Unidirectional Eccentric Compression Performance of Multi-Chamber Steel Tube Concrete Combined T-Section Short Columns

Literature Overview

This research presents an innovative structural system: multi-chamber steel tube concrete combined T-section short columns subjected to unidirectional eccentric compression. The T-section configuration, composed of multiple steel tubes arranged in a T-shape and filled with concrete, offers enhanced bending resistance in the flange direction while maintaining axial load capacity. The multi-chamber design provides internal voids that can be utilized for service installation or additional reinforcement. The eccentric loading condition introduces combined axial-flexural behavior that is critical for realistic structural applications such as column-beam joints, transfer structures, and eccentrically loaded columns.

Core Technical Findings

The multi-chamber T-section columns demonstrated excellent load-displacement behavior under eccentric compression, with the flange chambers providing significant resistance to bending moments while the web chambers maintained axial capacity. The eccentricity ratio (e/h) emerged as the primary variable governing failure mode transition. At low eccentricities (e/h < 0.15), the columns exhibited predominantly axial failure with concrete crushing in the compression zone. At higher eccentricities (e/h > 0.25), bending failure dominated with tensile fracture of steel tubes in the tension zone.

Section and Loading Parameters

The interaction between axial load and bending moment was characterized through P-M interaction diagrams. The multi-chamber configuration provided a broader interaction envelope compared to single-tube T-sections, indicating superior combined load capacity. The internal chamber walls contributed significantly to shear resistance and helped distribute stress concentrations at the web-flange junction.

Process and Fabrication Analysis

The fabrication of multi-chamber T-section columns requires careful attention to tube-to-tube connections and concrete placement. The steel tubes must be welded or bolted together to form the T-configuration, with full-penetration butt welds recommended for the web-flange junctions per ASME Section IX. Concrete placement in multi-chamber sections requires special consideration to ensure complete filling and avoid voids, particularly at the web-flange junction where access is limited.

Welding and Assembly Requirements

Concrete placement in multi-chamber sections requires the use of low-slump or self-consolidating concrete (SCC) with appropriate entrained air content (3-5%) to ensure complete filling. The concrete must be placed in layers not exceeding 300 mm thickness, with vibration applied to each layer. For sections with limited access, internal vibrators or external form-vibration methods must be employed to achieve adequate compaction.

Engineering Practice Applications

Multi-chamber T-section SRC short columns find application in transfer structures, column-base connections with eccentric loads, and composite bridge decks where the T-shape provides direct compatibility with beam elements. The internal chambers can house electrical conduits, hydraulic lines, or monitoring sensors, adding functional value beyond structural capacity. In seismic applications, the multi-chamber configuration provides multiple failure paths that enhance structural redundancy and ductility.

Study Insights and Outlook

The research demonstrates that multi-chamber T-section SRC columns offer a versatile and efficient structural solution for eccentrically loaded applications. The key advantage lies in the combination of high axial capacity from the web chambers and high bending resistance from the flange chambers, all within a single integrated member. For future development, engineers should explore the potential of adding internal spiral reinforcement within individual chambers to further enhance ductility, and consider hybrid configurations combining different steel grades in web versus flange chambers to optimize cost-performance ratios. The multi-chamber T-section represents an innovative advancement in composite structural engineering that warrants further standardization and practical implementation.