Falsework and Construction Method for Cast-in-Place Bridge Deck of Steel-Concrete Composite Beam

Abstract

The present invention discloses a bottom formwork for supporting a cast-in-place bridge deck of a steel-concrete composite beam and a construction method thereof, which includes a plurality of truss floor bearers; the truss floor bearers are all arranged under the bridge deck to be poured, and are all prefabricated components, each including a bottom plate, and a truss structure formed by a plurality of upper chord steel bars, a plurality of lower chord steel bars and a plurality of web bar steel bars; a top edge strengthening steel bar is arranged above the upper chord steel bar; bottom edge strengthening steel bars are arranged on the outer sides of two lower chord steel bars below the upper chord steel bar, and are fixed on the corresponding steel beam flange with pads, and at least one of the bottom edge strengthening steel bars extends and spans the nearest adjacent box chamber, so that the steel bar truss floor bearer of the cantilever section of the side beam bridge deck can stand by itself before pouring; L-shaped wooden formworks and U-shaped positioning steel bars are arranged on the outward side of each cantilever floor bearer. On the premise of meeting the structural safety, the present invention can eliminate the procedures of installing and removing formworks on site, reduce the risk of high-altitude operation on site, and save the formwork and support costs.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a bottom formwork and a construction method for supporting a cast-in-situ bridge deck of a steel-concrete composite beam. Background Art

[0002] A steel-concrete composite beam is a beam that is composed of a steel beam and a concrete slab connected as a whole and can bear stress together within the cross section.

[0003] In existing municipal engineering projects, large-span bridge structures such as those crossing major intersections mostly adopt steel-concrete composite beam simply supported structures. The construction process mostly adopts the form of prefabricating steel structure main beams in sections in the factory and then transporting them to the site for hoisting, while the reinforced concrete bridge deck structure is cast again after the steel main beam is hoisted and formed. The formwork support of steel-concrete composite beam concrete bridge deck has always been a difficult point for this type of bridge, especially the cantilever part.

[0004] In the past, in the current construction of the outer flange plate of the steel beam, triangular brackets were evenly distributed on the lower side of the flange plate to consolidate with the side web plate, and supporting square wood was set up on the top of the bracket. After assembly, high-quality bamboo plywood was laid as the flange plate bottom formwork. This method has many welding points, high labor intensity for workers, high safety risks, and the installation and removal of the bracket requires a lot of manpower and high cost. There are also methods that add steel plate bottom formwork and set up floor brackets, which are not good in terms of work efficiency and safety.

[0005] Due to the construction of cast-in-place slabs, a large number of brackets and formworks are still required, which deviates greatly from the on-site construction management requirements of steel structures and does not match the entire construction process.

[0006] Therefore, how to realize a construction platform and a construction method that do not require support and demoulding has become a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the present invention provides a bottom formwork and a construction method for supporting a cast-in-place bridge deck of a steel-concrete composite beam, the purpose of which is to avoid the on-site installation and removal of the formwork process, reduce the risk of high-altitude operations on site, and save the cost of support formwork while ensuring structural safety.

[0008] To achieve the above-mentioned purpose, the present invention discloses a bottom formwork for supporting a cast-in-place bridge deck of a steel-concrete composite beam, comprising a plurality of truss floor decks arranged in a rectangular array on a bridge plan.

[0009] Each of the truss floor decks is arranged below the bridge deck to be cast, is a prefabricated component, and includes a bottom plate and a truss structure formed by a plurality of upper chord steel bars, a plurality of lower chord steel bars, and a plurality of web steel bars;

[0010] Below multiple of the truss floor slabs is provided with a box girder structure including steel cross beams and steel longitudinal beams; among them, the truss floor slabs within the range of any box chamber of the box girder structure are all upper floor slabs of the box chamber, the truss floor slabs spanning two adjacent box chambers are all truss floor slabs between box chambers, and the two truss floor slabs located on the cantilever slabs outside the side girders on both sides are all cantilever floor slabs;

