Static Performance Degradation of Steel Tube Concrete Members Under Simulated Acid Rain Corrosion

Literature Overview

This paper by Chen Mengcheng, Fang Wei, and Huang Hong from East China Jiaotong University investigates the static mechanical performance degradation of steel tube concrete (SRC) members under simulated acid rain corrosion environments. Published in Engineering Mechanics in 2020, the study was supported by multiple National Natural Science Foundation grants (51878275, 51378206, 51868020). The research addresses a practical and increasingly relevant problem as industrial emissions and urban environments continue to expose steel structures to acidic atmospheric conditions.

Core Technical Approach

The study systematically examines four aspects of mechanical performance degradation:

1. Steel material mechanical properties after acid rain corrosion
2. Axial compression mechanical performance of SRC members
3. Pure bending mechanical performance of SRC members
4. Eccentric compression mechanical performance of SRC members

Two simulation methods for corrosion damage were evaluated: wall thickness reduction only, and wall thickness reduction coupled with material property degradation. The finite element analysis was conducted using ABAQUS software, with results validated against experimental test data.

Key Technical Parameters and Findings

Interpretation of Corrosion Damage Simulation Methods

The finding that wall thickness reduction alone outperforms the combined approach (wall thickness reduction plus material property degradation) is technically significant. This suggests that the dominant damage mechanism in acid rain corrosion of steel tubes is geometric section loss rather than bulk material property degradation. The corrosion pit depth and distribution effectively reduce the effective cross-sectional area, while the remaining material retains relatively intact mechanical properties.

This conclusion has important implications for corrosion assessment and remaining life prediction of steel tube concrete structures:

• NDT methods should prioritize wall thickness measurement (ultrasonic thickness gauging) over material property testing for corrosion assessment.
• Repair strategies should focus on restoring cross-sectional geometry (e.g., overlay welding, sleeve repair) rather than material replacement.
• The corrosion damage model for structural assessment should use section loss as the primary damage variable.

Engineering Practice Integration

From a steel pipe manufacturing and welding standpoint, this research has several direct applications:

Corrosion-resistant steel selection: The study provides quantitative data on how different corrosion rates affect steel properties, which can inform the selection of corrosion-resistant grades for SRC applications in acidic environments. For example, weathering steels (such as those conforming to EN 10216-5 or ASTM A606) may provide adequate protection in moderate acid rain environments without requiring external coatings.

Welding considerations under corrosion: When repairing corroded SRC members, the welding process must account for:

• Reduced wall thickness at the weld location, requiring lower heat input to prevent burn-through.
• Potential hydrogen-induced cracking susceptibility in the corroded HAZ due to trapped moisture and corrosion products.
• The need for preheating to counteract the combined effects of reduced section and potential residual hydrogen from the corrosion layer.

Quality control implications: The study's finding that local standards are more stringent than national standards suggests that engineers should adopt the more conservative approach in corrosion-damaged SRC member assessment. For welding repair of corroded sections, the acceptance criteria should be elevated accordingly, incorporating:

• Stricter NDT coverage (100% UT or PAUT for repair welds)
• Reduced acceptance thresholds for lack of fusion and porosity
• Mandatory hardness testing of the HAZ adjacent to corrosion pits

Study Insights and Implications

The research provides a valuable framework for understanding how acid rain corrosion affects SRC members across different loading conditions. The observation that the degradation patterns differ between axial compression, pure bending, and eccentric compression cases has important design implications. Members under bending are particularly vulnerable because corrosion-induced section loss preferentially affects the outer fibers where bending stresses are highest.

For steel pipe suppliers and fabricators, this research underscores the importance of:

• Providing detailed corrosion resistance data with material certifications for SRC applications.
• Offering corrosion-resistant steel grades with documented acid rain exposure performance.
• Developing welding procedures specifically qualified for repair of corroded sections, including procedures for welding onto surfaces with residual corrosion products.

The comparison between wall thickness reduction and combined degradation methods also informs NDT strategy. Since geometric damage dominates, phased array ultrasonic testing (PAUT) with calibrated section loss models provides the most reliable assessment of remaining structural capacity. Magnetic flux leakage (MFL) testing, as discussed in related literature, can also effectively detect through-wall corrosion defects in steel tubes.

Reference Value and Outlook

This study contributes significantly to the understanding of corrosion damage mechanisms in SRC structures. The practical conclusions about damage simulation methods and the comparative analysis of standards provide actionable guidance for engineers involved in SRC bridge and building maintenance. Future research should extend these findings to include dynamic loading conditions, fatigue life assessment under cyclic corrosion, and the effectiveness of various corrosion protection strategies including cathodic protection, advanced coatings, and corrosion-resistant alloy steels. The integration of corrosion monitoring data with structural health monitoring systems represents a promising direction for predictive maintenance of SRC structures in corrosive environments.