PRELIMINARY DESIGN OF CABLE STAYED BRIDGE USING INFLUENCE LINES

Abstract

Cable stayed bridges are very popular in European country and very large span cable stayed bridges are constructed there after 1950. But in India it is not that much popular and there are very few number of cable stayed bridges namely Hooghly river bridge, Akkar bridge and few other. This may be because of lack of standard design, procedure and technique In India cable stayed bridges are considered to be highly indeterminate structure whose design is not possible without using software and only few firms are able to construct this type of bridge. The design procedure and technique are not readily available in standard text book and bridge codes. In my thesis work I tried to develop an easy manual method to calculate bending moment in longitudinal girder, cable forces, bending moment and compressive force in tower and this leads to method of influence lines. In which symmetry of bridges are chosen and a part of symmetrical portion were modeled as planar in which cable connections were replace by roller supports . To find bending moment in girder Three moment's equation were used to draw ILD for bending moment at critical sections. To find cable forces simple static equation were used and with help of cable forces bending moment and compressive force in tower were easily calculated. In my thesis work to check the validity of manual result I modeled same structure in SAP2000 and result was compared and manually calculated values appears to be correct. After getting all design values an emphasis was given to design different component of cable stayed bridge. At last it was attempted to do economic evaluation cable stayed bridge against prestressed bridge of same span. Following are the work that got emphasis in my thesis 1. To develop an easy method to find design moment in longitudinal girder, cable forces, bending moment in tower and compressive forces that leads to influence line method. 2. Compare the result with available software as SAP2000 3. To design component of cable stayed bridge. 4. To do economic evaluation against prestressed bridge.