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Bond behavior of corroded reinforcements in concrete: an experimental study and hysteresis model

100%

Zhang Y. B. , Zheng S.-S. , Dong L.-G. , Zheng Y.

Archives of Civil and Mechanical Engineering

2023

tom Vol. 23, no. 2

art. no. e95, 2023

In order to study the effect of both longitudinal reinforcement and stirrups corrosion on the bond performances at steel-concrete interface under reversed cyclic loading, in this paper, the eccentric pull-out tests under reversed cyclic loading were carried out on reinforced concrete (RC) specimens with five corrosion degrees, three concrete cover thicknesses, and three stirrup spacings. The influence of the corrosion rate of longitudinal reinforcement, corrosion rate of stirrups, cover thickness, and stirrup spacing on bond performance indicators was examined, including the initial bond stiffness, peak bond stress, slip at peak bond stress, bond strength at unloading, unloading stiffness, frictional bond resistance, and cumulative energy dissipation. Moreover, the effects of coupling corrosion on cover cracking morphology and bond degradation mechanism were also analyzed. Results indicated that after severe corrosion of longitudinal reinforcement and stirrups, the cover appears cracking or local spalling, and the bond performances are signifcantly reduced. It was also showed that thickening cover or densifying stirrups could improve the interface bond performance and energy dissipation capacity. Each hysteresis parameter degrades apparently under the controlling slip corresponding to the peak bond stress. Subsequently, based on the analysis results and previous studies, empirical local bond stress-slip hysteresis models for corroded longitudinal reinforcement and corroded stirrup under reversed cyclic loading were proposed. Good consistency was observed for the hysteresis model with existing experimental data.

Seismic behavior of frost-damaged squat RC shear walls under artificial climate environment: a further experimental research

75%

Rong X.-L. , Zheng S.-S. , Zhang Y.-X. , Dong L.-G. , Liu H. , Dai K.-Y.

Archives of Civil and Mechanical Engineering

2020

tom Vol. 20, no. 4

103--124

In cold environment, the damage of freezing and thawing poses a great threat to the safety of concrete structures. In this study, six frost-damaged squat reinforced concrete (RC) shear walls were subjected to low cyclic reversal loading to investigate the effects of axial compression ratio, concrete strength and freeze-thaw cycles (FTCs) on the seismic performance of squat RC shear walls. The seismic behavior of the test specimens was evaluated in terms of the frost action at the microstructure level, frost-heave crack patterns, damage processes, failure patterns, hysteretic behaviors, skeleton curves, deformations, and energy dissipation capacities. It shows that the boundary elements and distributed reinforcements had obvious restraining effects on the development of frost-heave cracks. The FTC action weakened the load-carrying capacity, energy dissipation capacity, and shear resistance capacity of the walls. When the number of FTCs is kept at 200, with the increase of the concrete strength, the gel structure (C-S-H) gradually evolved from fibrous to nets, also the width and number of frost-heave cracks started to reduce, and the distribution of frost-heave cracks evolved from the middle of the specimen to the perimeter. Moreover, the energy dissipation capacity and the ratio of the shear displacement on the whole displacement after cracking loading condition started to increase.