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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]

To address the issue of local buckling in thin-walled steel tube concrete columns, a form of helical stiffening ribs was proposed. Axial compression tests were conducted on five sections of square steel tube concrete column specimens. The research revealed that, compared to ordinary steel tube concrete columns, the axial compression bearing capacity and deformation capacity of steel tube concrete columns with helical rib constraints increased by 18.5% and 7.7%, respectively. The helical ribs effectively enhanced the buckling resistance of the thin-walled steel tube concrete components. The failure pattern of this new type of component was characterized by diagonal cracks in the encased concrete aligning with the direction of the helical ribs, and the buckling of the steel tube walls was concentrated between the helical stiffening ribs. Based on the experiments, an analysis of the buckling performance of thin-walled steel tubes with helical rib constraints was conducted, and this was incorporated into the bearing capacity calculation. The test, simulation, and theoretical calculations showed that the bearing capacity error of the composite columns for each specimen was within 10%. Ultimately, a formula for the critical buckling bearing capacity of the helical rib steel tubes was proposed. The research findings provide a foundation for the engineering application of this new type of component. [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]