Impact Resistance of High-Strength Concrete-Filled Square Steel Tubes with Local Penetration Corrosion

Literature Overview

This paper by Zhang Qian, Wang Yulin, Zhao Junhai, and Gao Shan, published in Journal of Vibration and Shock in 2023 (Vol. 42, No. 3, pp. 112-120), investigates the impact resistance of high-strength concrete-filled square steel tubes (HSCFST) subjected to local penetration corrosion. Using ABAQUS finite element analysis, the study examines the effects of slit angle, slit length, impact face orientation, and impact energy on the dynamic response and energy absorption of HSCFST columns. This research is highly relevant to pipeline and structural engineers concerned with the integrity of steel tubes in corrosive environments, particularly in offshore platforms, marine structures, and industrial facilities where impact loading combined with corrosion damage is a significant hazard.

Core Technical Content and Numerical Methodology

The study establishes a numerical model of HSCFST columns with local penetration corrosion simulated as slits or notches on the tube surface. The corrosion damage is parameterized by slit angle (the orientation of the slit relative to the impact direction), slit length, impact face (front, side, or back), and impact energy. The finite element model captures the material nonlinearity of both the high-strength steel and the concrete infill, as well as the geometric nonlinearity associated with large deformations during impact.

The key findings reveal several important phenomena. First, under local penetration corrosion, front-facing impact members exhibit crack closure behavior, while side-impact members develop a triangular failure pattern. This is attributed to the different stress states and constraint conditions imposed by the corrosion damage on the tube walls during impact. Second, the impact force plateau value is primarily influenced by the impact face orientation, followed by the slit angle, while the slit length has a more significant effect on members subjected to back-face impact. Third, increasing the slit angle and decreasing the slit length are positively correlated with the impact force plateau value. Fourth, front-impact members exhibit superior impact resistance compared to side and back-impact members. Fifth, decreasing the slit angle increases the mid-span deflection, with front-impact members showing the smallest deflection. Sixth, the energy absorption ratio increases with slit length and decreases with slit angle, with back-impact members exhibiting the highest energy absorption.

Defect Analysis and Failure Modes

The following table summarizes the failure modes and their dependence on corrosion parameters:

From a materials science perspective, the interaction between corrosion damage and impact loading is complex. Local penetration corrosion reduces the effective cross-sectional area of the steel tube, creating stress concentrations at the slit edges. Under impact loading, these stress concentrations can initiate cracks that propagate through the tube wall, leading to progressive failure. The concrete infill provides confinement to the steel tube, but the effectiveness of this confinement is reduced by the corrosion damage, as the concrete can no longer fully constrain the deforming steel wall.

The triangular failure pattern observed in side-impact members is particularly concerning from a structural engineering standpoint. This pattern suggests that the corrosion damage creates a weak zone that redirects the impact energy into a concentrated failure path, potentially leading to sudden and catastrophic collapse. In contrast, the crack closure behavior in front-impact members suggests that the corrosion damage may actually improve the impact resistance by creating a mechanism that absorbs energy through crack opening and closing cycles.

Engineering Practice Implications

For pipeline and structural engineers, this study has several important implications. First, it highlights the need for regular corrosion inspection and monitoring of steel tubes in corrosive environments, particularly in areas where impact loading is possible, such as offshore platforms subject to wave impact or industrial facilities where equipment collision is a risk. Second, it provides a practical calculation method for the dynamic flexural bearing capacity influence coefficient of HSCFST columns under local penetration corrosion, which can be used for structural assessment and retrofitting decisions.

From a steel pipe fabrication and welding perspective, the study underscores the importance of corrosion protection systems for steel tubes. The integrity of corrosion protection coatings, cathodic protection systems, and material selection must be maintained to prevent local penetration corrosion from developing. Any welds in the steel tubes must be protected with equal or greater rigor than the base metal, as weld regions are often more susceptible to corrosion due to differences in microstructure and residual stress.

For quality control purposes, non-destructive testing methods such as ultrasonic thickness measurement, phased array ultrasonic testing (PAUT), and time-of-flight diffraction (TOFD) should be employed to detect and characterize local penetration corrosion in steel tubes. The results of these inspections should be fed into the structural assessment model to determine whether the remaining cross-sectional area is sufficient to maintain the required impact resistance.

Key Questions and Reflections

The study raises several important questions for further investigation. First, how does the rate of corrosion progression affect the impact resistance over time? A static assessment of a given corrosion state does not account for the continued degradation of the steel tube, which could lead to sudden failure when the remaining cross-sectional area falls below a critical threshold. Second, what is the effect of environmental factors such as temperature, humidity, and chemical composition of the corrosive medium on the interaction between corrosion and impact? These factors may influence both the corrosion rate and the mechanical properties of the corroded steel.

Additionally, the study does not address the effect of corrosion on the weld integrity of the steel tube. Welds are critical structural elements that must maintain their integrity under both static and dynamic loading. Corrosion-assisted cracking at weld regions, such as stress corrosion cracking (SCC) or hydrogen-induced cracking (HIC), could significantly reduce the impact resistance below the values predicted by the numerical model. Future research should incorporate corrosion-assisted cracking models into the impact analysis to provide a more comprehensive assessment of structural integrity.

Study Insights and Conclusions

This research provides valuable insights into the impact behavior of high-strength concrete-filled square steel tubes with local penetration corrosion. The identification of distinct failure modes for different impact face orientations and corrosion parameters offers practical guidance for structural engineers in assessing the remaining capacity of corroded steel tube structures. The proposed calculation method for the dynamic flexural bearing capacity influence coefficient is a useful tool for structural assessment and retrofitting decisions. For steel pipe engineers, this study reinforces the critical importance of corrosion protection and regular inspection in ensuring the long-term integrity of steel tube structures, particularly in environments where impact loading is a concern. The integration of corrosion assessment with impact resistance evaluation is essential for the safe operation of structures exposed to both corrosive and dynamic loading conditions.