Static equivalent method for the kinematic interaction analysis of single piles

This paper presents a static equivalent approach to estimate the maximum kinematic interaction effects on piles subjected to lateral seismic excitation. Closed-form expressions are reported for the evaluation of maximum freefield soil movements and for the computation of maximum pile displacements. The maximum free-field response is evaluated by means of a modal analysis combined with a suitable damped response spectrum. The pile is schematised as a Winkler’s beam subjected to equivalent static forces defined according to soil vibration modal shapes and amplitudes. Response spectra suggested by national standards or obtained from accelerograms may be used. The procedure may be implemented in simple spreadsheets. Method accuracy is demonstrated by comparing results with those obtained with a more rigorous model. Good results achieved by considering only the first soil vibration mode make the procedure straightforward for practical design purposes.