Seismic Response and Parameter Analysis of Concrete-Filled Steel Tube Lattice High Pier Continuous Curved Girder Bridge

Literature Overview

This paper by Ou Zhijing and colleagues from Fujian University of Technology investigates the seismic performance of a concrete-filled steel tube (CFST) lattice high pier continuous curved girder bridge, one of the emerging bridge types for expressways in severe earthquake zones. The study is grounded in the actual engineering project of the Ganhaizi Grand Bridge in Sichuan Province, China. Using Midas Civil finite element software, the authors constructed 26 three-span symmetrical curved continuous girder bridge calculation models and compared seismic response values under E1 earthquake loading. The research was supported by the National Natural Science Foundation of China (51408128), the Fujian Provincial Natural Science Foundation (2017J01471), and the Fujian Provincial University New Century Outstanding Talent Support Program (GY-Z15108).

Core Technical Parameters and Design Variables

The study systematically examines four key design parameters that govern the seismic behavior of this bridge type. The first parameter is the beam-pier stiffness ratio, which controls the load distribution between the superstructure and substructure during seismic excitation. The second is the curvature radius of the continuous girder, which directly influences the torsional demand and lateral force distribution. The third parameter is the lacing tube arrangement form, which determines the lattice pier's lateral stiffness and energy dissipation capacity. The fourth parameter is the presence or absence of seismic isolation and energy dissipation devices.

The seismic response quantities analyzed include bending moment, torsional moment, pier top displacement, and drift ratio at key control sections of both the CFST composite truss girder and the lattice pier.

Interpretation of Key Technical Points

The lattice pier system using CFST members represents an innovative substructure solution that combines the confining effect of concrete-filled steel tubes with the lightweight and high stiffness characteristics of a truss configuration. From a metallurgical and welding perspective, the lacing tubes in the lattice pier require careful attention to their fabrication quality, as these slender members are critical to the overall stability of the pier under seismic loading. The welding connections between lacing tubes and the main CFST columns are potential weak points that require rigorous quality control in accordance with standards such as GB/T 985.1 for welding procedures and SY/T 4103 for welding of steel pipe.

The torsional response of the curved girder is a particularly important consideration. Unlike straight girders, curved continuous beams experience significant torsional moments during lateral seismic excitation, and the coupling between bending and torsion can lead to complex stress states in the CFST composite truss members. The curvature radius plays a dual role: a smaller radius increases the geometric eccentricity and thus the torsional demand, but it also increases the bending stiffness in the horizontal plane.

Integration with Engineering Practice

The optimization verification performed on the first span of the Ganhaizi Bridge demonstrates the practical applicability of the research findings. In engineering practice, the recommended parameter ranges can serve as initial design guidelines for similar bridge types in high seismic zones. However, several practical considerations must be addressed during construction. The CFST lacing tubes, typically made from structural steel grades such as Q235B or Q345B per GB/T 1591, require precise dimensional control to ensure proper fit-up during field assembly. The welding of lacing tubes to the main columns should follow qualified welding procedures with appropriate preheat temperatures and interpass temperature controls to prevent cold cracking in the heat-affected zone.

The seismic isolation and energy dissipation devices, when incorporated, fundamentally alter the seismic force distribution and can reduce pier top displacements and drift ratios significantly. The selection and installation of these devices must comply with relevant standards such as GB 50011 for seismic design of buildings and JTG/T 2231 for bridge seismic design. The connection details between the isolation bearings and the pier cap require special attention to ensure reliable force transmission and prevent out-of-plane instability.

Study Insights and Implications

This research provides valuable theoretical support for the seismic optimization design of CFST lattice pier curved girder bridges. The parameter study approach of constructing 26 FEM models allows for a comprehensive understanding of the interaction effects among multiple design variables. The recommended parameter ranges offer practical guidance for engineers designing similar bridges. The study also contributes to the revision of seismic design codes for CFST composite structure bridges, which is an important development given the increasing use of these structures in seismic regions. The key insight is that the combination of CFST lattice piers with seismic isolation devices can achieve acceptable seismic performance even under severe earthquake conditions, provided that the design parameters are selected within the recommended ranges and construction quality is rigorously controlled.