Zhuojin Pipe Fitting Co., LtdSeismic Response and Parameter Analysis of Steel Tube Concrete Lattice Column Continuous Curved Girder Bridge
Literature Overview
This paper by Ou Zhijing, Lin Jianmao, Lin Shangshun, and Lin Wen (Fujian University of Technology, 2018) investigates the seismic performance of a steel tube concrete (SRC) lattice column continuous curved girder bridge system. The study is anchored in the actual engineering of the Ganhaizi Extra-Large Bridge in Sichuan Province, China, which is located in a high seismic intensity zone along a highway network. The authors constructed 26 finite element models using Midas Civil software to evaluate the influence of four key design parameters—column-to-beam stiffness ratio, curvature radius, lacing tube arrangement, and the presence of seismic isolation/damping devices—on the seismic response of the bridge under E1-type earthquake action.
Core Technical Points
Structural Configuration and Design Parameters
The bridge system studied combines two innovative structural features: a SRC composite truss girder for the superstructure and a lattice-type high column for the substructure. The lattice column, constructed using steel tubes as lacing members, provides high stiffness-to-weight ratio and is particularly suitable for tall piers in earthquake-prone regions.
| Design Parameter | Variable Range | Engineering Significance |
|---|---|---|
| Column-to-beam stiffness ratio | Multiple ratios investigated | Controls load distribution and ductility demand |
| Curvature radius | Varying geometric curvature | Affects torsional response and bending distribution |
| Lacing tube arrangement | Different spatial configurations | Influences column lateral stiffness and buckling behavior |
| Seismic isolation/damping | With/without devices | Directly modifies dynamic response characteristics |
Seismic Response Indicators
The authors monitored four critical response quantities at principal control sections: bending moment, torsional moment, column top displacement, and drift ratio. These indicators collectively capture the flexural, torsional, and global deformation behavior of the bridge under seismic excitation. The E1 earthquake type was selected as the design basis, consistent with Chinese seismic design code provisions for regions with peak ground acceleration of 0.20–0.30 g.
Interpretation of Technical Insights
The study reveals several important patterns regarding the interaction between geometric parameters and seismic performance. The column-to-beam stiffness ratio emerges as a dominant factor controlling the distribution of seismic forces between the superstructure and substructure. A higher column stiffness ratio tends to concentrate displacement demand in the columns while reducing girder deformation, but this can lead to excessive ductility demands at the column bases. Conversely, a lower ratio shifts demand to the girder but may result in unacceptably large column displacements.
The curvature radius has a non-trivial effect on torsional response. In curved continuous girders, the horizontal curvature introduces coupling between bending and torsion, and this coupling is amplified during seismic loading due to the geometric nonlinearity. The lattice column configuration, with its open-web geometry, exhibits different torsional stiffness characteristics compared to solid-section columns, which must be carefully considered in the seismic design.
The lacing tube arrangement directly affects the column's lateral stiffness and buckling resistance. Different arrangements—such as diagonal, cross, and vertical lacing patterns—produce varying degrees of shear deformation and flexural rigidity. The study demonstrates that the arrangement choice can significantly influence the overall bridge period and modal characteristics.
Standards and Code Relevance
The findings have direct implications for the revision of Chinese seismic design codes for steel tube concrete composite bridge structures. Current codes (such as JTG/T 2231 and GB 50011) provide general guidance for steel-concrete composite structures but lack specific provisions for lattice-type SRC columns in curved bridge configurations. The parameter ranges and response patterns identified in this study provide quantitative evidence that can inform code calibration.
Engineering Practice Integration
From a steel pipe manufacturing perspective, the lattice column configuration places specific demands on the steel tubes used as lacing members. The tubes must satisfy requirements for:
- Uniform wall thickness with tight tolerance (typically ±0.5 mm for ERW or seamless tubes)
- Consistent chemical composition to ensure predictable mechanical properties under cyclic loading
- Proper heat treatment to achieve the target yield strength without excessive embrittlement
- Surface quality suitable for field welding connections
The curved girder system requires steel tubes that can be formed or bent without significant loss of mechanical properties. This places additional demands on the material's strain hardening behavior and the welding procedures used for curved joint fabrication.
Key Questions and Reflections
Several questions arise from this study that merit further investigation. First, the study uses E1 earthquake time histories, but the bridge is located in Sichuan where the 2008 Wenchuan earthquake demonstrated the importance of long-period ground motion effects. The resonance between the bridge's fundamental period and long-period components of near-fault ground motion could be a critical design consideration. Second, the finite element model assumes elastic-perfectly plastic material behavior for the steel tubes, which may not capture the cyclic hardening and degradation observed in real seismic events. Third, the interaction between the lattice column buckling and the curved girder's torsional deformation under combined seismic action remains an area requiring more detailed study.
Study Insights and Implications
The study provides valuable parametric data for the seismic design of SRC lattice column curved bridge systems. The recommended parameter ranges offer practical guidance for engineers designing similar structures in high seismic zones. The optimization verification of the first span of the Ganhaizi Bridge demonstrates the applicability of the findings to real engineering projects. For steel pipe suppliers and fabricators, the study underscores the importance of maintaining consistent material properties and dimensional accuracy in the steel tubes used for lattice columns, as these directly affect the seismic performance of the completed structure. The work also highlights the need for more refined constitutive models and nonlinear dynamic analysis capabilities to fully capture the complex behavior of these innovative bridge systems under extreme seismic events.