An Analytical Model for Estimating the Vibration Frequency of Structures Located on the Pile Group in the Case of Floating Pilesand End-bearing Pile

Exact estimation of vibration fundamental period of structures plays a vital role in their designing procedure. The proposition ofa relatively exact expression which considers the effects of a pile group on the fundamental period of the structures was of lessinterest to previous researchers. This study aims to propose an analytical model and expression so as to estimate the free vibrationperiod of the structures located on a pile group. To reach the objectives of this study, several numerical analyses has been carriedout using the method of equivalent spring which takes into account the effects of soil-pile-structure interaction on the fundamentalperiod of the structures. In the next step of the study the effects of a pile group on the fundamental period of the structures havebeen analyzed analytically. In this analytical study two cases have been considered for the piles which are end-bearing and floatingpiles. In the case of floating piles a five degrees-of-freedom analytical model and its corresponding expression have been proposedconsidering the soil-pile-structure system. The numerical modelling has been performed using the direct method due to the neglectof the soil in analytical expression and the results have been compared with those of the proposed analytical expression. The soilmass participation coefficient has been obtained using the discrepancy between the results of the two different methods t omodify the analytical expression. In the case of end-bearing piles an analytical model with three degrees-of-freedom and itscorresponding expressions has been proposed. Then the soil has been neglected and a new analytical expression has been proposedusing the mass participation coefficients adopted from other researches to calculate the fundamental period of the structures. Thecomparison between the results of the proposed expression and those of case and numerical studies confirms that the proposedexpressions benefit from a relative accuracy and can be used as an initial criterion in designing procedure.

Keywords:

Soil-Pile-Structure Interaction , Frequency of Free Vibration , Analytical Formula , Steel Frame , Numerical Study