An optimized construction method for a steel-concrete composite girder cable-stayed bridge

Abstract

An optimized construction method for a steel-concrete composite girder cable-stayed bridge, which relates to a bridge construction method. The present invention is to solve the problem that the steel beam stress reaches the critical limit value in actual construction to ensure the safety of the bridge structure. The present invention can carry out multiple construction processes simultaneously, which is convenient for construction and significantly shortens the construction period, and has a certain degree of optimization effect on the stress of the main longitudinal beam. At the same time, it reduces the tensile stress of the bridge deck and avoids the cracking of the bridge deck. The present invention can accurately control the internal force of the stay cable and the extraction amount of the second anchor head of the stay cable, and further can well control the alignment of the bridge, and finally reduce some errors generated in terms of elevation during the construction process. The pouring sequence of the wet joint in the main longitudinal beam area is determined by the elevations of the upstream and downstream of the main longitudinal beam, which can solve the situation of easy upstream and downstream asymmetry in construction to a certain extent, thereby reducing the influence on the alignment of the subsequent beam segment installation. The present invention belongs to the technical field of bridge engineering construction.

Description

Technical Field

[0001] The present invention relates to a bridge construction method, specifically to an optimized construction method for a steel-concrete composite girder cable-stayed bridge, belonging to the technical field of bridge engineering construction. Background Art

[0002] In engineering construction, the steel-concrete composite girder makes full use of the characteristics of concrete in compression and steel in tension through shear studs and wet joints. Compared with the concrete beam structure, the steel-concrete composite girder has the advantages of low cost, convenient construction, high span, and good durability.

[0003] During the construction of a steel-concrete composite girder cable-stayed bridge, after the deck slab of the current main girder segment is hoisted, the wet joint of the current main girder segment is immediately poured. This method has a long construction period, is inconvenient for on-site construction, and is not conducive to the control of structural linearity and stress. Through summarizing and analyzing years of engineering practice, it is found that the pouring time and location of the wet joint of the steel-concrete composite girder cable-stayed bridge, as well as the cable-stayed cable tensioning time, have a great influence on the stress state of the structure.

[0004] The patent with the publication number CN113403945B discloses a construction method for a steel-concrete composite girder cable-stayed bridge. This technical solution can achieve the effect of shortening the construction period while ensuring that the structural stress meets the requirements by delaying the wet joint pouring process by two segments. Secondly, in this technical solution, the second cable tensioning is delayed by three segments to reduce the stress of the steel girder in the part where the wet joint is not poured, so as to ensure the safety of the bridge structure.

[0005] However, in actual construction, when the wet joint is not poured, each independent deck slab acts as an external load on the steel girder, resulting in an increasing trend in the stress of the steel girder. After a large number of numerical simulations and engineering practices, the stress is basically at the edge of the allowable stress of the steel girder at this time.

[0006] Therefore, it has become an urgent problem for those skilled in the art to solve the problem that the stress of the steel girder reaches the critical value through reasonable optimization of the construction process to ensure the safety of the bridge structure. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem that the stress of the steel girder reaches the critical value in actual construction at present to ensure the safety of the bridge structure. Furthermore, an optimized construction method for a steel-concrete composite girder cable-stayed bridge is provided.

[0008] The technical solution of the present invention is: an optimized construction method for a steel-concrete composite girder cable-stayed bridge, characterized in that: for i ≤ N - 1, the pouring processes of the wet joints in the main longitudinal girder area of the i-th main girder segment and the wet joints in the longitudinal and transverse girder area of the (i - 2)-th main girder segment are carried out simultaneously after the forward movement process of the deck crane corresponding to the (i + 1)-th main girder segment;

[0009] For i = N, the casting process of the wet joint in the main longitudinal beam area within the i-th main girder segment is carried out simultaneously with the casting process of the wet joints in the longitudinal and transverse beam areas within the main girder segments less than the N-th one;

[0010] wherein, i ≥ 3; N is the total number of main girder segments.

