The experimental
investigation here described had its motivation in doubts lifted about the
shear
strength behaviour
of high strength
concrete beams subjected to
alternate loads. It were experimentally analysed 12 beams with identical geometry and
longitudinal reinforcement. The concrete compression strength and the type of
load, normal or alternate, were the adopted variables. A first series
constituted by 6 beams without web reinforcement and a second series by beams
with this reinforcement. For each series, there were three ranges of concrete
compression strength. Of the beams with the same concrete compressions
strength, one was subjected to normal loads and another to alternate loads. It
was observed in the tests that the behaviour of the beams subjected to
alternate loads was not significantly altered by the variation of concrete
compression strength. The application of reversed loads can reduce the shear
strength of the beams in up to 50%.