Introduction to UHPC Column Tests: Static & Dynamic Compression

Cold-formed steel members filled with ultra-high-performance concrete (UHPC) have gained increasing attention in modern structural engineering due to their excellent mechanical performance, durability, and potential for lightweight, high-load-bearing applications. In particular, square cold-formed UHPC-filled dual steel stiffened slender columns consist of an outer cold-formed steel tube, an inner steel or stiffening element, and high-strength UHPC infill. The dual steel configuration provides improved confinement, enhanced local and global stability, and increased resistance to buckling, making these composite columns suitable for high-rise buildings, bridge components, protective structures, and other demanding environments.

All parts are modeled as 3D solids and shells. The Concrete Damaged Plasticity model is used to represent the compressive and tensile behavior of UHPC under loading. For the steel components, an elastic–plastic material model is selected. Both dynamic and static analyses are performed using explicit and general static steps.

To evaluate the performance of such columns under service and extreme loading conditions, both static and dynamic compression tests are generally conducted. Static compression tests are used to examine the load–deformation behavior, ultimate compressive capacity, stiffness, failure modes, and post-peak response under quasi-static loading. These tests provide fundamental mechanical parameters for design, modeling, and code development. Key performance aspects investigated include local buckling of the steel tube, interaction between steel and UHPC, gradual stiffness degradation, and the influence of geometric slenderness and stiffening configuration.

Dynamic compression tests, on the other hand, assess the column’s behavior under high strain-rate or impact-type loading, such as those caused by blasts, vehicle collisions, or seismic events. UHPC exhibits significant strain-rate sensitivity, and the confinement effect in dual steel systems can further enhance energy absorption and dynamic strength. Dynamic testing allows the study of rate-dependent failure mechanisms, energy dissipation capacity, stress–strain enhancement, and the suitability of analytical models for high-speed loading conditions.

Together, static and dynamic compression tests provide a comprehensive understanding of the mechanical performance of square cold-formed UHPC-filled dual steel stiffened slender columns. The results support the refinement of constitutive models, optimization of structural design, and development of engineering guidelines for both conventional and extreme-loading scenarios.