DEFERRED DEFORMATIONS OF CONCRETE STRUCTURES: THE CASE OF SAVINES AND CHEVIRÉ BRIDGES

Abstract

Since the beginning of the 20thcentury, it is known that concretestructures deform with time. The deformations resulting fromconcrete creep and shrinkage and steel relaxation are the sourceof serviceability troubles for users and may distribute unwantedstresses into the structure. The paper deals with tworepresentative examples: the Savines Bridge and the CheviréBridge. They were chosen on the one hand because of thespectacular delayed deformations observed and, on the secondhand, thanks to the large amount of available measurements.Theaim of the study is to compare the in-situ measurements withtheoretical deflections calculated on the basis of the currentdesign standards. The comparison shows that, at least for thesebridges, these laws systematically underestimate the long-termdeformation.In order to forecast the future state of the structure,it is proposed to adapt creep and shrinkage laws by means of aleast square minimization algorithm. It enables therefore topredict the evolution of deflection, potential redistribution ofstresses and identify adequate retrofitting. This report presents apossible adaptation of laws and discusses the assumptions,especially the evolution of the functions of creep and shrinkagefor concrete but also that of the steels relaxation function.