Abstract
The results of experimental long-term tension and bending tests carried out on four natural stones formely widely used in Italian traditional building (a white-veined Carrara marble, the “pietra Serena” and “Pietraforte” sandstones, and the Piobbico-Cesana limestone) are presented. The tests consisted of applying continually different fractions of the “instantaneous” fracture loads and monitoring the strain evolution of the specimens until a time-delayed fracture was reached. A typical three-stage creep response was obtained in all the tests. At the same time, a 60% reduction in tensile and bending strength was observed in relation to testing periods not much longer than one year. A phenomenological constitutive model is proposed for analytically reproducing the experimental viscoplastic behaviour. Furthermore, a creep time-to-rupture function giving direct estimates of the strength decay effects is provided, with a view to technical applications. The results of the identification analyses carried out to calibrate the characteristic parameters of the above laws are also reported.
Résumé
Dans cet article, on présente les résultats d'un certain nombre d'essais à long terme (en traction simple et en flexion) effectués sur quatre sortes de pierres naturelles utilisées très souvent autrefois en Italie pour la construction (le marbre blanc de Carrara, deux sortes de grès, la pierre de Florence et la “Pietraforte”, ainsi que sur la pierre calcaire de Piobbico-Cesana). Les essais ont été réalisés en appliquant de façon continue aux éprouvettes différentes fractions de charges “instantanées” de rupture, en relevant l'évolution de la déformation jusqu'à la rupture. En général, tous les essais ont montré un comportement caractérisé par les trois phases classiques du fluage. En même temps, on a constaté une diminution de 60% de la résistance, tant à la traction qu'à la flexion, par rapport à une durée d'essais peu supérieure à un an. Cet article présente un modèle constitutif phénoménologique permettant d'analyser le comportement visco-plastique observé. On indique ici, en vue d'applications techniques, une fonction de fluage qui perment l'évaluation directe des effets de la diminution de la résistance mécanique. Enfin, on présente les résultats de l'identification effectuée pour l'étalonnage des paramètres caractéristiques des lois analytiques qui règlent le modèle constitutif.
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Sorace, S. Long-term tensile and bending strength of natural building stones. Mat. Struct. 29, 426–435 (1996). https://doi.org/10.1007/BF02485993
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DOI: https://doi.org/10.1007/BF02485993