Numerical investigations on flexural behavior of I-shaped CFRP-encased high-strength square concrete filled steel tubes

To enhance the mechanical properties of high-strength concrete-filled high-strength steel tubular (HSCFHST) members, a new type of composite structure is proposed in which an I-shaped CFRP is encased inside the HSCFHST member. The objective of this research is to improve the theoretical foundation for HSCFHST members by analyzing the flexural behavior of inner I-shaped CFRP on HSCFHST members. HSCFHST members' nonlinear finite element models is created using ABAQUS and confirmed by comparing simulation and test data. It is subjected to pure bending stresses. The flexural behavior of the HSCFHST members are examined with respect to failure mode, complete curve, moment sharing ratio, longitudinal and contact stresses in steel tubes and con-crete. Additionally, material interaction mechanisms among three components are investigated to explore the range of restraint between the components. To assess a substance's effect and structural parameters on the flexural behavior of the members, including different combinations of the three types of materials, steel's yield strength, concrete's compressive strength, and the ratio of steel. The findings demonstrate that the steel tube's restraint of the concrete is mostly concentrated at its corners on the tensile side. The HSCFHST member's deformation capacity and stiffness were both increased by the usage of the CFRP encased in the member, which also decreased the height of the central axis' upward movement. The flexural load capacity is largely affected by the steel ratio, which also has an impact on steel strength.