Strain accumulation due to packages of cycles with varying amplitude and/or average stress – On the bundling of cycles and the loss of the cyclic preloading memory

• Published in: Soil dynamics and earthquake engineering (1984) Vol. 101; pp. 250 - 263
• Main Authors: Wichtmann, T., Triantafyllidis, T.
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01-10-2017; Elsevier BV
• Subjects: Accumulation; Amplitudes; Bundling; Cyclic loads; Deformation; Drained cyclic triaxial tests; Erasure of cyclic preloading memory; High-cycle accumulation model; Materials fatigue; Mathematical models; Packages; Packages of cycles; Random cyclic loading; Sand; Stress-strain curves; Studies; High-cycle accumulation model; Erasure of cyclic preloading memory; Drained cyclic triaxial tests; Random cyclic loading; Packages of cycles
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2017.07.012

In order to predict permanent deformations by means of a high-cycle accumulation (HCA) model, a random cyclic loading, i.e. a loading with frequently changing amplitudes, has to be grouped into packages of cycles each with a constant amplitude. Based on a series of drained triaxial tests on fine sand, in which the same cycles have been applied either in an order with frequently changing amplitudes or in packages of cycles, it is demonstrated that such bundling is conservative. Predictions by the HCA model of Niemunis et al. [19] are confronted with experimental data and with other approaches for the prediction of permanent deformations under packages of cycles, among them the frequently cited procedure of Stewart [26]. An effect not captured in the HCA model or in any other approach yet has been detected in another series of tests with a change of the average stress between bundles of cycles: The monotonic loading associated with this change can partially or fully erase the memory of the sand regarding its cyclic preloading history.
•The bundling of a random cyclic loading into packages of cycles is conservative.•Miner's rule was approximately fulfilled in the experiments.•The HCA model approximately implements both Miner's rule and the approach of Stewart.•The memory of cyclic preloading history can be erased by monotonic loading.•All actual procedures for packages of cycles do not consider this important effect.