Life line structures such as elevated flyovers and rail over bridges should remain functional after an earthquake event to avoid possible traffic delays and risk to general public. Generally, restraining the structure by reducing the degrees of freedom often cause serious damages that occurs during a seismic event through yielding of the structural components. By allowing the structure to rock through uplift using suitable arrangements can be a plausible seismic resilient technique. In this context, this article proposes a novel seismic resilient pile supported bridge pier foundation, which uses elastomeric pads installed at top of pile cap. The effect of pile soil interaction along with ground response analysis is also incorporated in the full bridge model adopted for the study. One dimensional equivalent linear site response analyses were performed to arrive at the amplified/attenuated ground motions along the depth of soil.The seismic performance of the proposed bridge with new rocking isolation concept is compared with existing bridge located in medium seismic zone of India. With the help of non-linear dynamic time history analysis and nonlinear static pushover analysis, the bridge modelled using the proposed novel rocking isolation technique shows good re-centering capability during earthquakes with negligible residual drifts and uniform distribution of ductility demand along the piers of the bridge considered in this study.

Introduction

Bridges and flyovers are major assets of any country and failure of such structures during seismic event leads to economic loss to the country and traffic disruptions to the general public. Despite their importance, these key infrastructure assets have been designed for many years, neglecting the fact that loads and geo-hazards may change drastically and thus significant upgrades may be required during their service life. Societies expect accelerated constructions, minimal damage and rapid upgrading for bridges which are sources of transportation and thus must be designed to face very strong earthquake in order to avoid permanent drift which are beyond repairs. Collapse of whole bridge caused by extended damage of the piers and/or unseating of the superstructure caused by insufficient deformation capacity of the bearing and other destruction of bridge structure often occurs in an earthquake [1].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 [2]. Although bridges designed in this manner may undergo damages due to severe earthquake excitations as observed in Fig. 1(a)–(d). 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 [3,4]. The design of South Rangitikei Railway Bridge in New Zealand in 1981 used structural rocking by adopting the concept of dissipative rocking at the pier-to-foundation interface by means of prestressing tendons which had more rocking sections contributing to dissipation of energy and thus less prone to heavy damages when subjected to severe earthquakes [5,6].