Long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge and its design method

Abstract

The present application relates to a long-span, double-deck, dual-purpose, road-rail, steel-truss combined-beam cable-stayed bridge and a design method thereof, comprising: a steel main truss, on which upper longitudinal and transverse beams and lower longitudinal and transverse beams are provided; a main span, comprising upper UHPC plates on the upper longitudinal and transverse beams, a steel bridge deck on the lower longitudinal and transverse beams, and a lower UHPC plate; the upper UHPC plates are combined with the upper longitudinal and transverse beams to form the upper bridge deck of the main span, and the lower longitudinal and transverse beams, the lower steel bridge deck, and the lower UHPC plates are combined to form the lower bridge deck of the main span; side spans, located on either side of the main span in the length direction of the bridge, comprising ordinary concrete bridge decks on the upper longitudinal and transverse beams, a steel bridge deck on the lower longitudinal and transverse beams, and a lower UHPC plate; the ordinary concrete bridge decks are combined with the upper longitudinal and transverse beams to form the upper bridge deck of the side span, and the lower longitudinal and transverse beams, the lower steel bridge deck, and the lower UHPC plates are combined to form the lower bridge deck of the side span. The above scheme achieves good economy and stability in a cable-stayed bridge designed for a long span scenario.

Description

Technical Field

[0001] The present 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 rail are basically made of steel trusses. Due to the advantages of orthotropic steel bridge decks such as light weight, large load-bearing capacity, and easy manufacturing and installation, steel truss railway and highway bridge decks for dual-purpose bridges for road and rail basically adopt this bridge deck system. Since there are sleepers and ballast under the railway tracks, which have a good diffusion effect on the train wheel loads, the problem of fatigue cracking in railway bridge decks is not prominent; however, for highways, fatigue cracking often occurs in orthotropic steel bridge decks, and the steel bridge deck pavement is also prone to defects.

[0003] Steel-truss composite beam bridge decks offer the advantages of high structural rigidity, excellent economic efficiency, and low overall maintenance costs. They not only effectively address the problem of fatigue cracking in steel bridge decks, but also address the vulnerability of bridge deck pavements to damage and difficulty repairing. Currently, they are being used in some small and medium-span dual-use cable-stayed bridges. However, the concrete deck thickness of steel-truss composite beams is often over 25 cm, resulting in heavy beam deadweight and poor overall economic efficiency, which limits the development and application of steel-truss composite beams to larger spans. Furthermore, in response to the increasing scarcity of multifunctional composite bridge sites, double-deck dual-use bridges have emerged, with a highway on the upper deck, a first-class highway on either side of the lower deck, and a railway in the middle. With highways on both the upper and lower decks, the design of the highway deck directly affects the overall load bearing of the main beam structure and the performance of the highway deck, making it a key technical and practical challenge in the design of these large-span, double-deck dual-use bridges.

[0004] Therefore, for large-span double-deck dual-use 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 road-rail dual-purpose steel truss combined beam cable-stayed bridge and a design method thereof, which can solve the relevant technical problems in the above-mentioned background technology.

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

[0007] A long-span double-deck steel truss combined beam cable-stayed bridge for 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 disposed above the upper longitudinal and transverse beams, a steel bridge deck disposed on the lower longitudinal and transverse beams, and a lower UHPC plate disposed above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC plate is less than that of the upper UHPC plate; the upper UHPC plate and the upper longitudinal and transverse beams are combined 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 plate arranged above at least a portion of the steel bridge deck; the upper ordinary concrete bridge deck and the upper longitudinal and transverse beams are combined to form the upper bridge deck of the side span, and the lower longitudinal and transverse beams, the lower steel bridge deck, and the lower UHPC plate are combined to form the lower bridge deck of the side span.

[0011] In combination with the first aspect, in one embodiment, the steel bridge deck includes 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 highway-rail dual-purpose steel truss combined beam cable-stayed bridge as described above, comprising 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 based on the main span length and the structural requirements of the upper UHPC panel;

[0015] Calculate and determine the main span girder parameters that minimize the overall bridge cost by using the upper UHPC slab as the deck plate for the upper deck of the main span and meeting the minimum thickness requirements for the upper UHPC slab.

