Chapter 2 Design for Shear - Engineering

← Back to document page

Chapter 2 Design for Shear By Richard W. Furlong Introduction Shear is the term assigned to forces that act perpendicular to the longitudinal axis of structural elements. Shear forces on beams are largest at the supports, and the Shear force at any distance x from a support decreases by the amount of load between the support and the distance x. Under uniform loading, the slope of the Shear diagram equals the magnitude of the unit uniform load. Shear forces exist only with bending forces. concrete beams are expected to crack in flexure, with such cracks forming perpendicular to longitudinal tension reinforcement, , perpendicular also to a free edge. Principal tension stresses change direction from horizontal at the longitudinal reinforcement to 45o at the neutral axis and vertical at the location of maximum compression stress. Consequently, cracks in concrete tend to point toward the region of maximum compression stress as indicated by the cracks shown in Fig.

show stress ranges for which design requirements change. No shear reinforcement (stirrups) are required if Vn/(bwd) is less than 1.0√fc’. The capacity Vc of concrete in sections reinforced for shear is 2.0bwd√fc’. The strength of stirrups can be added to the concrete strength Vc to determine the total strength of a section.

  Design, Chapter, Shares, Concrete, Reinforced