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Strengthening reinforced concrete (RC) beams with fiber-reinforced polymer (FRP) grids and engineered cement composites (ECCs) can significantly enhance their shear capacity. However, the specific contributions of the components in reinforced RC beams remain unclear, necessitating further investigation into the flexural shear performance of RC beams. The numerical model was used to analyze the flexural shear performance of RC beams strengthened with an FRP grid and ECCs. Subsequently, the parameters affecting the flexural shear performance of beams were discussed. This included the compressive strength of concrete prism, the shear span ratio, the tensile strength of ECCs, the thickness of the ECC cover, the cross-sectional area of the FRP grid, and the number of FRP grid layers. Finally, a calculation formula was established to predict the shear capacity and verified by the outcomes from numerical models and experimental data. The findings indicated that the ECC-strengthened layer significantly contributed to increasing the shear capacity. Additionally, the FRP grids helped to reduce stress concentration in the flexural shear zone, thereby preventing premature concrete cracking. The max load increased by 8.06% when the ECC's tensile strength increased from 4 MPa to 10 MPa. In addition, increasing the cover thickness from 8 mm to 20 mm caused the peak load to increase by 14.42%. The calculation formula introduced in this research accurately predicts the shear capacity of the oblique section of RC beams. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) concrete beams reinforced by carbon fiber reinforced polymer (CFRP) grid reinforced engineering cementitious composite (ECC) have excellent flexural performance and corrosion resistance in marine environments. However, the lack of a reliable theoretical model for predicting the flexural behavior of the hybrid beams makes it challenging apply them in the practical engineering. To address this issue, a series of numerical models were established to investigate the effects of key parameters on the flexural behavior of the hybrid beams, including the peak load, the neutral axis height, and the sectional stress distribution. Subsequently, based on the influence of the failures of different materials on the flexural performance of the hybrid beam, the loads of four feature points were calculated in the theoretical model to predict the entire load–displacement curve. Finally, the application range of the theoretical model was given based on the neutral axis height. The results showed that the cover thickness of the ECC, the GFRP reinforcement ratio and the cross‐sectional area of the CFRP grid were the key factors affecting the flexural performance of the hybrid beams. The theoretical model established in this study can predict the load–displacement curve accurately and can provide a reference for the subsequent design of the hybrid beams. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymer (CFRP) and engineered cementitious composites (ECC) have become universal materials for strengthening structural members, and their effectiveness in improving the mechanical behavior of concrete-filled steel tube (CFST) columns has been verified by experiments in previous studies. However, how the CFRP, ECC and CFST columns work together, and the mechanical mechanism of the strengthened column is still unclear. Therefore, to further reveal its mechanical behavior and working mechanism, combined with the experimental results of the CFST columns strengthened with CFRP textile grid-reinforced ECC, a detailed numerical analysis was conducted based on a series of finite element (FE) models in this paper. The load-displacement curve, N - M curve, lateral displacement, stress distribution, the contribution and influence degree of each part of materials to the load-bearing capacity of the strengthened columns were investigated. Finally, taking into consideration the confinement effects of the CFRP grid and the ECC on concrete, a novel theoretical model was established and verified. As a result, the concrete contributes approximately 60% to the peak load of the strengthened column. Under small eccentricity ratio, the mechanical behavior of the CFRP grid can be fully realized. The yield strength of the steel tube and the compressive strength of the concrete have a highly significant effect on enhancing the load-bearing capacity of the strengthened column. The theoretical model proposed in this study can accurately predict the load-bearing capacity of the strengthened columns under eccentric compression, thus offering valuable insights for the design and research of such strengthened columns. • The failure mode and working mechanism of the strengthened columns were studied by numerical model. • The variation of stresses of the strengthened column with different eccentricity ratios was investigated. • The variation patterns of the N - M curves influenced by different parameters was discussed. • A novel load-bearing capacity of the strengthened columns was proposed. [ABSTRACT FROM AUTHOR]

Corrosion of reinforced concrete (RC) columns due to chloride ions in marine environments is a significant problem. Reinforcement technologies, such as the engineered cementitious composite (ECC)-fiber reinforced polymer (FRP) reinforcement technology, have proven to be effective measures to improve the compressive capacity of RC columns. However, the confinement mechanism and design formula for this reinforcement technology remain unclear. In this study, the compressive behavior of corroded reinforced concrete column strengthened with basalt fiber reinforced polymer (BFRP) reinforced ECC was investigated by numerical analysis, including the load-displacement curves, the confinement mechanism, the stresses distributions and the effect of key parameters. Additionally, a theoretical model was developed to predict the peak load of the strengthened column. The results showed that the corrosion of the longitudinal steel bar and the stirrup were respectively significantly weakened the compressive capacity and the deformation capacity of the strengthened column; The stress in the BFRP grid reached 10% of its ultimate stress under point B, and increasing the number of BFRP grid layer was found to be beneficial in delaying the load degradation in the softening stage; The theoretical model established in this study could accurately predict the peak load of the strengthened column. • A series of numerical models was established by considering the local buckling and the corrosion ratio of steel bar. • The load-displacement curves, confinement mechanism and stress distribution of materials were studied by typical models. • The influences of key parameters on the compressive behavior of the strengthened column were investigated. • A theoretical model was developed by considering the confinement effect of ECC-FRP reinforcement technology. [ABSTRACT FROM AUTHOR]