[0016] Determine the maximum span length requirement of the main span main beam according to the main span main beam parameters;

[0017] Calculate and determine the main span main beam span length that meets the maximum span main beam span length requirements and minimizes the overall bridge cost;

[0018] Determine 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;

[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 total bridge cost are calculated and determined.

[0020] In conjunction with the second aspect, in one embodiment, determining the minimum thickness requirement of the upper UHPC panel based on the main span length and the structural requirements of the upper UHPC panel includes the following steps:

[0021] The minimum thickness requirement of the upper UHPC panel is determined based on the main span length, preset main truss structural parameters, the minimum spacing of steel bars in the upper UHPC panel, and the cover thickness requirement.

[0022] In conjunction with the second aspect, in one embodiment, the calculation and determination of the main span girder parameters with the lowest overall bridge cost using the upper UHPC panels as the bridge deck and meeting the minimum thickness requirements of the upper UHPC panels comprises 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] increasing the calculated thickness of the upper UHPC panel according to a preset thickness increase, and recalculating the entire bridge cost based on the new calculated thickness of the upper UHPC panel;

[0027] Determining 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 previous 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 panel comprises the following steps:

[0030] A calculation model of the upper bridge deck system with upper longitudinal beams, upper cross beams, and upper UHPC panels was established. Local wheel loads were applied, and the minimum longitudinal beam spacing and minimum cross section were calculated based on the forces acting on the upper UHPC panels.

[0031] According to the preset side span length, based on the minimum longitudinal beam spacing, minimum cross-section and the calculated thickness of the upper UHPC plate, the overall calculation model of the bridge is established and the load is applied. Then, 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 and determination of 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 construction cost includes the following steps:

[0033] Determine the maximum length required for the maximum inter-section length of the main span main beam as the calculated inter-section 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 inter-section of the main span main beam;

[0035] According to the preset reduction in the main span inter-section length, 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 inter-section length of the main span main beam;

[0036] Determining 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 previous full bridge cost will be used as the final main span main beam section length.

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

[0039] Determine the total number of main span intervals according to the main span length and the main span main beam interval 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 span length of the side span.

[0041] In conjunction with the second aspect, in one embodiment, calculating and determining, based on the minimum span length of the side span main beam, the side span main beam parameters that meet the minimum side span length requirement, use ordinary concrete as the side span upper deck, and have the lowest overall bridge cost, includes the following steps:

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

[0043] 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;

[0044] Calculate the cost of the entire bridge based on the side span main beam parameters;

[0045] increasing the length of the side span according to a preset side span length increase, and recalculating the full bridge cost based on the new side span length;

[0046] Determining 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 previous 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 conjunction 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] Calculate the average cable angle coefficient between the side span main tower and the auxiliary pier based on the number of cables between the side span main tower and the auxiliary pier;

[0050] Calculate, based on the average cable angle coefficient, a first thickness of the ordinary concrete bridge deck of the steel truss composite 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 composite beam between the side pier and the auxiliary pier;

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

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

[0053] The large-span dual-use cable-stayed bridge for highway and railway obtained by the design method provided in this application has an upper deck of its main span made of UHPC plates, so that the main span is formed as a main span ultra-high performance concrete steel truss composite beam. Compared with ordinary concrete steel truss composite beams, it has the characteristics of light weight and high tensile strength, and can make the main span exceed one kilometer, meeting the requirements for use in large span situations. At the same time, the side spans use thicker ordinary concrete steel truss composite beams, which can shorten the main beam length as much as possible and save construction costs. In addition, during the design process, this application first determines the main span main beam parameters with the lowest total bridge cost when the upper layer of UHPC plates is used as the bridge deck of the upper deck of the main span and meets the relevant requirements. The main span main beam inter-section length and the minimum inter-section length of the side span main beam are then calculated based on the main span main beam parameters. Furthermore, the minimum inter-section 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, ultimately achieving the lowest possible cost level for the obtained main span main beam parameters and side span main beam parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. 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 any 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 2This is a standard cross-sectional view of the main span of an ultra-high performance concrete steel truss composite beam without a crossbeam, in accordance with an embodiment of the application;

[0057] Figure 3 This 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 This is a standard cross-sectional view of the side span steel truss combined beam without a cross beam of a large-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to an embodiment of the application;

[0059] Figure 5 This 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 flow chart 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 present invention.

