International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 03 | Mar 2024
p-ISSN: 2395-0072
www.irjet.net
Design Details of Post-Tensioned Concrete Bridge Girder, Sustainability and Resilience Score Phani Ram Gollapudi 1, Satish Kumar Brahmalla 2 1 Lead Bridge Engineer, Ramboll Engineers 2 Assistant Professor, Department of Civil Engineering, Jayamukhi Institute of Technological Science
--------------------------------------------------------------------------***------------------------------------------------------------------Abstract: The bridge superstructure flyover built on National Highway route 16 (NH-16) near Benz circle in Vijayawada to act as grade separated highway for vehicles to cross over National Highway route 65 (NH-65) is made of precast and posttensioned concrete girders. The first part of this two-part publication discussed the analysis of the concrete bridge girders subjected to vehicular loads considered as per Indian Roads Congress Specifications. The design bending moments and shear forces for the girders and slab are computed using grillage analysis model. The current article, which is the second part of this study details the superstructure girder design of post-tensioned members precast at the concrete plant. The girders are twostage post-tensioned at precast yard and transported to the site for erection on piers. The post-tensioning design and details are presented in this paper along with sectional geometry and reinforcement detailing sketches for the girders and the diaphragms. The reinforcement schedule is presented. Finally the bridge superstructure is rated for sustainability and resiliency score based on the design and construction practices followed during the engineering of this bridge.
Keywords: Design, Post-tensioning, Sustainability, Resilience, Bridge, Concrete 1. Introduction The bridge on NH-16 near Benz Circle in the city of Vijayawada is built as two separate carriageways each of 3-lane posttensioned concrete girder bridges to cross over the at-grade vehicular traffic on NH-65. The bridge has a total carriageway of 11.5m curb to curb. The total deck width including crash barriers at both ends is 12.5m. The deck is supported by four posttensioned concrete girders spaced at 3.1 m on center and supporting an overhanging slab of 1.6m cantilevered on the edge girders. The four bridge girders are connected by three cross diaphragms one at each support location and one at the midspan. The concrete girders along with cross diaphragms are supported on elastomer bearing pads installed on top of reinforced concrete pedestals cast monolithic with pier caps. The girders are rectangular at support locations and taper to become Ishaped along the rest of their length. The first part of this two-phase article focused on the analysis methods and details of the bridge superstructure [1]. The bridge girders and slab system were analyzed as a grillage system in Staad Pro software. The maximum bending moments and shear forces were determined after considering Indian Roads Congress [2, 3, 4, 5, 6] vehicular load effects. The summary of design forces on the girder and slab system was provided at the end of the first phase article. Both the analyses and design of these bridge elements have been performed in accordance with IRC code specifications and recommendations [7, 8]. The seismic design has been performed in accordance with IS 1893 [9, 10]. The current article, which is the second phase of this study details the girder designs for this bridge superstructure. The girders are designed as post-tensioned concrete members. The girders are precast at the plant and then post-tensioned by four cables in multi-stage post-tensioning operations. The girders are post-tensioned when the girder concrete reaches the specific characteristic strength or specified age whichever is later. The girders are shipped to the site after the two-stage posttensioning is completed. This article provides the details of the post-tensioning such as jacking forces, number of cables, the strand type, size and number of strands, the horizontal and vertical profile of the cables along with any other details pertaining to post-tensioning of the cables. The article also provides the drawings showing the prestressing forces, cable profiles and anchor zone details. The article also provides the main reinforcement and shear reinforcement detailing followed in the girders to ensure composite beam action when tied with the cast-in-place deck slab reinforcement. Finally, the author discusses the engineering and construction practices followed in the design and construction of this bridge superstructure and assign a sustainability score to the bridge which is an indicator of the impact of the bridge construction on environmental sustainability and its resilience to major weather related disasters and accidental forces that exceed design basis loads.
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