Seismic Performance of I-Shaped Steel Tube Columns at Xiong'an Station

Literature Overview

This paper by Fan Chong and colleagues, published in Building Structures (2021, Vol. 51, No. 24), presents a comprehensive study on the seismic behavior of I-shaped steel tube columns applied in the Xiong'an High-Speed Railway Station project. The research combines scaled model testing with ABAQUS finite element numerical simulation to evaluate the flexural-compressive performance, failure modes, and energy dissipation characteristics of I-shaped steel tube columns under cyclic horizontal loading. The study is particularly significant because it provides direct technical support for the innovative use of I-shaped steel tube columns in a major transportation infrastructure project, where seismic resilience is a paramount design requirement.

Core Technical Findings

The experimental results reveal that the load-displacement hysteresis curves of I-shaped steel tube columns under cyclic horizontal loading exhibit a full spindle shape, indicating strong deformation capacity and energy dissipation capability. A critical directional asymmetry was observed: when loading is applied parallel to the flange direction, the member demonstrates higher load-bearing capacity, slower stiffness degradation, and reduced out-of-plane deformation compared to loading parallel to the web direction. This directional sensitivity is a crucial design consideration that must be accounted for in structural detailing.

Key Geometric Parameters and Their Influence

The numerical parametric study examined the effects of three primary geometric parameters on section stress distribution, load capacity, and deformation behavior. The following table summarizes the parameter influence hierarchy:

A particularly important finding is that the stress concentration at the root of both box-type and I-shaped steel tube columns is significant, making these locations the most probable crack initiation points. When loaded parallel to the web direction, the normal stress at the inner concave corners of I-shaped steel tube columns increases substantially compared to the corresponding locations in box columns, indicating pronounced shear lag effects. This shear lag phenomenon is a well-known challenge in steel tube structural design, and the quantification provided here offers valuable data for refined design methodologies.

Engineering Practice Integration

From a structural engineering perspective, the findings carry several practical implications. First, the directional loading asymmetry means that the orientation of I-shaped steel tube columns relative to seismic action directions must be deliberately selected during design. Aligning the flange direction with the principal seismic direction maximizes the member's effective capacity and ductility. Second, the stress concentration at column roots and inner concave corners demands careful weld detailing and potentially local reinforcement at these critical zones.

For welders and fabrication engineers, the inner concave corner regions represent high-stress areas where residual stresses from welding processes compound with operational stresses. In practice, this suggests that welding sequences should be planned to minimize residual stress accumulation at these locations, and post-weld stress relief or peening treatments may be warranted. The shear lag effect also implies that load transfer through the cross-section is non-uniform, which has implications for connection design where the full cross-sectional capacity is assumed.

The conclusion that I-shaped steel tube columns with a reduced dual-web-to-flange width ratio exhibit overall seismic performance superior to conventional box columns of the same wall thickness is a compelling argument for their adoption in seismic regions. However, engineers must recognize that this advantage is conditional upon proper geometric proportioning and adequate wall thickness control to prevent local buckling.

Study Insights and Implications

This research represents a valuable contribution to the expanding family of steel tube structural members. The I-shaped steel tube column occupies an interesting middle ground between solid I-sections and box steel tubes, potentially offering improved material efficiency while maintaining the composite action advantages of steel tube construction. The combination of scaled testing and numerical simulation provides a robust validation framework, though engineers should note that scaled model results may not fully capture size effects and should be supplemented with full-scale verification for critical applications. The identification of shear lag as a dominant failure precursor in the web-loading direction is particularly insightful and suggests that future design codes should incorporate explicit shear lag correction factors for I-shaped steel tube members.