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Influence of shear depth on seismic performance of shear wall reinforced with BFRP bars: mesoscale modelings

Jin Liu, Miao Liyue, Du Xiuli

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e4, 2023

EN

The seismic performances of 28 geometrically similar concrete shear walls reinforced with basalt fiber-reinforced polymer (BFRP) bars were simulated using a mesoscale modeling approach. In the modeling, concrete heterogeneities were explicitly described, and the interaction between BFRP bars and surrounding concretes was also considered. The influences of shear depth, shear span ratio and vertical reinforcement ratio on the failure of shear walls were investigated. The simulation results indicated that with the increase of shear depth, the failure modes were basically the similar, while the nominal shear strength decreased significantly, namely, the presence of size effect was demonstrated. The shear wall would exhibit different failure modes as the shear span ratio varies. Moreover, it was found that the vertical BFRP bar presented an ignorable influence on the failure mode, while the increase of vertical reinforcement ratio would obviously improve the shear strength of BFRP-RC shear wall. Finally, the present simulated shear strengths were compared with some available size effect laws and some codes.

2

Meso-scale modelling of size effect on pure torsional-shear of RC columns

Jin Liu, Zhu Huajie, Du Xiuli

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e36, 2022

EN

Under the action of earthquake, the reinforced concrete (RC) columns may subject to torsional moment, and the existence of torsion will change the failure mode of RC columns. Moreover, the torsional fracture of RC columns often presents a brittle fracture pattern, and thus may have an obvious size effect. In this work, a three-dimensional meso-scale simulation approach was utilized to study the torsional failure of RC columns. The influence of structural size, longitudinal reinforcement ratio, stirrup ratio and cross-sectional shape on torsional failure of RC columns was investigated. The results show that: (1) the tested RC columns show brittle failure patterns, the nominal torsional strength presents obvious size effect; (2) the longitudinal reinforcement presents little influence on the size effect; (3) columns with square cross-section present stronger size effect than the ones with circular shape; (4) stirrups can improve the torsional strength, while they would weaken the size effect on torsional strength. In addition, a novel size effect law that can describe the quantitative influence of stirrup ratio was established. Finally, based on the variable angle truss model, the formulas for calculating the pure torsional capacity of RC columns were modified, considering the quantitative influence of the stirrup ratio on the size effect.

3

Impact resistance of RC beams under different combinations of mass and velocity: mesoscale numerical analysis

Jin Liu, Lan Yuchang, Zhang Renbo, Du Xiuli

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

308--328

EN

The concrete structures under impact loading duress may be destroyed within an extremely short period of time. The importance and complexity of exploration on the impact resistance of concrete members make this area still open for discussion. In the present study, a 3-D mesoscale numerical model was established to investigate the effect of the combination of impact mass and velocity on the mechanical behavior of reinforced concrete (RC) beams subjected to impact loadings. Heterogeneity of concrete and strain rate effects of concrete and steel bars were taken into account. Furthermore, nonlinear interaction between the concrete and steel bars was considered herein. Results from macroscale and mesoscale simulation were compared with the available physical tests, indicating that the mesoscale numerical model can better represent the influence of heterogeneity of concrete on the mechanical behavior of RC beams. Five different impact energy levels were involved to study the effect of the combination of impact mass and velocity on the impact resistance of RC beams. At last, the residual bearing capacity and natural frequency of impacted RC beams were numerically calculated and their relationship was discussed. It is indicated that the deformation of RC beams is influenced strongly by the impulse, which increases with the increasing impact mass at identical impact energy. Besides, the failure mode of RC beams turns from shear-dominant failure mode to bending shear failure mode with the increase of impact mass, accompanied by the increase of energy dissipation of steel bars and the whole member. Despite this, in the present work, the combination of the impact mass and velocity had little influence on the damage extent (based on the performance) of the RC beams. Moreover, an empirical relationship between the residual bearing capacity and the natural frequency of the impacted RC beams was established as a rough reference for damage evaluation in engineering practice.