Title: Uncertainty Analysis of Creep and Shrinkage Effects in Concrete Structures

Author(s): Henrik 0. Madsen and Zdenek P. Bazant

Publication: Journal Proceedings

Volume: 80

Issue: 2

Appears on pages(s): 116-127

Keywords: concrete construction; creep properties; mathematical models; prob-ability theory; reliability; shrinkage; structural analysis; structural members; viscoelasticity .

DOI: 10.14359/10467

Date: 3/1/1983

Abstract:
A simple probabilistic model, which allows calculation of simple statistics for shrinkage and creep effects for structural elements, is presented. The statistics can be, in particular, the mean value function and the covariance function (including the variance function), which seem to be the most interesting statistics for serviceablity analysis. Any deterministic creep and shrinkage formula can be the basis for probabitalistic creep and shrinkage models. The formulas are randomized by introducing the entering parameters as random variables and by furthur introducing random model uncertainty factors to characterize the incompleteness or inadequacy of the deterministic formulas. Statistics for the model’s uncertainty factors are derived by a comparison between available test data and predictions for these tests by the formulas. The creep and shrinkage formulas developed by Bazant and Panula (BP model) are chosen. Structural analysis can be carried out by any conventional deterministic method. In this paper, the analysis is performed by a matrix method which gives essentially exact results if the time discretization is close enough. A large number of examples of practical relevance demonstrates the potential of the method. Some of the examples show that structural effects which in a deterministic anaylsis almost vanish can have a very large uncertainty, which should be taken into account in practical design.