Large-span double-layer highway-railway dual-purpose steel truss composite beam cable-stayed bridge and design method thereof

Abstract

The invention relates to a large-span double-layer highway-railway dual-purpose steel truss composite beam cable-stayed bridge and a design method thereof, and the large-span double-layer highway-railway dual-purpose steel truss composite beam cable-stayed bridge comprises a main steel truss which is provided with an upper layer longitudinal and transverse beam and a lower layer longitudinal and The main span comprises an upper-layer UHPC plate on the upper-layer longitudinal and transverse beams, a steel bridge deck plate on the lower-layer longitudinal and transverse beams and a lower-layer UHPC plate; the upper-layer UHPC board and the upper-layer longitudinal and transverse beams are combined to form a main-span upper-layer bridge deck, and the lower-layer longitudinal and transverse beams, the lower-layer steel bridge deck and the lower-layer UHPC board are combined to form a main-span lower-layer bridge deck; the side spans are located on the two sides of the main span in the bridge length direction and comprise common concrete bridge deck slabs on the upper-layer longitudinal and transverse beams, steel bridge deck slabs on the lower-layer longitudinal and transverse beams and lower-layer UHPC plates; the common concrete bridge deck and the upper-layer longitudinal and transverse beams are combined to form a side-span upper-layer bridge deck, and the lower-layer longitudinal and transverse beams, the lower-layer steel bridge deck and the lower-layer UHPC plates are combined to form a side-span lower-layer bridge deck. By means of the scheme, the cable-stayed bridge designed in a large-span scene has good economical efficiency and stability.

Description

Technical Field

[0001] The invention relates to the technical field of cable-stayed bridge design, and in particular to a large-span double-deck highway-rail dual-purpose steel truss combined beam cable-stayed bridge and a design method thereof. Background Art

[0002] At present, the main beams of large-span dual-purpose cable-stayed bridges for road and railway are basically in the form of steel trusses. Since orthotropic steel bridge decks have the advantages of light weight, large bearing capacity, and easy manufacturing and installation, steel truss railway and highway bridge decks for dual-purpose bridges for road and railway basically adopt this bridge deck system. Since there are sleepers and ballast under the railway track, which have a good diffusion effect on the train wheel load, the problem of fatigue cracking of railway bridge decks is not prominent; but for highways, fatigue cracking often occurs in orthotropic steel bridge decks, and steel bridge deck pavement is also prone to diseases.

[0003] The steel truss combined beam bridge deck system has the advantages of high structural rigidity, good economy, and low comprehensive cost of later operation and maintenance. It can not only effectively solve the problem of fatigue cracking of steel bridge decks, but also solve the problem that the bridge deck pavement is easy to damage and difficult to repair. At present, it has been applied in some small and medium-span dual-use cable-stayed bridges for highway and railway. However, the thickness of the concrete bridge deck of the steel truss combined beam is mostly above 25cm, the beam body is heavy, and the overall economy is poor, which limits the development and application of the steel truss combined beam in the direction of larger spans. At the same time, for multifunctional composite bridges with increasingly scarce bridge resources, there are double-deck dual-use bridges for highway and railway, with expressways arranged on the upper level, first-class highways arranged on both sides of the lower level, and railways arranged in the middle. For such double-deck bridges, there are highways on both the upper and lower levels. How to design the highway bridge deck directly affects the overall stress of the main beam structure and the performance of the highway bridge deck, which is the key technology and problem in the design of such large-span double-deck dual-use bridges for highway and railway.

[0004] Therefore, for large-span double-deck dual-purpose highway and railway bridges exceeding one kilometer level, it is necessary to invent a new type of steel truss combined beam structure suitable for ultra-large span cable-stayed bridges, which can effectively avoid or solve the fatigue and paving problems of highway steel bridge decks, and reasonably solve the overall economic problems of the structure. Summary of the invention

[0005] The present application provides a large-span double-deck steel truss combined beam cable-stayed bridge for road and rail use and a design method thereof, which can solve the relevant technical problems in the above-mentioned background technology.

[0006] In the first aspect, the embodiment of the present application provides a large-span double-deck steel truss combined beam cable-stayed bridge for road and railway use, which adopts the following technical solution:

[0007] A large-span double-deck steel truss combined beam cable-stayed bridge for both road and rail use, comprising:

[0008] A steel main truss with upper longitudinal and transverse beams and lower longitudinal and transverse beams;

[0009] A main span, comprising an upper UHPC plate arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC plate arranged above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC plate is less than the thickness of the upper UHPC plate; the upper UHPC plate is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the main span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC plate are combined to form a lower bridge deck of the main span;

[0010] The side span is located on both sides of the main span in the direction of the bridge length, and includes an ordinary concrete bridge deck arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC board arranged above at least a portion of the steel bridge deck; the upper ordinary concrete bridge deck is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the side span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC board are combined to form a lower bridge deck of the side span.

