Modelování vlivu velikosti betonových konstrukcí pomocí nelineární stochastické lomové mechaniky

Modeling size effect of concrete structures with nonlinear stochastic fracture mechanics

conference paper

Czech

We attempt the identification, study and modeling of possible sources of size effects in concrete structures acting both separately and together. We are particularly motivated by the interplay of sev-eral identified scaling lengths stemming from the material, boundary conditions and geometry. Meth-ods of stochastic nonlinear fracture mechanics are used to model the well published results of direct tensile tests of dog-bone specimens with rotating boundary conditions. Firstly, the specimens are mod-eled using microplane material law to show that a large portion of the dependence of nominal strength on structural size can be explained deterministically. Next, we model local material strength using an autocorrelated random field attempting to capture a statistical part of the complex size effect, scatter inclusive. In addition, the strength drop noticeable with small specimens which was obtained in the experiments is explained by the presence of a weak surface layer of constant thickness (caused e.g. by drying, surface damage, aggregate size limitation at the boundary, or other irregularities). All three named sources are believed to be the sources most contributing to the observed strength size effect; the model combining all of them is capable of reproducing the measured data. The computational ap-proach represents a marriage of advanced computational nonlinear fracture mechanics with simulation techniques for random fields representing spatially varying material properties.

We attempt the identification, study and modeling of possible sources of size effects in concrete structures acting both separately and together. We are particularly motivated by the interplay of sev-eral identified scaling lengths stemming from the material, boundary conditions and geometry. Meth-ods of stochastic nonlinear fracture mechanics are used to model the well published results of direct tensile tests of dog-bone specimens with rotating boundary conditions. Firstly, the specimens are mod-eled using microplane material law to show that a large portion of the dependence of nominal strength on structural size can be explained deterministically. Next, we model local material strength using an autocorrelated random field attempting to capture a statistical part of the complex size effect, scatter inclusive. In addition, the strength drop noticeable with small specimens which was obtained in the experiments is explained by the presence of a weak surface layer of constant thickness (caused e.g. by drying, surface damage, aggregate size limitation at the boundary, or other irregularities). All three named sources are believed to be the sources most contributing to the observed strength size effect; the model combining all of them is capable of reproducing the measured data. The computational ap-proach represents a marriage of advanced computational nonlinear fracture mechanics with simulation techniques for random fields representing spatially varying material properties.

computational stochastic, fracture mechanics, size effect, random field, weak boundary crack band

VOŘECHOVSKÝ, M.; MATESOVÁ, D.

2006

3. 10. 2006

Brno, ČR

80-214-3251-9

Pravděpodobnost porušování konstrukcí

269

284

16