Structural Concrete Beam Shear - Still a Riddle?


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Title: Structural Concrete Beam Shear - Still a Riddle?

Author(s): M.W. Braestrup

Publication: Special Publication

Volume: 265


Appears on pages(s): 327-344

Keywords: beams; failure; plasticity; shear; structural.

Date: 10/1/2009

The paper reviews the application of classical plasticity theory to shear failure of structural concrete beams. The resistance of concrete to shearing deformations is described by the modified Coulomb failure criterion. For beams with shear reinforcement, this leads to an upper bound solution based on yield lines minimizing the combined work of yielding stirrups and cracking concrete, the coinciding lower bound solution corresponding to an inclined compression field (the web-crushing criterion). For beams without shear reinforcement, the optimal failure mechanism is a single yield line (straight or hyperbolic) from load to support, the coinciding lower bound solution corresponding to a compressive strut between the load and support platens. The predicted failure mechanisms and ultimate loads are compared with experimental evidence, and it is concluded that the plasticity approach goes a long way toward solving the riddle of shear failure.