[0011] In combination with the first aspect, in one embodiment, the steel bridge deck comprises a highway steel bridge deck and a railway steel bridge deck distributed in the bridge width direction, and the lower layer UHPC plate is arranged above the highway steel bridge deck.

[0012] In a second aspect, an embodiment of the present application provides a design method for a large-span double-deck steel truss combined beam cable-stayed bridge as described above, which comprises the following steps:

[0013] Determine the minimum length of the main span and side span of the bridge;

[0014] Determining the minimum thickness requirement of the upper UHPC panel according to the main span length and the construction requirements of the upper UHPC panel;

[0015] Calculate and determine the parameters of the main span girder that uses the upper UHPC slab as the bridge deck of the upper deck of the main span and meets the minimum thickness requirements of the upper UHPC slab and has the lowest cost for the entire bridge;

[0016] According to the main span main beam parameters, the maximum span length requirement of the main span main beam is determined;

[0017] Calculate and determine the main span main beam section length that meets the maximum section length requirements of the main span main beam and has the lowest cost for the entire bridge;

[0018] Determine the minimum length of the side span main beam according to the minimum length of the side span and the length of the main span main beam;

[0019] According to the minimum span length of the side span main beam, the side span main beam parameters that meet the minimum length requirement of the side span, use ordinary concrete as the upper bridge deck of the side span and have the lowest cost for the entire bridge are calculated and determined.

[0020] In conjunction with the second aspect, in one embodiment, determining the minimum thickness requirement of the upper UHPC panel according to the main span length and the construction requirements of the upper UHPC panel comprises the following steps:

[0021] The minimum thickness requirement of the upper UHPC slab is determined according to the main span length and the preset main truss structure parameters, the minimum spacing of the steel bars in the upper UHPC slab, and the thickness requirement of the protective layer.

[0022] In conjunction with the second aspect, in one embodiment, the calculation determines the main span girder parameters with the lowest cost of the entire bridge using the upper UHPC plate as the bridge deck and meeting the minimum thickness requirement of the upper UHPC plate, including the following steps:

[0023] Determine the minimum thickness requirement of the upper UHPC panel as the calculated thickness of the upper UHPC panel;

[0024] Determine the parameters of the main span main beam according to the calculated thickness of the upper UHPC plate;

[0025] Calculating the cost of the entire bridge based on the calculated thickness of the upper UHPC plate and the parameters of the main span main beam;

[0026] According to the preset plate thickness increase, the calculated thickness of the upper UHPC plate is increased, and the cost of the entire bridge is recalculated based on the new calculated thickness of the upper UHPC plate;

[0027] Determine whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0028] If it increases, the main span and main beam parameters corresponding to the last full bridge cost will be used as the final main span and main beam parameters.

[0029] In conjunction with the second aspect, in one embodiment, determining the main span main beam parameters according to the calculated thickness of the upper UHPC plate comprises the following steps:

[0030] Establish a calculation model of the upper bridge deck system with upper longitudinal beams, upper cross beams and upper UHPC panels, apply local wheel loads, and calculate and determine the minimum longitudinal beam spacing and minimum cross section based on the force of the upper UHPC panels;

[0031] According to the preset side span length, based on the minimum longitudinal beam spacing, the minimum cross-section and the calculated thickness of the upper UHPC plate, the overall calculation model of the bridge is established and after the load is applied, the main span main beam parameters are calculated and determined according to the construction requirements.

[0032] In conjunction with the second aspect, in one embodiment, the calculation to determine the main span main beam inter-section length that meets the maximum inter-section length requirement of the main span main beam and has the lowest cost of the entire bridge includes the following steps:

[0033] Determine that the maximum length required for the maximum inter-node length of the main span main beam is the calculated inter-node length of the main span main beam;

[0034] Calculating the cost of the entire bridge based on the preset side span length and the calculated length of the main span main beam;

[0035] According to the preset main span inter-section length reduction, the calculated length of the main span main beam is reduced, and the cost of the entire bridge is recalculated based on the new calculated length of the main span main beam inter-section;

[0036] Determine whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0037] If it increases, the calculated length of the main span main beam section corresponding to the last full bridge cost shall be used as the final main span main beam section length.

