Feasibility Analysis of Using UHPC in Prestressed Bridge Girders

Abstract

Ultra high performance concrete (UHPC) is an emerging material which develops very high compressive strengths and exhibits improved tensile strength and durability properties. Recent construction of three UHPC bridges in the United States has sparked interest in the use of UHPC for prestressed bridge girders in several states. UHPC offers many advantages including longer spans, improved durability, and smaller structural members, making it an appealing material to use in prestressed bridge construction. This paper presents a case study conducted to investigate the feasibility of implementing UHPC in bridge design in New Mexico. Using a modified LFD procedure, bridge designs were developed considering the compressive strength, modulus of rupture, and modulus of elasticity of UHPC as well as design requirements for flexure and shear, girder cross-section geometry, and prestressing strand area. Comparisons with as-built bridge configurations show that using UHPC with compressive strengths between 100 MPa and 150 MPa may potentially lead to a reduction in required girder lines and reduce or eliminate mild steel shear reinforcement. Compared to regular concrete, a cubic yard of commercially available UHPC can cost as much as 10 times more, making designers and precasters hesitant to adopt this material. An economic analysis, assuming that local materials can be used to produce UHPC, indicates that the initial high cost can be offset by careful selection of materials, reduced construction time and maintenance, and the increased service life of the structure. Costs were evaluated based on local material prices, design parameters of the bridge, modified production practices, and a projected maintenance schedule. This study aids in the development of design procedures and recommendations for implementing UHPC as a prestressed concrete girder material.