Staged-implementation viaduct end structure and construction method thereof

Abstract

The invention relates to the technical field of bridges, and provides a stage-implemented viaduct end structure and a construction method thereof. Comprising a recently built first main line viaduct; the starting point ends of a pair of framing bridges built recently are connected with the end of the first main line elevated frame, the terminal point ends of the framing bridges are used for being connected with ramps, a middle-width bridge widening space is formed between inner side lines of bridge floors of the framing bridges, and the middle-width bridge widening space is used for widening the middle-width bridges in the long-term building stage. The transverse offset distance between the inner side line of the bridge floor and the center line of the viaduct is gradually increased from the starting point end to the ending point end. And during long-term construction, the whole bridge structure is realized by directly widening the middle bridge and the framing bridges on the two sides, so that the problems of resource waste and traffic interruption in the construction process are avoided.

Description

Technical Field

[0001] The present application relates to the field of bridge technology, and in particular to an elevated bridge end structure implemented in stages and a construction method thereof. Background Art

[0002] Urban elevated expressways are typically planned for long routes, require high project investments, and are constructed in phases. The immediate terminus of construction is typically located within the urban development boundary. However, urban development boundaries are not fixed but rather change dynamically with economic and social development. Therefore, the immediate terminus of urban elevated expressways must take into account long-term construction planning and its uncertainties.

[0003] In the current urban elevated expressway construction projects, the near-term construction destination can be divided into two situations:

[0004] One scenario involves the viaduct terminating at the general road section in the near future, with the mainline viaduct descending to the ground at the bridgehead roadbed. However, as urban transportation demands grow, the mainline viaduct may need to be extended again over time. This will necessitate the demolition of the bridgehead roadbed, and some existing bridge sections will need to be rebuilt or rebuilt by lifting. This results in a huge waste of investment and significant disruption to traffic during construction.

[0005] Another scenario involves a viaduct with a recently completed bridge end and a reserved diving platform in the middle, with interchange ramps connecting to the perpendicular expressway on both sides. While this scenario doesn't require demolition and reconstruction during future construction, a large portion of the mainline viaduct's reserved diving platform remains unused, resulting in wasted investment. Summary of the Invention

[0006] In view of this, an embodiment of the present application provides an elevated bridge end structure and a construction method thereof implemented in phases to solve the problems of investment waste and traffic disruption caused by demolition and reconstruction in urban elevated bridge construction when there is uncertainty in long-term construction.

[0007] A first aspect of an embodiment of the present application provides a viaduct end structure implemented in stages, comprising:

[0008] The recently constructed first main line elevated road;

[0009] A pair of recently constructed span bridges have their starting ends connected to the end of the first main line viaduct and their ending ends used to connect to the ramp. A middle span bridge widening space is formed between the inner edge lines of the bridge deck of the span bridges. The middle span bridge widening space is used to widen the middle span bridge in the long-term construction stage. The lateral offset distance between the inner edge line of the bridge deck and the center line of the viaduct gradually increases from the starting end to the ending end.

[0010] A second aspect of the embodiments of the present application provides a method for constructing an elevated bridge end structure in stages, comprising:

[0011] A split bridge has been constructed at the end of the recently constructed first main line viaduct. The starting end of the split bridge is connected to the end of the first main line viaduct, and the terminal end is used to connect to the ramp. The inner edge lines of the bridge deck of the split bridge form a mid-bridge width space, and the lateral offset distance between the inner edge line of the bridge deck and the center line of the viaduct gradually increases from the starting end to the terminal end.

[0012] The middle span bridge is constructed in the widening space of the middle span bridge in the long term, and is widened together with the inner edge of the bridge deck of the branch bridge;

[0013] A ramp will be constructed at the terminal end of the span bridge in the long term, and a second main line elevated road will be constructed at the terminal end of the middle span bridge in the long term.

