Dynamic response characteristics of reinforced concrete piles under varying levels of vertical and horizontal harmonic excitation are investigated in the present study. Single and group (2 × 2) piles are used in the investigation. The horizontal exciting force applied on the pile cap through the oscillator causes coupled motion to the foundation. Two different types of coupled vibration test are conducted to investigate the effect of the position of the center of gravity of the pile cap-loading system with respect to the position of the horizontal exciting force on the frequency amplitude response of piles. The effects of various influencing parameters, namely, static load on the pile, eccentric moment, length of pile, spacing of pile in a group, embedded condition of pile cap on the nonlinear dynamic response of piles are also investigated. The measured response is compared by the continuum approach of Novak with linear and nonlinear solution. In linear analysis, a perfect bonding is assumed between the pile and soil. Two different approaches are used in nonlinear analysis. For nonlinear analysis 1, the boundary zone concept which accounts for yielding of soil around the pile is incorporated into the linear elastic based model. For nonlinear analysis 2, allowance is made for the separation between the pile and soil in boundary zone model. Reasonable match between the measured and predicted response by nonlinear analysis 2 is found for both vertical and coupled motion. The test data are used to establish the empirical relationship between the extent of soil separation around the pile and the maximum vibration amplitudes under vertical and coupled vibration. Experimental and analytical investigation on two full-scale single piles under vertical vibration is also presented in this study. Keywords: Coupled vibration, Damping, Dynamic interaction factor, Horizontal excitation, Layered soil, Linear analysis, Nonlinear analysis, Pile foundation, Resonant amplitude, Resonant frequency, Rocking, Separation, Stiffness, Vertical vibration
Thesis Submitted To Indian Institute Of Technology, Kharagpur For The Award Of The Degree Of Doctor Of Philosophy By Bappaditya Manna Under The Guidance Of Prof. Dilip Kumar Baidya Department Of Civil Engineering Indian Institute Of Technology, Kharagpur May 2009 © 2009, Bappaditya Manna. All Rights Reserved.