A unified shear stress limit for reinforced concrete beam design

• Published in: Transactions (Hong Kong Institution of Engineers) Vol. 22; no. 4; pp. 223 - 234
• Main Authors: Looi, Daniel T W, Su, Ray K L, Lam, Eddie S S
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 02-10-2015
• Subjects: deep beam; high-strength concrete; shear enhancement factor; shear stress limit; strut-and-tie method; transfer girder
• ISSN: 1023-697X; 2326-3733
• DOI: 10.1080/1023697X.2015.1102654

Nine asymmetrically spanned reinforced concrete deep beams were designed and tested to unreinforced web crushing failure in this experimental study to establish the appropriate shear stress limit for beam design. The lower bound and mean shear design limits associated with the concrete strut crushing in the web of the beam are identified, based on the better correlated concrete compressive strength parameter rather than its square root. A unified shear stress limit model is proposed to anchor the maximum strut crushing limit and sectional shear stress in design codes via a generic shear enhancement factor. The proposed unified model exhibits modest conservatism compared to the Hong Kong Code of Practice for Structural Concrete 2013 and the Chinese Code for Design of Concrete Structures (GB 50010). Transfer beams, pile caps and corbels, which are typically accompanied by high shear demand, can be optimised in size to leverage construction material cost savings through the more relaxed shear stress limit proposed in this study, which is justified through experiments.