Numerical relationship between creep deformation coefficients of prestressed concrete beams

Abstract

It is important to precisely predict and control the long-term deformation of a prestressed concrete beam in engineering practice, where creep defection is the primary component. The key to precisely predicting the long-term deflection is clarifying the numerical relationship between the creep coefficient and creep deflection coefficient. In this paper, four simply supported prestressed beams (7.5 m in length) were loaded for 700 days. According to the creep strains at different heights in the mid-span cross section during the loading period, the plane-section assumption was verified for the prestressed beams under long-term loading. Meanwhile, geometry models of the creep strain were established for both fully prestressed and partially prestressed beams. By studying the models, the numerical relationships between the creep coefficient and creep deflection coefficient were derived; for the fully prestressed beams, the creep deflection coefficient is larger than the creep coefficient, while the opposite is true for partially prestressed beams. Moreover, an expression for the creep deflection coefficient was proposed; the coefficient is determined by the creep coefficient, prestress degree, prestress effect, and geometric properties of the cross section. A new method is thus proposed for the accurate calculation of the creep deflection of a prestressed concrete beam.