A method for midspan closure construction

Abstract

The application discloses a kind of midspan closure construction methods, it is related to bridge construction technical field, including the following steps: after the strength of side span concrete reaches design value, elastic modulus reaches design value, and after age period is not less than 7 days, install closure support, record each day temperature data in the age period of side span concrete strength, and temperature data is summarized into the temperature curve of each day, the low temperature interval of each day is counted, the intersection of low temperature interval is taken, to determine pouring time;Pouring of midspan closure section concrete is carried out in the lowest temperature period in a day;When the strength and elastic modulus of closure section concrete reach design value, unload the top force of beam body top and bottom plate on the both sides of midspan closure section, remove temporary locking rigidity;Remove closure hanger, tension and anchor longitudinal prestressed beam.The application is provided to continuously monitor local environmental temperature within the period after side span construction, and summarize the midspan closure construction method of temperature data.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a method for mid-span closure construction. Background Technology

[0002] A cable-stayed bridge, as the name suggests, is a type of bridge where at least one end of the stay cable is suspended from the main girder, and the other end or the middle is fastened to the pylon, and it is tensioned at an angle. A cable-stayed bridge is a type of bridge where the deck system is under compression and the support system is under tension. The deck system of a cable-stayed bridge consists of stiffening girders, and the support system consists of stay cables. The stiffening girders are suspended and tightened to the pylons via the stay cables, thus providing sufficient support and possessing aesthetic appeal, and are gradually gaining popularity. The stiffening girder or main girder is one of the main supporting structures of a cable-stayed bridge, and is composed of multiple beam segments connected one by one. Typically, the installation sequence of multiple beam segments is either unidirectional and sequential, or the two ends are joined towards the middle and closed at the center. The latter installation sequence is greatly affected by environmental factors, including wind vibration, temperature, water level, and weather. Combined with specific construction conditions, existing closure methods often require extensive observation and adjustments, thus extending the construction period.

[0003] Therefore, this invention proposes a method for mid-span closure construction that involves continuously monitoring the local ambient temperature within a certain period after the side span construction and summarizing the temperature data. Summary of the Invention

[0004] The purpose of this invention is to address the deficiencies in the existing technology by proposing a mid-span closure construction method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

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

[0007] S1: Construction preparation. After the concrete strength and elastic modulus of the side span reach the design value and the curing period is not less than 7 days, install the closure support. Record the temperature data for each day within the curing period of the concrete strength of the side span, and summarize the temperature data into a temperature curve for each day. Calculate the low temperature range for each day, and take the intersection of the low temperature ranges to determine the pouring time.

[0008] S2: Apply equal jacking force to the top and bottom plates of the beam in the mid-span closure section, and install the mid-span closure hanger to temporarily lock the rigid support components;

[0009] S3: Use a scaffolding system to suspend the steel shell formwork to the designated position;

[0010] S4: Concrete pouring for the mid-span closure section is carried out during the period of lowest temperature in a day;

[0011] S5: When the concrete strength and elastic modulus of the closure section reach the design value, unload the top and bottom plates of the beams on both sides of the mid-span closure section and release the temporary locking rigidity.

[0012] S6: Remove the closure 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 on the side span, moving the hanging baskets at both cantilever ends forward by one segment respectively, using the hanging baskets as closure supports, installing external supports for the closure section and temporarily tensioning them to lock the closure supports.

[0014] Furthermore, step S1 also includes observing the pouring status of the side span concrete when summarizing the temperature curve, and recording the relationship between the concrete and the temperature change curve to determine the time when the concrete pouring is completed.

[0015] Furthermore, step S3 also includes welding the gusset plate in the steel shell template to the embedded steel plate on one side of the span, and immediately locking the other side at the lowest temperature of the day, with the closure weld height not less than 8mm.

[0016] 5. The mid-span closure construction method according to claim 1, characterized in that, in step S3, the steel shell formwork is suspended by a hanging system, the steel shell formwork and the concrete are poured as a whole, the steel shell formwork is made of weather-resistant steel special steel plate as the outer formwork, the special steel plate is 12mm thick, and is retained with the concrete after the concrete is poured.

[0017] Furthermore, in step S4, the concrete pouring speed is controlled at 8-12 m / s. 3 The pouring time is determined based on the pouring speed, so that the concrete is poured 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 sprayed to reduce the temperature difference of the box girder cantilever under sunlight. Prestressing construction is carried out after the concrete strength and elastic modulus of the closure 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 shaped on the ground and transported to the closure section for binding and installation. During binding, the installation position of the stiffening frame is reserved, and additional binding is performed after the stiffening frame is locked.

[0020] Beneficial effects

[0021] Compared to existing technologies, the advantages of this invention are as follows: This invention proposes a method for mid-span closure construction that utilizes continuous monitoring of the local ambient temperature within a specified period after the side-span construction, and summarizes and generalizes the temperature data. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0023] Figure 1 This is a diagram showing the external support layout for the closure section.

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

[0025] Figure 3 This is a plan view of the top (bottom) plate connection support. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] Reference Figures 1-3 A method for mid-span closure construction includes the following steps:

[0029] S1: Construction preparation. After the concrete strength and elastic modulus of the side span reach the design value and the curing period is not less than 7 days, install the closure support. Record the temperature data for each day within the curing period of the concrete strength of the side span, and summarize the temperature data into a temperature curve for each day. Calculate the low temperature range for each day, and take the intersection of the low temperature ranges to determine the pouring time.

