Bending Performance of Novel Stainless Steel Pipe Solid Waste Concrete Composite Members

Literature Overview

This 2024 paper by Yu Xin, Ouyang Fan, Zhang Zuokuan, and Wang Zhibin from Fuzhou University and Fujian Yongzheng Engineering Quality Inspection Co., Ltd., published in Progress in Steel Building Structures (Vol. 26, No. 3), presents an experimental and analytical investigation of the pure bending performance of composite members using a novel S35657 austenitic stainless steel pipe combined with solid waste concrete (recycled aggregate concrete). The study combines six physical bending tests with finite element analysis and code comparison, representing a contemporary approach to sustainable structural engineering that addresses both material innovation and environmental concerns.

Core Technical Content

Material Characteristics

The study introduces two innovative material aspects:

S35657 Austenitic Stainless Steel: This is a novel austenitic stainless steel grade with a minimum yield strength of 355 MPa, offering:

• Superior corrosion resistance compared to conventional carbon steel (Q345/Q390)
• Excellent formability and ductility due to austenitic microstructure
• Higher ductility than typical structural steels, with elongation values typically exceeding 40%
• Sensitivity to strain hardening, which provides additional post-yield strength reserve

Solid Waste Concrete: This is a recycled aggregate concrete incorporating construction and demolition waste (such as crushed concrete, bricks, and ceramics) as partial or full replacement for natural aggregates. Key characteristics include:

• Reduced demand for virgin natural aggregates, contributing to sustainability
• Typically lower compressive strength and elastic modulus compared to conventional concrete (10–30% reduction depending on replacement ratio)
• Higher water absorption and potentially lower durability due to the porous nature of recycled aggregates
• Variable quality depending on the source and processing of the recycled aggregates

Experimental Program

Six stainless steel pipe concrete (SSC) specimens were tested under pure bending conditions:

Experimental Results and Key Findings

Failure Modes: The specimens exhibited ductile failure characterized by progressive yielding of the stainless steel tube followed by concrete crushing in the compression zone. The solid waste concrete did not significantly alter the overall failure mode compared to conventional concrete specimens.

Load-Displacement Behavior:

• All specimens exhibited the characteristic three-stage behavior: elastic stage, yielding stage, and post-yield hardening stage
• The stainless steel's pronounced strain hardening provided significant post-yield strength reserve
• Solid waste concrete specimens showed slightly reduced stiffness but comparable ultimate load capacity

Bending Capacity and Stiffness:

• Solid waste concrete contributed to improved bending capacity and stiffness compared to empty steel tubes, despite its lower material properties
• The composite action between the stainless steel tube and solid waste concrete was effective in all section shapes
• The section shape (circular, square, rectangular) influenced the moment-rotation relationship but not the fundamental composite behavior

Finite Element Analysis

The authors developed validated finite element models using ABAQUS that incorporated:

• A constitutive model for S35657 stainless steel accounting for its pronounced strain hardening behavior
• A concrete constitutive model calibrated for solid waste concrete properties
• Interface elements representing the bond between the steel tube and concrete core
• Geometric and material nonlinearities

The validated FE models were used to investigate parametric effects and to compare the predictions of various design codes.

Code Comparison

The study evaluated the applicability and accuracy of bending capacity calculation methods from various standards:

Engineering Practice Implications

Stainless Steel Tube Fabrication Considerations

The use of S35657 austenitic stainless steel in structural composite members presents unique fabrication challenges:

• Welding: Austenitic stainless steels are susceptible to sensitization (chromium carbide precipitation at grain boundaries) in the heat-affected zone during welding. Low-carbon grades (such as 304L or 316L equivalents) or controlled cooling rates are necessary to prevent intergranular corrosion. Welding filler metals must be matched to the base material composition.
• Work hardening: The pronounced strain hardening of austenitic stainless steel means that forming operations (such as bending of square or rectangular tubes) can significantly increase local hardness and reduce formability. Process parameters must be carefully controlled.
• Corrosion resistance maintenance: Any welding, machining, or surface damage must be followed by proper surface treatment (passivation, pickling) to restore the full corrosion resistance of the stainless steel.
• Thermal expansion: Stainless steel has a higher coefficient of thermal expansion than carbon steel (approximately 17 × 10⁻⁶/°C vs. 12 × 10⁻⁶/°C), which must be considered in composite member design where differential thermal expansion between the steel tube and concrete core can induce internal stresses.

Sustainability Benefits

The combination of stainless steel and solid waste concrete offers compelling sustainability advantages:

• Stainless steel has a long service life (50–100+ years) with minimal maintenance, reducing lifecycle environmental impact
• Recycled aggregate concrete diverts construction waste from landfills and reduces virgin aggregate extraction
• The combination addresses both durability (stainless steel) and resource efficiency (recycled concrete) in a single structural system
• End-of-life recyclability of both materials supports circular economy principles

Quality Control for Solid Waste Concrete

The use of solid waste concrete in structural applications requires rigorous quality control:

• Recycled aggregates must be sourced from clean, uncontaminated demolition waste
• Aggregate processing must remove contaminants (plastics, wood, gypsum, etc.) to levels acceptable for structural use
• Concrete mix design must account for the higher water demand and potentially lower strength of recycled aggregates
• Durability testing (freeze-thaw resistance, chloride penetration, carbonation) must be performed on solid waste concrete specimens to ensure long-term performance

Critical Reflections

This research represents a significant step toward sustainable structural engineering by combining two innovative material concepts: high-performance austenitic stainless steel and recycled aggregate concrete. The finding that solid waste concrete does not significantly compromise the bending performance of stainless steel pipe concrete members is encouraging for practical adoption. However, several questions remain for future investigation:

• Long-term durability of the composite interface between stainless steel and solid waste concrete under cyclic loading and environmental exposure
• The effect of solid waste concrete's higher permeability on the long-term corrosion protection of the stainless steel tube in aggressive environments
• Cost-benefit analysis comparing the higher material cost of stainless steel and recycled concrete against the reduced maintenance and longer service life
• Code provisions specifically addressing the design of stainless steel pipe solid waste concrete composite members, as existing codes are not fully calibrated for this material combination

The study demonstrates that material innovation in structural engineering can simultaneously address performance, sustainability, and economic objectives, provided that appropriate research, testing, and standardization efforts accompany the development of new material systems.

These five studies collectively illustrate the breadth of steel pipe and composite structure engineering, spanning from bridge construction technology to column strengthening, from wear-resistant composite pipes to sustainable material systems. Each topic highlights the critical importance of material selection, fabrication quality, welding integrity, and construction sequencing in achieving the intended structural performance and service life. The progression from 1999 to 2024 also reflects the evolution of engineering practice toward greater emphasis on sustainability, advanced materials, and comprehensive nonlinear analysis methods. Engineers working in steel pipe manufacturing, structural design, and construction management should draw upon these diverse insights to enhance the quality, reliability, and sustainability of their projects.