Publication Details and Research Context
A new study published in Engineering Structures examines the bond behavior between rebar and concrete under the coupled effects of rebar corrosion, rebar diameters, and cyclic loading. The paper appears in Volume 364 of the journal, dated 1 October 2026, as article 123152. Authors Xiaojun Wang, Shan Li, Yuhong Yan, and Yiyan Lu conducted the work, with Yiyan Lu providing supervision, methodology, and conceptualization; Shan Li handling project administration and funding acquisition; Yuhong Yan contributing writing review, editing, and funding; and Xiaojun Wang responsible for original draft, visualization, investigation, and data curation.
The research addresses critical factors in reinforced concrete structures, where bond performance ensures composite action and serviceability. Steel corrosion in chloride environments and cyclic loading from sources such as waves in offshore and port engineering pose significant threats to long-term performance.
Experimental Methodology
Researchers performed monotonic and cyclic centric pull-out tests, described as push-in tests under load reversal, on 72 ordinary concrete cubic specimens containing deformed rebars after accelerated corrosion. Variables included four target corrosion levels from 0 percent to 15 percent, three nominal rebar diameters of 20 mm, 22 mm, and 25 mm, and two loading modes consisting of monotonic and cyclic conditions. The 15 percent corrosion level reflects the point at which reinforced concrete structures nearly lose bearing capacity.
Specimens under monotonic loading showed failure modes transitioning from splitting-pullout at low corrosion levels to splitting failure as corrosion increased. Under cyclic loading, all specimens experienced splitting failure.
Key Findings on Corrosion Effects
Bond strength initially increases but then decreases with rising corrosion level, a trend more pronounced under cyclic loading. Cyclic loading amplifies improvement at low corrosion levels while intensifying degradation at high corrosion levels. Piecewise predictive models using linear and power functions were proposed for the two loading conditions and demonstrated good agreement with test results.
The bond stress-slip curves under cyclic conditions exhibit hysteresis featuring four typical branches per cycle: ascending and descending loading, unloading, and friction branches.
Influence of Rebar Diameter
Bond strength decreases linearly with increasing rebar diameter under monotonic loading. In contrast, bond strength increases with larger diameter under cyclic loading. Larger diameters benefit cyclic resistance, though this advantage diminishes with greater cyclic amplitude. Smaller-diameter rebars show lower resistance to cyclic deterioration.
Photo by teka nakazawa on Unsplash
Cyclic Loading Impacts and Degradation Patterns
Under cyclic loading, the most significant bond degradation occurs during the second constant-amplitude cycle and the final pre-failure variable-amplitude level. Larger cyclic amplitude diminishes bond improvement from corrosion and amplifies degradation overall. The coupled effects were analyzed using slopes of degradation coefficients.
Existing research on cyclic bond performance notes influences from cycle number, controlled slip amplitude, concrete strength, bonded length, concrete cover thickness, and stirrups. The current study builds on these by addressing gaps in coupled corrosion and cyclic effects, including inconsistencies in degradation coefficients and unified constitutive models.
Proposed Bond Stress-Slip Models
Bond stress-slip models were developed for both monotonic and cyclic loadings. These incorporate shape parameters, unloading stiffness, and residual stress. A four-branch model for monotonic loading uses a degradation coefficient due to corrosion along with a shape parameter for the ascending branch derived from statistical regression of test curves.
The models accurately reproduce the experimental responses observed in the tests.
Implications for Reinforced Concrete Structures
The findings carry direct relevance for the design and assessment of reinforced concrete structures exposed to corrosive environments and repeated loading, such as those in marine or seismic zones. Understanding how corrosion levels interact with diameter choices and loading patterns supports improved predictions of service life and structural integrity.
Funding for the research came from the National Natural Science Foundation of China under grant number 52378259 and the Special Project on Technical Innovation of Hubei Province under grant number 2025BCB102.
Future Research Directions
The study highlights remaining needs for consensus on degradation calculations and constitutive models under combined influences. Further work could extend these experimental approaches to additional variables or field conditions to refine predictive capabilities for infrastructure maintenance and new construction.
Access the full publication at https://www.sciencedirect.com/science/article/abs/pii/S0141029626010667.
Broader Context in Structural Engineering Research
This publication contributes to ongoing investigations into rebar-concrete interfaces. Related prior work has examined stochastic modeling for bond deterioration due to reinforcement corrosion and bond behavior under repeated loading or other confinement methods. The current experiments provide new data on diameter variations alongside corrosion and cyclic conditions.
Professionals in civil engineering and materials science can apply these insights to enhance modeling tools used in structural analysis software and durability assessments.