Form traveler construction for continuous beam of highway and bridge is an efficient bridge construction technology, mainly applied to the casting of cantilever beam bridges with large spans.

With the increasing demand for long-span bridges in transportation construction, traditional construction technologies can hardly meet the efficiency and safety requirements under complex working conditions. Relying on its core advantages of "segmented cantilever casting and no need for large-scale supports", the form traveler construction technology for continuous beam of highway and bridge has become a key construction solution for crossing obstacle sections such as valleys and rivers. Through the movable form traveler structure, this technology realizes the segmented casting and forming of bridge girders. It not only effectively reduces the dependence on the construction site, but also accurately controls the linear shape and quality of the girders, thus being widely used in the construction of modern long-span continuous beam bridges. This article will systematically analyze the implementation key points of this technology from three core links: the design and manufacture of form travelers, assembly and commissioning, and movement and positioning, so as to provide references for engineering practice.

1. Design and Manufacture of Form Travelers

The design and manufacture of form travelers is a fundamental link in the construction of continuous beam bridges, and its quality and performance directly affect the safety and efficiency of subsequent construction.

1.1 Design Key Points

The design of form travelers should meet the requirements of light weight, simple structure and clear force bearing to ensure structural safety. The form traveler should be mainly controlled by stiffness, and only elastic deformation with small magnitude occurs under heavy load. The operation system of the form traveler should be safe, reliable, firm and stable. The walking and suspension systems should be reasonably designed to facilitate on-site operation and maintenance. High-quality materials should be selected for the manufacture of form travelers. The type, specification and mechanical properties of steel should be strictly inspected, and the quality of welding materials and the standardization of welding processes should be guaranteed.

1.2 Composition

The form traveler is mainly composed of upper longitudinal beams, upper and lower crossbeams, triangular and rhombic load-bearing frames, bottom formwork platform, front and rear suspenders, bottom anchor beams and rear anchors. The main stress-bearing component of the form traveler is the upper main longitudinal beam. The load of the box girder and the self-weight of the formwork are transmitted from the lower longitudinal beam of the form traveler to the front and rear crossbeams, then to the upper crossbeam through the front suspension system, and finally to the cast concrete segment.

1.3 Specific Design Data

The strength and stiffness of the lower longitudinal beam should be checked and calculated. For example, the spacing of the box girder web is set at 30cm, while the spacing of other positions is set at 70cm. The lower longitudinal beam is designed with the web of the 1# segment of the cantilever casting section as the load, where the segment length is 3.5m and the design control length is 4m. The front crossbeam is calculated according to the box girder construction condition, and the rear crossbeam is calculated according to the walking condition.

1.4 Manufacturing Process

All components of the form traveler are processed into scattered parts in the processing site, transported to the construction site by cranes and flatbed trucks, and then assembled on-site by tower cranes. During the manufacturing process, the welding quality and process standards should be strictly controlled to prevent problems such as insufficient welding and missing welding.

2. Assembly and Commissioning of Form Travelers

The assembly and commissioning of form travelers is a key step to ensure the safe and stable operation of the form traveler.

2.1 Assembly Process

Before hoisting, the temporary cables at the front end of the Bailey bracket should be pre-tensioned to the specified tension one by one to ensure hoisting safety. The longitudinal beams cannot be hoisted in place at one time and need to be translated on the bracket. The hoisting sequence is: the second section of the longitudinal beam far from the tower crane, the first section of the longitudinal beam, the middle crossbeam, the front crossbeam, and the two sections of the longitudinal beam close to the tower crane. After the assembly of the longitudinal beams is completed, the assembly of the front crossbeam and the middle crossbeam is carried out, and finally the longitudinal beams and crossbeams are connected. During the assembly process, the dimensions of the form traveler should be checked, including the straightness, included angle and diagonal length of the longitudinal beams and crossbeams. After the assembly of the form traveler is completed, jacking and anchoring are required. Jacking should be carried out in stages with hydraulic jacks in accordance with the requirements of the design drawings. After jacking in place, the lower part of the longitudinal beam should be padded firmly, and the middle anchor rod and stay cable should be installed.

2.2 Commissioning Steps

After the form traveler is jacked in place, it is necessary to check whether the connecting bolts of each rod are loose and tighten them in time. Install the formwork system, protective platform, front crossbeam tension truss, etc., and tension them to the specified cable force. The form traveler needs to be pre-loaded in stages to test its load-bearing capacity and deformation. During the pre-loading process, data should be collected and sorted to provide references for subsequent construction.

3. Movement and Positioning of Form Travelers

The movement and positioning of form travelers is a key link in the construction of continuous beam bridges, and the movement speed and positioning accuracy must be strictly controlled.

3.1 Movement Steps

Before the form traveler walks, it is necessary to check whether the walking system and track connection are in good condition to ensure walking safety. The track should be straight and flat, and the number and spacing of sleeper beams at the fulcrum should meet the requirements. Install the walking chain hoist and safety chain hoist, and move the inner formwork and outer formwork walking trolleys forward. The walking of the form traveler requires pushing the middle fulcrum of the C-shaped beam with a jack, and the pushing should be slow and balanced. During the walking process, the sleeper beams under the walking rollers should be moved forward in time to ensure that there must be sleeper beams under the fulcrum during walking. The walking end point should be determined by surveying and setting out or measuring by technicians. After reaching the position, the tail beam should be pushed back with a jack to lift the form traveler in place stably, and anchoring should be carried out immediately.

3.2 Positioning Accuracy Control

After the form traveler is in place, the stay cable should be installed, and the bottom formwork of the main beam should be adjusted to the specified elevation. During the adjustment process, sensors should be used to monitor the deformation and stress to ensure adjustment accuracy. The binding of steel bars and the installation of prestressed pipelines should be carried out in accordance with the requirements of the design drawings. Before concrete casting, some holes should be pre-embedded to facilitate the transfer of anchor points in the later stage. After the transfer is completed, the form traveler can be lowered to prepare for the construction of the next segment.

To Wrap Up

In conclusion, all links of the form traveler construction technology for continuous beam of highway and bridge are closely connected. From the mechanical calculation of the form traveler design to the accuracy control of movement and positioning, omissions in any link may affect the construction safety and bridge quality. In practical engineering, it is necessary to optimize the structural parameters and construction process of the form traveler in combination with the specific conditions of the project, such as geological conditions and span requirements, and at the same time strengthen process monitoring and risk control. By strictly implementing the technical standards of each link, the efficiency and stability of form traveler construction can be fully exerted, the construction quality of long-span continuous beam bridges can be ensured, and a solid foundation can be laid for the safe operation of transportation infrastructure. In the future, with the integration of new materials and intelligent monitoring technologies, the form traveler construction technology will be further upgraded in the direction of light weight and automation, providing solutions for more complex bridge construction scenarios.

As a professional form traveler manufacturer, we have been deeply engaged in the industry for many years. We can customize the design and production of form travelers according to your project span, load requirements, construction conditions and other factors. We provide full-process technical support from material selection and structural calculation to on-site assembly guidance, ensuring that the form traveler meets the core requirements of "safety and reliability, small deformation and convenient operation". If you are promoting a continuous beam bridge construction project or need to optimize the form traveler equipment plan, please feel free to contact us to discuss and customize an efficient construction solution suitable for your project.