Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures

Description

Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures This report presents a unified approach to predicting the effect of moisture changes, sustained loading, and temperature on reinforced and prestressed concrete structures. Material response, factors affecting the structural response, and the response of structures in which the time change of stress is either negligible or significant are discussed.

Simplified methods are used to predict the material response and to analyze the structural response underservice conditions. While these methods yield reasonably good results, a close correlation between the predicted deflections, cambers, prestress losses, etc., and the measurements from field structures should not be expected. The degree of correlation can be improved if the prediction of the material response is based on test data for the actual materials used, under environmental and loading conditions similar to those expected in the fieldstructures.

These direct solution methods predict the response be-havior at an arbitrary time step with a computational ef-fort corresponding to that of an elastic solution. Theyhave been reasonably well substantiated for laboratoryconditions and are intended for structures designed using the ACI 318 Code.

They are not intended for the analy-sis of creep recovery due to unloading, and they applyprimarily to an isothermal and relatively uniform environment .Special structures, such as nuclear reactor vessels andcontainments,bridges or shells of record spans, or largeocean structures, may require further considerationswhich are not within the scope of this report. For struc-tures in which considerable extrapolation of the state-of-the-art in design and construction techniques is achieved,long-term tests on models may be essential to provide asound basis for analyzing serviceability response.

Reference 109 describes models and modeling techniques ofconcrete structures. For mass-produced concrete mem-bers, actual size tests and service inspection data willresult in more accurate predictions. In every case, usingtest data to supplement the procedures in this report willresult in an improved prediction of service performance.