[0011] Each of the bottom plates forms a connection with the corresponding steel beam flange by lapping;

[0012] Each two adjacent truss floor slabs are connected by snap fasteners;

[0013] Above each of the upper chord steel bars is provided with top edge strengthening steel bars;

[0014] Outside each two lower chord steel bars below each upper chord steel bar are provided with bottom edge strengthening steel bars, and they are all fixed on the corresponding steel beam flange by cushion blocks, and at least one of the bottom edge strengthening steel bars extends and spans the adjacent nearest box chamber and is fixed to the box chamber, so that each cantilever floor slab can stand by itself before pouring;

[0015] On the outward side of each cantilever floor slab is provided with an L-shaped wooden formwork and U-shaped positioning steel bars.

[0016] Preferably, multiple upper chord steel bars of each truss floor slab are arranged in parallel to form the upper surface of the truss structure;

[0017] On both sides below each upper chord steel bar are symmetrically provided with one lower chord steel bar respectively to form the lower surface of the truss structure;

[0018] Both ends of all the lower chord steel bars are respectively connected to the support cross bars at the corresponding ends;

[0019] Both ends of all the upper chord steel bars are respectively connected to the support cross bars at the corresponding positions through one support vertical bar at the corresponding end;

[0020] Multiple web member steel bars wind through all the lower chord steel bars and all the upper chord steel bars reciprocally to form the truss structure;

[0021] The bottom plate of each truss floor slab is fixed to the lower surface of the corresponding truss structure.

[0022] More preferably, each bottom plate is fixedly connected to the corresponding lower chord steel bar by resistance spot welding;

[0023] Each bottom plate is a profiled galvanized steel sheet with a thickness of less than 0.6 millimeters.

[0024] Preferably, the deck slab is located at the widened section of the bridge deck. The centerlines of all the steel cross beams located at the bearings are parallel to the span dividing line, and multiple steel cross diaphragms located at the mid-span are arranged in a broken line and perpendicular to the centerline of the corresponding box chamber of the box girder structure;

[0025] When arranging each truss floor slab, it is arranged in a positive staggered platform by passing parallel to the span dividing line and adjusting the lapping amount;

[0026] At the widened section of the bridge deck, formworks are provided in the local areas on both sides of each steel cross diaphragm located at the mid-span;

[0027] Each formwork is used for casting the longitudinal cantilever between the corresponding deck slab and the corresponding steel cross diaphragm.

[0028] More preferably, in the part of the deck slab where no camber needs to be set, all the top edge reinforcing bars and all the bottom edge reinforcing bars of all the cantilever floor slabs are placed obliquely according to the cross slope at the corresponding position of the deck slab;

[0029] In the part of the deck slab where camber needs to be set, all the top edge reinforcing bars and all the bottom edge reinforcing bars of all the cantilever floor slabs are bent in advance at the transverse cantilever position, and are fixedly connected by lap welding with the corresponding upper chord bars and the corresponding lower chord bars in the cantilever floor slab.

[0030] Preferably, each L-shaped formwork covers the lower surface and the outer side surface of the corresponding cantilever floor slab;

[0031] Each U-shaped positioning bar is bent around the upper surface, the outer side surface and the lower surface of the corresponding cantilever floor slab, and is fixedly connected with the corresponding upper chord bar.

[0032] The present invention also provides a construction method for the bottom formwork of the cast-in-place deck slab of the steel-concrete composite beam, including the following steps:

[0033] Step 1: Prefabricate all the truss floor slabs, all the steel cross beams and the steel longitudinal beams in the factory, and transport them to the construction site;

[0034] Step 2: Arrange temporary piers to erect all the steel cross beams and the steel longitudinal beams to form the box girder structure;

[0035] Step 3: Place all the truss floor slabs on the box girder structure;

[0036] Step 4: Set the top edge reinforcing bars and the bottom edge reinforcing bars on each cantilever floor slab;

[0037] Step 5: Set molds for the longitudinal cantilevers corresponding to each deck slab;

[0038] Step 6: Install the L-shaped wooden formwork and U-shaped positioning steel bars on the outer side of each cantilever floor slab.

