EFFICACY STUDY OF POST-TENSIONED I GIRDER MADE OF ULTRA HIGH PERFORMANCE FIBER REINFORCED CONCRETE AND ORDINARY CONCRETE FOR IRC LOADING

Abstract

In the contemporary era, there's an increased need for elevated structures to alleviate traffic congestion. Consequently, numerous viaducts, flyovers, and bridges are being erected globally. The design of bridge superstructures varies based on numerous factors, with the beam slab system, typically utilizing prestressed beams, being the most commonly employed type. Post-tensioned I-girder superstructures are rising in popularity due to their structural efficiency, enhanced stability, cost effectiveness, ease of construction, and quicker erection. In recent times, Ultra-high-performance fiber reinforced concrete (UHPFRC) has emerged as a groundbreaking material in the construction of bridges, revolutionizing the way we conceptualize and engineer infrastructure. This advanced concrete variant offers exceptional mechanical properties, including high compressive and tensile strength, enhanced durability. In bridge construction, the utilization of UHPFRC brings numerous benefits. Firstly, its remarkable strength-to-weight ratio allows for the design of lighter and more slender structural elements, facilitating longer spans and reduced material consumption. This not only enhances the aesthetic appeal of bridges but also minimizes environmental impact. Despite its numerous advantages, the widespread adoption of UHPFRC in bridge construction is still evolving, primarily due to factors such as cost, availability of materials, and standardization of design guidelines. Therefore, it is necessary to assess the practicality of using ultra-high-performance fiber-reinforced concrete instead of ordinary concrete in bridges, particularly regarding economic considerations. The objective of this research is to conduct a comparative efficacy study between post-tensioned I-girders fabricated from ultra-high-performance fiber reinforced concrete and ordinary concrete. This assessment is based on the costs related to concrete production, prestressed steel reinforcement, shear reinforcement, interface shear reinforcement, untensioned steel reinforcement, erection, and RE panels in approaches for a standard flyover with a clearance of 5.5 meters and a total carriageway width of 16.0 meters. Parametric modelling has been executed in MIDAS Civil to analyse and design superstructures across a range of span lengths, including 25m, 30m, 35m, 40m, and 45m. Subsequently, a comparative cost assessment between post-tensioned I-girders constructed from ordinary concrete and those fabricated from ultra-high-performance fiber-reinforced concrete has been conducted. The analysis of prestressed concrete girders is carried out for the standard loading specifications outlined in IRC:6-2017 for road bridges, while the design of vi post-tensioned girders adheres to IRC:112-2020 guidelines. In cases where relevant Indian codes for ultra-high-performance fiber-reinforced concrete are unavailable, NF P18-710 (French standard) is selectively utilized. The research findings indicate that post-tensioned I-girders constructed from ultra-high-performance fiber-reinforced concrete become cost-effective for spans exceeding 40.0m. This is attributed to several factors, including reduced depth of UHPFRC girder, elimination of untensioned steel requirements, reduced need for shear reinforcement owing to the contribution of steel fibers to shear strength, shallower depths resulting in decreased erection costs.