EFFICACY STUDY OF DIFFERENT CONFIGURATION OF PRETENSIONED AND POST TENSIONED I-GIRDERS FOR HIGHWAY VIADUCT

Abstract

In today’s world, there is a higher demand of roads and grade separated structures to avoid traffic congestion. Thus, a lot of elevated viaducts, flyovers and bridges are being constructed all over the world. The bridge superstructure is of various types and the type of superstructure to be adopted depends upon several factors. The most used superstructure type is beam slab system in which, generally, the beams are prestressed. Pre-Tensioned and Post Tensioned girders are the most used type of prestressed beams in beam slab bridges and the practice of Prestress I-Girder type bridges are gaining popularity in bridge engineering fraternity because of its structural efficiency, better stability, serviceability, elegance, economy, aesthetic appearance and shortened construction time. Parametric study has been done with different configurations in terms of span length and the number of girders to evaluate the total quantities of Pretensioned and Post Tensioned girders. Finally, the cost comparison between the two types of girders is done considering the concrete quantity, reinforcement and prestressing steel quantity. The scheme of launching and logistics involved are also considered for the cost comparison between the two types of girders. The theoretical comparison is also done in order to understand the

differences in bending moment & shear force between Pretensioned and Post tensioned I- Girders.

The design & analysis of prestressed concrete girders is carried out using IRC:112-2020 Concrete Road Bridges based on India Live Load as per IRC 6-2017. The IRC:112-2020 code is based on limit state design philosophy. Based on the comparative study done, it has been found that the Pretensioned girders are very economical and time efficient primarily because more than 5 to 7 girders can be prestressed at the same time using the same equipment. Further, there is no requirement of anchorages, sheathing and grouting. It has been found that Pretensioned Girders are more economical when compared to Post Tensioned Girders if the number of girders required in the project is more than 250 number of girders.