Mechanical Behavior of Curved Stainless Steel Pipe Concrete Columns Under Axial Compression

Literature Overview

This paper by Zheng Lianqiong, Wei Changgui, Chen Min, and Zheng Yongqian from Fujian University of Technology presents an experimental and numerical investigation into the compressive behavior of circular stainless steel pipe concrete (SSPC) curved columns. The study, published in the Journal of Xi'an University of Architecture and Technology in 2018, was supported by the National Natural Science Foundation of China (Project No. 51578152). The research fabricated 12 curved SSPC specimens, 3 straight SSPC specimens, and 1 empty stainless steel pipe curved column as reference, conducting center-to-center axial compression tests on curved specimens and eccentric compression tests on straight specimens. The main experimental parameters were nominal slenderness ratios (λn = 24, 48, and 72) and initial curvature amplitudes (u0 = 0 to 140 mm).

Core Technical Findings

The experimental results reveal a clear trend: as the nominal slenderness ratio and initial curvature amplitude increase, the initial stiffness of the SSPC curved columns decreases, and the ultimate load-bearing capacity correspondingly declines. A particularly noteworthy finding is that the load-bearing capacity and stiffness of SSPC curved columns are slightly higher than those of the corresponding eccentrically loaded straight columns, with the improvement being within 5%. This suggests that the P-Δ effect in curved columns is partially compensated by the confinement interaction between the stainless steel tube and the concrete core.

Key Experimental Parameters

Finite Element Analysis and Validation

The authors established numerical models using ABAQUS software to analyze the mechanical behavior of SSPC curved columns. The finite element results showed good agreement with experimental data, confirming the reliability of the numerical approach. The parameter study based on FEA further validated that the improvement in load capacity of curved SSPC columns over eccentric straight columns remains within 5%. Importantly, the study concludes that applying existing code methods for calculating the capacity of ordinary steel pipe concrete compression-bending members to SSPC curved columns is conservative.

Engineering Practice Implications

From a practical standpoint, this research has several implications for structural engineers working with stainless steel pipe concrete systems. First, the finding that curved SSPC columns perform comparably to eccentrically loaded straight columns suggests that initial geometric imperfections—inevitable in fabrication and erection—need not be treated with excessive conservatism in design. Second, the conservative nature of existing code provisions opens the door to more economical designs, particularly in applications where stainless steel pipe concrete is used for its corrosion resistance rather than pure structural efficiency.

Defect and Imperfection Considerations

Study Insights and Reflections

This research contributes meaningfully to the understanding of SSPC members with initial geometric imperfections, which is a practical concern in real-world construction. The use of stainless steel as the outer tube introduces unique material behavior—specifically, the pronounced strain-hardening capacity of austenitic stainless steels such as AISI 304 or 316—which provides additional post-yield ductility that carbon steel systems lack. The fact that the curved columns slightly outperform eccentric straight columns may be attributed to this enhanced strain-hardening behavior allowing the stainless steel tube to redistribute stresses more effectively under the combined bending and compression state inherent to curved members.

The limitation of this study lies in its relatively small specimen count and the specific range of slenderness ratios examined. Future work should extend to higher slenderness ratios (λn > 100) where local buckling of the stainless steel tube may become critical, and to different stainless steel grades with varying strain-hardening characteristics. Additionally, the study does not address the long-term behavior under sustained loads, which is important for creep and shrinkage effects in the concrete core.

For engineers involved in the design of SSPC structures—particularly in marine, chemical, or nuclear environments where stainless steel's corrosion resistance is the primary driver—the findings support a more rational and less conservative design philosophy, provided that fabrication tolerances for initial curvature are properly documented and incorporated into design calculations.