[0038] In combination with the second aspect, in one embodiment, determining the minimum inter-section length of the side span main beam according to the minimum length of the side span and the inter-section length of the main span main beam comprises the following steps:

[0039] Determine the total number of main span sections according to the main span length and the main span main beam section length;

[0040] The minimum span length requirement of the side span is determined based on the total number of spans of the main span and the minimum length of the side span.

[0041] In combination with the second aspect, in one embodiment, the calculation and determination of the side span main beam parameters that meet the minimum length requirement of the side span, use ordinary concrete as the upper deck of the side span and have the lowest overall bridge cost according to the minimum span length of the side span main beam comprises the following steps:

[0042] Determining the minimum length of the side span as the calculated length of the side span;

[0043] Determine the parameters of the side span girder using ordinary concrete as the upper deck of the side span based on the calculated length of the side span and the minimum span length of the side span girder;

[0044] Calculate the cost of the entire bridge according to the side span main beam parameters;

[0045] According to a preset increase in the side span length, the length of the side span is increased, and the cost of the entire bridge is recalculated based on the new side span length;

[0046] Determine whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0047] If it increases, the side span length corresponding to the last full bridge cost is used as the final side span length, and the side span main beam parameters corresponding to the side span length are determined.

[0048] In combination with the second aspect, in one embodiment, determining the parameters of the side span main beam using ordinary concrete as the side span upper deck based on the calculated length of the side span and the minimum span length of the side span main beam comprises the following steps:

[0049] According to the number of cables between the side span main tower and the auxiliary pier, calculate the average cable angle coefficient between the side span main tower and the auxiliary pier;

[0050] Calculate the first thickness of the common concrete bridge deck of the steel truss combined beam between the side span main tower and the auxiliary pier, and the second thickness of the common concrete bridge deck of the steel truss combined beam between the side pier and the auxiliary pier according to the average cable angle coefficient;

[0051] The side span main beam parameters are determined according to the first thickness and the second thickness.

[0052] The beneficial effects brought by the technical solution provided in the embodiments of the present application include:

[0053] The large-span dual-purpose cable-stayed bridge for highway and railway obtained by the design method provided by the present application has an upper deck of the main span made of UHPC plates, so that the main span as a whole forms a main span ultra-high performance concrete steel truss combined beam. Compared with ordinary concrete steel truss combined beams, it has the characteristics of light weight and high tensile strength, and can make the main span exceed one kilometer, which meets the use requirements of large spans; at the same time, the side spans use thicker ordinary concrete steel truss combined beams, which can shorten the main beam length as much as possible and save costs; in addition, in the process of scheme design, the present application first determines the main span main beam parameters with the lowest total bridge cost when the upper UHPC plate is used as the bridge deck of the upper deck of the main span and meets the relevant requirements, and then calculates the main span main beam inter-section length and the minimum inter-section length of the side span main beam based on the main span main beam parameters. Further, the side span main beam parameters with the lowest total bridge cost when ordinary concrete is used as the bridge deck can be determined by using the minimum inter-section length of the side span main beam, and finally the main span main beam parameters and the side span main beam parameters obtained have the lowest possible cost level. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0055] Figure 1 This is a standard cross-sectional view of a main span node of a large-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to an embodiment of the application;

[0056] Figure 2It is a standard cross-sectional view of the main span ultra-high performance concrete steel truss combined beam without cross beam of a large-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge in the application embodiment;

[0057] Figure 3 It is a standard cross-sectional view of a side span steel truss combined beam node of a large-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to an embodiment of the application;

[0058] Figure 4 It is a standard cross-sectional view of the side span steel truss combined beam without cross beam of a large span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge in the embodiment of the application;

[0059] Figure 5 is a general elevation view of a long-span cable-stayed bridge to which the present invention is applied;

[0060] Figure 6 The present invention is a flowchart of a design method for a large-span double-deck steel truss combined beam cable-stayed bridge for road and railway use according to an embodiment of the application.

[0061] Reference numerals:

[0062] 11. Upper UHPC board; 111. Upper ordinary concrete bridge deck; 21. Lower UHPC board; 22. Highway steel bridge deck; 23. Railway steel bridge deck; 31. Upper chord; 32. Lower chord; 41. Cross-joint; 42. Hanging column. DETAILED DESCRIPTION

[0063] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0064] The embodiment of the present application provides a large-span double-deck dual-purpose road-rail steel truss combined beam cable-stayed bridge and a design method thereof, which can solve the problem in the prior art that the bridge structure design and cost of large-span dual-purpose road-rail bridges of over a kilometer are difficult to effectively calculate.

