Cantilever hanging basket construction technology is one of the commonly used technologies in modern long-span continuous beam bridge construction. It provides an operating space for the main girder construction by using the hanging basket, and personnel can complete the construction operations such as erecting formwork, binding steel bars and pouring concrete on the hanging basket, thus avoiding the erection of supports and speeding up the construction progress. .

Keywords: bridge construction; Cantilever hanging basket; engineering application

1 project overview

This project is a reconstruction project of lishuiqiao, located in Da Qiao Road, yongding county, Zhangjiajie City, starting from the intersection of Gu Yong Road in the north and Nanzhuang Road in the south. This project is an urban trunk road, with a total length of 406m. The approach roads on the north and south banks are186.797m and190.938m respectively, and the bridge is a prestressed concrete continuous box girder bridge with variable cross section of 70m+100m+70m. The width of the bridge and approach road is 25m, with four lanes in two directions, and the width of the auxiliary road in the north bank is 8m, with one lane in one direction. The width of bend B and bend C on the south bank is 10.5m, and it is one-way. The total construction period of the project transformation is 18 months. This project is located in the center of the city, with the main bridge across the Lishui River with a clear width of 230m ... According to the site environment and hydrological conditions, the cantilever hanging basket construction technology is proposed for Fengliang construction.

2 Lishui Bridge Cantilever Hanging Basket Construction Technology

2. 1 Construction Technology of Block 0 of Main Bridge

Before cantilever hanging basket construction, 0# bracket construction is required. The construction support of 0# block consists of steel columns, horizontal joints, main beams, diagonal braces and distribution beams. In order to improve the stability of temporary pier in hanging basket construction, when pouring pier concrete, weldments are embedded and I-beams are used to connect pier and temporary pier into a whole. At the same time, the connection between piers adopts 128a I-beam, which greatly improves the stability of the block anchor.

2.2 hanging basket construction technology

2.2. 1 hanging basket assembly

The hanging basket in cantilever hanging basket is the main component in cantilever hanging basket construction, which is mainly composed of main truss, suspension system, walking system, external formwork system and anchoring system. The walking system is mainly composed of channel members, pulley structures and pulley structures. The sling beam system consists of welded I-beams. Truss system is the main load-bearing component in hanging basket construction. The external mold system mainly includes the external mold sliding beam and the external mold. The suspension system consists of front and rear bottom molds, front and rear outer molds and front and rear inner molds.

2.2.2 The hanging basket is assembled.

After the completion of hanging basket assembly, it is necessary to carry out static load test on the stability of hanging basket installation to ensure the assembly quality of cantilever hanging basket. Before the static load test, the loading value should be reasonably determined and loaded to 1.2 times of the maximum construction load according to the regulations. The loading mode is stacking, with a loading area of 5m and a width of 9m. The loading is divided into six stages. At each loading stage, the deformation data of the hanging basket should be obtained and recorded to ensure the reliability of the data. As a stacking load in the static load experiment, the sand bag needs to be symmetrically loaded on both sides to ensure the load balance. After the static load test, it is necessary to detect the weld structure of the key parts of the hanging basket in order to master the mechanical characteristics of the main frame.

2.2.3 Cantilever hanging basket mobile construction

Cantilever hanging basket structure is mainly divided into moving track and hanging basket moving forward when walking. Technical measures should be taken in the process of hanging basket construction, and every key point should be paid attention to. When moving the track, the track moves to the beam end of the concrete beam under the traction of chain block, and the position of the guide rail is determined according to the axis. In order to ensure that all parts of the hanging basket can meet the construction requirements and avoid the loosening and sliding of parts. After the concrete pouring construction is completed and the concrete strength reaches certain requirements, the hanging basket can move forward. Before the hanging basket walks, it is necessary to check the stability of all parts, walking system and suspension system of the hanging basket to ensure the safety during walking. At the same time, in the process of hanging basket walking, it is necessary to have a unified command by a special person, and it is not allowed to walk at will.