[0039] Preferably, in Step 5, a reversed T-shaped capping beam is provided between every two adjacent bridge decks.

[0040] In Step 5, on the bridge deck located at the top of the reversed T-shaped capping beam, supports for the wooden formwork are provided at the positions corresponding to each longitudinal cantilever, and the wooden formwork is used as the bottom formwork for construction.

[0041] Preferably, in Step 6, install the L-shaped wooden formwork and U-shaped positioning steel bars on the outer side of each cantilever floor slab. First, fix the corresponding L-shaped wooden formwork and U-shaped positioning steel bars, and then install the corresponding L-shaped wooden formwork and U-shaped positioning steel bars onto the cantilever floor slab and weld them fixedly to the corresponding upper chord steel bars.

[0042] Preferably, after laying all the truss floor slabs, construct the bridge deck, including the following steps

[0043] Step 8: Lay the bottom edge transverse main reinforcement and bottom edge longitudinal main reinforcement of the bridge deck successively on all the laid truss floor slabs.

[0044] Step 9: After laying the bottom edge transverse main reinforcement and bottom edge longitudinal main reinforcement, tie them with wire at the intersection points of the bottom edge transverse main reinforcement and bottom edge longitudinal main reinforcement.

[0045] Step 10: Lay the top edge longitudinal main reinforcement.

[0046] The top edge longitudinal main reinforcement is supported on the upper chord steel bars or first placed on the steel beam flange.

[0047] Step 11: Lay the top edge transverse main reinforcement and tie them with wire at the intersection points of the top edge longitudinal main reinforcement and top edge transverse main reinforcement.

[0048] For all the top edge longitudinal main reinforcements placed on the steel beam flange, lift them to the same height as the corresponding top edge transverse main reinforcement and fix and connect them with wire binding or tie bars.

[0049] Step 12: Pressurize all the truss floor slabs with heavy objects to ensure stability.

[0050] Step 13: Pour the bridge deck starting from the floor slab at the upper opening of each box chamber, and finally pour the corresponding part of the cantilever floor slab.

[0051] Step 14: Spray intermediate paint and topcoat on all the exposed parts of the truss floor slabs.

[0052] Advantages of the present invention:

[0053] The present invention uses a truss floor slab to solve the problem of supporting the bottom formwork of the concrete bridge deck of a steel-concrete composite beam. On the premise of meeting the structural safety, it can eliminate the procedures of installing and removing formwork on site, reduce the risk of high-altitude operations on site, and save the cost of support formwork.

[0054] The present invention solves the problems of difficult construction and high construction safety risk in the cantilever part of the bridge deck. The cantilever floor slab structure does not require scaffolding operations under the cantilever of the bridge deck, has a low input cost, is convenient and fast to install, occupies little space, has a low construction safety risk, has guaranteed safety performance, and effectively improves construction efficiency.

[0055] The truss floor slab of the present invention is automatically produced in the factory, which can ensure the production quality, improve the processing efficiency, realize the flow operation of the bridge deck, quickly construct, save the construction period, and reduce the impact on the on-site traffic during the construction period under the condition that the project cost is basically not increased.

[0056] In the present invention, the steel bar truss works together with the concrete. The upper and lower chord bars of the steel bar truss act like the steel bars arranged on the upper and lower parts of an ordinary reinforced concrete floor slab. The steel bar configuration of the bridge deck can be appropriately reduced to save the project cost.

[0057] In the present invention, the steel bar truss floor slab is welded as a whole with the floor slab truss steel bars on the inner and outer sides of the composite beam box through the top and bottom edge reinforcement bars and placed on the steel beam. Compared with welding supports on the steel beam, it saves welding work, is easy to construct, basically has no damage to the steel beam body, and is easy to adjust the deviation.

