Residual Capacity of HSC Thermally Damaged Deep Beams

High-strength concretes (HSCs) containing siliceous aggregates are very sensitive to high temperatures, as shown by the marked decrease of their mechanical properties both at high temperatures and after cooling down to room temperature (residual properties). However, because of the greater nonlinearity of concrete caused by thermal damage, the structural behavior is generally less affected by high temperatures than the constitutive behavior, as is shown in this study on the residual behavior of three lightly reinforced and three unreinforced deep beams (f sub c = 72 MPa). Four specimens were tested after a single thermal cycle (T = 250 deg C or 400 deg C) and two specimens were tested in the virgin state (T - 20 deg C), in order to measure the complete load-displacement response in three-point bending, to study crack formation, and to assess the roles of the various complementary capacity decreases markedly in the unreinforced specimens, but not as much as the tensile strength and that the role of the complementary shear-resistant mechanisms increases in both reinforced and unreinforced beams, in spite of the worsening mechanical properties of concrete.

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