[0030] S2: Apply equal jacking force to the top and bottom plates of the beam in the mid-span closure section, and install the mid-span closure hanger to temporarily lock the rigid support components;

[0031] S3: Use a scaffolding system to suspend the steel shell formwork to the designated position;

[0032] S4: Concrete pouring for the mid-span closure section is carried out during the period of lowest temperature in a day;

[0033] S5: When the concrete strength and elastic modulus of the closure section reach the design value, unload the top and bottom plates of the beams on both sides of the mid-span closure section and release the temporary locking rigidity.

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

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

[0036] ①The self-weight of the closure support and the loads acting on the closure support before concrete pouring.

[0037] ② Loads that act directly on the cantilever.

[0038] ③ The weight of the concrete in the closure section. The counterweight is added to the corresponding cantilever end before the closure is locked, so that the frame remains "stationary" after the closure is locked, avoiding shear damage to weak points.

[0039] In other preferred embodiments, step S1 further includes observing the pouring state of the side span concrete when summarizing the temperature curve, 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 setting state of the side span concrete under the local environment and the setting state of each temperature node near the low temperature, and selecting the ambient temperature at which the setting state is optimal as the completion time of the pouring.

[0040] In other preferred embodiments, step S3 further includes welding the gusset plate in the steel shell template to the embedded steel plate on one side span, and immediately locking the other side at the lowest temperature of the day, with the closure weld height not less than 8mm.

[0041] In other preferred embodiments, step S3 further includes suspending the steel shell formwork using a hanger system, with the steel shell formwork and concrete being poured as a whole. The steel shell formwork uses weather-resistant special steel plates as the outer mold, with a thickness of 12mm. After the concrete is poured, it is retained with the concrete to avoid the impact of dismantling the supports or hangers on the railway.

[0042] In other preferred embodiments, in step S4, the concrete pouring speed is controlled to be 8-12 m / s. 3 The pouring time is determined based on the pouring speed, so that the concrete is poured 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 sprayed to reduce the temperature difference of the box girder cantilever under sunlight. Prestressing construction is carried out after the concrete strength and elastic modulus of the closure section reach 100% of the design value and the concrete age is not less than 5 days.

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

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of midspan closure construction, characterized by, The method comprises the following steps: S1: construction preparation, after the strength and elastic modulus of the side span concrete reach the design values, and the age period is not less than 7 days, the closure support is installed, the temperature data of each day is recorded during the age period of the side span concrete, the temperature data is summarized into the temperature curve of each day, the low temperature interval of each day is counted, the intersection of the low temperature intervals is taken to determine the pouring time; S2: the top force is evenly applied to the top and bottom plates of the mid-span closure section beam body, the mid-span closure hanger is installed, and the rigid support member is temporarily locked; S3: the steel shell formwork is suspended to the determined position by using the hanger system; S4: the pouring of the mid-span closure section concrete is carried out at the lowest temperature period in a day; S5: when the strength and elastic modulus of the closure section concrete reach the design values, the top force of the top and bottom plates of the mid-span closure section beam body is unloaded, and the temporary locking rigid is released; S6: the closure hanger is removed, the longitudinal prestressed tendon is tensioned and anchored; In step S1, when the temperature curve is summarized, 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 pouring of the concrete is completed, that is, the coagulation state of the side span concrete under the local environment and the coagulation state of the temperature nodes near the low temperature are determined, and the time of the environmental temperature when the coagulation state is optimal is selected as the completion time of the pouring.

2. The construction method of a midspan closure as claimed in claim 1, wherein In step S1, the cantilever end is temporarily connected with the side span cast-in-place section, the hanging baskets on both sides of the cantilever end are moved forward by one segment respectively, the hanging basket is used as the closure support, the external support of the closure section is installed and temporarily tensioned to lock the closure support.

3. The construction method of a midspan closure as claimed in claim 1, wherein In step S3, the panel in the steel shell formwork is welded on the pre-buried steel plate of one side span, and the other side closure is immediately locked at the lowest temperature of the day, and the height of the closure weld is not less than 8 mm.

4. The construction method of a midspan closure as claimed in claim 1, wherein In step S3, the steel shell formwork is suspended by using the hanger system, the steel shell formwork and the concrete pouring form an integral whole, the steel shell formwork uses the weather-resistant steel special steel plate as the outer form, the thickness of the special steel plate is 12 mm, and the steel shell formwork is reserved after the pouring of the concrete.

5. The construction method of a midspan closure as claimed in claim 1, wherein In step S4, the pouring speed of the concrete is controlled to be 8-12 m³ per hour, and the pouring time is determined according to the pouring speed, so that the pouring of the concrete is completed before the end of the low temperature period.

6. The construction method of a midspan closure as defined by claim 1 wherein, In step S6, before tensioning, the cantilever section of the box girder is covered and water is sprinkled to reduce the solar temperature difference of the cantilever of the box girder, the prestress construction is carried out when the strength and elastic modulus of the closure section concrete reach 100% of the design values and the concrete age period is not less than 5 days.

7. The construction method of a midspan closure as defined by claim 1 wherein, Before step S6, the ordinary steel bars are concentratedly processed on the ground, transported to the closure section for binding and installation, the installation position of the stiff skeleton is reserved during the binding, and the binding is supplemented after the stiff skeleton is locked.

Images