[0058] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the drawings to fully understand the purpose, features and effects of the present invention. Description of the Drawings

[0059] Figure 1 Shows the layout diagram of the bottom formwork of the characteristic section of the steel-concrete composite beam according to an embodiment of the present invention.

[0060] Figure 2 Shows the elevation layout diagram of the bottom formwork of the composite beam bridge deck according to an embodiment of the present invention.

[0061] Figure 3 Shows the plan layout diagram of the bottom formwork of the composite beam bridge deck in the widened section of the bridge according to an embodiment of the present invention.

[0062] Figure 4 Shows the plan layout diagram of the bottom formwork of the composite beam bridge deck in the equal-width section of the bridge according to an embodiment of the present invention.

[0063] Figure 5Shows the elevation view of the standard-section steel bar truss floor slab as a finished product at the factory in an embodiment of the present invention.

[0064] Figure 6 Shows the sectional view of the standard-section steel bar truss floor slab as a finished product at the factory in an embodiment of the present invention.

[0065] Figure 7 Shows the sectional layout drawing of the bottom formwork of the cast-in-place bridge deck of the composite beam in an embodiment of the present invention.

[0066] Figure 8 Shows the sectional view of the steel bar truss floor slab of the cantilever section of the bridge deck in an embodiment of the present invention.

[0067] Figure 9 Shows the detailed layout drawing of the formwork at the end of the transverse cantilever of the bridge deck in an embodiment of the present invention.

[0068] Figure 10 Shows the detailed layout drawing of the steel bar section of the bridge deck in an embodiment of the present invention. Detailed implementation manners

[0069] Embodiment

[0070] As Figures 1 to 10 shown, the bottom formwork supported by the cast-in-place bridge deck of the steel-concrete composite beam includes a plurality of truss floor slabs 1 arranged in a rectangular array on the bridge plan.

[0071] Among them, each truss floor slab 1 is arranged under the bridge deck 2 to be poured, and is a prefabricated component, and each includes a bottom plate 3 and a truss structure formed by a plurality of upper chord steel bars 4, a plurality of lower chord steel bars 5 and a plurality of web member steel bars 6;

[0072] Below the plurality of truss floor slabs 1 is provided with a box girder structure including a steel cross beam 7 and a steel longitudinal beam 8; among them, the truss floor slab 1 within the range of any box chamber of the box girder structure is the floor slab 9 at the upper opening of the box chamber, and the truss floor slab 1 straddling two adjacent box chambers is the truss floor slab 10 between the box chambers, and the two truss floor slabs 1 located on the cantilever slabs outside the side girders on both sides are the cantilever floor slabs 11;

[0073] Each bottom plate 3 is connected to the corresponding steel beam flange 12 by overlapping;

[0074] Every two adjacent truss floor slabs 1 are connected by snap fasteners;

[0075] Above each upper chord steel bar 4 is provided with a top flange strengthening steel bar 13;

[0076] On the outer sides of the two lower chord reinforcing bars 5 below each upper chord reinforcing bar 4, bottom edge reinforcing bars 14 are provided, and they are all fixed on the corresponding steel beam flange 12 by spacer blocks. And at least one of the bottom edge reinforcing bars 14 has a length extending and spanning the nearest adjacent box chamber and is fixed to the box chamber, so that each cantilever floor slab 11 can stand by itself before pouring;

[0077] On the outward side of each cantilever floor slab 11, an L-shaped formwork 15 and a U-shaped positioning reinforcing bar 16 are provided.

[0078] In practical applications, each truss floor slab is produced by an automated factory production line, and is produced according to the actual planar layout requirements of the floor slab and then hoisted to the site.

[0079] Among the two bottom edge reinforcing bars corresponding to each upper chord reinforcing bar of each cantilever floor slab, at least one bottom edge reinforcing bar has a length extending and spanning the nearest adjacent box chamber, which can ensure that each side beam bridge deck cantilever section reinforced bar truss floor slab can stand by itself before pouring. And the bottoms of the two bottom edge reinforcing bars are both fixed on the steel beam flange 12 plate by spacer blocks and shall not be welded to the steel beam flange 12 plate.

