Open Access

ARTICLE

Cracking and Creep Role in Displacements at Constant Load: Concrete Solids in Compression

by E. Ferretti¹, A. Di Leo¹

1 DISTART, Scienza delle Costruzioni, Facoltà di Ingegneria, Alma Mater Studiorum, Università degli Studi di Bologna, Viale Risorgimento 2, 40136, Bologna, ITALY.

Computers, Materials & Continua 2008, 7(2), 59-80. https://doi.org/10.3970/cmc.2008.007.059

Abstract

The main assumption on the basis of the identifying model of the effective law, developed by the Author, is the impossibility of considering the specimen as a continuum, when an identifying procedure from load-displacement to stress-strain in uniaxial compression is attempted. Actually, a failure mechanism with propagation of a macro-crack was found to activate from the very beginning of the uniaxial compression test forth. This leads to considering the acquired displacements as composed by two quotes: one constitutive, due to the material strain, and one of crack opening. Since the ratio between these two quotes is not constant during the compression test, the properties of the displacement field (which attains to structural properties) cannot be transposed to the strain field (which attains to material properties) through a mere scale factor. In this context, also creep takes on a different meaning, in the sense that time-dependence is an effect observed in the displacement field that does not necessarily correspond to a property of the strain field, i.e., the creep. In other words, it is not possible to exclude a-priori that the time-dependence of displacements is induced by crack propagation alone. A time-dependent motion of crack opening could activate and affect the displacements acquisition. The aim of the present work is to investigate the role played in displacement time-dependence both by creep and crack propagation. Results of an experimental program are presented here, stating the strict relationship existing between the increasing of displacement and the propagation of cracks at constant load.

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Keywords

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