The crosshead structure is a key top-level structural component of piers in road and bridge engineering, and ensuring the quality of this structure through effective methods is of great significance. In the process of constructing crosshead structures, cast-in-situ construction technology is usually the most frequently used. To fundamentally guarantee construction quality, it is necessary to select the most appropriate pouring method based on actual conditions and requirements, while ensuring the quality of concrete. This paper conducts a comprehensive analysis and research on cast-in-situ crosshead scaffolding construction technology, hoping to contribute to the sound development of road and bridge engineering.

1. Actual Status of Road and Bridge Crosshead and Scaffolding Construction

Generally, crosshead structures are located at the top of road and bridge pier columns and play a crucial role in the entire beam-slab structure. In the construction of crosshead structures, the cast-in-situ construction method is most commonly adopted. Analysis shows that factors related to construction quality include: the selected construction method, the quality of construction materials, and the scaffolding structure. Ensuring the good performance of the scaffolding structure can effectively mitigate the impact of adverse external forces, guarantee the quality and safety of engineering construction, and avoid structural deformation of the project. When constructing crosshead structures, the appropriate scaffolding method can be selected based on actual conditions from the following types: freestanding scaffolding, hoop bracket scaffolding, and embedded bracket scaffolding.

Freestanding scaffolding essentially involves installing supporting steel pipes at the lower part of the crosshead structure to form a full-space scaffolding. Subsequently, formwork, pallets, and square wood materials are erected on the scaffolding structure for lap connection. Hoop bracket scaffolding involves installing steel hoops at the lower part of the crosshead structure, followed by reinforcing bolts, and using corbels to support the formwork and horizontal crossbeams. Embedded bracket scaffolding involves drilling horizontal holes at the top of the pier columns. After the formwork removal process is completed, the structural strength must be inspected. Only after confirming that there are no issues can steel bars be inserted into the holes, and finally, the two ends of the entire structure are effectively utilized. When selecting the scaffolding structure type, it is necessary to consider various factors to choose the most appropriate method, while ensuring the maximum possible economic benefits. Due to the vital role of scaffolding structure types in road and bridge engineering construction, they require focused attention.

2 Practical Application of Various Scaffolding Types

(1) Freestanding Scaffolding

It is most suitable for projects where crosshead pouring is carried out on the ground. The crosshead structure has a high height and strong structural stability, with no risk of water scouring (as shown in the figure). During actual construction, the following issues require key attention: strictly control the vertical placement angle of the column structure to ensure that the error does not exceed the specified range; install wind ropes, diagonal braces, or bottom rails according to actual conditions and requirements; when constructing with vertical poles, use connecting fasteners for connection and install special auxiliary structures; construct a complete drainage system at the construction site to avoid water accumulation.

(2) Hoop Bracket Scaffolding

It is usually used in the improvement and pouring of water projects and is also suitable for high crosshead construction. However, the self-weight of the crosshead structure must be properly ensured to avoid adverse impacts on construction. When using this scaffolding structure for construction, the following issues require key attention: the surface of the pier column structure must meet flatness requirements, and professional methods can be used for roughening treatment to improve surface friction; reasonably control the tightening torque during bolt assembly; focus on the welding effect between the hoop steel plate and the supporting structure; conduct a load test before official operation to ensure that the friction force meets the design standards.

(3) Embedded Bracket Scaffolding

This scaffolding type is suitable for cast-in-situ construction of crosshead structures over water and can also be used in the construction of high crosshead structures. The crosshead itself has a large self-weight and load, and the spacing between supporting steel bars in the lower structure is relatively large. During construction, the following content requires key attention: select hollow steel pipes for the steel material, and the diameter of the steel pipe must be larger than that of the steel ingot to ensure the effect of subsequent pipe penetration work; the cantilever length of the steel ingot must meet the standards for erecting the main crossbeam, and the crossbeam and backing plate are often connected by welding; if the spacing between pier column steel bars is smaller than the reserved holes, the steel bars can be bent, and auxiliary steel bar structures can be installed at appropriate positions.

3 Practical Application of Cast-in-Situ Crosshead Scaffolding Construction Technology

3.1 Surveying and Setting Out

The level and effect of surveying and setting out are closely related to the overall quality of engineering construction, so construction personnel need to conduct comprehensive control. In the actual process of carrying out various tasks, it is necessary to accurately determine the axis and elevation of the crosshead structure and provide the obtained information to the supervisor for in-depth research. To ensure that the surveying and setting out results meet the needs of practical work, construction personnel need to focus on the thickness of the concrete protective layer and accurately mark the position of the main steel bars during actual construction. Secondly, comprehensively compare the original data with the setting out data, and after confirming that there are no errors, provide all data information to technical personnel for review.

3.2 Foundation Structure Construction

In the construction of cast-in-situ crosshead scaffolding structures, the most important task is to ensure the stability of the entire scaffolding structure. To achieve the above goal, it is necessary to harden the scaffolding structure according to actual conditions, which can also lay a good foundation for the subsequent installation of the scaffolding structure and the construction of the cast-in-situ crosshead structure. During the entire engineering construction process, effectively treat the underlying soil layer of the crosshead structure, and determine the top elevation based on the specifications of the scaffolding and the square wood of the crosshead. Secondly, uniformly collect and dispose of various impurities and wastes generated during construction, and compact the soft soil layer. In the actual construction process, it is also necessary to pay attention to the treatment of the crushed stone layer. Use lime soil to cover its surface, ensuring that the thickness of the covering layer meets the standard requirements, so as to make the overall strength of the crushed stone layer consistent with the design requirements. Through the above methods, the stability of the crosshead structure is guaranteed, avoiding foundation deformation caused by the continuous increase of subsequent structural loads.

3.3 Scaffolding Erection

After the foundation structure is completed, the erection of the supporting frame can be carried out. During this process, sleeper wood is installed on the upper part of the foundation structure to lay a good foundation for the subsequent erection of the scaffolding structure. Secondly, effectively adjust the erection position of the scaffolding to ensure that both the top and bottom supporting structures are in a stable state, avoiding adverse impacts on the overall structural stability from later construction. After the completion of scaffolding erection, professional personnel need to test the structural load to ensure that the load-bearing capacity of the structure meets the standard requirements.

3.4 Installation of Bottom Formwork

When constructing the side formwork and bottom formwork of the crosshead, steel should be selected as the construction material as much as possible, and the quality of the construction materials must be effectively guaranteed to fully exert the role of the formwork. Construction personnel need to effectively control deflection to fundamentally avoid formwork deformation. When the height of the crosshead exceeds the standard range, it should be avoided to connect with the steel cage as much as possible. During the installation process, cables need to be installed to ensure the fixing effect of the formwork. Square wood structures are installed on the upper part of the I-steel structure to lay a solid foundation for the smooth progress of subsequent work. Sponge strips should be pasted at the junction of the bottom formwork and the pier structure, and the gaps should be sealed with pure cement slurry. The top of the pier should be treated according to the measured elevation. Set up the steel reinforcement cage according to the actual situation of surveying and setting out.

4 Conclusion

Based on the above elaboration, we conclude that in the construction of crosshead scaffolding structures, it is necessary to carry out various tasks in combination with actual conditions and requirements, and summarize and analyze various construction work to ensure that the construction quality meets the standard requirements.