DYNAMIC BEHAVIOUR OF PILE CONSIDERING SOIL. STRUCTURE INTERACTION

Abstract

k abedded structures - like pile or pier-well . system of bridges subjected to earthquake type of excitation, are affected by input motion. _1n.-_ this -tbeziaL. ezpex theztsl and a1alytical studies have been taken up to study the fii».dameute.1 . frequenciea and displacements of top of pile in dry and dense sand for the purpose of assessing its behaviour, when used as foundation of any atruoture sub1eeted to dynamic loads.. The experiments were conducted on model pile of. 1.17 em diameter embedded in dense ` sand deposit,, in a tank* Tests were conducted. with four different conditions of pile top: ti) Pile top. without bearing (2) Pile top with bearing (3) Pile top with stetio load .transferred through bearing (4) load equivalent to static load attached at bearing level of pile. Each pile model was placed in sand container (tsuk), which was excited by oscillator and motor system„ Two ac'cele' ration pick--ups were placed on 'pile top to measure the accele-ration of pile top. One ecceleration pick—up was placed at: the base of oscillating tank to ;record the input acceleration.... The pile soil .system was analysed with the help of mathematical._ model. The elastic soil stiffness . functions including croseterms were taken into account,, Energy disci'-- pat ion in soil ;, ,n the form of v scoua radiation damping, Was considered, The important oonolusioi a deduced from these invests.. gations include the :following: The fundamental, fregi enoy., of . p.tIe inoreaiwas with increase in embedment depth but displacement of pile top dec eaaes with increase in embedment depth. The diaplaoa e . of pile top increases with increase in excitation intensity,' The fundamental frequency as well ss •displacement of pi ,e top decreases with increase in static load. The response of the • pile top obtained from two set' of experiments: (1) •attach ng. the added, mass at . pi.le top and (2) the load. xa~ts sw3 ths~a1t,$ bearing, are not same. The analytical. results show that the theory given by Novak =derest.imatea . the first ,.re azint-peak and overestimate the eoox l._ .reaso n peak.