NOVATEUR PUBLICATIONS International Journal of Research Publications in Engineering and Technology [IJRPET] ISSN: 2454-7875 VOLUME 3, ISSUE 1, Jan. -2017 34 | Page INFLUENCE OF PRESTRESSING FORCE ON BOX GIRDER BRIDGE SUBJECTED TO SEISMIC LOAD D. VENKATESH P.G Student, Visakha Technical Campus, Narava, Visakhapatnam. V. BHARGAVI Assistant professor, Visakha Technical Campus, Narava, Visakhapatnam. E. V. RAGHAVA RAO Professor, Head of the Dept. Visakha Technical Campus, Narava, Visakhapatnam. ABSTRACT: Bridges are often considered to be engineering marvels. Whether we need to cross rivers or valleys, connect islands to mainland, carry cars people etc are obstacles that are achieved only by bridges. Pre stressed concrete is ideally suited for the construction of medium to long span bridges. The composition of pre stressed concrete is nothing but high strength concrete and high tensile steel which is aesthetically appealing and economical. The present study deals with the analysis of reinforced concrete and prestressed concrete bridges. Reinforced concrete and Post-tensioned bridges of spans 15m, 30m and 45m are considered. Analysis of these bridges is performed with SAP2000 software for various Earthquake zones. The bending moments due to load combinations, viz.,(Dead load+ live load), (Dead load+ Earthquake load in X-direction), (Dead load+ Earthquake load in Y-direction), (Dead load+ live load+ Earthquake load in X-direction) and (Dead load+ live load+ Earthquake load in Y-direction) by considering with and without application of prestressing are obtained and compared. Maximum deflections under these load combinations are obtained by considering with and without application of prestressing and compared. INDEX TERMS: Box girder bridge, SAP 2000 INTRODUCTION: The reduction of commuting time not only saves on precious man hours but also saves on fuel consumption and depreciation on vehicles, apart from giving added convenience. Majority of existing buildings in India and abroad can be grouped as follows. One group includes structurally deficient bridges that have deteriorated to such a condition that they cannot carry the load for they were designed. The second group includes functionally obsolete bridges that are in good conditions, but whose current loading requirement may have exceeded the original design load. Therefore, it is necessary to find easy, simple and cost-effective methods to meet current and future loading and traffic requirements. Three possible solutions this problem are bridge replacements, posting load restrictions or to strengthen these existing bridges. As the existing bridges are vital assets and preservation of these bridges is necessary form the aspect of historic and cultural heritage, strengthening of these buildings are appropriate solutions. Also, proper maintenance of these bridges and timely rehabilitation work may well save substantial capital expenditure of any country .Pre stressing with high strength steel tendons is the one of the best methods of strengthening of these bridges. The basic concept of pre-stressing is to introduce the internal stresses of such magnitude and distribution that the stresses resulting from given external loadings are counteracted to a desired level. It can be applied to a single member or group of remembers and can be in a single stage or multi stages. METHODOLOGY THE DATA ADOPTED FOR 15M SPAN BRIDGE: • Effective span = 15m • Width of road = 7.5m • Kerbs = 600mm on each side • Foot path = 1.5m wide on each side • Thickness of wearing coat = 80mm • Live load = IRC class AA tracked vehicle • Material used for deck slab = M-20 grade concrete • Material used concrete girders = M-50 grade concrete • Prestressing Force in each cable = 571kN • Total prestressing Force = 2855kN • No of cables used = 5 • Seismic zones considered = Zone II, III, IV&V Figure.1 Wire frame Model of box Girder Bridge of span 15m from SAP200