Novel Rocking Pier on Pile Foundation

I. I.INTRODUCTION The concept of ductility is used in the conventional design of bridge pier wherein the pier reinforcement is detailed to develop flexural plastic hinges at the base and top of pier. Although bridges designed in this manner may be safe from collapse but not from damages due to severe earthquake excitations as seen in Fig1. Rocking isolation in the form of structural rocking or geotechnical rocking of the bridge pier experience far less damage when subjected to high intensity earthquake ground motion with added bonus of pier that recenter due to the increased period of vibration owing to the flexibility of the resilient pier. Antonellis and Panagiotou (2014) investigated the three-dimensional seismic response of conventional fixed based pier and piers rocking on pile foundations that are designed to remain elastic. The rocking of pile foundation was achieved by wrapping the protruding part of piles into the pile cap by neoprene sheet and rubber pad. Marriott et al (2011) experimentally investigated biaxial response of post-tensioned precast bridge pier with external replaceable mild steel dissipaters which maintains the structural integrity during severe biaxial loading and thus reduces the repairs cost by simple replacement of the external dissipaters. Quinn et al (2016) modeled soil-structure interaction by using nonlinear discrete Winkle springs and adopted force-deformation (p-y) curves to model soil springs as per American Petroleum Institute Standard (API 1993). Boulanger et al (1999) validated nonlinear Winkler foundation analysis method for analyzing seismic soil-pile interaction by means of results of a series of dynamic centrifuge model tests. For Free-field site response analysis a 1D equivalent linear site program SHAKE 91 was used. This paper compares a fixed base pier at pile cap top having a soil profile varying from loose sand to dense sand as depicted in Brahmaputra River near Guwahati with a novel rocking resilient pier having elastomeric pad above the pile cap and external restrainer (SMA) attached to footing over the pads. Considering amplification of ABSTRACT Considering the current scenario in which we see major earthquakes where the structures are damaged severely beyond repairs, we need such a foundation which shall suffer only minimal damage. This paper proposes novel rocking pier with elastomeric pad installed at top of pile cap along with external restrainers made up of shape memory alloy (SMA) bars. The effect of pile soil interaction along with ground response analysis is also incorporated in the individual pier model adopted for the study. The earthquake waves amplify at the ground surface and the response of soil profile was analyzed using a 1D equivalent site response program. By performing non-linear dynamic time history analysis, a comparison with a fixed based pier at pile cap top and the novel rocking pier is been studied. It has been found that the proposed pier has good recentering capability and better performance during seismic than the conventional pier adopted in current design practice.The novel rocking pier experienced lesser forces and negligible permanent drifts due to its controlled rocking behaviour by using smart material in the form of SMA bars.