Midspan closure construction method

Abstract

The invention discloses a mid-span closure construction method, which relates to the technical field of bridge construction, and comprises the following steps of: after the side span concrete strength reaches a design value, the elastic modulus reaches the design value and the age is not less than 7 days, mounting a closure bracket, recording temperature data of each day in the side span concrete strength age, and calculating the temperature data of each day; summarizing the temperature data into a temperature curve of each day, counting low-temperature intervals of each day, and taking an intersection of the low-temperature intervals to determine the pouring time; mid-span closure section concrete pouring is conducted in the lowest-temperature period of one day; when the concrete strength and the elastic modulus of the closure section reach design values, the opposite jacking force of the top plate and the bottom plate of the beam body on the two sides of the midspan closure section is unloaded, and temporary locking rigidity is relieved; and the closure hanging bracket is dismantled, and the longitudinal prestressing tendons are tensioned and anchored. According to the mid-span closure construction method, the local environment temperature is continuously monitored within the period after mid-span side span construction, and temperature data are summarized and concluded.

Description

Technical Field

[0001] The invention relates to the technical field of bridge construction, and in particular to a mid-span closure construction method. Background Art

[0002] A cable-stayed bridge, as the name implies, is a bridge that is diagonally tensioned with at least one end of the cable hanging the main beam and the other end or the middle fastened to the cable tower. A cable-stayed bridge is a bridge whose deck system is under compression and whose supporting system is under tension. The deck system of a cable-stayed bridge is composed of stiffening beams, and the supporting system is composed of cable-stayed cables. The stiffening beams are hoisted and hung on the cable towers through the cable-stayed cables, thereby providing sufficient support. It is also beautiful enough and gradually becomes popular. The stiffening beam or main beam is one of the main supporting structures of a cable-stayed bridge, and is formed by connecting multiple beam sections one by one. Usually, the installation order of multiple beam sections is one-way installation one by one, or the two ends are connected to the middle and jointed in the middle. The latter installation order is greatly affected by environmental factors, including wind vibration, temperature, water level, weather, etc. Combined with the specific construction conditions, the existing jointing method often requires a lot of observation and adjustment, which prolongs the construction period.

[0003] To this end, the present invention proposes a mid-span closure construction method that continuously monitors the local ambient temperature within a period after the side span construction and summarizes the temperature data. Summary of the invention

[0004] The purpose of the present invention is to solve the defects in the prior art and to propose a mid-span closure construction method.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A mid-span closure construction method comprises the following steps:

[0007] S1: Construction preparation: After the side span concrete strength reaches the design value, the elastic modulus reaches the design value, and the age is not less than 7 days, install the joint support, record the temperature data of each day within the side span concrete strength age, and summarize the temperature data into a temperature curve for each day, count the low temperature intervals of each day, and take the intersection of the low temperature intervals to determine the pouring time;

[0008] S2: Apply the top force evenly on the top and bottom plates of the beam body at the middle span joint section, install the middle span joint hanger, and temporarily lock the rigid support member;

[0009] S3: Use the hanger system to suspend the steel shell formwork to the predetermined position;

[0010] S4: pouring concrete of the middle span closure section during the period of the day when the temperature is the lowest;

[0011] S5: When the concrete strength and elastic modulus of the section to be closed reach the design value, the top and bottom forces of the beams on both sides of the middle span closure section are unloaded to release the temporary locking rigidity;

[0012] S6: Remove the joint hanger, tension and anchor the longitudinal prestressed tendons.

[0013] Furthermore, step S1 also includes temporarily connecting the cantilever end with the cast-in-place section of equal height of the side span, moving the hanging baskets of the cantilever ends on both sides forward one segment respectively, using the hanging baskets as the joint support, installing the external support of the joint section and temporarily tensioning it to lock the joint support.

[0014] Furthermore, in step S1, when summarizing the temperature curve, the pouring state of the side span concrete is observed, and the relationship between the concrete and the temperature change curve is recorded to determine the time when the concrete pouring is completed.

[0015] Furthermore, step S3 also includes welding the tie plate in the steel shell formwork to the embedded steel plate of one side span, and immediately locking the other side at the lowest temperature of the day, with the height of the joint weld being no less than 8 mm.

