Product Overview:

This tutorial investigates the flexural behavior of a Concrete-Filled Square Steel Tube (CFST) with an inner Circular Tube made of Carbon Fiber Reinforced Polymer (CFRP), using Abaqus for analysis. The advances in concrete technology, coupled with the increasing demands of practical engineering applications, have led to the widespread use of high-strength concrete in construction. However, high-strength concrete is often prone to brittleness. One effective solution to enhance its performance is to encase it within a steel tube. This hybrid structural member consists of concrete-filled square steel tube columns with an inner CFRP circular tube, combining the strengths of the CFRP inner tube, the steel outer tube, and the concrete infill.

The composite structure effectively leverages the mechanical properties of its constituent materials, with the composite action between the elements offering significant structural advantages. The steel and CFRP tubes exert confining pressure on the concrete, inducing a triaxial state of stress that enhances the concrete’s strength. Simultaneously, the concrete core provides stiffness to the steel tube, which helps prevent buckling and improves the overall stability and strength of the column. It is important to note that while the flexural performance of CFSTs is notable, it generally does not match their compression performance.

In this simulation, the outer steel tube and the CFRP component are modeled as three-dimensional shell parts, while the concrete core is modeled as a three-dimensional solid part.

The Concrete Damaged Plasticity (CDP) model is employed to characterize the concrete’s response under bending loads. For the steel box, an elastic-plastic model with a ductile damage criterion is utilized, while the CFRP is modeled using elastic properties along with Hashin’s damage criterion. These material models effectively predict damage and failure throughout the simulation. A dynamic explicit procedure is adopted to simulate the dynamic bending behavior; however, by applying a smooth amplitude, a quasi-static simulation can also be achieved. A general contact algorithm is used to manage interactions between all components, alongside specific parameters between the steel box and concrete to account for separation during the simulation, including friction coefficients, shear stress limits, and elastic slip properties. Fixed boundary conditions are assigned to the bottom of the structure, while displacements are applied to the top rigid body. A fine mesh is essential to accurately predict damage and failure patterns.

Following the simulation, a range of results—including damage, stress, and strain—are available for analysis.