[0014] The first aspect of the embodiment of the present application provides a viaduct end structure implemented in phases, including a first main line viaduct to be constructed in the near future; a pair of span bridges to be constructed in the near future, with the starting end connected to the end of the first main line viaduct and the terminal end used to connect to the ramp, a middle span bridge widening space formed between the inner edge lines of the bridge deck of the span bridge, the middle span bridge widening space is used to widen the middle span bridge in the long-term construction stage, and the lateral offset distance between the inner edge line of the bridge deck and the center line of the viaduct gradually increases from the starting end to the terminal end. The structural form of the left and right span bridges is adopted, which functionally meets the short-term traffic requirements, and the long-term construction will basically not affect the traffic of the left and right span bridges. The uninterrupted traffic on the ground auxiliary road can be ensured by setting up a portal support. In the near future, there is no need to implement the terminal pile number 1 pair of central piers, abutments, pile foundations and the bridge deck of the middle span bridge, saving short-term investment. Moreover, during future construction, the entire bridge structure will be realized by directly widening the middle bridge and the two side bridges. Except for the inner anti-collision guardrails, nothing else needs to be removed. Only two longitudinal invisible expansion joints need to be added, and no additional investment will be required in the long run.

[0015] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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 embodiments or descriptions of the prior art. 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.

[0017] Figure 1 This is a schematic structural diagram of an elevated bridge end structure implemented in stages according to an embodiment of the present application;

[0018] Figure 2 This is a structural diagram of an elevated bridge end structure implemented in stages, provided by another embodiment of the present application;

[0019] Figure 3 yes Figure 1 An enlarged schematic diagram of

[0020] Figure 4 This is a transverse schematic diagram of an elevated bridge end structure implemented in stages provided by an embodiment of the present application. DETAILED DESCRIPTION

[0021] In the following description, specific details such as specific system structures and techniques are provided for purposes of illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it will be apparent to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obscuring the description of the present application with unnecessary detail.

[0022] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0023] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof all mean "including but not limited to," unless otherwise specifically emphasized.

[0025] like Figure 1 As shown, an embodiment of the present application provides an elevated bridge end structure implemented in stages, comprising:

[0026] The recently constructed First Main Line Elevated 1;

[0027] A pair of recently constructed span bridges 2 have their starting ends connected to the ends of the first main line elevated road 1 and their ending ends used to connect to the ramp 4. A space for widening the middle span bridge 3 is formed between the inner edge lines 22 of the bridge deck of the span bridge 2. The space for widening the middle span bridge 3 is used to widen the middle span bridge 3 in the long-term construction stage. The lateral offset distance between the inner edge line 22 of the bridge deck and the center line 6 of the elevated road gradually increases from the starting end to the ending end.

[0028] In the application, it also includes structures such as beams, piers, pedestals, pile foundations, etc. The split bridge 2 includes the left bridge and the right bridge. The first main line elevated road 1 is a two-way six-lane road, and the second main line elevated road 5 to be built in the future is a two-way four-lane road with a design speed of 60km / h. The standard section of the main line elevated road in the near future is half the width of the bridge B. n =13m, half the width of the bridge in the standard section of the main line viaduct in the future f =9.5m, half of the width of the central dividing strip b0 = 0.75m.

[0029] The embodiment of the present application keeps the ground auxiliary road carriageway straight and unobstructed, and there is no need to demolish the bridgehead roadbed section or jack up and transform the main line elevated downhill section during the long-term extension construction of the main line elevated road. When connecting the interchange ramp, there is no need to reserve a diving platform in the recent construction. In combination with engineering practice, taking into account factors such as traffic demand, economic rationality, and construction convenience, the above structure is used to solve the problems of waste of investment, traffic interruption, or "unfinished bridge" and other adverse social impacts caused by demolition and reconstruction when there is uncertainty in long-term construction. A single-unit (three-span or four-span) bridge at the end of the recent construction of an urban elevated road with uncertainty in long-term construction. The structural form of the left and right split bridge is adopted, which meets the functional requirements of recent traffic passage, and the bridge sideline is smooth and natural, with a good landscape effect. The bridge piers are portal piers that do not affect the straight layout of the ground auxiliary road. The long-term construction construction will basically not affect the traffic of the left and right split bridges. The uninterrupted traffic on the ground auxiliary road can be guaranteed by setting up portal supports. To save short-term investment, there is no need to implement the terminal pile number 1 pair of central piers, abutments, pile foundations and the bridge deck of the middle span bridge in the near future. Based on the length of the middle span bridge of 90 to 120 meters and the width gradually changing from 3 meters to 21 to 30 meters, the bridge deck area of the middle span bridge is estimated to be about 1400 to 2000m 2 , directly saving at least 10 to 13 million yuan in near-term investment. Furthermore, during future construction, all but the inner crash barrier need not be removed, requiring only the installation of two longitudinal invisible expansion joints, requiring no additional investment in the long term. Regarding social impact, the near-term construction adopts a left-right split-bridge structure, eliminating the conventional truncated bridge design with a reserved diving platform. This will avoid negative social criticism such as "unfinished bridges" and address the uncertainties in future urban development brought about by an aging society. Even if the elevated highway is no longer built in the future, there will be no adverse impact.

