Eccentric Compression Behaviour of Rectangular Steel Tube Concrete H-Shaped Honeycomb Composite Columns

Literature Overview

This paper, published in Journal of Northeast Petroleum University (2020, Vol. 44, No. 4), presents a systematic study on the eccentric compression performance of Steel Tube Honeycomb Concrete Composite (STHCC) columns. The research was conducted by Ji Jing and colleagues from Northeast Petroleum University, Harbin Institute of Technology, and the Institute of Engineering Mechanics, Chinese Academy of Sciences, supported by multiple funding agencies including the National Natural Science Foundation (Grant No. 51178087). The study involves 17 physical specimens and extensive finite element parametric analysis using ABAQUS.

Structural Configuration and Key Parameters

The STHCC column is a hybrid composite system where rectangular steel tube concrete (SRC) sections form the flanges of an H-shaped column, with a honeycomb concrete web connecting them. This configuration aims to combine the high confinement effect of steel tube concrete with the structural efficiency of H-sections.

Parameter	Range of Variation	Purpose
Eccentricity ratio (e/h)	0 (axial) to 0.3	Study eccentric compression behaviour
Slenderness ratio (λ)	10–30	Investigate buckling effects
Flange steel tube thickness (t)	4–10 mm	Evaluate confinement effect
Core concrete strength (f_cu)	30–60 MPa	Assess material strength contribution
Number of specimens	17 physical + 10 FE models	Parametric study

The finite element models were validated against experimental data, showing good agreement in load-displacement curves, confirming the modelling approach including the confinement-based concrete constitutive model and simplified steel model.

Key Technical Findings

Strain Distribution and Plane Section Assumption

The study confirmed that under eccentric compression, the cross-sectional strain distribution of STHCC columns largely follows the plane section assumption. This is significant because it validates the applicability of classical beam theory for design calculations, simplifying the analytical framework for engineers.

Load Capacity Influencing Factors

The parametric analysis revealed clear trends:

Eccentricity: Increasing eccentricity reduces the ultimate load capacity progressively. At high eccentricity ratios, the tensile zone of the cross-section experiences significant concrete cracking and steel yielding, leading to a sharp drop in capacity.
Slenderness ratio: Higher slenderness ratios reduce load capacity due to increased second-order effects (P-Δ effects). The reduction becomes more pronounced at slenderness ratios exceeding 20.
Core concrete strength: Higher concrete strength directly improves the ultimate load capacity. The relationship is approximately linear within the studied range (30–60 MPa).
Flange steel tube thickness: Thicker steel tubes provide stronger confinement (hoop effect), delaying concrete crushing and increasing the ultimate load capacity. The improvement is most significant when transitioning from thin tubes (4 mm) to moderate thickness (6–8 mm).

Empirical Design Formula

The authors developed a regression-based empirical formula for the eccentric compression ultimate load capacity of STHCC columns. This formula accounts for the key parameters and provides a practical design tool. The formula's accuracy was validated against both experimental and numerical results, showing acceptable deviation within engineering tolerance (typically ±10%).

Welding and Fabrication Considerations

From a steel pipe and welding engineering perspective, the STHCC column configuration presents several fabrication challenges:

Component	Welding/ Fabrication Requirement	Critical Quality Parameter
Rectangular steel tubes	Longitudinal welds (LSAW or HFW)	Weld tensile strength ≥ parent metal
Flange-to-web connection	Full-penetration butt welds or fillet welds	No lack of fusion, no undercut > 0.5 mm
Honeycomb web	Prefabricated or field-welded	Dimensional accuracy ±2 mm
Steel tube concrete interface	Concrete infill after weld inspection	UT verification of welds before pour

The rectangular steel tubes used as flanges require careful control of corner radius and wall thickness uniformity. Non-uniform wall thickness would create stress concentrations under eccentric loading, potentially initiating premature local buckling.

Study Insights and Implications

This study makes a meaningful contribution to the structural engineering literature on composite columns. For steel pipe engineers, the key takeaway is that the confinement effect of steel tubes in composite columns is directly related to tube thickness and material properties, both of which are within the control of steel pipe manufacturers. The recommendation to use thicker tubes (6–10 mm) for enhanced confinement aligns with the understanding that increased wall thickness improves the tube's resistance to local buckling under concrete pressure. The validation of the plane section assumption simplifies design calculations and reduces the need for complex numerical modelling in routine design practice. The empirical formula developed by the authors provides a practical tool that can be directly incorporated into design software and hand calculations, facilitating the wider adoption of STHCC columns in seismic-prone regions.