A Comparative Design of RCC and Prestressed Concrete Flyover Along With RCC Abutments

Flyover construction today has achieved a worldwide level of importance. Flyovers are the key elements in any road network. Use of PSC Girder has gained popularity in bridge engineering because of its better stability, serviceability, economy, aesthetic appearance and structural efficiency. In the present study a simply supported PSC Girder Bridge of 25m span is analyzed for moving loads as per Indian Road Congress codes- IRC: 6 and IRC: 18 specifications. The analysis and design will be carried out using Working Stress Methodology. Firstly, proportioning of the girder and calculation of section properties will be carried out. Then, the different loads- dead, superimposed and live loads, coming onto the structure will be estimated. The analysis will be performed and section forces- bending moments, shear forces and stresses are arrived at to proceed with the further design. All the analysis will be carried out for two sections- running section and end section and internal, external and cross girders. As a conclusion, the analysis results will be presented and an optimization of the design is discussed. Prestressed (Post tensioning) concrete is well suited for the construction of Flyovers in the medium to large span range. These structures gained popularity due to their versatility in construction and economy in cost and maintenance; also they can be cast in any convenient shapes and forms to meet architectural requirement as well as can utilize locally available materials such as stone chips, gravels, sand etc. it can be cast at site thereby eliminating carriage of heavy bridge components hence are widely used in construction of medium to large span structures. Precast PSC (Post tensioning) girder is by far the most commonly adopted type in the span range of 20m to 30m. The structure so named because the main longitudinal girders are designed as I girders integral with the part deck slab, which is cast monolithically with the girders. For a particular girder span and structure width, a large number of parameters control the design of the structure such as girder spacing, cross sectional dimensions of girder, grade and type of high tensile steel, type of tensioning, first stage stressing, no. of prestressing stages, deck slab thickness, deck slab reinforcement, concrete strength, materials of construction, reinforcement in cross girder and intermediate girders etc. By studying proper design procedures of Precast PSC (Post tensioning) I girder we will get pre assigned parameters, design variables or decision variables, design constraints, design vectors and objective functions. By using these all parameters we can convert normal design problem of Precast PSC I (Post tensioning) girder into optimization problem and this optimization problem can be solved with the help of various optimization techniques or software’s which are available so as to achieve desired objective function, so as to optimize the design.