Due to the high risk of cantilever construction with form travelers for cast-in-place beams, strict quality control of the box girder structure is essential. Additionally, during construction, the steel pipes need to be sunk to a great maximum depth, resulting in high stress on the pipes when they are close to the riverbed during water-filling sinking. Therefore, it is crucial to strictly control the sinking speed and balance of the steel pipes during the sinking process to ensure the sinking quality of the immersed pipes. Moreover, reliable quality control measures should be formulated based on specific construction conditions.

1. Quality Control of Technical Construction

When applying the cantilever construction technology with form travelers for continuous beam bridges, the construction unit shall arrange professional and technical personnel to take charge of the work. Before the specific construction, it is necessary to conduct load tests on the bearing capacity of structures such as diamond trusses, so as to ensure that the parameters, specifications, and quality of the relevant structural components of the bridge meet the basic requirements of the engineering design and the actual on-site conditions. Considering the complexity of the form traveler’s own structure, all concealed parts and components must be inspected one by one. Load tests can be carried out to ensure that the overall bearing capacity of the form traveler meets the requirements.

During the movement of the form traveler, it is necessary to maintain the balance of both ends. Installation personnel shall provide guidance and assistance to adjust deviations (e.g., the positions of the bottom formwork and side formwork) after ensuring that the design requirements are met, and tighten the finish-rolled deformed steel bars of the form traveler. In addition, during the movement of the form traveler, the direction and position of the truss must be kept consistent to prevent it from bearing excessive gravity.

2. Quality Control of Concrete Construction

When pouring the beam segment, a symmetrical pouring method shall be adopted to ensure that the concrete on both sides of the web is poured simultaneously, so as to avoid position inconsistency. It is also necessary to ensure the synchronous pouring of the symmetrical segments of the T-structure, ultimately improving the symmetry of concrete pouring at both ends of the continuous beam. If asymmetry occurs, inspection shall be conducted to control the unbalanced amount of concrete within the specification requirements of the design drawings.

In general, the weight of concrete filling materials shall be scientifically controlled, and the material delivery shall be strictly managed. Concrete pouring shall be carried out in accordance with the designed pouring sequence. During the pouring process, professional personnel shall be arranged to conduct on-site guidance and supervision, and monitor the concrete condition at all times.

When formulating the concrete mix ratio, the following aspects shall be comprehensively considered:

• A scientific proportion of expansive agent shall be added to the concrete, and the particle size of aggregates in the concrete shall be strictly controlled to improve the fluidity and workability of the concrete.

• After the concrete is compacted and leveled, it shall be covered with appropriate materials in a timely manner to prevent external factors from affecting the temperature and humidity changes of the concrete during the initial setting period, thereby reducing the occurrence of temperature cracks. Only after the initial setting is completed can the concrete be finished to ensure the structural stability of the concrete and the flatness of the beam top surface.

After finishing, the concrete shall be covered and cured in accordance with the specification requirements, and the curing time shall be well controlled. Later, the test pieces for beam tension inspection shall be scientifically stored, usually on the beam top and inside the beam.

3. Quality Control of Closure Segment Construction

In the construction of the closure segment, the following aspects of control shall also be well implemented:

• Scientifically design the concrete mix ratio: The mix ratio of the concrete for the closure segment shall be higher than that of the concrete for other ordinary segments. Micro-expansive agents shall be added during concrete mixing. The pouring process of the closure segment concrete shall be carried out at the time of the lowest temperature of the day, and the pouring time shall be controlled within 2 hours.

• Calculate the stress of the rigid locking pre-tensioning of the beam body, and speed up the welding speed during rigid locking to control the pre-tensioning stress of the prestress and ensure that it meets the engineering design specification requirements.

• Scientifically calculate the counterweight of the cantilever end before closure. After the pouring of the closure segment concrete is completed, the counterweight shall be unloaded in a timely manner to ensure that the alignment of the entire beam body meets the design requirements after closure.

4. Integral Control of Beam Body Alignment

The control of the alignment and elevation of each segment of the continuous beam is a difficult point in the entire continuous beam engineering construction. The alignment and elevation of the beam body directly affect the aesthetics of the beam body and the stress distribution of the bridge. Considering that the camber, internal force, elevation, and deflection of the continuous beam are in dynamic changes during construction, and they will also be affected by factors such as construction technology, construction deviation, concrete shrinkage, prestress loss, and temperature change during the specific construction process, it is necessary to strengthen the control in this regard.

On the basis of ensuring the structural safety of the beam body, the alignment of the completed bridge shall be controlled to ensure that its deviation meets the requirements. Each segment of the continuous beam body shall be tracked and adjusted at any time. Forward analysis, backward analysis, and parameter adjustment shall be carried out using measured data. The geometric deformation of the beam structure during the construction process shall be analyzed and corrected using control software, so as to make the bridge alignment reach the ideal state.

5. Conclusion

In conclusion, construction units should attach importance to the application of the cantilever construction technology with form travelers for continuous beams, flexibly adopt this technology in accordance with the actual on-site conditions and design specifications, and strengthen the quality control during the construction process. Only in this way can the construction efficiency and quality be improved, and the development of the highway and bridge construction industry be promoted.