Kazuki YAMANOUCHI

Comparative examination of computational methods for time-dependent deflection of concrete bridges subjected to non-uniform drying in the cross-section

Takumi Shimomura

Concrete structures, especially prestressed concrete (PC) bridges, need to ensure various performances such as safety and maintainability during construction and service. For this purpose, long-term stress, deformation, and displacement analysis of structures is important. In general, for structures made of concrete, prestressed steel, and reinforcing steel, it is necessary to consider the effects of drying shrinkage, creep, and relaxation, as well as the effects of restraining the deformation of members. Based on this, various analysis methods have been researched and proposed to date, but there are few examples of comparative studies of the simplicity and applicability of constraint conditions between the methods. Therefore, in this study, we introduce various analysis methods: one that introduces drying shrinkage uniformly across the cross section, one that divides the member cross section into several component elements, and one that introduces drying shrinkage for each location based on moisture movement analysis in concrete. The purpose was to compare and verify the applicability to each condition.
We conducted a case study assuming an actual structure based on the results of the most accurate method among three stress analysis methods. As a result of comparing analysis results under different drying conditions, we confirmed the effectiveness of an analysis method that takes into account the influence of cross-sectional curvature, which promotes deformation due to uneven drying distribution within the cross-section. We confirmed the analysis accuracy and superiority under different drying conditions for structures subjected to drying shrinkage and sustained loads. The case study confirmed that the simple method has good accuracy depending on the drying conditions.
From the free drying shrinkage test, we confirmed the characteristics using the drying shrinkage analysis method. We confirmed that even a simple method can be analyzed with high accuracy by performing appropriate calibration.
A sustained bending loading test was conducted on a T-shaped PC beam member under laboratory conditions with precisely controlled drying and loading conditions. It was confirmed that the spatial distribution of uneven drying inside the member generates cross-sectional curvature that promotes deformation and affects deformation behavior. In addition, stress analysis was performed using two analysis methods that take uniform drying shrinkage into account, and the effects of non-uniform drying shrinkage were generally reproduced.