A statistical investigation to determine dominant frequency of layered soil profiles

Energy based seismic design getting attraction since it accounts for all structural (hysteretic behavior of structural members), earthquake (amplitude, duration and frequency content) and soil (bearing capacity, frequency content) characteristics. To develop an efficient energy based seismic design procedure, accurate determination of the fundamental periods of the soil deposits is crucial. Hence, several analytical, numerical and approximate methods were suggested in the literature to find out fundamental periods of layered soil profiles. However, practitioners tend to use the simplest and the roughest methods, generally. In this particular research, a statistical study was performed to find out the best fit coefficient for the total travel time having minimum standard deviation. In the analyses, the calculated fundamental periods of 459 different soil profiles are compared with the results of almost exact analytical equations. Resultantly, the equation generally preferred by the practitioners is improved. It is proved that the improved equation has higher accuracy with lowest standard deviation and higher correlation. Therefore, using the improved equation to determine fundamental period of the layered soil profiles is highly suggested.