Vehicle-Bridge Resonance Analysis of Steel Pipe-Concrete-Filled Steel Pipe Composite Arch Bridges

Literature Overview

This paper, authored by Chen Youjie and colleagues from the College of Civil Engineering and Architecture at Fuzhou University, was published in the Journal of Fuzhou University (Natural Science Edition), Volume 33, Issue 2, 2005, pages 207-211. The research is based on dynamic load testing of the Fuding Shanqian Bridge, a composite arch bridge utilizing both steel pipe and concrete-filled steel pipe (CFST) structural elements. The study establishes a bridge-vehicle interaction mechanical model and employs finite element analysis to compute vehicle vibration effects on the bridge structure. The work is funded by the Fuzhou University Science and Technology Development Fund (XKJ(YM)-0113).

Core Technical Content

The study addresses vehicle-bridge resonance phenomena in composite arch bridges that incorporate steel pipe and CFST elements. Vehicle-bridge resonance occurs when the natural frequencies of the bridge structure coincide with or are close to the excitation frequencies generated by moving vehicles, leading to amplified vibrations that can compromise structural safety, serviceability, and user comfort. The research is significant because arch bridges with steel pipe and CFST arch ribs have been increasingly adopted in China for medium and long-span applications, and understanding their dynamic behavior under traffic loading is essential for safe design and operation.

Bridge-Vehicle Interaction Model

The mechanical model developed in this study considers the coupled dynamic response of the bridge deck and the moving vehicle. Key parameters in the model include:

Interpretation of Technical Points

From the perspective of steel pipe and CFST engineering, the dynamic behavior of the arch bridge is directly influenced by the material properties and construction quality of the steel pipe and CFST arch ribs. The concrete-filled steel pipe arch ribs provide higher stiffness and damping compared to empty steel pipe arch ribs, which shifts the natural frequencies of the bridge structure and potentially moves them away from critical vehicle excitation frequencies. However, the increased mass of CFST ribs also lowers the natural frequencies, creating a complex interaction that must be carefully analyzed.

The welding quality of the steel pipe arch ribs is particularly relevant to dynamic performance. Weld defects in the longitudinal or circumferential welds of the arch rib segments can create localized stiffness reductions, which may alter the dynamic characteristics of the structure. In particular, incomplete penetration welds or weld defects at segment splices in the arch rib can act as stress concentrators under dynamic loading, potentially initiating fatigue cracks. The use of ultrasonic testing (UT) and phased array ultrasonic testing (PAUT) for weld inspection becomes especially important in dynamic loading applications.

Connection to Pipe Standards and Quality Control

The steel pipe arch ribs in such bridges typically conform to standards such as GB/T 21835 (hot-rolled carbon steel pipes for structural purposes), SY/T 5037 (welded steel pipe for petroleum industry), or API 5L for line pipe. For CFST applications, the concrete mixture must be carefully designed to ensure complete filling of the pipe interior without voids, which requires proper concrete workability and pumping procedures. The quality of the CFST construction directly affects the composite action between steel and concrete, which in turn influences the dynamic properties of the bridge.

Engineering Practice Implications

The impact coefficient derived from this study has direct implications for bridge load design. According to Chinese bridge design codes (JTG D60), the impact coefficient is used to amplify static traffic loads to account for dynamic effects. An accurate impact coefficient is essential for both safety and economy: an overestimated coefficient leads to oversized structural elements and unnecessary cost, while an underestimated coefficient may result in inadequate structural capacity.

For the welding and fabrication of steel pipe arch ribs, the following quality control measures are particularly important in the context of dynamic loading: pre-qualification of welding procedures with consideration of cyclic loading conditions; rigorous non-destructive testing of all welds, with particular attention to segment splice welds; fatigue assessment of welded connections based on the expected number of vehicle passages over the design life; and regular inspection programs that include visual examination and ultrasonic testing of critical welds.

Key Questions and Reflections

The study raises important considerations for the design and maintenance of steel pipe arch bridges. First, the long-term degradation of weld integrity due to fatigue cycling under traffic loads is a critical concern that requires systematic monitoring. Second, the interaction between the dynamic response of the bridge and the construction quality of the CFST arch ribs (such as the degree of concrete filling, the presence of voids, and the bond quality between concrete and steel pipe) warrants further investigation. Third, the study should be extended to consider the effects of different vehicle types and speeds on the resonance characteristics of the bridge, as heavy trucks and high-speed vehicles may excite different bridge modes.

This research contributes valuable insights into the dynamic behavior of composite arch bridges with steel pipe and CFST structural elements, and the bridge-vehicle interaction model developed provides a useful analytical tool for engineers. The findings underscore the importance of integrating structural dynamics considerations into the design, fabrication, and quality control of steel pipe arch bridges.