[0065] In a first aspect, the present application provides a large-span double-deck steel truss combined beam cable-stayed bridge for road and rail use.

[0066] A large-span double-deck steel truss combined beam cable-stayed bridge for both road and rail use, comprising:

[0067] A steel main truss with upper longitudinal and transverse beams and lower longitudinal and transverse beams;

[0068] A main span, comprising an upper UHPC (ultra-high performance concrete) plate arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC plate 21 arranged above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC plate 21 is less than the thickness of the upper UHPC plate 11; the upper UHPC plate 11 is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the main span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC plate 21 are combined to form a lower bridge deck of the main span;

[0069] The side span is located on both sides of the main span in the direction of the bridge length, and includes an ordinary concrete bridge deck arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC plate 21 arranged above at least part of the steel bridge deck; the upper ordinary concrete bridge deck 111 is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the side span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC plate 21 are combined to form a lower bridge deck of the side span.

[0070] Furthermore, in one embodiment, the steel bridge deck comprises a highway steel bridge deck 22 and a railway steel bridge deck 23 distributed in the bridge width direction, and the lower layer UHPC plate 21 is arranged above the highway steel bridge deck.

[0071] Specifically, in this embodiment, the main span includes an upper UHPC plate 11, a lower UHPC plate 21, a highway steel bridge deck 22, a railway steel bridge deck 23, a steel main truss, an upper longitudinal and transverse beam, a lower longitudinal and transverse beam, a cross-joint 41, and a suspender 42. The upper UHPC plate 11 is combined with the upper longitudinal and transverse beams and the top surface of the upper chord 31 of the steel main trusses on both sides through shear keys to form the upper bridge deck of the main span; the lower UHPC plate 21 and the highway steel bridge deck 22 are connected through shear keys to form a highway UHPC composite bridge deck of the lower layer of the main span; the lower highway steel bridge deck 22 is welded to the lower railway steel bridge deck 23 to finally form the lower bridge deck of the main span; the upper and lower bridge decks of the main span are connected with the upper chord 31 and the lower chord 32 of the steel main trusses on both sides, and participate in the overall force of the structure; a cross-joint 41 and a suspender 42 are arranged at each node.

[0072] The side span includes an upper ordinary concrete bridge deck 111, a lower UHPC board 21, a lower highway steel bridge deck 22, a lower railway steel bridge deck 23, a steel main truss, an upper longitudinal and transverse beam, a lower longitudinal and transverse beam, a cross-joint 41, and a suspender 42. The upper ordinary concrete bridge deck 111 is combined with the upper longitudinal and transverse beams and the top surface of the upper chord rods 31 of the main trusses on both sides through shear keys to form the upper bridge deck of the side span; the lower UHPC board 21 and the lower highway steel bridge deck 22 are connected through shear keys to form the lower highway UHPC composite bridge deck of the side span; at the same time, the lower highway steel bridge deck 22 and the lower railway steel bridge deck 23 are welded to finally form the lower bridge deck of the side span; the upper and lower bridge decks of the side span are connected to the upper and lower chord rods 32 of the main trusses to participate in the overall force of the structure; a cross-joint 41 and a suspender 42 are set at each node.

[0073] Compared with the prior art, the advantages of the present invention are:

[0074] (1) The upper deck of the main span is formed by combining the upper UHPC plate 11 with the upper longitudinal and transverse beams and the top surface of the upper chord rods 31 of the main trusses on both sides to form an upper combined deck, which avoids the fatigue and paving problems of highway steel bridge decks; compared with ordinary concrete plates, the upper UHPC plates of the main span are thin, light, have no shrinkage and low creep after steaming, and have strong tensile resistance, which reduces the tensile stress value and range of the upper concrete deck of the main span;

[0075] (2) The lower highway deck of the main span and side span is formed by connecting the steel deck plate and UHPC plate through shear keys to form a lower highway composite deck. The UHPC plate is used to improve the local stiffness of the highway steel deck and enhance the ability of the highway steel deck to resist fatigue and pavement problems; the steel deck is used to improve the overall tensile resistance of the lower deck to adapt to the tension problem of the main beam of the large-span double-deck cable-stayed bridge under the action of live loads;

[0076] (3) The main span adopts the upper UHPC combined bridge deck, the lower two sides of the road composite bridge deck, and the middle railway steel bridge deck, which forms the main span ultra-high performance concrete steel truss combined beam, which has the characteristics of light weight and high tensile strength, and can achieve a main span of more than one kilometer for cable-stayed bridges;

[0077] (4) The upper deck of the side span is made of thicker ordinary concrete. While meeting the crack resistance requirements of the upper ordinary concrete deck, the weight of the side span main beam can be increased, thereby increasing the pressure on the main span, thereby shortening the main beam length as much as possible and saving construction costs.

