H-Shaped Steel Pipe Column Seismic Performance at Xiong'an Station

Literature Overview

The paper by Fan Chong, Chen Yuchen, and colleagues from China Academy of Building Research and CITIC Construction Engineering Research Institute investigates the structural behavior of H-shaped steel pipe columns (also referred to as I-section hollow steel columns) under cyclic lateral loading, specifically in the context of the Xiong'an Station high-speed railway project. The study combines scaled model experiments with ABAQUS finite element simulations to characterize the moment-curvature response, energy dissipation capacity, and damage evolution of this relatively novel composite section type. Published in Building Structure (Vol. 51, No. 24, 2021, pp. 26-34), the work addresses a practical engineering challenge: whether an H-shaped hollow section can replace conventional box-section steel columns in large-span station roofs without compromising seismic resilience.

Core Technical Findings

The experimental campaign employed scaled specimens subjected to low-cycle reversed loading protocols. The resulting load-displacement hysteresis loops exhibited a characteristic spindle-shaped morphology, indicating adequate ductility and energy dissipation. A critical observation is the directional asymmetry in structural response: loading parallel to the flange direction yielded higher ultimate load capacity, slower stiffness degradation, and reduced out-of-plane panel deformation compared to loading parallel to the web direction. This asymmetry is directly attributable to the geometric differences between the flange and web panels and has important implications for column orientation in seismic design.

Parameter	Loading Parallel to Flange	Loading Parallel to Web
Ultimate load capacity	Higher	Lower
Stiffness degradation rate	Slower	Faster
Out-of-plane panel deformation	Reduced	More pronounced
Shear lag effect at inner corners	More significant	Less pronounced
Hysteretic energy dissipation	Adequate	Adequate

A particularly noteworthy finding concerns stress concentration at the column base. Both box-section and H-shaped columns exhibited significant stress concentration at the root joint, with crack initiation occurring preferentially in these regions. For the H-shaped column loaded parallel to the web, the normal stress at the internal concave corners was substantially higher than the corresponding stress in a box-section column of equivalent wall thickness. This pronounced shear lag effect is a direct consequence of the re-entrant corners in the H-section geometry, which create stress discontinuities under bending.

Parametric Study Insights

The numerical parametric study examined the influence of the double-web-to-flange width ratio, wall slenderness ratio, and column slenderness ratio on cross-sectional stress distribution, load capacity, and deformation capacity. The following trends were identified:

As the double-web-to-flange width ratio decreases, both load-bearing capacity and deformation capacity increase progressively.
The stiffness degradation rate, equivalent viscous damping coefficient, and out-of-plane panel deformation all decrease significantly with a reduced double-web-to-flange width ratio.
Overall seismic performance of the H-shaped column with optimized proportions is superior to that of a conventional box-section column of the same wall thickness.

From a welding and fabrication standpoint, the internal concave corners of the H-section represent critical weld locations. The high stress concentrations identified in this study underscore the necessity of employing full-penetration groove welds with thorough preheating and post-weld heat treatment at these junctions. The weld metal should be matched to the base steel grade, and weld toe grinding or TIG dressing should be considered to mitigate crack initiation risks.

Engineering Practice Implications

For the Xiong'an Station project and similar large-span structures, the following recommendations emerge from this study:

Column orientation should be carefully selected to align the flange direction with the primary seismic loading axis, thereby maximizing load capacity and minimizing panel instability.
The base joint of H-shaped columns requires special attention in detailing and fabrication. A thickened base plate with extended fillet welds or a welded haunch can effectively redistribute stress concentrations.
Wall slenderness ratios should be controlled within the range specified by GB 51246-2017 (Code for Seismic Design of Building Structures) and GB/T 19804 to prevent local buckling before global instability.
The shear lag effect at internal corners necessitates the use of strain gauges or digital image correlation (DIC) during full-scale testing to validate analytical predictions.

This study provides valuable technical justification for the adoption of H-shaped steel pipe columns in seismic zones, while simultaneously highlighting the fabrication and welding challenges that must be addressed to realize the theoretical performance gains.

Study Reflection

Having reviewed this work, I am struck by how the geometric complexity of the H-section introduces both advantages and vulnerabilities. The enhanced load capacity and ductility are encouraging, but the shear lag-induced stress concentrations at re-entrant corners demand rigorous quality control during welding and assembly. In my experience with similar composite sections, the transition from laboratory-scale specimens to full-scale structural members often reveals additional stress concentrations at weld attachments, bolted connections, and embedded anchor plates that scaled models cannot capture. Engineers should treat the numerical predictions in this paper as lower-bound estimates and apply appropriate safety factors in design.