[0016] 5. A mid-span closure construction method according to claim 1 is characterized in that, in step S3, it also includes: the steel shell formwork is suspended by a hanger system, the steel shell formwork and the concrete are cast as a whole, the steel shell formwork uses a special weathering steel plate as an outer mold, the special steel plate is 12 mm thick, and is retained with the concrete after pouring.

[0017] Furthermore, in step S4, the pouring speed of concrete is controlled to be 8-12 m / h. 3 , and determine the pouring time according to the pouring speed, so that the concrete pouring is completed before the end of the low temperature period.

[0018] Furthermore, in step S6, before tensioning, the cantilever section of the box girder is covered and water is sprinkled to reduce the temperature difference of the box girder cantilever due to sunlight, and prestressing construction is carried out when the concrete strength and elastic modulus of the joint section reach 100% of the design value and the concrete age is not less than 5 days.

[0019] Furthermore, before step S6, ordinary steel bars are processed and formed on the ground, transported to the joint section for binding and installation, and the installation position of the rigid frame is reserved during binding, and additional binding is performed after the rigid frame is locked.

[0020] Beneficial Effects

[0021] Compared with the prior art, the beneficial effect of the present invention is that: through the setting of the present invention, a mid-span closure construction method is proposed, which continuously monitors the local ambient temperature within a period after the side span construction and summarizes the temperature data. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0023] Figure 1 This is the external support layout diagram of the joint section.

[0024] Figure 2 This is the elevation drawing of the top (bottom) plate connection support.

[0025] Figure 3 This is the top (bottom) plate connection support plan. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] Reference Figure 1-Figure 3 , a mid-span closure construction method, comprising the following steps:

[0029] S1: Construction preparation: After the side span concrete strength reaches the design value, the elastic modulus reaches the design value, and the age is not less than 7 days, install the joint support, record the temperature data of each day within the side span concrete strength age, and summarize the temperature data into a temperature curve for each day, count the low temperature intervals of each day, and take the intersection of the low temperature intervals to determine the pouring time;

[0030] S2: Apply the top force evenly on the top and bottom plates of the beam body at the middle span joint section, install the middle span joint hanger, and temporarily lock the rigid support member;

[0031] S3: Use the hanger system to suspend the steel shell formwork to the predetermined position;

[0032] S4: pouring concrete of the middle span closure section during the period of the day when the temperature is the lowest;

[0033] S5: When the concrete strength and elastic modulus of the section to be closed reach the design value, the top and bottom forces of the beams on both sides of the middle span closure section are unloaded to release the temporary locking rigidity;

[0034] S6: Remove the joint hanger, tension and anchor the longitudinal prestressed tendons.

[0035] In other preferred embodiments, step S1 further includes temporarily connecting the cantilever end with the cast-in-place section of equal height of the side span, moving the hanging baskets of the cantilever ends on both sides forward by one segment respectively, using the hanging baskets as the joint closure bracket, installing the external support of the joint closure section and temporarily tensioning it to lock the joint closure bracket; during the construction of the joint closure section, the loading of each cantilever at the beam end is as symmetrical and balanced as possible. Before the joint closure, the cantilever is mainly subjected to bending moment, so the balance design follows the principle of bending moment balance at the pier position, and the following construction loads are considered in the balance design:

[0036] ① The deadweight of the closure hanger and the load acting on the closure hanger before concrete pouring.

[0037] ② Load acting directly on the cantilever.

[0038] ③ The concrete weight of the joint section. The balancing weight is added to the corresponding cantilever end before the joint is locked, which can make the frame "immobile" after the joint is locked, avoiding shear damage at the weak point.

[0039] In other preferred embodiments, step S1 also includes, when summarizing the temperature curve, observing the pouring status of the side span concrete, and recording the relationship between the concrete and the temperature change curve to determine the time when the concrete pouring is completed, that is, determining the coagulation state of the side span concrete under the local environment and the coagulation state of each temperature node adjacent to the low temperature, and selecting the ambient temperature when the coagulation state is optimal as the completion time of the pouring.

[0040] In other preferred embodiments, step S3 also includes welding the tie plate in the steel shell formwork to the embedded steel plate of one side span, and immediately locking the other side at the lowest temperature of the day, and the height of the joint weld is not less than 8 mm.

