Stiffening Performance of Cold-Formed C-Section Beam Filled with Lightweight-Recycled Concrete Mixture

Area of Science:

• Structural Engineering
• Materials Science
• Sustainable Construction

Background:

• Conventional composite beams face limitations in load-carrying capacity, self-weight, and cost for modern flooring systems.
• Slender cold-formed steel C-sections are prone to buckling and twisting under bending loads, necessitating improved composite action.
• The integration of lightweight-recycled aggregates presents an opportunity to enhance concrete properties and reduce structural weight.

Purpose of the Study:

• To investigate the flexural performance of a novel steel-concrete composite beam system utilizing cold-formed steel C-sections filled with concrete.
• To evaluate the impact of incorporating various lightweight-recycled aggregates (recycled concrete aggregate, expanded polystyrene beads, crumb rubber aggregates, fine glass aggregates) on the composite beam's behavior.
• To assess the effectiveness of different stiffening techniques (steel strips, screw connectors) in enhancing the composite action and load-bearing capacity.

Main Methods:

• Experimental testing of 14 concrete-filled cold-formed galvanized steel C-section samples with varying percentages (0-100%) of recycled aggregates.
• One control sample (hollow C-section) tested for baseline comparison.
• Finite element analysis (FEA) employed to explore additional parameters beyond experimental scope.

Main Results:

• Concrete-filled C-sections with recycled aggregates demonstrated significantly improved flexural stiffness, bending capacity, and ductility compared to hollow sections.
• Bending capacity increased substantially, with 0% and 100% recycled aggregate replacement yielding approximately 11.4 and 8.6 times higher capacity, respectively.
• Stiffening elements (steel strips, screw connectors) enhanced composite behavior and further increased bending capacities, with improvements correlating to the number of stiffeners used.

Conclusions:

• The proposed steel-concrete composite beam system, incorporating recycled aggregates, offers a viable solution for enhanced structural performance in flooring applications.
• The use of lightweight-recycled aggregates effectively improves the mechanical properties of the infill concrete, leading to superior flexural performance.
• Stiffening strategies are crucial for optimizing the composite action of slender cold-formed sections, making the system more robust and efficient.