Size and Scale Effects on the Shear Strength of Concrete Beams

by Lesley H. Sneed,
Julio A. Ramirex,

Document Type: Proceeding Paper

Part of: Structures Congress 2008: Crossing Borders


This paper identifies and discusses the role of proper geometric scale of relevant parameters in the size effect in shear, particularly in terms of practical beam design. In the overall design of a beam, factors such as shear span-to-depth ratio, uniaxial concrete compressive strength, longitudinal reinforcing bar size, distribution of longitudinal reinforcement, concrete cover, and maximum aggregate size are selected based on practical and code-related considerations. These same factors, however, can play an important role in influencing the interaction of different shear transfer mechanisms. The effect of geometric scale (or lack thereof) associated with practical design and material selection limitations can have a larger influence on the shear strength of deeper beams than shallower beams. As a result, the size effect can be exacerbated by the effect of scale, which can lead to significantly lower shear strengths (in terms of average shear stress) of deeper beams than shallower beams. In this context, practical considerations for the shear design of relatively deep beams are presented.

Subject Headings: Shear strength | Concrete beams | Shear stress | Structural strength | Strength of materials | Reinforced concrete | Size effect

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