[0030] In one embodiment, it further includes:

[0031] The middle span bridge 3 to be constructed in the future is used to be set in the widened space of the middle span bridge 3, and its two sides are connected with the inner edge line 22 of the bridge deck of the segment bridge 2 by widening;

[0032] The second main line viaduct 5 to be constructed in the future is set between the ramps 4 , and its starting end is connected to the terminal end of the middle span bridge 3 .

[0033] In the application, ramps include on-ramps and off-ramps. On-ramps are ramps on bridges or merging ramps at interchange nodes, and off-ramps are ramps on bridges or diverging ramps at interchange nodes. Figure 2 As shown, the bridge ramp includes a rising / falling grounding structure 41, which adopts the rising and falling grounding form of the upper and lower bridge ramps to keep the ground auxiliary roadway straight and unobstructed. In the long-term extension construction of the main line elevated road, there is no need to demolish the bridge head roadbed section or lift and transform the main line elevated road downhill section. z1 , down ramp width B z2 The gap width w between the on-ramp or off-ramp and the future main line elevated junction and junction nose. Specifically, both the on-ramp and off-ramp are one-way two-lane, with a design speed of 40km / h, and the width of the on-ramp is B. z1 =9.5m, down ramp width B z2 =11.5m. The gap width w=1m at the nose of the on-ramp or off-ramp and the future main line elevated junction and junction.

[0034] In one embodiment, the lateral offset distance between the inner edge line 22 of the bridge deck of the frame bridge 2 and the center line 6 of the viaduct is calculated according to the following formula:

[0035] x0≤x≤x E ;

[0036] Where y is the lateral offset distance between the inner edge line 22 of the bridge deck of the framing bridge 2 and the center line 6 of the viaduct, b is the lateral offset distance between the inner edge line 22 of the bridge deck of the framing bridge 2 and the center line 6 of the viaduct at the starting pile number, and B f is the half-bridge width of the standard section of the second main line elevated road 5, w is the width of the gap between the junction and confluence of ramp 4 and the second main line elevated road 5, x is the current pile number, x0 is the starting pile number, x E is the end pile number, and l0 is the length of the branch bridge 2.

[0037] In the application, the left bridge and the right bridge are divided into left and right according to the route direction from the near future to the far future. It is the last three spans of the terminal of the near future main line elevated road. The starting pile number is x0=K4+053 and the ending pile number is x E =K4+174, length is l0=121m, x0+l0=x E , the starting and ending points should be at the bridge piers. Figure 3As shown, the left bridge connects the near-term main line elevated road and the on-ramp, and the bridge deck junction is a conventional transverse expansion joint; the right bridge connects the near-term main line elevated road and the off-ramp, and the bridge deck junction is a conventional transverse expansion joint. The outer edge lines of the bridge decks of the left and right bridges are determined in accordance with the current "Urban Road Intersection Design Code" for the length, width, and gradient rate of the acceleration and deceleration lanes of the entire bridge to be completed in the long term. The merging point of the acceleration lane is the dividing line between the left bridge and the on-ramp, and the diverging point of the deceleration lane is the dividing line between the right bridge and the off-ramp. The above two dividing lines are at the same road pile number x E It is also the dividing line between the medium-span bridge and the future main line elevated road.

[0038] In the application, the lateral offset distances y1 and y2 between the inner edge of the bridge deck of the left bridge and the right bridge and the design center line of the viaduct gradually change from b at the x0 pile number to x E B at the pile number f +w, theoretically b should be 0, but to ensure smooth traffic in the near future and to take into account the rationality of the structural force and construction feasibility of the widened middle bridge in the long term, b can be 1 to 2m. In the embodiment of this application, the lateral offset distances y1 and y2 between the inner edge of the bridge deck of the left and right bridges and the design center line of the viaduct gradually change from b = 1.5m at the x0 pile number to x E B at the pile number f +w = 9.5 + 1 = 10.5m. To maintain the aesthetics of the left and right spans, the inner edge of the bridge deck is gradually gradiented using a cubic parabola. The relationship between y1, y2, and pile number x can be calculated using the following formula.

