Time-dependent analysis and application of high-performance concrete in bridges

High performance concrete (HPC) is now gaining popularity for use in building bridges. The features of HPC include low water-cementitious material ratio, high strength, low permeability, and improved durability. With these characteristics, highway bridges built with HPC are expected to have longer service life and less maintenance than those with conventional concrete. HPC also provides greater design flexibility by allowing designers to design bridges with longer spans and requiring fewer girders with smaller sections. As the materials used in HPC mix are different in different states, and as properties of HPC are largely dependent on materials used, it is necessary to investigate the performance characteristics of HPC with local materials. Time dependent deformation due to concrete shrinkage, creep, interaction between concrete and prestressing strands, and interaction between precast and cast-in-place concrete affect the stresses and deflection of precast prestressed bridge girders. Time-dependent analysis of continuous span bridges indicated the need for special design and construction considerations. This dissertation covers details of the selection of HPC mixes, experimental program of time-dependent properties of HPC, discussion and suggestions on structural design of HPC bridges, time-dependent analysis of HPC bridges on the long term deflection, and time-dependent analysis on the behavior of continuous prestressed concrete bridges. This research study showed that creep and shrinkage of HPC are lower than that of conventional concrete. New factors related to the compressive strength of concrete are introduced in predicting creep and shrinkage performance of HPC and conventional concrete. The deflection multipliers for prestressed girders at time of erection and at final time are recommended according to the analysis results. Design recommendations are given for construction sequence in order to avoid cracking at continuous joint sections. Details of continuous joints are discussed. The structural design and construction of the HPC bridge at 120th and Giles Road is presented as a demonstration of the application of HPC