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Evaluation of Options to Extend Span Range of Precast Prestressed Concrete Bridge Girders During Preliminary Design Open Access

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Abstract of DissertationEvaluation Of Options To Extend Span Range Of Precast Prestressed Concrete Bridge Girders During Preliminary DesignDesign of highway bridges passes through the following two phases: 1- Preliminary design where the design engineer decides on the major artifact type and configuration parameters such as girder type, number of spans and intermediate supports (piers), possible road closure and overall cost of the project. 2- Final design where every component of the bridge is designed in accordance with the AASHTO LRFD Specifications.Longer spans result in minimizing the number of the intermediate supports, which can significantly lower the project cost and minimize road closures. One of the very principal issues that come up during preliminary design of new highway precast/prestressed concrete bridges is how to extend the span length as much as possible while maintaining the cost effectiveness of the project. However, using longer spans with the traditional material and design options lead to deeper and heavier sections that may reverse the cost savings achieved by eliminating some of the intermediate supports. Therefore, there is a need to investigate the effect of using new construction materials and design options on extending the span range and cost effectiveness of the bridge.During the past two decades, engineering and material technologies have advanced significantly and many technological trends/options were developed to extend the span length and/or girder spacing of prestressed concrete girders. These trends/options include, but not limited to:- High Performance Normalweight Concrete (with f_c^' up to 15 ksi)- High Performance Lightweight Concrete (with f_c^' up to 12 ksi)- Large Diameter Strands (0.6- and 0.7-in. Diameter) and High Strength Strands (Grade 300 ksi) - Bridges made Continuous for Superimposed Dead Loads and Live Loads- Bridge made Continuous for Superimposed Dead Loads, Live Loads, and the Deck Slab WeightThis research presents a parametric study that addresses these trends/options and investigates the impact of using them individually and simultaneously on the maximum span range and the corresponding cost of the superstructure. The results of this study will help design engineers to decide which option(s) should be considered based on the project criteria.

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