[0039] 4053≤x≤4174

[0040] 4053≤x≤4174

[0041] In one embodiment, the inner edge of the frame bridge 2 and the two sides of the frame bridge 2 are connected via invisible expansion joints 7 .

[0042] In one embodiment, if the formula is not satisfied:

[0043] Then increase the length of the framing bridge by l0;

[0044] Among them, l 0min is the minimum allowable length of the sectional bridge, V is the design speed of the ramp connected by the sectional bridge, and B f is the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, and b0 is half of the width of the central dividing strip.

[0045] In application, in order to ensure safe and smooth driving in the near future and avoid excessive lateral movement in a short distance during driving, the minimum length of the width gradient section should be checked for the left and right branch bridge lengths l0. The design speed V of the ramp connecting the left and right branch bridges is 40km / h, so the minimum length of the width gradient section l 0min for

[0046]

[0047] In this example, the length of the left and right bridges is l0=121m>l 0min =100.65m, meets the requirements.

[0048] In the application, the middle span bridge is located between the left span bridge and the right span bridge. It will not be built in the near future. When the main line elevated road is built in the long term, it will be widened together with the left span bridge and the right span bridge to form the whole span bridge. The width of the middle span bridge is y1+y2, which is 2b at the x0 pile number and 2b at the x1 pile number. E The pile number is 2B f +2w.

[0049] In one embodiment, the span bridge 2 adopts a steel box girder 23 structure, and the bridge deck pavement includes a steel fiber concrete layer, a waterproof layer and an asphalt concrete layer.

[0050] Due to the complex boundary changes of the left, right, and center spans, steel box girder structures were used. The bridge decks were paved with 8cm thick C50 steel fiber reinforced concrete, a waterproof layer, and a 10cm thick asphalt concrete layer. Specifically, the decks consisted of 4cm thick SMA-13 modified mastic asphalt concrete, 6cm thick AC-20C medium-grained SBS modified asphalt concrete, a PB(I) waterproof coating for roads and bridges, a water-based penetrating inorganic waterproofing agent, and 8cm thick C50 steel fiber reinforced concrete.

[0051] In application, anti-collision guardrails should be installed on both sides of the left and right bridges in the near future to ensure driving safety. Ancillary facilities such as street lights and attached signs are installed on the outer anti-collision guardrails. The inner anti-collision guardrails need to be removed when the middle bridge is widened in the future.

[0052] In practice, invisible expansion joints are designed at the junction of the future-widened middle span bridge and the recently constructed left and right span bridges. These joints form a cubic parabola gradient along the longitudinal direction of the roadway. To maintain the aesthetics of the entire bridge deck and driving comfort over the long term, invisible expansion joints should be employed. Invisible expansion joints are a rigid-flexible composite structure. Currently, they primarily utilize the expansion and contraction properties of a high-viscosity, high-elasticity asphalt mixture to accommodate displacements caused by temperature, load, and other factors. When ambient temperature changes cause the beam to expand or contract, the invisible expansion joint exhibits plastic properties; when vehicles pass by, the invisible expansion joint exhibits elastic properties. As invisible expansion joint technology advances, more advanced materials can be employed to maximize bridge deck smoothness and driving comfort under temperature fluctuations and vehicle loads.

[0053] The piers and beams support the recently constructed left and right spans, as well as the future widened middle span. The piers and beams were designed and verified based on the loads expected for the entire span. The central piers, side piers, and beams of the recently constructed left and right spans are designed as portal piers. After the future widening of the middle span, there will be virtually no exposed beams, resulting in a positive overall landscape for both the near- and long-term bridges.

[0054] The locations of the bridge piers and abutments should be arranged within the green belt of the ground auxiliary road to ensure the smooth operation of the ground auxiliary road carriageway, non-motorized vehicle lane and sidewalk in the short and long term.

[0055] The steel box girders, cross beams, piers, abutments and pile foundations of the left and right span bridges shall be subjected to sufficient structural stress stability verification and analysis according to various working conditions, including permanent, variable and accidental effects of the left and right span bridges in the near term and the entire span bridge in the long term, as well as temporary effects during the near and long term construction processes. The design dimensions of various structures shall be determined based on the verification and analysis results. The thickness of the steel box girder shall be 1.9m, the cross-section of the central pier shall be 1.7m×1.7m, the thickness of the I-shaped abutment shall be 3m, and there shall be 4 φ1.6m bored cast-in-place piles. The cross-section of the auxiliary piers on both sides shall be 1.5m×1.5m, the thickness of the rectangular abutment shall be 2.5m, and there shall be 2 φ1.5m bored cast-in-place piles.