[0061] Reference numerals:

[0062] 11. Upper UHPC slab; 111. Upper ordinary concrete bridge deck; 21. Lower UHPC slab; 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 present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, 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 of difficulty in effectively calculating the bridge structure design and construction cost for large-span dual-purpose road-rail bridges exceeding one kilometer.

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

[0066] A long-span double-deck steel truss combined beam cable-stayed bridge for 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) slab disposed above the upper longitudinal and transverse beams, a steel bridge deck disposed on the lower longitudinal and transverse beams, and a lower UHPC slab 21 disposed above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC slab 21 is less than that of the upper UHPC slab 11; the upper UHPC slab 11 and the upper longitudinal and transverse beams combine 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 slab 21 combine 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 a portion of the steel bridge deck; the upper ordinary concrete bridge deck 111 is combined with the upper longitudinal and transverse beams to form the 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 the 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-connection 41, and a suspender 42. The upper UHPC plate 11 is connected to the upper longitudinal and transverse beams and the top surface of the upper chords 31 of the steel main trusses on both sides via shear keys to form the upper deck of the main span; the lower UHPC plate 21 and the highway steel bridge deck 22 are connected via shear keys to form the highway UHPC composite bridge deck on the lower level of the main span; the lower highway steel bridge deck 22 is further welded to the lower railway steel bridge deck 23 to ultimately form the lower deck of the main span; the upper and lower decks of the main span are connected to the upper chords 31 and lower chords 32 of the steel main trusses on both sides, participating in the overall load-bearing of the structure; a cross-connection 41 and a suspender 42 are provided at each node.

[0072] The side span comprises an upper conventional concrete deck 111, a lower UHPC slab 21, a lower highway steel deck 22, a lower railway steel deck 23, a steel main truss, upper longitudinal and transverse beams, lower longitudinal and transverse beams, cross-ties 41, and suspenders 42. The upper conventional concrete deck 111 is bonded to the upper longitudinal and transverse beams and the top surfaces of the upper chords 31 of the main trusses on both sides via shear keys to form the upper deck of the side span. The lower UHPC slab 21 and the lower highway steel deck 22 are connected via shear keys to form the lower highway UHPC composite deck of the side span. Simultaneously, the lower highway steel deck 22 and the lower railway steel deck 23 are welded to form the lower deck of the side span. The upper and lower decks of the side span are connected to the upper and lower chords 32 of the main trusses, participating in the overall load-bearing of the structure. Cross-ties 41 and suspenders 42 are provided at each node.

[0073] Compared with the existing technology, 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 chords 31 of the main trusses on both sides to form an upper combined deck, which avoids the fatigue and pavement problems of highway steel bridge decks. Compared with ordinary concrete slabs, the upper UHPC plate of the main span has the characteristics of thin thickness, light weight, no shrinkage and low creep after steam curing, and strong tensile strength, which reduces the tensile stress value and range of the concrete bridge deck of the main span.

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

[0076] (3) The main span is formed by using an upper UHPC composite bridge deck, a lower road composite bridge deck on both sides, and a middle railway steel bridge deck. The main span ultra-high performance concrete steel truss composite beam has the characteristics of light weight and high tensile strength, which 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 of the upper ordinary concrete deck, the weight of the side span main beam can be increased, thereby increasing the weight effect on the main span, thereby shortening the main beam length as much as possible and saving construction costs.

