Computation of equivalent number of uniform strain cycles for seismic compression of sand subjected to multi-directional earthquake loading

Dynamic triaxial tests on different types of sand under multi-directional earthquake loading are simulated using finite element method.155 groups of ground motions with multi-components from far and/or near field of moderate and/or strong earthquake events at different site conditions are used as input motions for strain controlled dynamic tri-axial tests.A new method of computation of equivalent number of strain cycles for seismic compression of sand induced by multi-directional earthquake loading is developed.Effects of earthquake magnitude,site-to-source distance and properties of sand on the ratio of equivalent number of strain cycles are also studied.The study shows that the ratio of equivalent number of strain cycle is not affected much by earthquake magnitude and site-to-source distance,but is dominated by the properties of sand.Corresponding to the relative densities 45%,60%,80% and 100% of sands,the mean ratio is 1.58,1.75,1.93 and 2.08,respectively.The ratio of equivalent number of strain cycles increases with the relative density of sand,which is useful in the computation of equivalent number considering multi-directional earthquake loading.