[0056] The present application also provides a method for constructing an elevated bridge end structure in stages, comprising:

[0057] A framing bridge 2 has recently been constructed at the end of the recently constructed first main line viaduct 1. The starting end of the framing bridge 2 is connected to the end of the first main line viaduct 1, and the terminal end is used to connect to the ramp 4. The inner edge lines 22 of the bridge deck of the framing bridge 2 form a widening space for the middle bridge 3. The lateral offset distance between the inner edge line 22 of the bridge deck and the center line 6 of the viaduct gradually increases from the starting end to the terminal end.

[0058] The middle span bridge 3 will be constructed in the long term in the widening space of the middle span bridge 3, and the inner edge of the bridge deck of the segmented span bridge 2 will be widened;

[0059] The ramp 4 will be constructed at the terminal end of the span bridge in the long term, and the second main line elevated road will be constructed at the terminal end of the middle span bridge 3 in the long term.

[0060] In one embodiment, Figure 4 As shown in the figure, a split bridge has been constructed at the recently constructed end of the first main line viaduct, including:

[0061] Construct the piers 10, beams 9, caps 11 and pile foundations 12 of the span bridge 2, and reserve the widening space for the middle span bridge 3;

[0062] Construct the steel box girder 23 and anti-collision guardrail 8 of the span bridge, and pave the bridge deck;

[0063] Construction of ancillary facilities for the split-bridge.

[0064] In the application, the piers, beams, caps and pile foundations required for the left and right bridges will be constructed first. E =The central bridge pier and its abutment and pile foundation at pile number K4+174 do not need to be implemented in the near future), then the steel box girder, anti-collision guardrail and bridge deck paving will be constructed, and finally the street lights, traffic signs and markings and other ancillary facilities will be constructed before opening to traffic.

[0065] In one embodiment, the middle span bridge is constructed in the widening space of the middle span bridge in the future, and is widened together with the inner edge of the bridge deck of the branch bridge, including:

[0066] Pile foundation, cap and pier at the construction end pile number;

[0067] Erecting portal supports;

[0068] Connect the crossbeams of the span bridges into a whole and hoist the steel box girder of the middle span bridge;

[0069] Remove the inner side anti-collision guardrails of the two side bridges and construct the central anti-collision guardrail of the bridge deck;

[0070] Construction of bridge deck pavement and invisible expansion joints 7;

[0071] Treat the split bridge and the middle bridge as a whole and adjust the traffic signs and markings.

[0072] In application, when widening the medium-width bridge in the future, first construct x E =K4+174 pile number, the pile foundation, abutment, and bridge piers were then constructed. A portal support was then erected to ensure continuous ground traffic flow. The crossbeams of the left and right spans were connected as a whole, and the steel box girder of the middle span was hoisted. The inner crash barriers of the left and right spans were then removed, and the central crash barrier of the bridge deck was constructed. The bridge deck pavement and invisible expansion joints were then constructed. Finally, traffic signs and markings were readjusted for the entire span. A central median 13 was formed between the lower piers of the middle span. Paving was allowed between the left pier of the middle span and the piers of the left span, forming the left carriageway 14. Paving was also allowed between the right pier of the middle span and the piers of the right span, forming the right carriageway.

[0073] In one embodiment, the lateral offset distance between the inner edge of the bridge deck of the frame bridge and the centerline of the viaduct is calculated according to the following formula:

[0074] x0≤x≤x E ;

[0075] Where y is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct, b is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct at the starting pile number, and B fis the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, x is the current pile number, x0 is the starting pile number, x E is the end pile number, and l0 is the length of the branch bridge.

[0076] In one embodiment, it further includes:

[0077] If the formula is not satisfied Then increase the length of the framing bridge by l0;

[0078] Among them, l 0min is the minimum allowable length of the sectional bridge, V is the design speed of the ramp connected by the sectional bridge, and B f is the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, and b0 is half of the width of the central dividing strip.