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

[0079] A design method for a long-span double-deck highway-railway 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] The length of the bridge's main span will be determined based on navigation, hydrological, and topographical requirements. This is a state-of-the-art technique and is not detailed in this application. The minimum length of the side spans is determined by considering the maximum size of the outermost cables of the side spans, based on the principle that the horizontal components of the dead loads at the tower tops are equal for the side and main span segments, assuming the side spans span embankments and roads on both sides.

[0082] S200, determining a 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 for the upper UHPC slab 11 is determined based on the main span length, the preset main truss structural parameters, the minimum spacing of the steel bars within the upper UHPC slab 11, and the required cover thickness. The preset main truss structural parameters specifically include the main truss span length, the longitudinal and transverse beam layout, and other parameters initially planned based on the main span length.

[0084] S300, calculating and determining the parameters of the main girder of the main span 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 overall bridge cost;

[0085] Specifically, S300 includes the following steps:

[0086] S310, determining the minimum thickness requirement of the upper UHPC panel 11, and using the minimum thickness specified as the calculated thickness of the upper UHPC panel 11;

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

[0088] For example, a calculation model of the upper bridge deck system with upper longitudinal beams, upper transverse beams, and upper UHPC panels 11 is first established, and local wheel loads are applied. Based on the forces acting on the upper UHPC panels 11, the minimum longitudinal beam spacing and minimum cross-section are calculated and determined. After the minimum longitudinal beam spacing and minimum cross-section are obtained, an overall bridge calculation model is established based on a preset side span length (in this embodiment, the side span length is initially assumed to be 0.5 times the main span length), the minimum longitudinal beam spacing, the minimum cross-section, and the calculated thickness of the upper UHPC panels 11. After loads are applied to the overall bridge calculation model, other construction parameters of the main span main beams are calculated and determined according to construction requirements, ultimately obtaining the complete parameters of the main span main beams.

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

[0090] S340: Increasing the calculated thickness of the upper UHPC panel 11 according to a preset thickness increase, and recalculating the full bridge cost based on the new calculated thickness of the upper UHPC panel 11; wherein the preset thickness increase may be 1 cm or other reasonable value, and this application does not impose any further restrictions thereon;

[0091] S350, determining whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0092] S360: If it increases, the main span main beam parameters corresponding to the previous full bridge cost are used as the final main span main beam parameters; if it does not increase, repeat steps S340 to S360.

[0093] This arrangement allows the calculation to be started from the minimum thickness of the upper UHPC plate 11, the main span girder parameters at the corresponding calculated thickness are calculated, and the final corresponding full-bridge cost is obtained. It will be understood by those skilled in the art that, as the thickness of the upper UHPC plate 11 gradually increases and the main span girder parameters and other structural adaptive changes occur, in the initial stage of the change, before the thickness of the upper UHPC plate 11 is increased to the most appropriate level, the full-bridge cost will be affected by the fact that the high performance of the upper UHPC plate 11 can be fully utilized during this period, resulting in relatively smaller demand for other components, and ultimately showing a gradually decreasing trend until the thickness of the upper UHPC plate 11 exceeds a certain value, making it impossible to fully utilize its performance at this time. This will also affect other components, ultimately causing the full-bridge cost to show an upward trend. Therefore, when determining the first price increase, the main span girder parameters corresponding to the previous full-bridge cost and the calculated thickness of the upper UHPC plate 11 are used as the final main span girder parameters and thickness of the upper UHPC plate 11.

[0094] S400, determining a maximum span length requirement of the main span main beam according to the main span main beam parameters;

[0095] Specifically, the weight per linear meter q of the main span steel truss combined beam and the maximum specification Tmax of the existing inclined cables are determined according to the main span main beam parameters, and the maximum span length lmax=Tmax×cosθmid / q of the main span steel truss combined beam is calculated; wherein cosθmid is the average angle between the inclined cables on the main span and the horizontal direction.

[0096] S500, calculating and determining the main span main girder inter-section length that meets the maximum inter-section length requirement of the main span main girder and minimizes the overall bridge construction cost;

[0097] Specifically, S500 includes the following steps:

[0098] S510, determining the maximum length required for the maximum inter-section length of the main span main beam as the calculated inter-section length of the main span main beam;

[0099] S520. Calculate 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, the 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 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 inter-section length of the main span main beam; wherein, the main span inter-section length reduction is 0.5m in this embodiment, and other reasonable values ​​may be taken in other embodiments.

