Towards a Consistent Simplified Approach on the Strength of a Pier Based on Piles Founded on a Ground of Insufficient Stability

When a construction presents a huge vertical concentrated load (e.g. a bridge) and has to be founded on a ground of insufficient stability, the procedure to be followed is the use of pillars. However, in the case of a seismic event, the pillars are in danger due to: a) their fraction owed to high bending moments, due to the presence of significant horizontal soil movements along their length, b) shear failure of the foundation soil, in the case where the shear stress on a sliding surface, due to the static loading along with the seismic excitation, exceeds the local soil strength, c) a usually upwards pillar shift with respect to its surrounded soil, owed to the liquification of the underground. A description on the methods of analysis corresponding to the dynamic behavior of pillars along with the seismic event, concerning the collapse of the Higashi – Nada bridge of Kobe in Japan – after the earthquake of 17th January 1995 – is then to be presented.