[0011] Furthermore, for i ≤ N - 3, the second tensioning process of the stay cables corresponding to the i-th main girder segment is carried out after the hoisting process of the bridge deck corresponding to the (i + 3)-th main girder segment;

[0012] For N - 2 ≤ i ≤ N, the second tensioning process of the stay cables corresponding to the i-th main girder segment is carried out after the casting process of the wet joint in the N-th main girder segment is completed.

[0013] Furthermore, in the second tensioning process of the stay cables corresponding to each main girder segment, the extraction amount of each stay cable anchor head is used as the control value.

[0014] Furthermore, the adjustment of the elevation difference between the upstream and downstream of the already constructed main girder segments or the alignment of the splicing line between two adjacent already constructed main girder segments is achieved through the second tensioning process of each stay cable.

[0015] Furthermore, after all standard segments are constructed, the elevation difference between the upstream and downstream of the main girder segments and the relative elevation difference between the main girder segments on both sides of the closure segment are adjusted through the second tensioning process of the stay cables corresponding to the main girder segments with N - 2 ≤ i ≤ N, and then the closure is carried out after the adjustment.

[0016] Furthermore, in the first tensioning process of the stay cables corresponding to each main girder segment, the internal force value of each stay cable and the elevation of the main longitudinal beam are used for double control.

[0017] Furthermore, the main longitudinal beam corresponding to each main girder segment can be a box-section beam or an I-section beam.

[0018] Furthermore, the main longitudinal beams between two adjacent main girder segments are connected by welding; the main longitudinal beam and the cross beam within each main girder segment and between the cross beam and the minor longitudinal beam are all connected by bolts.

[0019] Furthermore, the casting sequence of the wet joint in the main longitudinal beam area is determined by the elevations of the main longitudinal beams on the upstream side and the downstream side of the site.

[0020] Furthermore, if the elevation of the main longitudinal beam on the upstream side is greater than that on the downstream side, the wet joint in the main longitudinal beam area is cast in the order of first the upstream side and then the downstream side;

[0021] if the elevation of the main longitudinal beam on the upstream side is less than that on the downstream side, the wet joint in the main longitudinal beam area is cast in the order of first the downstream side and then the upstream side;

[0022] If the elevation of the main longitudinal beam on the upstream side is equal to that of the main longitudinal beam on the downstream side, then the wet joints in the main longitudinal beam area are cast by advancing simultaneously from both the upstream and downstream sides towards the mid-span direction.

[0023] The present invention has the following beneficial effects compared with the prior art:

[0024] 1. In the present invention, the casting processes of the wet joints 5 in the main longitudinal beam area within the i-th main beam segment and the wet joints 5 in the longitudinal and transverse beam area within the (i - 2)-th main beam segment are carried out simultaneously; when constructing the (i + 1)-th main beam segment, the wet joints 5 in the main longitudinal beam area of the N - 1 and N - 2 main beam segments have been cast. After the concrete solidifies, the cast wet joints 5 and the adjacent bridge deck 4 become an integral whole, making more full use of the characteristics of "the steel beam in tension and the deck in compression". The steel beam and the deck jointly bear the force, thereby reducing the stress of the steel beam at the uncast wet joint, and at the same time reducing the stress on the bridge deck 4 to avoid cracking of the bridge deck 4.

[0025] Using the construction method in the prior art where the casting process of the wet joint 5 lags behind two segments, the construction period of each segment is 7 days. After adopting the present method, the construction period of each segment is shortened to 5 days, further shortening the construction period, thus alleviating the problem of tight on-site construction period.

[0026] 2. The present invention increases the stress reserve of the structure: After using this construction method, the stress of the steel beam at the uncast wet joint 5 has decreased, and the decreased stress becomes the stress reserve of the structure, which can effectively prevent uncontrollable factors during the construction process, such as the stress increase caused by the loading of temporary loads, or the second tensioning of the stay cables 6 in the subsequent process, which will both increase the stress of the steel beam. The increased stress reserve can ensure that the stress during the construction process is controllable and the safety of the construction process.