[0080] In some embodiments, multiple upper chord reinforcing bars 4 of each truss floor slab 1 are arranged in parallel to form the upper surface of the truss structure;

[0081] On both sides below each upper chord reinforcing bar 4, one lower chord reinforcing bar 5 is symmetrically provided respectively to form the lower surface of the truss structure;

[0082] Both ends of all the lower chord reinforcing bars 5 are respectively connected to the support cross bars 17 at the corresponding ends;

[0083] Both ends of all the upper chord reinforcing bars 4 are respectively connected to the support cross bars 17 at the corresponding positions through a support vertical bar 18 at the corresponding end;

[0084] Multiple web bar reinforcing bars 6 reciprocally wind around all the lower chord reinforcing bars 5 and all the upper chord reinforcing bars 4 to form a truss structure;

[0085] The bottom plate 3 of each truss floor slab 1 is fixed to the lower surface of the corresponding truss structure.

[0086] In some embodiments, each bottom plate 3 is fixedly connected to the corresponding lower chord reinforcing bar 5 by resistance spot welding;

[0087] Each bottom plate 3 is a profiled galvanized steel sheet with a thickness of less than 0.6 millimeters.

[0088] In some embodiments, the bridge deck 2 is located at the widened section of the bridge deck. The centerlines of all the steel cross beams 7 at the support 20 are parallel to the dividing line of the spans. The multiple steel cross diaphragms 19 at the mid-span are arranged in a broken line and perpendicular to the centerline of the corresponding box chamber of the box girder structure;

[0089] When each truss floor slab 1 is arranged, it is arranged in a positive staggered platform manner by passing through the parallel perforation line and adjusting the lapping amount.

[0090] At the widened section of the bridge deck, wooden molds 21 are provided in the local areas on both sides of each steel cross diaphragm 19 at the mid-span.

[0091] Each wooden mold 21 is used for pouring the longitudinal cantilever 22 between the corresponding bridge deck 2 and the corresponding steel cross diaphragm 19.

[0092] In practical applications, when each steel bar truss floor slab 1 is arranged, it is arranged in a positive staggered platform manner by passing through the parallel perforation line and adjusting the lapping amount, which can avoid the diagonal interweaving of the steel bars of the bridge deck 2.

[0093] In some embodiments, in the part of the bridge deck 2 where no camber needs to be set, all the top edge reinforcement bars 13 and all the bottom edge reinforcement bars 14 of the corresponding all cantilever floor slabs 11 are placed obliquely according to the cross slope at the corresponding position of the bridge deck 2.

[0094] In the part of the bridge deck 2 where camber needs to be set, all the top edge reinforcement bars 13 and all the bottom edge reinforcement bars 14 of the corresponding all cantilever floor slabs 11 are bent in advance at the transverse cantilever position, and are fixedly connected to the corresponding upper chord bars 4 and the corresponding lower chord bars 5 in the cantilever floor slab 11 by lap welding.

[0095] In some embodiments, each L-shaped wooden mold 15 covers the lower surface and the outer side surface of the corresponding cantilever floor slab 11.

[0096] Each U-shaped positioning steel bar 16 is bent around the upper surface, the outer side surface and the lower surface of the corresponding cantilever floor slab 11, and is fixedly connected to the corresponding upper chord bar 4.

[0097] In practical applications, when the transverse cantilever length of the cast-in-place bridge deck is long and camber needs to be set, the cantilever floor slab can adjust the cantilever camber by bending the reinforcement bars, which can avoid the problem of difficult bending of the formwork.

[0098] The present invention also provides a construction method for the bottom formwork of the cast-in-place bridge deck of the steel-concrete composite beam, including the following steps:

[0099] Step 1: Prefabricate all truss floor slabs 1, as well as all steel cross beams 7 and steel longitudinal beams 8 in the factory, and transport them to the construction site.

