CALCULATION OF THE NATURAL VIBRATIONAL FREQUENCY OF THE PULSE-LOADED EMBEDDED FOUNDATION

Abstract

Applicability of formulas obtained within the framework of wave model and Russian design code SP 26.13330.2012 were considered to determine the dynamic stiffness in respect to vertical and horizontal vibrations of shallow and pile embedded foundations. The target is to calculate the system’s varying natural vibrational frequencies regarding the deepening. Obtained results are compared with experimental data of a series of pulse dynamic loadings under half-full-scale conditions on foundation models. Values of transversal wave velocities are found directly on test section from test results. It is found that deepening results in natural vibrational frequencies growth, both in case of pile and shallow foundations. Full deepening of more than 1.6 times increases frequencies at horizontal vibrations, and up to 1.4 times at vertical vibrations; the effect is stronger for shallow foundations. Benefit of the results obtained by wave model against the SP 26.13330.2012 method is demonstrated, as well as the good agreement between calculation and experimental results, which permits finding reliable amplitude-frequency characteristics of the foundations. Results obtained in accordance with SP 26.13330.2012 show lower values of natural vibrational frequencies and do not completely regard the deepening effect. Maximal discrepancy with experimental data is 33% for vertical vibrations on shallow and pile foundations. In case of horizontal vibrations, the maximal discrepancy is from 20% for shallow foundation to 27% for shallow and pile foundation.