Analytical approaches for the time-dependent behaviour of the continuos-span concrete bridges made up of precast elements

Abstract

Actual time-dependent analysis can hardly be avoided in evolving concrete structures, due to the generally relevant effects of creep and shrinkage. Changes in structural configuration, together with creep and shrinkage, cause delayed compatibility effects (that, in general, are not negligible) when passing from one stage to another. A new technology of bridges has begun to be used in Spain. These bridges, composed of both precast pretressed concrete and reinforced concrete elements, and a cast-in-place concrete deck slab, are made continuous later. Their double evolution, until reaching their final structural configuration, made necessary to develop a general procedure for the accurate analysis of their delayed effects. This work presents analytical approaches for the time-dependent analysis of concrete structures with longitudinal and transersal evolution. Such aproaches are complementary of the general procedure and, at the very beginninf, they were developed in order to validate its results. But, besides, they are an interesting tool for the design. The approaches are divided in two groups, concerning the actions which are involved in creep: mechanical actions (permanent loads) and geometrical actions (shrinkage). On the other hand, both groups of approaches are applied to a real three-span bridge for obtaining practical results (mainly, delayed redistribution of moments). Finally, conclusions about such approaches are pointed out, particularly those concerning their application to the design of this type of bridges.