[0041] In other preferred embodiments, step S3 also includes that the steel shell formwork is suspended by a hanger system, the steel shell formwork and the concrete are cast as a whole, the steel shell formwork uses special weathering steel plates as outer molds, the special steel plates are 12 mm thick, and are retained with the concrete after pouring, thereby eliminating the impact of removing the bracket or hanger on the railway.

[0042] In other preferred embodiments, in step S4, the pouring speed of concrete is controlled to be 8-12 m / h. 3 , and determine the pouring time according to the pouring speed, so that the concrete pouring is completed before the end of the low temperature period.

[0043] In other preferred embodiments, in step S6, before tensioning, the cantilever section of the box girder is covered and water is sprinkled to cool it down so as to reduce the solar temperature difference of the box girder cantilever. The concrete strength and elastic modulus of the joint section to be closed reach 100% of the design value, and the prestressing construction is carried out when the concrete age is not less than 5 days.

[0044] In other preferred embodiments, before step S6, ordinary steel bars are processed and formed on the ground, transported to the joint section for binding and installation, and the installation position of the rigid frame is reserved during binding, and additional binding is performed after the rigid frame is locked.

[0045] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A mid-span closure construction method, characterized in that: The following steps are involved: S1: Construction preparation: After the side span concrete strength reaches the design value, the elastic modulus reaches the design value, and the age is not less than 7 days, install the joint support, record the temperature data of each day within the side span concrete strength age, and summarize the temperature data into a temperature curve for each day, count the low temperature intervals of each day, and take the intersection of the low temperature intervals to determine the pouring time; S2: Apply the top force evenly on the top and bottom plates of the beam body at the middle span joint section, install the middle span joint hanger, and temporarily lock the rigid support member; S3: Use the hanger system to suspend the steel shell formwork to the predetermined position; S4: pouring concrete of the middle span closure section during the period of the day when the temperature is the lowest; S5: When the concrete strength and elastic modulus of the section to be closed reach the design value, the top and bottom forces of the beams on both sides of the middle span closure section are unloaded to release the temporary locking rigidity; S6: Remove the joint hanger, tension and anchor the longitudinal prestressed tendons.

2. A mid-span closure construction method according to claim 1, characterized in that: Step S1 also includes temporarily connecting the cantilever end with the cast-in-place section of equal height of the side span, moving the hanging baskets of the cantilever ends on both sides forward one segment respectively, using the hanging baskets as the joint support, installing the external support of the joint section and temporarily tensioning it to lock the joint support.

3. A mid-span closure construction method according to claim 1, characterized in that: In step S1, it also includes, when summarizing the temperature curve, observing the pouring state of the side span concrete, and recording the relationship between the concrete and the temperature change curve to determine the time when the concrete pouring is completed.

4. A mid-span closure construction method according to claim 1, characterized in that: Step S3 also includes welding the tie plate in the steel shell formwork to the embedded steel plate of one side span, and immediately closing and locking the other side at the lowest temperature of the day, with the height of the closing weld being no less than 8 mm.

5. A mid-span closure construction method according to claim 1, characterized in that: Step S3 also includes that the steel shell formwork is suspended by a hanger system, the steel shell formwork and the concrete are cast as a whole, the steel shell formwork uses a special weathering steel plate as an outer mold, the special steel plate is 12 mm thick, and is retained with the concrete after pouring.

6. A mid-span closure construction method according to claim 1, characterized in that: In step S4, the pouring speed of concrete is controlled to 8-12 m / h. 3 , and determine the pouring time according to the pouring speed, so that the concrete pouring is completed before the end of the low temperature period.

7. A mid-span closure construction method according to claim 1, characterized in that: In step S6, before tensioning, the cantilever section of the box beam is covered and water is sprinkled to reduce the temperature difference of the cantilever of the box beam under sunlight. The prestressing construction is carried out when the concrete strength and elastic modulus of the joint section reach 100% of the design value and the concrete age is not less than 5 days.

8. A mid-span closure construction method according to claim 1, characterized in that: Before step S6, ordinary steel bars are processed and formed on the ground, transported to the joint section for binding and installation, and the installation position of the rigid frame is reserved during binding, and additional binding is performed after the rigid frame is locked.

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