[0078] In the second aspect, the present application provides a design method for a large-span double-deck highway-rail dual-purpose steel truss combined beam cable-stayed bridge as described above, which adopts the following technical solution:

[0079] A design method for a long-span double-deck highway-rail dual-purpose steel truss combined beam cable-stayed bridge comprises the following steps:

[0080] S100, determine the minimum length of the main span and side span of the bridge;

[0081] Among them, the length of the main span of the bridge will be determined according to the requirements of navigation, hydrology, topography, etc., which is a prior art in this field and will not be elaborated in this application. The minimum length of the side span is determined by controlling the maximum specification of the outermost cable of the side span based on the principle that the horizontal component of the constant load of the side and main span segments at the tower top is equal, under the premise that the side span crosses the embankments and roads on both sides, and then determining the minimum length of the side span.

[0082] S200, determining the minimum thickness requirement of the upper UHPC panel 11 according to the main span length and the structural requirements of the upper UHPC panel 11;

[0083] The minimum thickness requirement of the upper UHPC plate 11 will be determined specifically based on the main span length and the preset main truss structural parameters, the minimum spacing of the steel bars in the upper UHPC plate 11, and the thickness requirement of the protective layer. The preset main truss structural parameters specifically include the main truss internode length, the longitudinal and transverse beam arrangement of the bridge deck, and other parameters initially planned based on the main span length.

[0084] S300, calculating and determining the parameters of the main span girder that uses the upper UHPC plate 11 as the bridge deck of the upper bridge deck of the main span and meets the minimum thickness requirement of the upper UHPC plate 11 and has the lowest cost for the entire bridge;

[0085] Specifically, S300 includes the following steps:

[0086] S310, determining the minimum thickness of the upper UHPC plate 11 as the calculated thickness of the upper UHPC plate 11;

[0087] S320, determining the main span main beam parameters according to the calculated thickness of the upper UHPC plate 11;

[0088] Exemplarily, a calculation model of an upper bridge deck system with an upper longitudinal beam, an upper cross beam and an upper UHPC plate 11 is first established, and a local wheel load is applied. According to the force of the upper UHPC plate 11, the minimum longitudinal beam spacing and the minimum cross section are calculated and determined; after the minimum longitudinal beam spacing and the minimum cross section are obtained, the overall calculation model of the bridge is further established based on the preset side span length (in this embodiment, the side span length is first assumed to be 0.5 times the main span length) and the minimum longitudinal beam spacing, the minimum cross section and the calculated thickness of the upper UHPC plate 11. After the load is applied to the overall calculation model of the bridge, other construction parameters of the main span main beam are calculated and determined according to the construction requirements, and finally the complete parameters of the main span main beam are obtained.

[0089] S330, calculating the cost of the entire bridge based on the calculated thickness of the upper UHPC plate 11 and the main span main beam parameters;

[0090] S340. Increase the calculated thickness of the upper UHPC slab 11 according to a preset slab thickness increment, and recalculate the total bridge cost based on the new calculated thickness of the upper UHPC slab 11. The preset slab thickness increment can be 1 cm or other reasonable values, and the present application does not make further limitations thereto.

[0091] S350. Determine whether the total bridge cost has increased compared to the previous total bridge cost.

[0092] S360. If it has increased, use the main span main girder parameters corresponding to the previous total bridge cost as the final main span main girder parameters; if it has not increased, repeat steps S340 - S360.

[0093] With such a setting, starting from the minimum thickness of the upper UHPC slab 11 as the calculated thickness, the main span main girder parameters corresponding to the calculated thickness are calculated, and the final corresponding total bridge cost is obtained. Those skilled in the art can understand that as the thickness of the upper UHPC slab 11 gradually increases and other structures of the main span main girder parameters change adaptively, in the initial stage of the change, since the thickness of the upper UHPC slab 11 has not reached the most appropriate level, the total bridge cost will be affected by the fact that the high performance of the upper UHPC slab 11 can be fully utilized during this stage, resulting in relatively smaller requirements for other components, and thus ultimately showing a gradually decreasing trend until the thickness of the upper UHPC slab 11 exceeds a certain value, making its performance unable to be fully utilized at this time, and at the same time also affecting other components, ultimately resulting in an increasing region of the total bridge cost. Therefore, when the present application determines the first price increase, the main span main girder parameters corresponding to the previous total bridge cost and the calculated thickness of the upper UHPC slab 11 are used as the final main span main girder parameters and the thickness of the upper UHPC slab 11.