[0100] Step 2: Arrange temporary piers to erect all steel cross beams 7 and steel longitudinal beams 8 to form a box girder structure.

[0101] Step 3: Place all truss floor slabs 1 on the box girder structure.

[0102] Step 4: Set the top-edge reinforcing bars 13 and bottom-edge reinforcing bars 14 on each cantilever floor slab 11;

[0103] Step 5: Set molds corresponding to each longitudinal cantilever 22 of each bridge deck 2;

[0104] Step 6: Set the L-shaped wooden molds 15 and U-shaped positioning steel bars 16 on the outer side surface of each cantilever floor slab 11.

[0105] In some embodiments, in Step 5, an inverted T-shaped capping beam 23 is provided between every two adjacent bridge decks 2;

[0106] In Step 5, for the bridge deck 2 located at the top of the inverted T-shaped capping beam 23, supports for the wooden molds are set at the positions corresponding to each longitudinal cantilever 22, and the wooden molds are used as the bottom molds for construction.

[0107] In some embodiments, in Step 6, when setting the L-shaped wooden molds 15 and U-shaped positioning steel bars 16 on the outer side surface of each cantilever floor slab 11, first fix the corresponding L-shaped wooden molds 15 and corresponding U-shaped positioning steel bars 16, and then install the corresponding L-shaped wooden molds 15 and corresponding U-shaped positioning steel bars 16 onto the cantilever floor slab 11 and weld them fixedly to the corresponding upper chord steel bars 4.

[0108] In some embodiments, after laying all the truss floor slabs 1, the construction of the bridge deck 2 is carried out, including the following steps

[0109] Step 8: Lay the bottom-edge transverse main reinforcing bars 24 and bottom-edge longitudinal main reinforcing bars 25 of the bridge deck 2 in sequence on all the laid truss floor slabs 1;

[0110] Step 9: After laying the bottom-edge transverse main reinforcing bars 24 and bottom-edge longitudinal main reinforcing bars 25, tie them with iron wires at the intersection points of the bottom-edge transverse main reinforcing bars 24 and bottom-edge longitudinal main reinforcing bars 25;

[0111] Step 10: Lay the top-edge longitudinal main reinforcing bars 26;

[0112] The top-edge longitudinal main reinforcing bars 26 are supported above the upper chord steel bars 4 or first placed on the steel beam flanges 12;

[0113] Step 11: Lay the top-edge transverse main reinforcing bars 27 and tie them with iron wires at the intersection points of the top-edge longitudinal main reinforcing bars 26 and top-edge transverse main reinforcing bars 27;

[0114] For all the top-edge longitudinal main reinforcing bars 26 placed on the steel beam flanges 12, lift them to the same height as the corresponding top-edge transverse main reinforcing bars 27 and fix and connect them with iron wires or tie bars 28;

[0115] Step 12: Pressurize all the truss floor slabs 1 with heavy objects to ensure stability;

[0116] Step 13: Start pouring the bridge deck 2 from the upper floor formwork 9 of each compartment, and finally pour the part corresponding to the cantilever floor formwork 11.

[0117] Step 14: Spray the intermediate paint and finish paint on all exposed parts of the truss floor formwork 1.