[0027] 3. In the present invention, the second tensioning process of the stay cables 6 lags behind three segments. The adjustment of the elevation difference between the upstream and downstream of the constructed main beam segment or the alignment of the splicing line between two adjacent constructed main beam segments is achieved through the second tensioning process of each stay cable 6, so as to achieve the purpose of reducing the elevation difference between the upstream and downstream and reducing the error during the construction process, and further more precisely control the main span alignment of the bridge, enabling the bridge to finally reach a more precise completed bridge state. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of hoisting the main longitudinal beam 1;

[0030] Figure 3 It is a schematic diagram of hoisting the cross beam 2 and the small longitudinal beam 3;

[0031] Figure 4 It is a schematic diagram of the first tensioning of the stay cable 6, where the arrow at the stay cable 6 indicates the first tensioning process of the stay cable 6;

[0032] Figure 5 It is a schematic diagram of hoisting the bridge deck 4;

[0033] Figure 6 It is a schematic diagram of the second tensioning of the stay cable 6, where the arrow at the stay cable 6 indicates the second tensioning process of the stay cable 6;

[0034] Figure 7 It is a schematic diagram of the forward movement of the bridge deck crane 7;

[0035] Figure 8 It is a schematic diagram of the simultaneous pouring of the wet joint 5 in the main longitudinal beam area of the i-th main girder segment and the wet joint 5 in the longitudinal and transverse beam area of the (i - 2)-th main girder segment.

[0036] In the figure: 1, main longitudinal beam; 2, cross beam; 3, small longitudinal beam; 4, bridge deck; 5, wet joint; 6, stay cable; 7, bridge deck crane. Specific implementation manner

[0037] The following further describes the technical solution of the present invention in combination with the accompanying drawings and through specific implementation manners. Obviously, the following described implementation manners are only a part of the implementation manners of the present invention, rather than all implementation manners. All other implementation manners obtained by those of ordinary skill in the art based on the implementation manners in the present invention without creative efforts belong to the scope of protection of the present invention.

[0038] Specific implementation manner one: Combining Figures 1 to 8 To illustrate this implementation manner, an optimized construction method for a steel-concrete composite girder cable-stayed bridge in this implementation manner is characterized in that:

[0039] For i ≤ N - 1, the pouring process of the wet joint 5 in the main longitudinal beam area of the i-th main girder segment and the wet joint 5 in the longitudinal and transverse beam area of the (i - 2)-th main girder segment is carried out simultaneously after the forward movement process of the bridge deck crane 7 corresponding to the (i + 1)-th main girder segment;

[0040] For i = N, the pouring process of the wet joint 5 in the main longitudinal beam area of the i-th main girder segment is carried out simultaneously with the pouring process of the wet joint 5 in the longitudinal and transverse beam area less than that in the N-th main girder segment;

[0041] Among them, i ≥ 3; N is the total number of main girder segments.

[0042] In this embodiment, the casting process of the wet joint 5 in the main longitudinal girder area of the i-th main girder segment and the wet joint 5 in the longitudinal and transverse girder area of the (i - 2)-th main girder segment are carried out simultaneously; when constructing the (i + 1)-th main girder segment, the wet joints 5 in the main longitudinal girder areas of the N - 1 and N - 2 main girder segments have been cast, and after the concrete solidifies, the cast wet joints 5 and the adjacent bridge deck 4 become an integral whole, making more full use of the characteristics of "the steel girder in tension and the deck in compression", the steel girder and the deck share the force, thereby reducing the stress of the steel girder at the uncast wet joint, and at the same time reducing the stress on the bridge deck 4 to avoid cracking of the bridge deck 4.

[0043] In this embodiment, the construction method of the prior art in which the casting process of the wet joint 5 lags behind two segments is used, and the construction period of each segment is 7 days. After adopting this method, the construction period of each segment is shortened to 5 days, further shortening the construction period, thus alleviating the problem of tight on-site construction period.

[0044] This embodiment increases the stress reserve of the structure: after using this construction method, the stress of the steel girder at the uncast wet joint 5 has decreased, and the decreased stress becomes the stress reserve of the structure, which can effectively prevent uncontrollable factors during the construction process, such as: the stress increase caused by the loading of temporary loads, or the second tensioning of the subsequent stay cables 6 will increase the stress of the steel girder, and the increased stress reserve can ensure that the stress during the construction process is controllable and the safety of the construction process.

