multi-line coefficient of the components of the first side span (71) of the cable-stayed bridge is obtained by taking the interpolation value according to the multi-line coefficients of the components at the auxiliary pier (92) of the cable-stayed bridge and the multi-line coefficients of the components at the mid-span of the secondary side span (7) of the cable-stayed bridge; the multi-line coefficient of the components of the second side span (72) of the cable-stayed bridge is obtained by taking the interpolation value according to the multi-line coefficients of the components at the mid-span of the secondary side span (7) of the cable-stayed bridge and the multi-line coefficients of the components at the bridge tower (93) of the cable-stayed bridge; the multi-line coefficient of the components of the main span (8) of the cable-stayed bridge is obtained by taking the interpolation value according to the multi-line coefficients of the components at the bridge tower (93) of the cable-stayed bridge and the multi-line coefficients of the components at the mid-span of the main span (8) of the cable-stayed bridge.

5. The fatigue design method of the double-deck four-track railway steel truss girder cable-stayed bridge according to claim 4, characterized in that The double-deck four-track railway steel truss girder cable-stayed bridge includes an upper deck system (101) and a lower deck system (102). The upper deck system (101) is located directly above the lower deck system (102). There are two railways (103) on the upper deck system (101), and there are two railways (103) on the lower deck system (102). The upper deck system (101) has the same width as the lower deck system (102). The two railways (103) on the upper deck system (101) are located directly above the two railways (103) on the lower deck system (102); When all the railways (103) are high-speed railways or intercity railways, the multi-line coefficients corresponding to the stresses of the components at the beam end (91), auxiliary pier (92), mid-span of the secondary side span (7), bridge tower (93), and mid-span of the main span (8) of the cable-stayed bridge are as follows in the table: When all the railways (103) are passenger and freight co-line railways, the multi-line coefficients corresponding to the stresses of the components at the beam end (91), auxiliary pier (92), mid-span of the secondary side span (7), bridge tower (93), and mid-span of the main span (8) of the cable-stayed bridge are as follows in the table:

6. The fatigue design method of the double-deck four-track railway steel truss girder cable-stayed bridge according to claim 1, characterized in that By studying the probability of train encounters, the damage degree in various train encounter situations is studied to obtain the calculation expression of the multi-line coefficient. Through the analysis of the mechanical characteristics of the double-deck four-track railway steel truss girder, the load effects and transverse distribution coefficients under the action of each line of trains are studied. Then, according to the calculation expression of the multi-line coefficient of the train encounter probability, the load effects, and the transverse distribution coefficients, the multi-line coefficient of the components is obtained.

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