[0118] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning, or limited experiments based on the concept of the present invention on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. The bottom formwork for supporting the cast-in-place bridge deck of the steel-concrete composite beam; characterized in that, It includes multiple truss floor slabs (1) arranged in a rectangular array on the bridge plan view; Each of the truss floor slabs (1) is arranged under the bridge deck (2) to be poured, and each is a precast member, including a bottom plate (3), and a truss structure formed by multiple upper chord steel bars (4), multiple lower chord steel bars (5), and multiple web member steel bars (6); Below the multiple truss floor slabs (1) is provided with a box girder structure including steel cross beams (7) and steel longitudinal beams (8); among them, the truss floor slabs (1) within any box chamber range of the box girder structure are all upper floor slabs (9) of the box chamber, the truss floor slabs (1) spanning two adjacent box chambers are all truss floor slabs (10) between box chambers, and the two truss floor slabs (1) located on the cantilever slabs outside the side beams on both sides are all cantilever floor slabs (11); Each of the bottom plates (3) and the corresponding steel beam flange (12) are lap-connected to form a connection; Every two adjacent truss floor slabs (1) are connected by snap fasteners; Above each of the upper chord steel bars (4) is provided with a top edge reinforcement bar (13); On the outer sides of the two lower chord steel bars (5) below each of the upper chord steel bars (4) are provided with bottom edge reinforcement bars (14), and they are all fixed on the corresponding steel beam flange (12) by spacers, and at least one of the bottom edge reinforcement bars (14) extends and spans the adjacent nearest box chamber and is fixed to the box chamber, so that each cantilever floor slab (11) can stand by itself before pouring; On the outward side of each of the cantilever floor slabs (11) are provided with L-shaped formwork (15) and U-shaped positioning steel bars (16); The bridge deck (2) is located at the widened section of the bridge deck. The centerlines of all the steel cross beams (7) located at the supports (20) are parallel to the dividing line of the spans. Multiple steel cross diaphragms (19) located at the mid-span are arranged in a broken line and perpendicular to the centerlines of the corresponding box chambers of the box girder structure; When each of the truss floor slabs (1) is arranged, it is arranged in a positive staggered platform manner by adjusting the lap amount parallel to the dividing line of the spans; At the widened section of the bridge deck, wooden formwork (21) is provided in the local areas on both sides of each of the steel cross diaphragms (19) located at the mid-span; Each of the wooden formworks (21) is used for pouring the longitudinal cantilever (22) between the corresponding bridge deck (2) and the corresponding steel cross diaphragm (19); In the part of the bridge deck (2) where no camber needs to be set, all the top edge reinforcement bars (13) and all the bottom edge reinforcement bars (14) of all the cantilever floor slabs (11) are placed obliquely according to the cross slope at the corresponding position of the bridge deck (2); In the part of the bridge deck (2) where camber needs to be set, all the top edge reinforcement bars (13) and all the bottom edge reinforcement bars (14) of all the cantilever floor slabs (11) are bent in advance at the transverse cantilever position, and are lap-welded and fixed to the corresponding upper chord steel bars (4) and corresponding lower chord steel bars (5) in the cantilever floor slabs (11).

2. The bottom formwork for supporting the cast-in-place bridge deck of the steel-concrete composite beam according to claim 1, wherein Multiple upper chord steel bars (4) of each of the truss floor slabs (1) are arranged in parallel to form the upper surface of the truss structure; On both sides below each of the upper chord steel bars (4), a lower chord steel bar (5) is symmetrically arranged respectively to form the lower surface of the truss structure; Both ends of all the lower chord steel bars (5) are respectively connected to the support transverse bars (17) at the corresponding ends; Both ends of all the upper chord steel bars (4) are respectively connected to the support transverse bars (17) at the corresponding positions through a support vertical bar (18) at the corresponding end; Multiple web bar steel bars (6) reciprocally wind around all the lower chord steel bars (5) and all the upper chord steel bars (4) to form the truss structure; The bottom plate (3) of each of the truss floor slabs (1) is fixed to the lower surface of the corresponding truss structure.

3. The bottom formwork for supporting the cast-in-place bridge deck of the steel-concrete composite beam according to claim 2, characterized in that Each of the bottom plates (3) is fixedly connected to the corresponding lower chord steel bar (5) by resistance spot welding; Each of the bottom plates (3) is a profiled galvanized steel plate with a thickness of less than 0.6 mm.

