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Showing papers by "Zdenek P. Bazant published in 1976"


Journal ArticleDOI
TL;DR: In this paper, the intrinsic time model for concretes is extended to concrete and it is demonstrated that the proposed model predicts quite closely: (1) stress-strain diagrams for concrete of different strength; (2)uniaxial, biaxial and triaxial stressstrain diagram and failure envelopes; (3) failure envelopes for combined torsion and compression; (4) lateral strains and volume expansion in uniaxia and biaaxial tests; (5) the behavior of spirally confined concrete; (6)
Abstract: A gradual accumulation of inelastic strain can be most conveniently described in terms of the so-called intrinsic time, whose increment depends on the time increment as well as the strain increments, and was previously developed for metals and is extended herein to concrete. It is demonstrated that the proposed model predicts quite closely: (1)Stress-strain diagrams for concretes of different strength; (2)uniaxial, biaxial, and triaxial stress-strain diagrams and failure envelopes; (3)failure envelopes for combined torsion and compression; (4)lateral strains and volume expansion in uniaxial and biaxial tests; (5)the behavior of spirally confined concrete; (6) hysteresis loops for repeated high compression; (7)cyclic creep up to 10 6 cycles; (8)the strain rate effect; (9)the decrease of long time strength; and (10)the increase of short-time strength due to low stress creep.

188 citations


Journal ArticleDOI
TL;DR: In this paper, a nonlinear constitutive law is developed, together with the previously established model for an inelastic two-phase medium, to give a realistic prediction of the pore pressure buildup and associated liquefaction of sand due to cyclic shear.
Abstract: A nonlinear constitutive law is developed, together with the previously established model for an inelastic two-phase medium, to give a realistic prediction of the pore pressure buildup and associated liquefaction of sand due to cyclic shear. The law is of the endochronic type and consists of quasi-linear first-order differential equations expressed in terms of intrinsic time, which is an independent variable whose increments depend on the strain increments. This accounts for the accumulation of particle rearrangements, which are characterized by a parameter termed the rearrangement measure. The basic extensions of this work with regard to the application of endochronic theory to metals are due to the fact that sands densify upon shearing and are sensitive to confining stress; these two features are shared with the formulation of endochronic theory for concrete. Several typical examples are given to illustrate densification, hysteresis, and liquefaction tendency of sands subjected to cyclic shear in laboratory tests.

81 citations


Journal ArticleDOI
01 Jul 1976
TL;DR: In this paper, the changes of relative humidity and temperature in a program-controlled environmental chamber have been gradual, so as to minimize the differences in pore humidity throughout the specimen wall and the accompanying residual stresses and microcracking.
Abstract: Tests of creep under axial load and torque have been made using tubular specimens of extremely small wall thickness (0.7 mm) in order to achieve sufficiently rapid moisture exchange with the environment. The changes of relative humidity and temperature in a program-controlled environmental chamber have been gradual, so as to minimize the differences in pore humidity throughout the specimen wall and the accompanying residual stresses and microcracking. A number of different humidity and temperature histories, including the drying before and during the creep test, and the humidity changes during the creep test and during the recovery, have been tested. The measurements have revealed a decline of the slope of creep curve in log-time after a sufficiently long drying period; acceleration of creep as well as recovery by both drying and wetting; a smaller and more delayed acceleration at lower humidities; a delay of this acceleration with respect to the weight loss; a similarity of these effects in axial and torsional creep; a higher recovery as well as creep at higher humidities when moisture equilibrium has been approached before loading; a higher creep acceleration by temperature increases or decreases when the humidity is below saturation, but a smaller acceleration at nearly dry state; and other effects.

46 citations