2.3 hanging basket concrete pouring construction

In the process of hanging basket concrete pouring construction, the following points should be paid attention to: First, in the pouring process, strictly control the concrete pouring construction load to ensure the load balance at both ends; Secondly, the weight deviation of concrete at both ends of the cantilever is reasonably controlled, and the method of pumping concrete at both ends is adopted to ensure the symmetrical pouring of concrete at both ends and improve the safety of hanging basket construction; Third, when pouring concrete, the order of bottom plate, web plate and top plate should be adopted, and the pouring order should not be reversed; Fourthly, during concrete vibrating construction, attention should be paid to avoid the vibrating rod contacting the corrugated pipe of prestressed steel bar to ensure that the corrugated pipe is not deformed or damaged.

2.4 Prestressed steel bar construction technology

Pay attention to the control of prestressed construction technology and the installation quality of prestressed bellows to ensure the stress stability of the main girder structure. Before concrete pouring construction, it is necessary to install rubber lining on prestressed pipeline and then pour concrete. After concrete pouring construction, we should pay attention to the protection of bellows, check whether there is any dislocation of bellows, ensure its comprehensive performance is good, and effectively ensure that bellows have leakage, local deformation or pipeline blockage.

2.5 Construction of closed section

Side span closure section adopts bracket construction, and middle span closure section adopts hanging basket bottom formwork hanger construction. Pre-press the cantilever section before the construction of the closure section, and temporarily lock the two cantilever ends when the temperature is low. Then formwork erection, steel binding, prestressed steel pipe erection and concrete pouring are carried out. When pouring concrete, it is necessary to take cooling measures to improve the strength of concrete in the closed section by one grade, so as to apply prestress as soon as possible.

3 bridge hanging basket construction quality management measures

3. 1 Improve the quality responsibility consciousness of hanging basket construction personnel

The construction quality of continuous beam hanging basket in bridge engineering plays a key role in the later operation reliability. In the hanging basket construction, the constructors are direct participants, and their proficiency in the operation of construction equipment and quality control of all aspects of hanging basket construction directly affect the later stage of bridge engineering, while skilled technicians, high quality responsibility awareness and experienced personnel can ensure the construction quality.

3.2 Strictly control the quality of building materials.

The quality management of bridge engineering materials mainly includes the following aspects: first, in the stage of selecting concrete mixing station manufacturers, we should choose mixing stations with stable supply quality, strong performance ability and high reputation; Second, when building materials enter the site, they should check the certificate and performance test sheet of the materials and conduct spot checks.

3.3 Select the appropriate type of auxiliary construction equipment.

In view of the auxiliary equipment used in the hanging basket project construction, it is necessary to optimize the configuration reasonably according to the characteristics of the project construction and choose the appropriate type and quantity of auxiliary equipment. Ensure that the auxiliary equipment for continuous beam construction is in the best working condition, thus producing the best working efficiency.

4 conclusion

To sum up, in the construction of main girder of long-span continuous beam bridge, cantilever hanging basket construction technology can reduce the erection of supports, and use hanging basket to complete a series of construction of main girder, which can not only ensure the construction quality of concrete pouring of main girder, but also ensure the construction period and reduce the impact on river course and traffic. This technology can be widely used in the construction of long-span continuous beams.

refer to

[1] Hu huixuan, exploration on the application of cantilever hanging basket technology in bridge construction [J] China Building Metal Structure, 2013,04: 63.

Chen. Application of Cantilever Hanging Basket Technology in Bridge Construction [J] Transportation Science and Technology Heilongjiang, 20 1 1, 04: 78+80.

Zhang. Application of cantilever hanging basket technology in bridge construction [J] traffic world (traffic. Vehicle), 20 15, 06: 52-53.

Wang Qianqian. Application of Cantilever Hanging Basket Technology in Bridge Construction [J]. Traffic World, 2017,08: 78-79.

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