MINIMUM REINFORCEMENT IN CONCRETE MEMBERS
members. The minimum amount of reinforcement is defined as that for which "peak load at first
concrete cracking" and "ultimate load after steel yielding" are equal. In this way, any brittle behaviour
is avoided as well as any localized failure, if the member is not over-reinforced. In other words, there is
a reinforcement percentage range, depending on the size-scale, within which the plastic limit analysis
may be applied with its static and kinematic theorems.
Lange-Kornbak and Karihaloo compare experimental observations with approximate nonlinear
fracture mechanics predictions of the ultimate capacity of three-point bend, singly-reinforced concrete
beams without shear reinforcement. The previous model, based on a zero crack opening condition and
a fracture toughness accounting for slow crack growth, appears to be in good agreement with the
observed failure mechanisms, although the test results indicate that a non-zero crack opening condition
would improve the prediction, especially for lightly reinforced beams.
Ruiz, Elices and Planas introduce the so-called effective slip-length model, where the concrete
fracture is described as a cohesive crack and the effect of reinforcement bond-slip is incorporated.
Although the beams considered are of reduced size, the properties of the microconcrete were selected
so that the behaviour observed is representative of beams of ordinary size made of ordinary concrete.
fracture mechanics predictions of the ultimate capacity of three-point bend, singly-reinforced concrete
beams without shear reinforcement. The previous model, based on a zero crack opening condition and
a fracture toughness accounting for slow crack growth, appears to be in good agreement with the
observed failure mechanisms, although the test results indicate that a non-zero crack opening condition
would improve the prediction, especially for lightly reinforced beams.
Ruiz, Elices and Planas introduce the so-called effective slip-length model, where the concrete
fracture is described as a cohesive crack and the effect of reinforcement bond-slip is incorporated.
Although the beams considered are of reduced size, the properties of the microconcrete were selected
so that the behaviour observed is representative of beams of ordinary size made of ordinary concrete.
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