4. The bottom formwork for supporting the cast-in-place bridge deck of the steel-concrete composite beam according to claim 1, characterized in that, Each L-shaped wooden form (15) covers the lower surface and the outer side surface of the corresponding cantilever floor slab (11); Each U-shaped positioning steel bar (16) is bent around the upper surface, the outer side surface and the lower surface of the corresponding cantilever floor slab (11), and is fixedly connected to the corresponding upper chord steel bar (4).

5. The construction method of the bottom formwork for the cast-in-place bridge deck support of the steel-concrete composite beam according to claim 1, characterized in that, It includes the following steps: Step 1: Prefabricate all the truss floor slabs (1), as well as all the steel cross beams (7) and the steel longitudinal beams (8) in the factory, and transport them to the construction site; Step 2: Arrange temporary piers to erect all the steel cross beams (7) and the steel longitudinal beams (8) to form the box girder structure; Step 3: Place all the truss floor slabs (1) on the box girder structure; Step 4: Set the top edge reinforcement bars (13) and the bottom edge reinforcement bars (14) on each of the cantilever floor slabs (11); Step 5: Set up molds for each longitudinal cantilever (22) of the corresponding bridge deck (2); Step 6: Set the L-shaped wooden form (15) and the U-shaped positioning steel bar (16) on the outer side surface of each of the cantilever floor slabs (11).

6. The construction method of the bottom formwork for the cast-in-place bridge deck support of the steel-concrete composite beam, characterized in that, In Step 5, an inverted T capping beam (23) is provided between every two adjacent bridge decks (2); In Step 5, for the bridge deck (2) located at the top of the inverted T capping beam (23), supports for the wooden form are set at the position corresponding to each longitudinal cantilever (22), and the wooden form is used as the bottom form for construction.

7. The construction method of the bottom formwork for the cast-in-place bridge deck support of the steel-concrete composite beam, characterized in that, In Step 6, when setting the L-shaped wooden form (15) and the U-shaped positioning steel bar (16) on the outer side surface of each of the cantilever floor slabs (11), first fix the corresponding L-shaped wooden form (15) and the corresponding U-shaped positioning steel bar (16), and then install the corresponding L-shaped wooden form (15) and the corresponding U-shaped positioning steel bar (16) to the cantilever floor slab (11) and weld them fixedly to the corresponding upper chord steel bar (4).

8. The construction method of the bottom formwork for the cast-in-place bridge deck support of the steel-concrete composite beam according to claim 5, characterized in that After completing the laying of all the truss floor slabs (1), the construction of the bridge deck (2) is carried out, including the following steps Step 8: Lay the bottom-edge transverse main reinforcement bars (24) and bottom-edge longitudinal main reinforcement bars (25) of the bridge deck (2) in sequence on all the laid truss floor slabs (1). Step 9: After the bottom-edge transverse main reinforcement bars (24) and bottom-edge longitudinal main reinforcement bars (25) are laid, tie them with wire at the intersection points of the bottom-edge transverse main reinforcement bars (24) and bottom-edge longitudinal main reinforcement bars (25). Step 10: Lay the top-edge longitudinal main reinforcement bars (26). The top-edge longitudinal main reinforcement bars (26) are supported above the upper chord reinforcement bars (4) or first placed on the steel beam flange (12). Step 11: Lay the top-edge transverse main reinforcement bars (27), and tie them with wire at the intersection points of the top-edge longitudinal main reinforcement bars (26) and the top-edge transverse main reinforcement bars (27). For all the top-edge longitudinal main reinforcement bars (26) placed on the steel beam flange (12), lift them to the same height as the corresponding top-edge transverse main reinforcement bars (27), and fix and connect them with wire tying or tie bars (28). Step 12: Pressurize all the truss floor slabs (1) with heavy objects to ensure stability. Step 13: Start pouring the bridge deck (2) from the floor slab (9) at the upper opening of each chamber, and finally pour the corresponding part of the cantilever floor slab (11). Step 14: Spray intermediate paint and finish paint on all the exposed parts of the truss floor slabs (1).

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