Creep Analysis of Structures with Variable Statistical Scheme-Unified Approach

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Title: Creep Analysis of Structures with Variable Statistical Scheme-Unified Approach

Author(s): M. A. Chiorino, L. Dezi, and A. M. Tarantino

Publication: Special Publication

Volume: 194

Issue:

Appears on pages(s): 155-186

Keywords: age; aging materials; concrete; creep creep properties; delayed restraint; prediction stress redistribution; structural analysis; struct coelasticity analysis; models; ures; vis

Date: 5/1/2000

Abstract:
Variation of statistical scheme of reinforced and prestressed concrete struc-tures is frequent in modern construction techniques. Construction sequences may include application of permanent loads and of prestressing in one or more steps, and connection of different portions of the structure, or introduction of additional restraints (sometime forcedly applied to correct the internal stress conditions), at different ages during or after the construction process. The resulting stress distribution is largely influenced by the time-dependent deformability of concrete. The paper presents a unified approach for its evalu-ation based on the linear theory of viscoelasticity for aging materials, which is normally adopted for modeling concrete creep, evidencing the important role played by the non-dimensional redistribution function (t, to, t1) describing the creep induced stress variation at time t for loading at t, and variation of re-straint conditions at t,. The obtained solutions are exact for all problems of variation of restraint conditions in homogeneous structures with rigid restraints, and normally suffkiently accurate for problems concerning structures charac-terized by heterogeneities in the properties of concrete along their structural configuration. Redistribution function may be computed from the creep function J characterizing the creep prediction model under consideration and made available in terms of design aids (graphs or tables). The computational procedure is illustrated and an example of application to a typical structural problem is presented.