PARTIALLY PRESTRESSED COMPOSITE BEAMS UNDER SUSTAINED AND CYCLIC LOADS.

Abstract

A general time-step analysis procedure for prestressed and partially prestressed concrete composite beams is presented. The analytical model considers the effects of creep (time and cyclic dependent), shrinkage of concrete, and relaxation of prestressing steel. The model developed satisfies equilibrium of forces and compatibility of strains with time and leads to the prediction of stresses and strains in the constituent materials at any time t and number of cycles N//t. For the initial time or the first cycle, the model is shown to reduce to existing models applicable to the analysis of partially prestressed beams under short-term static loading. Solutions for uncracked composite sections as well as cracked and uncracked noncomposite sections are derived as special cases. A computerized parametric evaluation is briefly described and numerical examples are developed to illustrate the application of the method.