H. Walter, H.A. Mang:
"Finite Element-Implementation of Creep of Concrete for Thin-Shell Analysis Using Nonlinear Constitutive Relations and Creep Compliance Functions";
in: "Proceedings of the Fourth IUTAM Symposium on Creep in Structures", Springer, Berlin-Heidelberg-New York-Tokyo, 1990, 667 - 675.
A procedure for combining nonlinear short-time bahcior of concrete with nonlinear creep complicance functions is presented. It is an important ingredient of a computer code for nonlinear finite element (FE) analysis of prestressed concrete shells, considering creep, shrinkage and ageing of concrete, and relaxation of the prestressing steel. The program was developed at the Institute for Strength of Materials of Technical University of Vienna, Austria.The procedure has resulted from efforts to extend the range of application of a Finite Element program, abbreviated as FESIA [1], which originally was capable of modeling reinforced concrete in the context of thin-shell analysis, using nonlinear constitutive relations for both, concrete and steel. The extension encompasses the time-dependent bahvior of concrete: creep, shrinkage and ageing. It is documented in detail in [2]. Creep is modeled with the help of creep compliance functions which may be nonlinear to conform with the shrot-time constitutive relations. Ageing causes an interdependence between long-time and short-time deformations.
The paper contains a description of the physical background of the procedure and hints on the implementation of the algortihm. The focus is on generla aspects. Details of the aforementioned computer program are considered only where this is inevitable.
[1] Flögl, J.: Traglastermittlung dünner Schalbetonschalen mittels der Methode der Finiten Elemente unter Berücksichtigung wirklichkeitsnahen Werkstoffverhaltens sowie geometrischer Nichtlinearität. Dissertation, Technical University of Vienna, Austria, 1981.
[2] Walter, H.: Finite Elemente Berechnungen von Flächentragwerken aus Stahl- und Spannbeton unter Berücksichtigung von Langzeitverformungen und Zustand II. Dissertation. Technical University of Vienna, Vienna, Austria, 1988.