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

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

[0103] This arrangement allows the determined main span main beam parameters to be used as a basis, and the same cost comparison principle to be further used 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 intervals N will be determined based on the main span length and the main span main beam interval length; and the minimum interval length requirement of the side span will be determined based on the total number of main span intervals 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. Based on 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: Determine the minimum length of the side span as the calculated length of the side span;

[0110] S720: Determine the parameters of a 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;

[0111] Among them, S720 includes:

[0112] S721. Calculate an average cable angle coefficient between the side span main tower and the auxiliary pier based on 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 stay cables on the main span and the horizontal direction, and cosθside is the average angle between the stay cables on the side span and the horizontal direction.

[0115] S722. Calculate, based on the average cable angle coefficient, a first thickness of the ordinary concrete bridge deck of the steel truss composite 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 composite 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 components of the side and main span segments are equal at the tower top, combined with the main span segment weight, main span segment length, side span segment length, average cable angle coefficient α and side span segment weight.

[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 side span length increase, and recalculating the full bridge cost based on the new side span length;

[0122] Specifically, based on the determined minimum side span length lbmin, a preset side span length increment is added, which can be 0.5×N meters. Repeat the calculation to obtain the new side span length, the first thickness and the second thickness of the ordinary concrete slab, and then calculate the total cost of the entire bridge.

[0123] S750: Determine whether the full-bridge construction cost has increased compared to the previous full-bridge construction cost;

[0124] S760: If it increases, the side span length corresponding to the previous 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] This arrangement enables further determination of the side span main beam parameters with the lowest cost based on the determined main span main beam parameters, ultimately achieving 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 this application has a main span that adopts UHPC plates, so that the main span is formed as a main span ultra-high performance concrete steel truss composite beam. Compared with ordinary concrete steel truss composite beams, it has the characteristics of light weight and high tensile strength, which can make the main span exceed one kilometer and meet the use requirements in large span situations; at the same time, the side spans adopt thicker ordinary concrete steel truss composite beams, which can shorten the main beam length as much as possible and save construction costs; in addition, in the design process, this application first determines the main span main beam parameters with the lowest total bridge cost when the upper layer 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 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 minimum inter-section 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 lowest possible cost level for the main span main beam parameters and side span main beam parameters.

[0127] In the description of this application, it should be noted that the terms "upper" and "lower" and the like 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 this application and simplifying the description, and do not indicate or imply 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 this 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 an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this 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 used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any 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 comprising 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, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0129] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A design method for a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge, characterized in that: The large-span double-deck highway-rail dual-purpose steel truss combined beam cable-stayed bridge comprises: A steel main truss with upper longitudinal and transverse beams and lower longitudinal and transverse beams; a main span comprising an upper UHPC plate disposed above the upper longitudinal and transverse beams, a steel bridge deck disposed on the lower longitudinal and transverse beams, and a lower UHPC plate disposed above at least a portion of the steel bridge deck, wherein the thickness of the lower UHPC plate is less than that of the upper UHPC plate; the upper UHPC plate and the upper longitudinal and transverse beams are combined to form an upper bridge deck of the main span, and the lower longitudinal and transverse beams, the 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 length direction of the bridge, and includes a conventional concrete bridge deck disposed above the upper longitudinal and transverse beams, a steel bridge deck disposed on the lower longitudinal and transverse beams, and a lower UHPC plate disposed above at least a portion of the steel bridge deck; the upper conventional concrete bridge deck and the upper longitudinal and transverse beams combine to form the upper deck of the side span, and the lower longitudinal and transverse beams, the steel bridge deck, and the lower UHPC plate combine to form the lower deck of the side span; The design method comprises 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 based on the main span length and the structural requirements of the upper UHPC panel; Calculate and determine the main span girder parameters that minimize the overall bridge cost by using the upper UHPC slab as the deck plate for the upper deck of the main span and meeting the minimum thickness requirements for the upper UHPC slab. Determine the maximum span length requirement of the main span main beam according to the main span main beam parameters; Calculate and determine the main span main beam span length that meets the maximum span main beam span length requirements and minimizes the overall bridge cost; Determine the minimum span length of the side span main beam based on the minimum span length and the span length of the main span main beam; Based on the minimum span length of the side span main beam, the side span main beam parameters that meet the minimum length requirements of the side span, use ordinary concrete as the upper bridge deck of the side span and have the lowest construction cost of the entire bridge are calculated and determined.

2. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 1, 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 panel is determined based on the main span length, the preset steel main truss structural parameters, the minimum spacing of the steel bars in the upper UHPC panel, and the cover thickness requirement.

3. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 1, characterized in that: The calculation to determine the parameters of the main span girder that uses the upper UHPC slab as the bridge deck and meets the minimum thickness requirement of the upper UHPC slab and has the lowest overall bridge cost includes the following steps: Determine the minimum thickness requirement of the upper UHPC panel as the calculated thickness of the upper UHPC panel; Determine 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; increasing the calculated thickness of the upper UHPC panel according to a preset thickness increase, and recalculating the entire bridge cost based on the new calculated thickness of the upper UHPC panel; Determine whether the recalculated full-bridge cost is higher than the previous full-bridge cost; If it increases, the main span and main beam parameters corresponding to the previous full bridge cost will be used as the final main span and main beam parameters.

4. The design method of a long-span double-deck steel truss combined beam cable-stayed bridge for road and rail use according to claim 3 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: A calculation model of the upper bridge deck system with upper longitudinal beams, upper cross beams, and upper UHPC panels was established. Local wheel loads were applied, and the minimum longitudinal beam spacing and minimum cross section were calculated based on the forces acting on the upper UHPC panels. According to the preset side span length, based on the minimum longitudinal beam spacing, minimum cross-section and the calculated thickness of the upper UHPC plate, the overall calculation model of the bridge is established and the load is applied. Then, the main span main beam parameters are calculated and determined according to the construction requirements.

5. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 1, 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 construction cost comprises the following steps: Determine the maximum length required for the maximum inter-section length of the main span main beam as the calculated inter-section 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 inter-section of the main span main beam; According to the preset reduction in the main span inter-section length, 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 inter-section length of the main span main beam; Determine whether the recalculated full-bridge cost is higher than the previous full-bridge cost; If it increases, the calculated length of the main span main beam section corresponding to the previous full bridge cost will be used as the final main span main beam section length.

6. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 1, characterized in that: Determining the minimum span length of the side span main beam according to the minimum span length and the main span main beam span length includes the following steps: Determine the total number of main span intervals based on the main span length and the main span main beam interval length; Determine the minimum span length requirement for the side span based on the total number of spans in the main span and the minimum span length.

7. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 1, characterized in that: Based on the minimum span length of the side span main beam, the side span main beam parameters that meet the minimum side span length requirements, use ordinary concrete as the side span upper deck, and have the lowest overall bridge cost are calculated and determined, including the following steps: Determine the minimum length of the side span as the calculated length of the side span; 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; Calculate the cost of the entire bridge based on the side span main beam parameters; increasing the length of the side span according to a preset side span length increase, and recalculating the full bridge cost based on the new side span length; Determine whether the recalculated full-bridge cost is higher than the previous full-bridge cost; If it increases, the side span length corresponding to the previous 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.

8. The design method of a long-span double-deck highway-railway dual-purpose steel truss combined beam cable-stayed bridge according to claim 7, 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: Calculate the average cable angle coefficient between the side span main tower and the auxiliary pier based on the number of cables between the side span main tower and the auxiliary pier; Calculate, based on the average cable angle coefficient, a first thickness of the ordinary concrete bridge deck of the steel truss composite 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 composite beam between the side pier and the auxiliary pier; The side span main beam parameters are determined according to the first thickness and the second thickness.

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