Analysis and design of precast/prestressed concrete spliced-girder bridges

A survey of the current practices in the design and construction of spliced-girder bridges was conducted. Based on the results of this survey, the state-of-the-art of these bridges is reported here. The techniques used to field splice the girder segments to achieve a continuous multispan bridge are discussed. A number of example bridges are presented in some detail for illustrative purposes. The basic theory of time-dependent effects of creep and shrinkage of concrete and relaxation of steel is reviewed. The effect of temperature variation in segmental composite I-girder bridges is described. The development of the equations necessary for the analysis is given. The analysis uses a step-by-step numerical procedure in which the service life of the structure is divided into time intervals. In each interval, time-dependent effects are evaluated, and external loads, if any, are applied. A stiffness analysis is then performed, and the resulting stress and strain increments are added to those obtained at the end of the previous interval. The incremental nature of this method is most suited for the sequential construction and loading schedules inherent to spliced-girder bridges. A computer based procedure for analysis of composite precast concrete girder bridges with cast-in-place topping is presented. Girder splicing with or without post-tensioning can be used to introduce continuity in the bridge superstructure. The method of analysis presented here is also applicable to other types of multi-stage construction and prestressing involving the use of temporary falsework. The computer program can be employed to evaluate stresses in concrete and steel at any cross section in a statically indeterminate composite beam or plane frame. It also gives the deflection at various stages of construction. A numerical example is presented to illustrate the hand calculations involved and compare the results to the computer solution.