[0079] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A viaduct end structure implemented in stages, characterized in that: include: The recently constructed first main line elevated road (1); A pair of recently constructed span bridges (2) have a starting end connected to the end of the first main line viaduct (1) and a terminal end used to connect to a ramp (4). A middle span bridge widening space is formed between the inner edge lines (22) of the bridge deck of the span bridge (2). The middle span bridge widening space is used to widen the middle span bridge (3) in the long-term construction stage. The lateral offset distance between the inner edge line (22) of the bridge deck and the center line (6) of the viaduct gradually increases from the starting end to the terminal end.

2. The viaduct end structure implemented in stages according to claim 1, characterized in that: Also includes: A middle span bridge (3) to be constructed in the future is used to be arranged in the widened space of the middle span bridge, and its two sides are connected to the inner edge lines (22) of the bridge deck of the branch bridge (2) by widening; The second main line viaduct (5) to be constructed in the long term is arranged between the ramps (4), and its starting end is connected to the terminal end of the middle span bridge (3).

3. The viaduct end structure implemented in stages according to claim 1, characterized in that: The lateral offset distance between the inner edge line (22) of the bridge deck of the frame bridge (2) and the center line (6) of the viaduct is calculated according to the following formula: Where y is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct, b is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct at the starting pile number, and B f is the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, x is the current pile number, x0 is the starting pile number, x E is the end pile number, and l0 is the length of the branch bridge.

4. The viaduct end structure implemented in stages according to claim 1, characterized in that: The inner edge of the frame bridge (2) and the two sides of the frame bridge (2) are connected via invisible expansion joints (7).

5. The viaduct end structure implemented in stages according to claim 1, characterized in that: The span bridge (2) adopts a steel box girder (23) structure, and the bridge deck pavement includes a steel fiber concrete layer, a waterproof layer and an asphalt concrete layer.

6. A method for constructing an elevated bridge end structure in stages, characterized in that: include: A split bridge was recently constructed at the end of the recently constructed first main line viaduct; The starting end of the splayed bridge is connected to the end of the first main line viaduct, and the terminal end is used to connect to the ramp. The inner edge lines of the bridge deck of the splayed bridge form a mid-bridge widening space, and the lateral offset distance between the inner edge line of the bridge deck and the center line of the viaduct gradually increases from the starting end to the terminal end. The middle span bridge is constructed in the widening space of the middle span bridge in the long term, and is widened together with the inner edge of the bridge deck of the branch bridge; A ramp will be constructed at the terminal end of the span bridge in the long term, and a second main line elevated road will be constructed at the terminal end of the middle span bridge in the long term.

7. The method for constructing an elevated bridge end structure in stages according to claim 6, wherein: The recently constructed first main line elevated end will soon be constructed with a split bridge, including: Construct the piers, beams, caps and pile foundations of the span bridges, and reserve the widening space for the middle span bridge; Construct the steel box girder and anti-collision guardrail of the span bridge, and pave the bridge deck; Construction of ancillary facilities for the split-bridge.

8. The method for constructing an elevated bridge end structure in stages according to claim 6, wherein: The method of constructing the middle span bridge in the widening space of the middle span bridge in the long term and widening the inner edge of the bridge deck with the branch bridge includes: Pile foundation, cap and pier at the construction end pile number; Erecting portal supports; Connect the crossbeams of the span bridges into a whole and hoist the steel box girder of the middle span bridge; Remove the inner side anti-collision guardrails of the two side bridges and construct the central anti-collision guardrail of the bridge deck; Construction of bridge deck pavement and invisible expansion joints; The split bridge and the middle bridge are taken as a whole, and traffic signs and markings are adjusted.

9. The method for constructing an elevated bridge end structure in stages according to claim 6, wherein: The lateral offset distance between the inner edge of the bridge deck of the said section bridge and the center line of the viaduct is calculated according to the following formula: Where y is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct, b is the lateral offset distance between the inner edge of the bridge deck of the sectional bridge and the center line of the viaduct at the starting pile number, and B f is the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, x is the current pile number, x0 is the starting pile number, x E is the end pile number, and l0 is the length of the branch bridge.

10. The method for constructing an elevated bridge end structure in stages according to claim 6, wherein: Also includes: If the formula is not satisfied Then increase the length of the framing bridge by l0; Among them, l 0min is the minimum allowable length of the sectional bridge, V is the design speed of the ramp connected by the sectional bridge, and B f is the half-bridge width of the standard section of the second main line elevated road, w is the width of the gap between the ramp and the second main line elevated road, and b0 is half of the width of the central dividing strip.

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