Design Aids for the Evaluation of Creep Induced Structural Effects


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Title: Design Aids for the Evaluation of Creep Induced Structural Effects

Author(s): M. Sassone and M. A. Chiorino

Publication: Special Publication

Volume: 227


Appears on pages(s): 239-260

Keywords: compliance; concrete; creep; creep analysis; design aids; numerical solver; prediction models; redistribution function; relaxation; structural analysis; web site

Date: 3/1/2005

Many structural problems involving creep in concrete structures can be solved in very compact closed forms through the fundamental theorems of linear viscoelasticity of aging materials. This general approach requires the knowledge of three basic functions: the compliance function J, derived directly from the creep prediction models available in the literature and in technical guidance documents, and the relaxation (R) and redistribution () functions, that can be calculated from J. This paper presents an interactive web site for quick automatic calculation of these three basic functions, with reference to the principal creep models presently considered by international civil engineering societies. Starting from the approach suggested by Bazant for the numerical solution of the fundamental Volterra integral equation relating R to J, identically applied to derive ~ from J, a complete procedure has been developed, including the user interface necessary for setting input data and handling output results. The immediate availability of the basic functions allows extended comparisons of the outputs of the different models and evaluation of the influence that the selection of a particular model has on the assessment of structures. The web site has a flexible architecture and will be progressively extended to include calculation of other functions of interest for the creep analysis of structures, e.g. the aging coefficient X of the age-adjusted-effective-modulus-method, and the reduced relaxation functions R* that extend the field of application of the fundamental theorems to the analysis of heterogeneous structures, such as e.g. cable-stayed bridges.