Zhuojin Pipe Fitting Co., LtdSeismic Response of UHPC Lacing-Steel Tube Concrete Composite Columns
Research Significance and Structural Configuration
The study by Wei Jiangang, Ying Haodong, and Yang Yan from Fuzhou University and Fujian University of Technology investigates the seismic performance of ultra-high performance concrete (UHPC) lacing-steel tube concrete composite columns. Funded by the National Natural Science Foundation of China (Grant No. 52278158) and the Fujian Provincial Industry-Academia-Research Joint Innovation Project (2022H6009), this research was published in the Journal of Traffic and Transportation Engineering (2025, Vol. 25, Issue 3, pp. 82-100, classification U442.5). The composite column configuration combines UHPC lacing plates with concrete-filled steel tube legs, connected by steel lacing members, creating a lattice-like structural system with enhanced seismic resilience.
The motivation for this research is rooted in bridge engineering applications, where composite columns must withstand severe seismic demands while maintaining serviceability and preventing progressive collapse. The use of UHPC as the lacing material represents a significant advancement over conventional concrete, offering compressive strengths exceeding 120 MPa, superior durability, and enhanced crack resistance.
Pseudo-Dynamic Testing Program and Test Parameters
Two 1:8 scale specimens were designed and fabricated for pseudo-dynamic testing. The test parameters included seismic wave characteristics, seismic wave intensity, axial compression ratio, and lacing material type. The pseudo-dynamic testing methodology allows for the simulation of realistic seismic loading sequences with precise control over loading rate and displacement amplitude, providing more reliable data than quasi-static cyclic testing for seismic performance evaluation.
| Test Parameter | Specimen S1 | Specimen S2 | Purpose |
|---|---|---|---|
| Axial compression ratio | Lower | Higher | Evaluate axial load effect on seismic behavior |
| Lacing material | UHPC | Conventional concrete | Compare UHPC vs. conventional performance |
| Seismic wave type | Multiple waveforms | Multiple waveforms | Evaluate seismic wave characteristic sensitivity |
| Seismic intensity | E1, E2 levels | E1, E2 levels | Progressive damage assessment |
Key Seismic Performance Findings
The research yielded several important findings with direct implications for seismic design of composite columns:
- Seismic wave characteristics significantly influence structural response. Under identical low-intensity seismic loading, specimens S1 and S2 exhibited maximum response displacements that were 4.16 times and 4.89 times their respective minimum response displacements under different seismic waveforms, demonstrating the critical role of frequency content and duration in seismic demand.
- With increasing seismic intensity, specimens progressed through elastic, elasto-plastic, and plastic failure stages in a predictable manner.
- Both specimens exhibited similar failure modes characterized as overall flexural compression failure: UHPC lacing plates cracked at the bottom, steel lacing members underwent local buckling deformation, and the column leg steel tubes formed buckling rings or experienced full-section tearing at the base.
- The axial compression ratio had minimal effect on initial lateral stiffness but significantly influenced failure severity — higher axial ratios led to earlier yielding and buckling of the column leg steel tubes and more violent final failure.
- Compared to conventional concrete lacing, UHPC lacing improved initial lateral stiffness by approximately 13.7%, delayed stiffness degradation, and increased cumulative hysteretic energy dissipation by approximately 41.2%.
- Full-scale numerical simulation using OpenSees software revealed that the slenderness ratio is the key factor influencing seismic response and response amplification coefficient.
- A calculation method for full-scale structural response displacements under E1 and E2 seismic loads was proposed and validated with good accuracy.
Steel Tube and Welding Engineering Considerations
From the perspective of steel tube manufacturing and welding quality, several aspects of this research are particularly relevant. The column leg steel tubes are the primary load-bearing elements, and their buckling behavior under seismic loading is governed by tube slenderness ratio, wall thickness, material grade, and welding quality. The formation of buckling rings at the tube base indicates that the tube walls undergo significant plastic deformation, and the full-section tearing represents the ultimate failure mode.
The welding connections between steel lacing members and the column leg steel tubes are critical structural details. These welds must withstand cyclic tensile and compressive stresses without fatigue cracking. The local buckling of steel lacing members observed in testing highlights the importance of proper weld geometry, adequate throat thickness, and weld penetration to ensure full load transfer between the lacing and the tube legs. Welding procedure specifications (WPS) for these connections should specify appropriate preheat temperatures, interpass temperature limits, and post-weld inspection requirements including ultrasonic testing (UT) or phased array ultrasonic testing (PAUT) for volumetric defect detection.
The numerical simulation results indicating that slenderness ratio is the governing parameter for seismic response have direct implications for steel tube specification. Engineers should select tube dimensions that provide adequate stiffness while maintaining sufficient ductility, avoiding excessively slender tubes that buckle prematurely and overly stocky tubes that may exhibit brittle failure characteristics.
Study Insights and Design Recommendations
The 13.7% improvement in initial lateral stiffness and 41.2% increase in cumulative hysteretic energy dissipation achieved by UHPC lacing plates represent substantial performance enhancements that justify the additional material cost of UHPC in seismic-critical applications. The pseudo-dynamic testing methodology provides more realistic seismic demand simulation than conventional quasi-static testing, and the proposed calculation method for full-scale response displacements offers a practical design tool that bridges the gap between scale-model testing and full-scale structural design.
The consistent failure mode observed across specimens — bottom UHPC lacing cracking, steel lacing local buckling, and column leg tube buckling — provides a clear basis for developing acceptance criteria in seismic design codes. Engineers can use these failure characteristics to establish performance-based design targets and to develop inspection protocols for post-earthquake structural assessment.
In summary, this research demonstrates that UHPC lacing-steel tube concrete composite columns offer significantly enhanced seismic performance compared to conventional concrete lacing alternatives, with quantifiable improvements in stiffness, energy dissipation, and damage progression characteristics. The identification of slenderness ratio as the governing design parameter and the development of a validated full-scale response calculation method provide practical tools for the seismic design and quality verification of these advanced composite column systems in bridge engineering applications.