TIME HISTORY ANALYSIS OF STRUCTURES ON VLASOV TYPE ELASTIC SUBGRADE

The Winkler soil model is generally considered as a subgrade model in analysis of structures under static or earthquake loads. In this soil model, it is assumed that the soil stresses are proportioned to soil displacements at the same points i.e. the interaction between the neighboring soil points is neglected. Vlasov soil model which is more realistic soil model assumes that differantial equilibrium equation may be represented by a second parameter together with the Winkler parameter as a first parameter so as to the interaction between neighboring soil points can be considered. Furthermore, the effect of subgrade height and the effect of outher zone of the foundation can also be considered in the analyses by the Vlasov soil model. Vlasov parameter or so called second parameter represents the shear deformation effects of the subgrade soil. General purpose structural analysis and design programs can not consider the second parameter of the Vlasov model, but this parameter may be indirectly considered by the adaptation of Mindlin plate elements as soil elements in the libraries of the mentioned programs by changing the elastic properties of the materials. In this time however, the second parameter cannot be correctly considered as some soil parameters may change between the time intervals of time history analysis. In the computer code which is devoloped for time history analysis of structures on Vlasov foundation, necessary soil parameters may be updated between the time intervals and more realistic results may be obtained. For the comparison, choosen structural systems are analyzed by the developed computer code and the results are compared with those obtained by a general purpose structural analysis program before, so as to show the effects of the mentioned soil parameters on time history analyses.