Introduction

Concrete-Filled Steel Box Columns (CFSBCs) are a type of composite structural member that combines the advantages of both steel and concrete. A typical CFSBC consists of a hollow rectangular or square steel section filled with concrete. This hybrid design offers enhanced strength, stiffness, ductility, and energy dissipation capabilities, making it highly suitable for seismic regions and structures requiring high axial and lateral load resistance, such as bridges, high-rise buildings, and industrial facilities.

To evaluate the performance of CFSBCs under earthquake-like loading conditions, researchers perform cyclic test analysis, which involves subjecting the column to repeated and reversed lateral loads (with or without axial load) to simulate the effects of seismic activity.

Explanation of Cyclic Test Analysis

Cyclic Test Analysis refers to the experimental and/or numerical evaluation of a structural element’s behavior under repeated loading and unloading cycles. For CFSBCs, this type of test helps to understand their:

• Strength and stiffness degradation
• Energy dissipation capacity
• Failure modes (local buckling, crushing, bond failure, etc.)
• Hysteretic behavior (load-displacement response)

Key Components of the Analysis

1. Test Setup:
   • A typical test involves applying an axial load (constant or variable) to the column while imposing lateral cyclic displacements at the top.
   • The setup is designed to mimic the boundary conditions found in real structures (e.g., fixed base, pinned top).
2. Loading Protocol:
   • Lateral displacement is applied in cycles of increasing amplitude.
   • Standard protocols (e.g., FEMA, AISC) define the amplitude and number of cycles for consistency.
3. Instrumentation and Measurements:
   • Load cells, LVDTs (Linear Variable Differential Transformers), and strain gauges measure force, displacement, and strain.
   • Data collected includes hysteresis loops (force vs. displacement curves), stiffness degradation plots, and energy dissipation.
4. Observed Behavior:
   • Initial elastic response, followed by yielding, plastic deformation, and eventual failure.
   • Local buckling of the steel plates, concrete cracking/crushing, and interface slip may occur.
   • Confinement from the steel box improves ductility and post-peak strength retention.
5. Parameters Evaluated:
   • Peak lateral load capacity
   • Energy dissipation per cycle
   • Stiffness and strength degradation ratios
   • Cumulative damage indicators

Purpose and Applications

Cyclic test analysis helps to:

• Improve the seismic design and detailing of composite columns.
• Validate and calibrate analytical models or finite element simulations.
• Support code development and performance-based design practices.
• Identify failure modes and inform retrofitting strategies.

ABAQUS is widely used for nonlinear simulation of structural components under static, dynamic, and cyclic loading. Simulating CFSBCs under cyclic loading involves advanced modeling techniques to accurately capture the composite behavior, including material nonlinearities, geometric nonlinearity, and contact interactions.

This example is based on the paper here: Cyclic Tests of Concrete-Filled Steel Box Columns