Short-line match casting, as an important construction method for prestressed concrete box girder bridges, effectively ensures construction accuracy and structural performance through factory-like precasting, precise assembly, and systematic quality control. This article systematically outlines the entire process of this technology, including segment precasting, transportation and storage, on-site assembly, prestressing, and whole-process quality monitoring. It provides an in-depth analysis of the technical key points and control measures for each stage, offering a reference for similar projects.

1. Precast of Segments

The precasting of segments form the foundational stage of the construction process for prestressed box girder bridges using the short-line method. Before production begins, the precast yard must be meticulously planned to ensure it is level, has adequate drainage, and includes designated areas for reinforcement processing, formwork installation, concrete pouring, and curing. The reinforcement cage must be assembled strictly according to the construction drawings, ensuring the rebar's specifications, quantity, position, and connection methods all meet design requirements. The selection and installation of formwork are equally critical; high-precision, high-stiffness formwork must be used to guarantee the segments' dimensions and geometry conform to the design. Before concrete pouring, the formwork must be cleaned and lubricated to reduce friction and improve the surface quality of the segments. During pouring, the concrete slump, vibration intensity, and pouring rate must be controlled to ensure uniform and dense concrete. After pouring, adequate curing is essential for the concrete to achieve its design strength. Quality inspections, including dimensional checks, visual inspections, and strength tests, must be conducted during precasting to ensure segment quality meets specifications. Key technical points: The reinforcement cage should be built following the sequence of bottom rebars first, then web rebars, and finally top rebars to ensure accurate positioning and spacing. Formwork installation must guarantee flatness and verticality, preventing deformation during concrete placement. Concrete should be poured in layers, with each layer's thickness controlled to ensure uniformity and compaction. Attention must also be paid to the duration and method of curing to prevent cracking or insufficient strength due to improper curing practices.

2. Transportation and Storage of Segments

The transportation and storage of segments are crucial links in the construction process. During transportation, the stability and safety of the segments must be ensured. This is typically achieved using flatbed trucks or specialized transport frames, where segments are properly secured and supported to prevent deformation or damage en route. For storage, a level and firm site must be selected to prevent deformation caused by uneven ground or insufficient bearing capacity. Segments should be numbered and categorized for quick and accurate identification during construction. Key technical points: Transport speed and turning radius must be strictly controlled to avoid damage from jolting or collision. During storage, support points must be reasonably distributed to prevent localized overstress and deformation. Considerations for moisture protection, sun shielding, and corrosion prevention are also necessary to maintain segment quality against environmental factors.

3. Assembly and Connection of Segments

The assembly and connection of segments are critical steps in the construction process. Before assembly, the dimensions, geometry, and quality of the segments must be re-inspected to confirm compliance with design requirements. Specialized assembly equipment and tools are used to ensure precision and stability during joining. Connection methods typically involve either cast-in-place (wet) joints or dry joints. Wet joints require concrete pouring and curing, while dry joints utilize methods like high-strength bolts or welding. Alignment and positioning during assembly are crucial to ensure the completed structure acts as an integral unit. Key technical points: Assembly accuracy must be strictly controlled to prevent misalignment or deformation. The choice of connection method should be based on a comprehensive consideration of design requirements, site conditions, and segment characteristics. For wet joints, parameters such as concrete slump, vibration, and curing time must be meticulously controlled to ensure joint quality. For dry joints, high-strength bolting or welding must ensure the strength and stability of the connection points.

4. Prestressing Application and Adjustment 

The application and adjustment of prestress are core activities in the construction of prestressed concrete box girder bridges. Prestressing is applied according to the design, typically by tensioning strands or prestressing bars. Before tensioning, the jacking equipment must be calibrated to ensure the accuracy of the applied force. The tensioning sequence and rate must be strictly controlled to prevent segment damage or deformation due to improper stressing. After initial stressing, prestress losses must be monitored and compensated for to ensure the final prestress meets design requirements. Key technical points: A comprehensive check and debugging of the tensioning equipment are essential before operation. Controlling the tensioning rate and sequence is vital to avoid excessive stress concentrations or deformations. Monitoring of prestress losses, often using strain gauges or pressure sensors, should be conducted as per the design, with adjustments made based on the monitoring results.

5. Construction Quality Control and Monitoring

Quality control and monitoring are vital for ensuring the construction quality and safety of prestressed box girder bridges. Throughout the construction process, rigorous quality control and monitoring must be implemented for all stages: reinforcement cage assembly, formwork installation, concrete pouring and curing, segment transportation and storage, assembly and connection, and prestressing application and adjustment. Simultaneously, key parameters during construction, such as concrete slump, vibration intensity, and tensioning speed, must be monitored and recorded in real-time. Key technical points: Quality control and monitoring should adhere to the principles of being comprehensive, meticulous, and accurate. Strict quality inspections and approvals are necessary for each stage to ensure compliance with design specifications. Modern monitoring technologies and equipment, like strain gauges, pressure sensors, and displacement sensors, should be employed for real-time monitoring of critical parameters. Any identified quality issues or anomalies must be addressed and corrected promptly. Establishing a sound quality management system and a clear quality responsibility matrix is crucial for ensuring controllability and traceability of construction quality.

Short-line match casting technology embodies the development direction of modern bridge engineering towards "factory precasting and assembled construction." By strictly controlling the aforementioned stages, it not only ensures project quality and structural safety but also significantly enhances construction efficiency and reduces on-site work, yielding good economic and social benefits. With the continuous maturation of precast segmental technology and the widespread application of intelligent monitoring methods, the short-line method is poised to play an increasingly important role in future bridge engineering projects.