[0045] Specific embodiment two: Figures 1 to 6 This embodiment is described as follows. For i ≤ N - 3, the second tensioning process of the stay cable 6 corresponding to the i-th main girder segment is carried out after the hoisting process of the bridge deck 4 corresponding to the (i + 3)-th main girder segment; for N - 2 ≤ i ≤ N, the second tensioning process of the stay cable 6 corresponding to the i-th main girder segment is carried out after the casting process of the wet joint 5 of the N-th main girder segment is completed. Other technologies and steps are the same as those in specific embodiment one.

[0046] Specific embodiment three: Figure 6 This embodiment is described as follows. In the second tensioning process of the stay cable 6 corresponding to each main girder segment, the pull-out amount of the anchor head of each stay cable 6 is used as the control value. Preferably, the cable length in the prestress-free state before tensioning is converted through the measured cable force on site, and the cable length in the prestress-free state after tensioning is the design theoretical value. Other technologies and steps are the same as those in specific embodiment one or two.

[0047] Specific embodiment four: Figures 1 to 6To describe this embodiment, the adjustment of the elevation difference between the upstream and downstream of the main girder segments that have been constructed in this embodiment or the splicing linearity between two adjacent main girder segments that have been constructed is achieved through the second tensioning process of each stay cable 6. With such a setting, it is beneficial to reduce the elevation difference between the upstream and downstream and reduce the errors during the construction process, thereby more precisely controlling the main span linearity of the bridge and enabling the bridge to finally reach a more precise completed bridge state. Other technologies and steps are the same as those in the first, second, or third specific embodiments.

[0048] Specific Embodiment Five: In combination with Figures 1 to 6 To describe this embodiment, after all standard segments have been constructed in this embodiment, the elevation difference between the upstream and downstream of the main girder segments and the relative elevation difference between the main girder segments on both sides of the closure segment are adjusted through the second tensioning process of the stay cables 6 corresponding to the main girder segments where N - 2 ≤ i ≤ N, and then the closure is carried out after the adjustment. Other technologies and steps are the same as those in the first, second, third, or fourth specific embodiments.

[0049] Specific Embodiment Six: In combination with Figures 1 to 4 To describe this embodiment, in the first tensioning process of the stay cables 6 corresponding to each main girder segment in this embodiment, the internal force value of each stay cable 6 and the elevation of the main longitudinal beam 1 are used for dual control. Other technologies and steps are the same as those in the first, second, third, fourth, or fifth specific embodiments.

[0050] Specific Embodiment Seven: In combination with Figures 1 to 8 To describe this embodiment, the main longitudinal beam 1 corresponding to each main girder segment in this embodiment can be a box-shaped cross-section beam or an I-shaped cross-section beam. With such a setting, it is beneficial to expand the application range of this method and facilitate the construction of the steel-concrete composite girder cable-stayed bridge. Other technologies and steps are the same as those in the first, second, third, fourth, fifth, or sixth specific embodiments.

[0051] Specific Embodiment Eight: In combination with Figures 2 to 4 To describe this embodiment, the main longitudinal beams 1 between two adjacent main girder segments are connected by welding in this embodiment; the main longitudinal beam 1 within each main girder segment is connected to the cross beam 2 and the cross beam 2 is connected to the small longitudinal beam 3 by bolts. Other technologies and steps are the same as those in the first, second, third, fourth, fifth, sixth, or seventh specific embodiments.

[0052] Specific Embodiment Nine: In combination with Figures 1 to 8 To describe this embodiment, the pouring sequence of the wet joint 5 in the main longitudinal beam area is determined by the elevations of the main longitudinal beams 1 on the upstream side and the downstream side of the site in this embodiment. Other technologies and steps are the same as those in the first, second, third, fourth, fifth, sixth, seventh, or eighth specific embodiments.

