Factors affecting creep and shrinkage of hardened concrete and guide for modelling
  Mario A. Chiorino and Domingo J. Carreira
  The paper presents the most relevant and recent international guidance documents on factors affecting creep and shrinkage of concrete and on the related criteria for prediction models, giving a general summary of their scope and contents and of their status of publication. Special attention is given to ACI documents ACI 209.1R-05 and ACI 209.2R-08, specifically dedicated to these aspects and incorporating the presentation of current most widely diffused prediction models. Mention is made also of fib Structural Concrete Textbook (2009) and of fib Model Code 2010 for the parts providing the information on time-dependent deformations of concrete and presenting former CEB, now fib, shrinkage and creep prediction models. Open problems and some aspects of the related current debate in the literature and in the scientific community at the international level are also outlined. A few recommended measures are finally illustrated to counteract the effects of persisting prediction model uncertainties.
  Evaluation of the structural response to the time-dependent behaviour of concrete: Part 1 - An internationally harmonized format
  Mario A. Chiorino and Carlo Casalegno
  Modern concrete structures, realized through complex sequential construction techniques and characterized by significant non-homogeneities, are in general very sensitive to the effects of the delayed deformations of concrete (creep and shrinkage). Guidelines and design manuals for the evaluation of the structural response to the time-dependent behaviour of concrete were developed in the last years by international pre-standard and standard institutions on the basis of a common, although progressively evolving, scientific background and of a substantially worldwide harmonized format. The authors discuss this favourable scenario, evidencing areas of well established consensus and open problems.
  Evaluation of the structural response to the time-dependent behaviour of concrete: Part 2 - A general computational approach
  Mario Sassone and Carlo Casalegno
  The paper presents an integral-type general computational approach for the analysis of structural effects of time-dependent behaviour of concrete, with particular regard to creep, based on the coupling of the finite elements method with a numerical solution of the hereditary Volterra integral equations of aging linear viscoelasticity ensuing from the application of the linear principle of superposition. This approach does not require the conversion to a rate-type form of the integral-type viscoelastic creep constitutive law adopted by most of current creep prediction models. Simple and complex structures (as non-homogenous structures realized through sequential construction procedures), can be modelled through the adoption of this general numerical approach. Two examples of application, relative to a cable-stayed bridge and to a multi-storey building, are presented.
  Costanera Center - Shortenings due to elastic deformation, creep and shrinkage of concrete in a 300-m tall building
  René C. Lagos, Marianne C. Kupfer, Simón T. Sanhueza and Francisco V. Cordero
  This paper describes the considerations and studies made to predict differential shortenings in a 300m tall office building at the Costanera Center Complex located in Santiago Chile. Differential shortenings in reinforced concrete vertical elements are important to consider in tall buildings, as they distort the levelness of the slabs, causing damage to nonstructural elements (partitions, terminations, pipes, etc) and redistribution of stresses in beams, columns and walls. During the construction stage, corrective measures were taken to compensate the expected differential shortenings in order to maintain the slabs as close to horizontal as possible, during the life span of the building. For the prediction of creep and shrinkage, lab tests were performed in order to establish a predictive model. Alternatively, a theoretical approach was developed with the European method CEB-FIP, with the purpose of comparing and calibrating the predictive model. Additional parameters for design, such as the construction date of each floor, are considered with current data of the construction. Finally, a computer program was developed on the basis of the methodology of Fintel, Ghosh e Iyengar (1987) to calculate long-term shortenings.