Lifetime-Oriented Structural Design Concepts- P9: At the beginning of 1996, the Cooperative Research Center SFB 398 financially supported by the German Science Foundation (DFG) was started at Ruhr-University Bochum (RUB). A scientists group representing the fields of structural engineering, structural mechanics, soil mechanics, material science, and numerical mathematics introduced a research program on “lifetimeoriented design concepts on the basis of damage and deterioration aspects”. | 198 3 Deterioration of Materials and Structures sodium chloride increases the scaling by more than a factor of 4 see Subsection . High-Cycle Laboratory Tests on Soils Authored by Torsten Wichtmann Andrzej Niemunis and Theodoros Triantafyllidis The accumulation phenomenon has been studied systematically on quartz sand with sub-angular grain shape. Most of the tests were performed on a grain size distribution curve No. 3 in Figure with a mean grain size d50 mm and a uniformity index Cu . Numerous cyclic triaxial tests and cyclic multi-dimensional simple shear tests have been performed. A scheme of the cyclic triaxial device four similar devices were available in the present study is given in Figure . Details are explained . in 837 835 . Cylindrical specimens with 10 cm diameter and 20 cm height were used. They were prepared by dry pluviation and afterwards they were water-saturated in order to measure volume changes via the pore water. The tests were performed under drained conditions. In the stress-controlled tests the axial effective stress a1 and the lateral effective stress a3 could be varied simultaneously using pneumatic loading devices. In Figure typical stress paths with in-phase and out-of-phase cycles are presented in the p-q-plane. p a1 2a3 3 and q a1 a3 denote Roscoe s invariants. The average stress is described by pav and qav or the ratio pav qav pav. Alternatively the isomorphic variables P 3p and Q y 2 3q are used in the following. In most tests the cycles were applied with a frequency f 1 Hz . inertial forces were negligible small. The axial strain 1 and the volumetric strain v 1 2 3 were calculated from the measured changes of specimen height and volume. The deviatoric strain q 3 1 3 the total strain y m 2 2 3 2 and the isomorphic strain variables P y 1 3 v and q y 3 2 q are derived quantities. In a cyclic test the residual strain in the first cycle may differ significantly from the strain in the .
