Zhuojin Pipe Fitting Co., LtdSeismic Performance of Prefabricated Assembled Steel Tube Concrete Bridge Piers
Literature Overview
This 2021 paper published in the China Journal of Highway and Transport by Liu Xueshan, Li Jianzhong, Zhang Hongjie, and Chen Ziyang from Tongji University and Linnton International Engineering Consulting (China) Limited investigates the seismic mechanical properties of prefabricated assembled steel tube concrete (SRC) bridge piers. The research was funded by the National Natural Science Foundation of China (Grant No. 51678434). The study addresses the growing demand for rapid, damage-tolerant bridge construction by examining different assembly joint configurations and their influence on seismic performance.
Experimental Program and Design Parameters
The authors designed and fabricated eight scaled models based on a reference actual bridge pier. The test matrix included six rocking-type prefabricated prestressed SRC piers and two comparison piers (one rocking-type prestressed reinforced concrete pier and one socket-type prestressed SRC pier). The experimental parameters considered were assembly joint type, energy-dissipating steel bar reinforcement ratio, and prestressed axial compression ratio.
Test Specimen Configuration
| Specimen Group | Type | Key Variable | Number of Specimens |
|---|---|---|---|
| Group A | Rocking-type prestressed SRC | Different energy-dissipating steel bar ratios | 6 |
| Group B | Rocking-type prestressed RC | Comparison specimen | 1 |
| Group C | Socket-type prestressed SRC | Comparison specimen | 1 |
The pseudo-static testing method was employed, combined with numerical simulation through finite element fiber models to reveal the ductility capacity, self-centering performance, hysteretic energy dissipation characteristics, failure modes, and failure mechanisms of the prestressed prefabricated SRC piers.
Key Experimental Results
Rocking-Type vs. Socket-Type Performance Comparison
The experimental results demonstrate that the rocking-type piers exhibit superior ductility and energy dissipation capacity compared to the socket-type piers. The rocking mechanism allows a controlled range of rotational movement at the pier base, which, combined with prestressed tendons and energy-dissipating steel bars, creates an effective self-centering and energy dissipation system. At the same target displacement, the rocking-type specimens exhibit smaller residual displacements than the socket-type specimens, confirming their superior self-centering characteristics.
Effect of UHPC Seat Layer
The installation of an ultra-high performance concrete (UHPC) seat layer at the pier base significantly reduces the damage to the pile cap during loading. This improves the damage tolerance of the bridge pier, which is a critical consideration for post-earthquake bridge functionality and repair.
Effect of Energy-Dissipating Steel Bar Reinforcement Ratio
Increasing the reinforcement ratio of energy-dissipating steel bars causes the damage state of the specimens to appear at a later stage, enhances the energy dissipation capacity, and reduces the severity of joint damage at the pier base. However, this also results in an increase in residual displacement, indicating a trade-off between energy dissipation and self-centering.
Effect of Prestressed Axial Compression Ratio
Increasing the prestressed axial compression ratio further enhances the self-centering capability of the specimens by constraining their deformation, thereby reducing residual displacement. This is beneficial for the rapid restoration of bridge functionality after an earthquake.
Engineering Practice Considerations
From a steel pipe fabrication and welding standpoint, the prefabricated assembled SRC bridge piers present several technical challenges. The steel tubes used for the piers must be manufactured to precise dimensional tolerances to ensure proper assembly and joint fit-up. The welding of steel tube segments at field joints requires strict quality control, particularly for the circumferential welds that form the primary structural connections.
Welding Quality Requirements for Prefabricated SRC Piers
| Welding Aspect | Requirement | Inspection Method |
|---|---|---|
| Fit-up tolerance | ±2 mm for circumferential joints | Visual and dimensional check |
| Weld penetration | Full penetration for structural joints | UT or RT |
| Weld surface quality | No undercut, porosity, or slag inclusion | MT or PT |
| Heat-affected zone | Controlled HAZ width to prevent embrittlement | Macro/micro examination |
| Post-weld treatment | Stress relief for high-strength steels | PWHT or vibration stress relief |
The assembly joints in prefabricated SRC piers are particularly critical because they serve as both structural connections and controlled deformation zones during seismic events. The welding procedure must be qualified to ensure that the weld metal and heat-affected zone possess adequate ductility and toughness to accommodate the cyclic strains imposed during earthquake loading.
Study Insights and Reflections
This research provides a solid experimental foundation for the design and application of prefabricated assembled SRC bridge piers. The validated finite element fiber models offer a reliable numerical tool for parametric studies and design optimization. The findings suggest that the rocking-type configuration with appropriate prestress levels and energy-dissipating reinforcement represents the optimal solution for seismic bridge design where rapid post-earthquake functionality is required. Future work should focus on full-scale testing and the development of standardized design guidelines that incorporate the experimental findings into practical engineering codes.