Novel approach for strengthening T-beams deficient in shear with near-surface mounted CFRP ropes in form of closed stirrups

• Published in: Developments in the built environment 2024-04, Vol.18, p.100394, Article 100394
• Main Authors: Zapris, Adamantis G., Kytinou, Violetta K., Gribniak, Viktor, Chalioris, Constantin E.
• Format: Article
• Language: English
• Subjects: Carbon fiber-reinforced polymer (CFRP); CFRP rope; CFRP rope anchorage; Reinforced concrete (RC); Shear strengthening; T-beam; U-shaped sheet
• ISSN: 2666-1659; 2666-1659
• DOI: 10.1016/j.dibe.2024.100394

Existing reinforced concrete buildings frequently require shear-strengthening to ensure structural integrity, and externally bonded carbon fiber-reinforced polymers (EB-CFRP) have become a wide-applicable approach. However, slabs and geometric restrictions impede wrapping the element, necessitating incomplete U-shaped applications vulnerable to debonding failures. This experimental study introduces a novel approach for shear-strengthening nine full-scale T-beams using near-surface mounted CFRP ropes forming closed stirrups. Their effectiveness as shear reinforcement is investigated compared to an alternative method incorporating EB-CFRP sheets with CFRP rope anchorage. Test results indicate that both techniques enhance the beams’ strength and performance. The load capacity increased 2 times for the reference specimen and 1.4-1.9 times for the strengthened beam with FRP sheets. The displacement at the maximum load increased 5.2-7.8 and 6.6-7.5 times, respectively. The rope stirrup arrangement outperforms the rope anchorage system in mechanical and construction efficiency. A thorough protocol for executing these processes to mitigate construction-related defects is introduced. •Novel CFRP ropes as primary shear-retrofitting reinforcement, closed-type stirrups.•Compared to an alternative combination of EB-CFRP sheets with CFRP rope anchorage.•Formation of CFRP ropes embedded through the slab or web section of the beams.•Test program of 9 full-scale T-beams strengthened in shear with various techniques.•Comprehensive, step-by-step procedures to minimize construction-related defects.