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The travelling formwork system mainly includes the main frame, traveling system and tensioning operating platform. It is not affected by the foundation or river, and is suitable for the construction of large and medium-span bridges. This article mainly introduces the construction of cantilever form traveler in bridge construction from three aspects: the construction characteristics, the construction steps, and the issues to be noted when applying cantilever form traveler in bridge construction.
Cantilever Form Traveler Project Under Construction
(1) The cantilever forming traveler has significant characteristics, allowing for segmented operations on-site without the need for large cranes or scaffolding, which is beneficial for cost savings and facilitates smooth construction of continuous beam pouring.
(2) With the development of cantilever hanging basket technology, the performance has been continuously improved and construction efficiency has gradually increased, making its superiorities more apparent in construction.
(3) The cantilever form traveler construction can bear beam segment construction loads and its own weight, with high rigidity so that even in its load-bearing state, the deformation of the form traveler structure is minimal.
(4) The cantilever form traveler structure is simple and lightweight, allowing for quick movement when used for concrete pouring, which is beneficial for overall concrete pouring construction.
(5) The travelling formwork system can be reused and has strong adaptability to the surrounding environment, making it suitable for a wide range of applications in continuous girder bridge construction.
The cantilever form traveller technology has high requirements for the design and production of form traveller, and should be based on the actual situation of the project. The key to the application of cantilever hanging basket technology is effective control of the construction site. The main supporting frame and formwork are important components of the forming traveller. Therefore, when making the forming traveller, the angle, height and other parameters should be determined according to the design drawings to ensure that the forming traveler has the corresponding load-bearing capacity and ensure the reliability of the construction. At the same time, during the bridge construction process, experiments should be conducted on the anchorage precision rolled exposed ribbed steel suspension rods, and the construction work of the pier top beam section should be completed before assembly to ensure that its load-bearing capacity meets the standard. After the form traveller is completed, compression resistance, load-bearing capacity and other tests should be carried out, and only after passing the inspection can it be put into use to ensure the quality of the project.
After the installation of the travelling formwork system, it is necessary to conduct preloading and static load tests at the bridge position to ensure the stability, strength, and rigidity of the formwork system. The preloading test mainly uses a jack to tension the steel wire rope, which is inserted into the front bottom crossbeam and the jack by means of embedded earth anchors. Then, the steel wire rope is anchored using anchor devices and the traveler is subjected to graded loading and preloading treatment by means of a hydraulic jack. During the preloading process, the load is gradually increased to the design load, and the welds of each component are inspected, and the force applied and its corresponding displacement data are effectively recorded.
In the construction of formwork systems for bridges, steel bars inside the beams must be tensioned and pre-stressed before removing the formwork. After removing the bottom formwork, the outer sliding beam is anchored to the side of the main structure with anchor rods, and the rear support beam is suspended on the side with a reverse chain when lifting. The track with the same length as the longest concrete block is laid in the position where the concrete is poured, and welded with the original track to ensure the integrity of the track. During the process of moving the cantilever forming carriage, the suspension points needed by the sliding beam are installed in a timely manner at the reserved hole positions on the top plate, thereby increasing the stability and strength of the bridge structure.
As an important part of bridge cantilever form traveler construction, when pouring concrete, strict requirements are placed on its slump and molding temperature. It is necessary to ensure the uniformity of pouring on both sides of the construction and prevent uneven pouring. Real-time on-site recording is required during the construction process, such as recording changes in the hanging basket elevation, differences in pouring volume, etc.
The removal of a travelling formwork system is usually carried out after the completion of construction work on the relevant beam section. Generally, the bottom basket is placed on the ground, and then the upper components of the cantilever form traveler and the main framework are retracted to a safe distance before removal.
Apart from mastering the key construction techniques, there are also several issues to note when applying travelling formwork system technology in bridge construction.
Get the construction raw materials ready, strengthen quality inspection and acceptance, ensure the quality of templates, components, concrete raw materials, and so on. Arrange the entry of mechanical equipment, strengthen the training of construction personnel, carry out technical disclosure for construction, and lay the foundation for quality control.
Before pouring the concrete, do quality inspection work to ensure that the travelling formwork system meets the construction requirements, the lifting rod functions properly, and the size of the template matches the quality of the concrete infusion. Concrete pouring needs to be slow, uniform, and continuous, and do good vibration work to ensure that the concrete has plasticity and flowability.
When moving a cantilever form traveler , ensure that the installation position is precise and the form traveler track is usable. Firstly, install the rear anchor of the main truss. When moving the cantilever forming carriage, observe weather conditions. If encountering strong winds, rain, snow or other adverse weather, construction needs to be stopped.
Micro-expansion concrete materials are generally selected for the the closure segment's construction , and the overhang weight can be appropriately increased before closure operation to enhance accuracy in construction. Prior to pouring concrete, embedded parts should be fixed and jointing of box beams should be completed, after which prestressing strands are stretched. During the closure operation construction, concrete maintenance should also be carried out. Once the concrete strength is qualified, prestressing strands can be stretched.
The application of travelling formwork system technology in bridge engineering can promote the timely completion of construction tasks, meet project deadlines, effectively control engineering quality, and improve bridge construction efficiency. Therefore, bridge construction units should attach importance to the application of cantilever form traveler, grasp the process, strictly follow the requirements, and effectively control the engineering quality. In addition, attention should be paid to on-site supervision and management, and the comprehensive quality of construction personnel should be improved. This will promote the better role of cantilever form traveler in bridge construction and ensure the safety and stability of the bridge structure.
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