[0094] S400. Determine the maximum panel length requirement of the main span main girder according to the main span main girder parameters.

[0095] Specifically, according to the main span main girder parameters, determine the weight per unit length q of the main span steel truss composite girder and the maximum specification Tmax of the existing stay cables, and calculate and determine the maximum panel length lmax of the main span steel truss composite girder = Tmax × cosθmid / q; where cosθmid is the average angle between the upper stay cables of the main span and the horizontal direction.

[0096] S500. Calculate and determine the panel length of the main span main girder that meets the maximum panel length requirement of the main span main girder and has the lowest total bridge cost.

[0097] Specifically, S500 includes the following steps:

[0098] S510, determining that the maximum length required for the maximum inter-node length of the main span main beam is the calculated inter-node length of the main span main beam;

[0099] S520, calculating the cost of the entire bridge based on the preset side span length and the calculated length of the inter-section of the main span main beam; wherein the preset side span length is 0.5 times the main span length. When calculating the cost of the entire bridge, the calculated length of the inter-section determined in S510 is used as the basis, an overall calculation model of the bridge is established, loads are applied, sizes of other components are calculated, and the engineering quantity of the entire bridge is calculated, thereby calculating the total cost of the entire bridge.

[0100] S530. According to the preset main span section length reduction, the calculated length of the main span main beam is reduced, and the cost of the entire bridge is recalculated based on the new main span section length calculation; wherein, the main span section length reduction is 0.5 m in this embodiment, and other reasonable values ​​may be taken in other embodiments.

[0101] S540, determining whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0102] S550: If it is increased, the calculated length of the main span main beam section corresponding to the last full bridge cost is used as the final main span main beam section length. If it is not increased, repeat steps S530-S550.

[0103] By setting it in this way, it is possible to use the determined main span main beam parameters as a basis and further use the same cost comparison principle to determine the main span main beam segment length with the lowest cost.

[0104] S600, determining the minimum inter-section length of the side span main beam according to the minimum side span length Lbmin and the inter-section length of the main span main beam;

[0105] Specifically, the total number of main span sections N will be determined based on the main span length and the main span main beam section length; and the minimum section length requirement of the side span will be determined based on the total number of main span sections and the minimum length of the side span. The calculation formula is as follows:

[0106] The minimum internode length of the side span lbmin = Lbmin × 2 / N;

[0107] S700. According to the minimum span length of the side span main beam, calculate and determine the side span main beam parameters that meet the minimum length requirement of the side span, use ordinary concrete as the upper bridge deck of the side span and have the lowest overall bridge cost.

[0108] Specifically, S700 includes the following steps:

[0109] S710, determining the minimum length of the side span as the calculated length of the side span;

[0110] S720, based on the calculated length of the side span and the minimum span length of the side span main beam, determine the parameters of the side span main beam using ordinary concrete as the upper deck of the side span;

[0111] Among them, S720 includes:

[0112] S721. Calculate the average cable angle coefficient between the side span main tower and the auxiliary pier according to the number of cables between the side span main tower and the auxiliary pier;

[0113] Specifically, the cables between the side span main tower and the auxiliary pier are numbered 1-n, and the average cable angle coefficient α between the side span main tower and the auxiliary pier is calculated;

[0114] Where cosθmiddle is the average angle between the inclined cables on the main span and the horizontal direction, and cosθside is the average angle between the inclined cables on the side span and the horizontal direction.

[0115] S722, calculating, based on the average cable angle coefficient, a first thickness of the ordinary concrete bridge deck of the steel truss combined beam between the side span main tower and the auxiliary pier, and a second thickness of the ordinary concrete bridge deck of the steel truss combined beam between the side pier and the auxiliary pier;

[0116] Specifically, the first thickness will be adaptively derived and calculated based on the principle that the horizontal force components of the side and main span segments are equal at the tower top, combined with the weight of the main span segment, the length of the main span segment, the length of the side span segment, the average cable angle coefficient α and the weight of the side span segment.

[0117] When calculating the second thickness, it is necessary to establish an overall calculation model of the bridge, apply loads, calculate the negative reactions of the side piers and auxiliary piers, and calculate the thickness of the ordinary concrete slab of the steel truss combined beam between the side pier and the auxiliary pier based on the principle that the negative reactions are equal to the weight increment of the concrete slab between the side pier and the auxiliary pier.

