A gradual accumulation of inelastic strain can be most conveniently described in terms of the so-called intrinsic time, whose increment de¬pends on the time increment as well as the strain increments. This approach, which gives a particularly simple description of irreversi¬bility of strain at unloading and cyclic loading, was previously developed for metals and is extended herein to concrete by introducing the hydro¬static pressure sensitivity of inelastic strain, the inelastic dilatancy produced by deviator strains, and the strain-softening tendency at high stress. Failure envelopes are obtained as a collection of the peaks of stress-strain diagrams.
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