Research on Lateral Impact Resistance of Concrete-Filled Circular Steel Tubular Columns Stiffened with Encased with I-Section CFRP Profile

Concrete-filled steel tubular(CFST) members and various new-typed composite members derived from them have excellent mechanical properties and construction properties and are widely used in bridges and buildings. Encasing the CFRP profile into CFST members improves the bearing capacity of CFST members and reduces the section size, which has a great application prospect in bridges and high-rise buildings. Collisions between vehicles and bridge structures or buildings are frequent, and the destruction of buildings and bridges will have catastrophic consequences for human life and infrastructure systems. So it is particularly inportant to study the impact resistance performance of such components.However, the current design code generally adopts the equivalent static analysis method for the impact design of such members, which ignores the real influence process. Therefore, the finite element analysis(FEA) software ABAQUS was used to reveal the dynamic response of the concrete-filled circular steel tubular columns stiffened with encased with I-section CFRP profile(CFCST-CFRP) under lateral impact. Firstly, a CFCST-CFRP model coupled with axial force and impact was established, and its accuracy was verified based on the existing test data. Then, based on the impact force, displacement, stress and strain obtained by the verified FEA model, the failure mechanism of the CFCST-CFRP column under lateral impact was revealed. On this basis, the effects of CFRP profile configuration rate, impact velocity, axial compression ratio, slenderness ratio, steel ratio and impact direction on the impact resistance of CFCST-CFRP columns were explored. Finally, the energy dissipation mechanism of the CFCST-CFRP column under the coupling of axial force and impact was also explored. The results show that compared with ordinary CFST columns, the lateral impact resistance of CFCST-CFRP columns is significantly improved, and to give full play to the configuration rate of I-shaped CFRP profiles, it is recommended that the I-shaped CFRP profiles configuration rate should be between 6.2% and 7.4%. By analyzing the influence of the axial compression ratio, it is found that when the axial compression ratio is lower than 0.5, the axial force strengthens the lateral impact resistance of CFCST-CFRP columns. While the axial pressure ratio exceeds 0.5, the axial force weakens the lateral impact resistance of CFCST-CFRP columns. Under the same impact velocity, the impact resistance of CFCST-CFRP columns in the strong axial direction is better than that of the weak shaft impact direction, and when the impact velocity is large, it has the greater the influence on the deformation of the CFCST-CFRP column under impact load. The plastic energy dissipation of the steel tube is the main energy consumption mode of the CFCST-CFRP column. Although the energy dissipated by the CFRP profile accounts for a small proportion of total impact energy, it improves the deformation resistance of the CFCST-CFRP column.