[0053] Specific Embodiment Ten: In combination with Figures 1 to 8 To describe this embodiment, in this embodiment:

[0054] If the elevation of the upstream main longitudinal girder 1 is greater than that of the downstream main longitudinal girder 1, then the wet joint 5 in the main longitudinal girder area is poured in the order of upstream side first and then downstream side;

[0055] If the elevation of the upstream main longitudinal girder 1 is less than that of the downstream main longitudinal girder 1, then the wet joint 5 in the main longitudinal girder area is poured in the order of downstream side first and then upstream side;

[0056] If the elevation of the upstream main longitudinal girder 1 is equal to that of the downstream main longitudinal girder 1, then the wet joint 5 in the main longitudinal girder area is poured by advancing simultaneously from the upstream and downstream towards the mid-span direction. Other technologies and steps are the same as those in the first, second, third, fourth, fifth, sixth, seventh, eighth or ninth specific embodiments.

[0057] The following further describes the specific embodiments of the present invention with reference to the accompanying drawings:

[0058] Embodiment 1:

[0059] Combined with Figures 1 to 8 To illustrate this embodiment, taking the nth main girder segment in construction as an example, the optimized construction method for the steel-concrete composite girder cable-stayed bridge is carried out according to the following steps:

[0060] Step 1, hoist the main longitudinal girder 1 corresponding to the nth main girder segment;

[0061] Step 2, hoist the cross beam 2 and the small longitudinal girder 3 corresponding to the nth main girder segment;

[0062] Step 3, perform the first tensioning of the stay cable 6 corresponding to the nth main girder segment. The first tensioning process of the stay cable 6 is controlled by the internal force values of each stay cable 6;

[0063] Step 4, hoist the bridge deck 4 corresponding to the nth main girder segment. After the bridge deck 4 of the nth beam is hoisted, tie the steel bars at the bridge deck 4 in the main longitudinal girder area of the nth segment and the steel bars at the bridge deck 4 in the cross beam and longitudinal girder area of the (n - 2)th segment. This way of tying steel bars will not be affected by the front support and the rear anchor point of the bridge deck crane 7.

[0064] Step 5, perform the second tensioning of the stay cable 6 corresponding to the (n - 3)th main girder segment. The second tensioning process of the stay cable 6 is controlled by the anchor head pull-out amount of each stay cable 6. Among them, the cable length without prestress before tensioning is converted through the cable force measured on site, and the cable length without prestress after tensioning is the design theoretical value;

[0065] Step 6, move the bridge deck crane 7 forward;

[0066] Step 7: Pour the wet joints 5 of the deck slab 4 in the crossbeam and longitudinal beam areas of the (n - 2)-th main girder segment and the wet joints 5 of the deck slab 4 in the main longitudinal beam area of the n-th main girder segment. The curing and strength equalization of the concrete are carried out during the hoisting of the steel girder of the (n + 1)-th main girder segment and need to be completed before the first tensioning of the (n + 1)-th stay cable 6.

[0067] In this embodiment, the beneficial effects of the method of the present invention have been verified by tests: Using the construction method in the prior art where the pouring process of the wet joint 5 lags behind two segments, the construction period of each segment is 7 days. After adopting this method, the construction period of each segment is shortened to 5 days, further shortening the construction period, thus alleviating the problem of tight on-site construction period. Moreover, after adopting the method of the present invention, during the on-site construction process, there is no cracking of the deck slab 4, and the stress reserve of the steel girder is also improved to a certain extent.

[0068] Since the pouring of the wet joints 5 in the crossbeam and longitudinal beam areas lags behind two segments, during the construction of the first two segments, there is only the pouring process of the wet joints 5 of the deck slab in the main longitudinal beam area. And the wet joints 6 of the last segment and the wet joints 5 of the deck slab in the crossbeam and longitudinal beam areas of the two adjacent segments (i.e., the un-poured wet joints 5 of the three segments before the closure segment) can be poured together. When hoisting the deck slab 4, if the elevations of the upstream and downstream are different, on the side of the main longitudinal beam with a larger elevation, hoisting is carried out from the direction with a larger elevation to the direction with a smaller elevation. After hoisting the deck slab, the elevation value is measured again to determine the pouring sequence of the wet joints in the main longitudinal beam area.

[0069] Since the second tensioning process of the stay cable 6 lags behind three segments, during the construction of the first three main girder segments, there is no second tensioning process of the stay cable 6. And the second tensioning processes of the stay cables 6 of the last four segments can be coordinated and carried out together. Therefore, in the second tensioning processes of the last four pairs of stay cables 6, the stress-free curvature of the main bridge can be adjusted without adding counterweights on the deck slab 4, providing conditions for the precise closure of the mid-span.

