Analysis of time-dependent effects on segmental prestressed concrete curved box-girder bridges

In the present thesis, a numerical technique is introduced and a computer program is developed for the time-dependent analysis of segmentally erected curved prestressed box-girder bridges and other structures. The program is capable of predicting the response of such structures throughout their various stages of construction and service load history. The analysis accounts for the effects of concrete creep and shrinkage, prestressed steel relaxation, differences in age between concrete segments, sequence of construction and changes in geometry and support conditions. Deviations in the positions of new segments due to the deformation of completed part of the structure needed to calculate formwork adjustment are accounted for in the analysis. The procedure is based on the displacement method of analysis where multi-node variable cross-section beam elements curved in space, as well as conventional prismatic straight elements, are used to model bridges of arbitrary geometry. Prestressed tendons can have any profile in the space and can be prestressed, restressed or removed at any construction stage. Prestress losses due to friction and anchor setting are automatically evaluated by the program. A Step-by-Step approach is used to model the construction processes and to calculate the time-dependent effects at any instant during and after construction