High-strength self- consolidating concrete girders subjected to elevated compressive fiber stresses, part 2: Structural behavior

摘要

The design of prestressed concrete members is restricted by the requirement that the extreme compressive fiber stress at midspan be less than 60% of the concrete compressive strength at release of prestressing. The purported purpose of this limit is to provide serviceability performance, but it places unnecessary limits on the capability of the materials. For this research program, six prestressed concrete girders were produced with high-strength, self-consolidating concrete and subjected to elevated compressive fiber stress levels ranging from 65% to 84% of initial concrete compressive strength at release of prestressing. Part 1 of this series analyzed time-dependent prestress losses and camber behavior and compared these values with the results from typical prediction methods. This second part examines the flexural and shear behavior of the same girders. The results of structural testing indicated little reduction in flexural capacity of girders subjected to elevated stress levels, but further testing in shear is needed to reduce the variability in the results. The results reported here suggest that an increase in the allowable compressive stress limit up to at least 70% of the initial concrete compressive strength at release of prestressing at any location is feasible.