[0070] The present invention has been disclosed in the above preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the relevant art, without departing from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. An optimized construction method for a steel-concrete composite girder cable-stayed bridge. The steel-concrete composite girder includes main girder segments, and each main girder segment includes main longitudinal girders (1) located on both sides of the bridge deck. Cross girders (2) and minor longitudinal girders (3) are arranged between the two main longitudinal girders (1). The minor longitudinal girders (3) are parallel to the main longitudinal girders (1), and the cross girders (2) are perpendicular to the minor longitudinal girders (3). It is characterized in that: For i ≤ N - 1, the pouring process of the wet joint (5) in the main longitudinal girder area of the i-th main girder segment and the pouring process of the wet joint (5) in the cross and minor longitudinal girder area of the (i - 2)-th main girder segment are carried out simultaneously after the forward movement process of the bridge deck crane (7) corresponding to the (i + 1)-th main girder segment; For i = N, the pouring process of the wet joint (5) in the main longitudinal girder area of the i-th main girder segment and the pouring process of the wet joint (5) in the cross and minor longitudinal girder area less than that of the N-th main girder segment are carried out simultaneously; wherein, i ≥ 3; N is the total number of main girder segments.

2. The optimized construction method for a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: For i ≤ N - 3, the second tensioning process of the stay cable (6) corresponding to the i-th main girder segment is carried out after the hoisting process of the bridge deck (4) corresponding to the (i + 3)-th main girder segment; For N - 2 ≤ i ≤ N, the second tensioning process of the stay cable (6) corresponding to the i-th main girder segment is carried out after the pouring process of the wet joint (5) of the N-th main girder segment is completed.

3. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 2, characterized in that: In the second tensioning process of the stay cables (6) corresponding to each main girder segment, the extraction amount of the anchor head of each stay cable (6) is used as the control value.

4. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: The adjustment of the elevation difference between the upstream and downstream of the already constructed main girder segments or the alignment of the splicing line between two adjacent already constructed main girder segments is achieved through the second tensioning process of each stay cable (6).

5. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: After all standard segments are constructed, the elevation difference between the upstream and downstream of the main girder segments and the relative elevation difference between the main girder segments on both sides of the closure segment are adjusted through the second tensioning process of the stay cables (6) corresponding to the main girder segments where N - 2 ≤ i ≤ N, and then the closure is carried out after the adjustment.

6. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: In the first tensioning process of the stay cables (6) corresponding to each main girder segment, the internal force value of each stay cable (6) and the elevation of the main longitudinal girder (1) are used for double control.

7. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: The main longitudinal girders (1) corresponding to each main girder segment are box-section beams or I-section beams.

8. The optimized construction method for a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: The main longitudinal girders (1) between two adjacent main girder segments are connected by welding; Between the main longitudinal girders (1) and the cross girders (2) within each main girder segment and between the cross girders (2) and the minor longitudinal girders (3), they are all connected by bolts.

9. The optimized construction method of a steel-concrete composite girder cable-stayed bridge according to claim 1, characterized in that: The pouring sequence of the wet joint (5) in the main longitudinal girder area is determined by the elevations of the main longitudinal girders (1) on the upstream side and the downstream side of the site.

10. The optimized construction method for a steel-concrete composite girder cable-stayed bridge according to claim 8, characterized in that: If the elevation of the main longitudinal girder (1) on the upstream side is greater than that on the downstream side, the wet joint (5) in the main longitudinal girder area is poured in the order of first the upstream side and then the downstream side; If the elevation of the main longitudinal girder (1) on the upstream side is less than that on the downstream side, the wet joint (5) in the main longitudinal girder area is poured in the order of first the downstream side and then the upstream side; If the elevation of the upstream main longitudinal girder (1) is equal to the elevation of the downstream main longitudinal girder (1), then the wet joint (5) in the main longitudinal girder area is cast by advancing simultaneously from the upstream and downstream towards the mid-span direction.

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