Volume 35, Issue 6 (November 2012)
The Nonlinear Coupled Response of Single and Group Piles under Various Horizontal Excitations: Experimental and Theoretical Study
Dynamic response characteristics of reinforced concrete single piles and 2 × 2 group piles subjected to varying levels of horizontal harmonic excitation are investigated by both experimental and analytical study. Two different types of coupled vibration tests, namely, type 1—horizontal exciting force above the center of gravity (c.g.), and type 2—horizontal exciting force below the c.g. of the pile cap-loading system, are conducted in the field. The tests are conducted for different eccentricities to determine the frequency-amplitude response of piles for horizontal and rocking motion separately. The influence of excitation intensity, static load on pile, spacing of piles in group, and different contact condition of pile cap with soil on the coupled dynamic response of piles are reported. The measured responses of type 1 and type 2 are compared with the results obtained by the continuum approach of Novak with nonlinear solution. For nonlinear analysis, the boundary zone concept, which accounts for yielding of soil around the pile, is incorporated into the linear elastic-based model and the allowance is made for the separation between the pile and soil. A reasonable match between the measured and predicted response by nonlinear analysis has been observed after introducing appropriate boundary zone parameters and soil–pile separation length. The differences between the dynamic characteristics of piles for coupled vibration type 1 and type 2 in terms of frequency response curves for amplitude, stiffness, and damping constants are also discussed.