FEA and Application of Short Carbon Fiber Composite Reinforcement for RC Wall Opening Corners

The Taipei Structural Engineers Association's Structural Forum published research by structural engineer Shen De-Hou on crack-control reinforcement at rectangular openings in reinforced concrete (RC) walls. While rectangular openings are common for lighting and ventilation, stress concentrations from lateral seismic loads, concrete shrinkage, or thermal variations frequently cause 45-degree diagonal cracking. Standard diagonal rebar placement often causes severe congestion in 12–15 cm thick walls, leading to aggregate jamming and honeycomb defects. The study evaluates a reinforcement element (StrongEdge™) composed of 30% recycled short carbon fibers and polypropylene, designed with a multi-ring curved geometry functioning as stress redistribution, crack arrest, and energy dissipation zones. ANSYS modeling of a 3000 mm × 3000 mm × 120 mm RC wall under distributed lateral pressure showed that using the composite element alone decreased corner shear strain to approximately 25% of the unreinforced state (a 75% deformation reduction), surpassing conventional diagonal bars. A hybrid combination yielded the greatest reduction. The author noted that this method preserves rebar clearance and improves pour quality, with physical push-over load testing planned for future validation.

Key takeaways

• Conventional diagonal rebar reinforcement in 12–15 cm walls often causes rebar congestion, risking aggregate blocking and concrete honeycombing.
• The reinforcement element blends 30% recycled short carbon fiber with polypropylene, featuring 154 MPa flexural strength, 0.02% water absorption, and corrosion resistance.
• ANSYS simulations ranked corner shear strain as: Unreinforced > Diagonal rebar only > Composite element only > Composite combined with diagonal rebar.
• The composite element alone lowered corner shear strain to 25% of the baseline, reducing stress concentration without crowding primary rebar spacing.