A Proposal for An Alternative to Seismic Isolation Practice: Implementation in a Seismic Isolated Railway Bridge

Abstract eng:
The present study proposes an alternative to seismic isolation practice, which aims at the reduction in the bridge seismic actions mainly for the longitudinal design earthquake, which is more critical than the transverse one. The aforementioned purpose is achieved through the improved seismic participation of the bridge abutments. The deck slab is extended onto the embankments and is rigidly connected either with transversely directed RC walls or with transversely directed rows of hollow section steel tubes. This system is constructed into a concrete box-shaped substructure which replaces the conventional wing-walls. As a result the approach embankment does not affect the response of the proposed system. The efficiency of the proposed system was assessed by utilizing a conventional seismic isolated railway bridge. The analytical investigation was performed by means of non-linear dynamic time history analysis implemented with the FE commercial code SAP 2000. The bridge systems were subjected to artificial earthquake motion that is compatible to Eurocode 8 elastic spectra. The assessment of the efficiency was mainly carried out by comparing the response of the resulting modified bridge system with the response of the initial bridge system. The proposed system has the ability to accommodate the in-service movements of the deck, by means of the flexibility of the restraining members. The seismic response of the bridge is also enhanced. The displacements of the deck in the longitudinal direction of the bridge were found to be significantly reduced. The restraining effect also reflects on the seismic actions of the piers (shear actions and bending moments) leading to cost-effective bridge design.

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