Pseudo-Static Test Study of Steel Pipe Confined Concrete Bridge Piers

Literature Overview

This study, published in the Journal of Lanzhou University (Natural Science Edition) in 2023 by Ou Zhijing et al. from Fujian University of Technology, presents a systematic pseudo-static test investigation on steel pipe confined concrete bridge piers with different connection methods. The research was supported by the National Natural Science Foundation of China (Grant No. 51878172) and two provincial-level projects. Three full-scale specimens were designed and fabricated, each representing a different connection strategy: integral steel pipe confinement, steel pipe shear key connection only, and a combined steel pipe shear key with grouted sleeve connection. The specimens were subjected to cyclic horizontal loading to evaluate their seismic performance through hysteresis curves, ductility, equivalent viscous damping ratio, stiffness degradation, strength decay, and residual displacement. ABAQUS finite element models were also developed for parametric analysis of axial compression ratio, slenderness ratio, confinement coefficient, and shear key embedment depth to pier height ratio.

Core Technical Content and Key Findings

The study addresses a critical challenge in precast bridge engineering: how to achieve seismic performance comparable to cast-in-place integral structures while enabling prefabrication and field assembly. The three connection methods tested represent progressive levels of sophistication in seismic design philosophy.

The combined connection method—integrating steel pipe shear keys with grouted sleeves—demonstrated superior seismic performance compared to the shear key-only approach. The horizontal peak load increased by 12.93%, and the displacement ductility coefficient improved by 27.17%. The hysteresis curves were notably more plump, indicating better energy dissipation capacity. The equivalent viscous damping ratio was larger, self-centering capability was enhanced, and residual displacements were reduced. These results confirm that the combined connection effectively transfers forces and restrains relative displacement between pier segments while maintaining sufficient deformation capacity.

The finite element parametric analysis identified four critical parameters governing seismic performance. The axial compression ratio directly influences the compressive stress state and confinement effectiveness. The slenderness ratio determines the balance between flexural and shear demands. The confinement coefficient—defined as the ratio of steel tube cross-sectional area to concrete cross-sectional area—controls the level of lateral confinement provided to the concrete core. The shear key embedment depth to pier height ratio governs the connection stiffness and moment resistance at the joint.

Standards and Engineering Practice Implications

From a standards perspective, the seismic design of steel pipe confined concrete piers intersects with multiple code provisions. In China, GB 50011-2010 (Code for Seismic Design of Buildings) and JTG/T 2232-01 (Specifications for Seismic Design of Highway Bridges) provide the framework for ductility and energy dissipation requirements. The steel pipe material typically conforms to GB/T 8163 or GB/T 3091, while the concrete follows GB/T 50081 for material testing. The grouted sleeve connection details should reference JG/T 161-2009 for mechanical connection requirements.

The findings have direct implications for bridge engineering practice. The combined connection method offers a practical solution for prefabricated bridge piers in seismic zones, enabling factory fabrication of pier segments with field assembly through shear keys and grouted sleeves. This approach reduces on-site construction time and quality variability while maintaining seismic resilience. Engineers should note that the optimal shear key embedment depth is critical—too shallow a depth compromises moment transfer, while excessive depth may cause stress concentrations at the connection interface. The parametric analysis provides quantitative guidance for optimizing this ratio in design.

Study Insights and Reflections

This research exemplifies the integration of experimental testing with numerical simulation to address practical engineering problems. The choice of pseudo-static testing is appropriate for evaluating the cyclic deformation and energy dissipation characteristics of pier structures, though quasi-dynamic testing would provide more accurate dynamic response predictions. The ABAQUS models, validated against experimental results, extend the parametric study beyond the limited number of physical specimens.

One observation from a materials and welding perspective is that the connection details—particularly the shear key fabrication and grouted sleeve assembly—involve critical welding operations. The shear keys are typically fabricated from steel plates welded to the pipe end, requiring full-penetration groove welds with stringent quality control per NB/T 47014 or ASME Section IX qualification. The welding procedure specification (WPS) must account for the steel grade, thickness, and the cyclic loading environment to prevent fatigue cracking at the weld toe. Post-weld heat treatment or peening may be beneficial for enhancing fatigue resistance in seismic applications.

Summary

This study provides valuable experimental and numerical evidence that combined steel pipe shear key and grouted sleeve connections can achieve seismic performance comparable to integral steel pipe confined concrete piers. The quantitative improvements in peak load capacity (12.93%) and ductility (27.17%) demonstrate the practical viability of this approach for prefabricated bridge construction in seismic regions. Engineers should consider the interaction between connection design, material selection, and welding quality when implementing these systems in practice.