Mechanics and Design of Prestressed Girder Bridges using Ultra High-Performance Concrete

Abstract

The aim of this study is to propose stress-strain models which predict the material behavior in compression and tension, analyze the moment-curvature behavior of UHPC structural sections and to demonstrate the design of an UHPC bridge. A detailed literature review of the past studies on stress-strain models for both normal concrete and UHPC, moment-curvature analysis of reinforced concrete sections and design of prestressed girder bridges is carried out. First, stress-strain models for UHPC in tension and compression are developed based on the experimental results of previous studies; model predictions are compared with experimental results and the corresponding stress blocks are proposed. Second, moment-curvature analysis of standard reinforced and prestressed UHPC sections are carried out. The behavior of the UHPC sections and the influence of the fiber volume is predicted and the optimal range of fiber volumes are proposed. Third, design of a simply supported UHPC bridge, based on flexural and shear considerations, is performed and the amount of fibers that should be added to the mix for good performance is suggested. Based on the investigation, it is concluded that the proposed tensile stress-strain model and the adapted compressive stress-strain model describe the behavior of UHPC including the post-peak behavior with good accuracy. It is found that the reinforced and prestressed UHPC sections have considerable ductility, comparable to that of a conventional confined concrete section, before failure. This is attributed to the confinement offered by the steel fibers in the mix to the concrete matrix. It is found that UHPC bridges may require less girder lines compared to conventional concrete bridges with a similar span.