[0118] S723. Determine side span main beam parameters according to the first thickness and the second thickness.

[0119] After obtaining the first thickness and the second thickness, the established overall calculation model of the bridge will be modified to determine the side span main beam parameters.

[0120] S730, calculating the cost of the entire bridge according to the side span main beam parameters;

[0121] S740, increasing the length of the side span according to a preset increase in the side span length, and recalculating the cost of the entire bridge based on the new side span length;

[0122] Specifically, based on the determined minimum side span length lbmin, the preset side span length increase is increased, which can be 0.5×N meters, and the new side span length, the first thickness and the second thickness of the ordinary concrete slab are calculated repeatedly, and then the total cost of the whole bridge is calculated;

[0123] S750, determining whether the full-bridge construction cost is increased compared with the previous full-bridge construction cost;

[0124] S760: If it increases, the side span length corresponding to the last full bridge cost is used as the final side span length, and the side span main beam parameters corresponding to the side span length are determined.

[0125] With this arrangement, it is possible to further determine the side span main beam parameters with the lowest cost based on the determined main span main beam parameters, and ultimately achieve a bridge structure solution with a relatively good overall cost.

[0126] Finally, the large-span dual-purpose cable-stayed bridge for highway and railway obtained by the design method provided by the present application, because its main span adopts UHPC plate, the main span as a whole forms a main span ultra-high performance concrete steel truss combined beam, which has the characteristics of light weight and high tensile strength compared with ordinary concrete steel truss combined beam, and can make the main span exceed one kilometer, which meets the use of large span conditions; at the same time, the side span adopts thicker ordinary concrete steel truss combined beam, which can shorten the main beam length as much as possible and save cost; in addition, in the process of scheme design, the present application first determines the main span main beam parameters with the lowest total bridge cost when the upper UHPC plate 11 is used as the bridge deck of the upper bridge deck of the main span and meets the relevant requirements, and then calculates the main span main beam interval length and the minimum interval length of the side span main beam based on the main span main beam parameters. Further, the minimum interval length of the side span main beam can be used to determine the side span main beam parameters with the lowest total bridge cost when ordinary concrete is used as the bridge deck, and finally achieves the main span main beam parameters and side span main beam parameters with the lowest possible cost level.

[0127] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0128] It should be noted that, in this application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0129] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A large-span double-deck steel truss combined beam cable-stayed bridge for both road and rail use. It is characterized in that It includes: A steel main truss with upper longitudinal and transverse beams and lower longitudinal and transverse beams; A main span, comprising an upper UHPC plate arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC plate arranged above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC plate is less than the thickness of the upper UHPC plate; the upper UHPC plate is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the main span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC plate are combined to form a lower bridge deck of the main span; The side span is located on both sides of the main span in the direction of the bridge length, and includes an ordinary concrete bridge deck arranged above the upper longitudinal and transverse beams, a steel bridge deck arranged on the lower longitudinal and transverse beams, and a lower UHPC board arranged above at least a portion of the steel bridge deck; the upper ordinary concrete bridge deck is combined with the upper longitudinal and transverse beams to form an upper bridge deck of the side span, and the lower longitudinal and transverse beams, the lower steel bridge deck and the lower UHPC board are combined to form a lower bridge deck of the side span.

2. The long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 1, It is characterized in that The steel bridge deck comprises a highway steel bridge deck and a railway steel bridge deck distributed in the bridge width direction, and the lower layer UHPC board is arranged above the highway steel bridge deck.

3. A design method for a long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in any one of claims 1 and 2, It is characterized in that It includes the following steps: Determine the minimum length of the main span and side span of the bridge; Determining the minimum thickness requirement of the upper UHPC panel according to the main span length and the construction requirements of the upper UHPC panel; Calculate and determine the parameters of the main span girder that uses the upper UHPC slab as the bridge deck of the upper deck of the main span and meets the minimum thickness requirements of the upper UHPC slab and has the lowest cost for the entire bridge; According to the main span main beam parameters, the maximum span length requirement of the main span main beam is determined; Calculate and determine the main span main beam section length that meets the maximum section length requirements of the main span main beam and has the lowest cost for the entire bridge; Determine the minimum length of the side span main beam according to the minimum length of the side span and the length of the main span main beam; According to the minimum span length of the side span main beam, the side span main beam parameters that meet the minimum length requirement of the side span, use ordinary concrete as the upper bridge deck of the side span and have the lowest cost for the entire bridge are calculated and determined.

4. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 3, It is characterized in that Determining the minimum thickness requirement of the upper UHPC panel according to the main span length and the structural requirements of the upper UHPC panel comprises the following steps: The minimum thickness requirement of the upper UHPC slab is determined according to the main span length and the preset main truss structure parameters, the minimum spacing of the steel bars in the upper UHPC slab, and the thickness requirement of the protective layer.

5. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 3, It is characterized in that The calculation method for determining the main span girder parameters with the upper UHPC slab as the bridge deck and meeting the minimum thickness requirement of the upper UHPC slab and with the lowest cost for the entire bridge comprises the following steps: Determine the minimum thickness requirement of the upper UHPC panel as the calculated thickness of the upper UHPC panel; Determining the parameters of the main span main beam according to the calculated thickness of the upper UHPC plate; Calculating the cost of the entire bridge based on the calculated thickness of the upper UHPC plate and the parameters of the main span main beam; According to the preset plate thickness increase, the calculated thickness of the upper UHPC plate is increased, and the cost of the entire bridge is recalculated based on the new calculated thickness of the upper UHPC plate; Determining whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost; If it increases, the main span and main beam parameters corresponding to the last full bridge cost will be used as the final main span and main beam parameters.

6. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 5, It is characterized in that Determining the parameters of the main span main beam according to the calculated thickness of the upper UHPC plate comprises the following steps: Establish a calculation model of the upper bridge deck system with upper longitudinal beams, upper cross beams and upper UHPC panels, apply local wheel loads, and calculate and determine the minimum longitudinal beam spacing and minimum cross section based on the force of the upper UHPC panels; According to the preset side span length, based on the minimum longitudinal beam spacing, the minimum cross-section and the calculated thickness of the upper UHPC plate, the overall calculation model of the bridge is established and after the load is applied, the main span main beam parameters are calculated and determined according to the construction requirements.

7. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 3, It is characterized in that The calculation to determine the main span main beam inter-section length that meets the maximum inter-section length requirement of the main span main beam and has the lowest overall bridge cost comprises the following steps: Determine that the maximum length required for the maximum inter-node length of the main span main beam is the calculated inter-node length of the main span main beam; Calculating the cost of the entire bridge based on the preset side span length and the calculated length of the main span main beam; According to the preset main span inter-section length reduction, the calculated length of the main span main beam is reduced, and the cost of the entire bridge is recalculated based on the new calculated length of the main span main beam inter-section; Determining whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost; If it increases, the calculated length of the main span main beam section corresponding to the last full bridge cost shall be used as the final main span main beam section length.

8. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 3, It is characterized in that Determining the minimum inter-section length of the side span main beam according to the minimum length of the side span and the inter-section length of the main span main beam comprises the following steps: Determine the total number of main span sections according to the main span length and the main span main beam section length; The minimum span length requirement of the side span is determined based on the total number of spans of the main span and the minimum length of the side span.

9. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 3, It is characterized in that The method of calculating and determining the side span main beam parameters that meet the minimum length requirement of the side span, use ordinary concrete as the upper deck of the side span and have the lowest overall bridge cost based on the minimum internode length of the side span main beam comprises the following steps: Determining the minimum length of the side span as the calculated length of the side span; Determine the parameters of the side span girder using ordinary concrete as the upper deck of the side span based on the calculated length of the side span and the minimum span length of the side span girder; Calculate the cost of the entire bridge according to the side span main beam parameters; According to a preset increase in the side span length, the length of the side span is increased, and the cost of the entire bridge is recalculated based on the new side span length; Determining whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost; If it increases, the side span length corresponding to the last full bridge cost is used as the final side span length, and the side span main beam parameters corresponding to the side span length are determined.

10. The design method of the long-span double-deck steel truss combined beam cable-stayed bridge for road and railway use as claimed in claim 9, It is characterized in that Determining the parameters of the side span main beam using ordinary concrete as the side span upper deck based on the calculated length of the side span and the minimum span length of the side span main beam comprises the following steps: According to the number of cables between the side span main tower and the auxiliary pier, calculate the average cable angle coefficient between the side span main tower and the auxiliary pier; Calculate the first thickness of the common concrete bridge deck of the steel truss combined beam between the side span main tower and the auxiliary pier, and the second thickness of the common concrete bridge deck of the steel truss combined beam between the side pier and the auxiliary pier according to the average cable angle coefficient; The side span main beam parameters are determined according to the first thickness and the second thickness.

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