Zhuojin Pipe Fitting Co., LtdConstruction Technology for Steel Tube Concrete Columns at Nanjing South Railway Station
Overview of the Study
The paper by Liu Xiaogang, Dai Yaojun, and Gu Haiyong (2011), published in Construction Technology, documents the construction technology and quality control measures implemented for the steel tube concrete columns at Nanjing South Railway Station. This is a third-generation passenger station featuring innovative structural design and large-scale composite construction. The first floor utilizes steel tube concrete composite columns (superimposed columns), while floors above the second level up to the roof use conventional steel tube concrete columns. The maximum steel tube diameter reaches 1600 mm, representing one of the largest steel tube concrete column applications in China at the time.
Key Construction Technologies and Challenges
The construction of large-diameter steel tube concrete columns presents several unique challenges that required innovative solutions. The following table summarizes the major technical challenges and corresponding solutions implemented on the project.
| Construction Challenge | Technical Solution |
|---|---|
| Anchor bolt installation | Innovative anchor bolt positioning and fixation method |
| Steel tube column hoisting | Specialized lifting equipment and alignment procedures |
| Welding of steel tube segments | Controlled welding sequence and residual stress management |
| Concrete placement inside large tubes | Modified concrete mix and placement technique |
| Quality verification | Mock-up testing and scaled model sectioning |
The superimposed column concept on the first floor combines steel tube concrete with reinforced concrete to create a hybrid column that accommodates the transition between the foundation and the superstructure. This design approach addresses the challenge of differential settlement and provides a smooth load transfer path from the heavy station structure to the foundation.
Quality Control and Verification Methods
Quality assurance for large-diameter steel tube concrete columns requires a multi-faceted approach. The project team conducted mock-up tests to validate construction methods before full-scale implementation. Scaled models were fabricated and sectioned open to verify the internal quality of the concrete fill, including compaction, void formation, and bond quality between the steel tube and concrete. This destructive verification of scaled models provided confidence in the construction methods applied to full-size columns.
The welding of steel tube segments is a critical quality control point, particularly for columns with 1600 mm diameter where wall thickness and weld length are substantial. Welding procedures must be carefully controlled to manage residual stresses and prevent distortion. The welding sequence should be designed to minimize angular and longitudinal distortion, and post-weld inspection using ultrasonic testing or radiographic testing is essential to verify weld integrity.
Study Insights and Reflections
This case study provides valuable practical insights for engineers working on large-scale composite structure projects. The scale of Nanjing South Station, with its 1600 mm diameter steel tube columns, pushes the boundaries of conventional construction practice and demonstrates that large-diameter steel tube concrete columns are feasible with appropriate construction technology and quality control. The use of mock-up testing and scaled model sectioning is a particularly commendable quality assurance strategy that provides direct evidence of construction quality. Engineers should consider implementing similar verification approaches on their own projects, particularly when new or unproven construction methods are employed. The successful execution of this project contributes significantly to the body of knowledge on large-diameter steel tube concrete column construction.