Creep and shrinkage prediction models for concrete

In autumn 2020, the revision of EN 1992-1-1:2004 (Eurocode 2) was completed, resulting in the draft prEN 1992-1-1:2020. It provides practice with numerous improved and new design concepts. This also applies to the models for shrinkage and creep of structural concrete, some of which have undergone significant changes. This three-part paper (Part 1 Shrinkage, Part 2a and 2b Creep) presents the new models for predicting the deformation behaviour of concrete. It also highlights the background that led to the development of the improved approaches. Part 1 has already been published (Beton- und Stahlbetonbau 116 (2021), issue 1). The article at hand (Part 2a) deals with the creep of concrete. In an overview, the components of creep, their characteristics and influencing parameters as well as the corresponding constitutive relationships are first presented. They are crucial for understanding the creep models. Then, the normative developments that have led to the creep model in DIN EN 1992-1-1:2011 valid today in the year 2021 are shown. The focus is on the analysis of the reliability and accuracy of this model. It revealed certain deficiencies, which were the reason for corrections and further developments being included in prEN 1992-1-1:2020. The new prediction model is presented and justified in Part 2b of this paper. Statistical considerations on the reliability of the new model and the presentation of a concept for the inclusion of laboratory test data to improve the prediction of the model conclude the entire paper.