International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 12 | Dec 2024
p-ISSN: 2395-0072
www.irjet.net
ANALYSIS AND DESIGN OF SEISMIC ISOLATED RC BRIDGE USING BEARINGS Sahana K1, Dr. Dharmesh N2, Dr. L Govindaraju3 1P.G Student, Department of Civil Engineering, U.V.C.E, Bangalore University, Bengaluru 2Assistant Professor, Department of Civil Engineering, R.N.S.I.T, Bengaluru
3Professor, Department of Civil Engineering, U.V.C.E, Bangalore University, Bengaluru. ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract Seismic isolation is recognized as one of the most effective strategies for mitigating earthquake hazards. In bridges, seismic isolation bearings are typically installed between the substructure and superstructure, effectively decoupling the superstructure from the horizontal components of ground motion. As a result, during an earthquake, inelastic deformations are concentrated in the isolation bearings, reducing the forces transmitted to the substructure and superstructure, thereby allowing them to remain elastic. This study focuses on an RC T-beam bridge equipped with different bearing systems, including elastomeric bearings and lead rubber bearings. Using Finite Element Analysis, the behavior of the isolated bridge is examined. The bridge’s performance is assessed through modal and time history analyses, evaluating parameters such as fundamental time period, base shear, acceleration, and displacement. The findings suggest that elastomeric bearings can be effectively replaced with lead rubber bearings, as they increase the fundamental time period and significantly reduce the base shear coming on the piers.
bridge spanning a bay, the different types of bridges play an integral role in shaping our world and supporting the growth and prosperity of our communities.
Key Words: Seismic isolation, Ground motion, Seismic isolation bearings, elastomeric bearings, lead rubber bearings, Finite element analysis, time history analysis.
Lead Rubber Bearings (LRB) are specialized seismic bearings designed to provide both load support and seismic isolation for structures like bridges and buildings in earthquake-prone areas. The bearing combines an elastomer (rubber) with a lead core, which together help isolate the superstructure from ground motion, reducing the amount of seismic force transmitted during an earthquake. Lead core is Positioned at the centre of the bearing, the lead core serves as an energy-dissipating element by absorbing seismic energy. Lead is used because it can undergo plastic deformation (permanent change in shape) repeatedly without losing its structural integrity. Rubber Layers Surrounding the lead core are layers of natural or synthetic rubber. These rubber layers absorb horizontal movements and provide flexibility. Steel plates are embedded within the rubber layers, reinforcing the bearing, controlling deformation, and increasing its loadbearing capacity. Outer steel plates are located on the top and bottom of the bearing, these plates connect the bearing to the bridge superstructure and substructure.
1.1 Elastomeric bearing Elastomeric bearings are one of the most common types of bridge bearings, made from elastomers, usually rubber, which may be reinforced with steel laminates. These bearings provide flexibility for bridges by allowing limited movement in multiple directions, accommodating small rotations, and providing essential resilience to handle minor displacements due to traffic loads, temperature changes, and seismic forces. elastomeric bearing isolators consist of upper and lower steel plates with a series of alternating layers of natural, or synthetic, rubber bonded to intermediate steel shim plates. The rubber provides lateral flexibility while the steel provides vertical stiffness.
1.2 Lead rubber bearing
1.INTRODUCTION Bridges are structures built to span physical obstacles like water, valleys, or roads, providing a passage over them. They are essential for transportation, connecting people and places that would otherwise be inaccessible or require lengthy detours. Bridges play a crucial role in modern infrastructure, connecting communities and facilitating the flow of goods, services, and people. They are a testament to human ingenuity, embodying our ability to overcome obstacles and connect distant lands. Bridges are an important infrastructure because they allow people to cross waterways, canyons, and other obstacles easily and safely, which would otherwise be difficult or impossible to navigate. Bridges are critical links in transportation networks, connecting roads, highways, and railway systems, helping reduce traffic congestion and improve travel time. In addition, they help to spur economic growth by enabling the efficient movement of goods and people and facilitating the development of new business and residential areas. Whether a simple footbridge over a creek or a massive suspension
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2. OBJECTIVES 1.
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To design the Elastomeric bearing for R C T Beam bridge in accordance with IRC 83 (Part 2) 2018
ISO 9001:2008 Certified Journal
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