Arturo Alejandro MENCHACA SOSA 

Size effect on long-term deflection of RC and PC bridges

Takumi Shimomura

This research was focused to study the nonlinear characteristics of size effect on long-term deflection of concrete structures, to understand its importance on structural design, as it is considered in failure strength criteria. The long-term deflection behavior of RC and PC structures was studied by considering the factors of ambient conditions as well as phenomena of drying shrinkage and creep. 
In order to evaluate time-dependent deflection, a long-term loading test was conducted, utilizing specimens with various surfaces sealed and exposed to natural environments such as rain and solar radiation. Experimental results proved that time-dependent deflection changes with the changing of surfaces number opened to drying-swelling. Also, a numerical approach to predict long-term deflections by hygrothermal analysis and stress-strain analysis, was verified through a comparison of analytical results with experimental data. 
Furthermore, size effect on long-term deflection was investigated through numerical simulations, varying sizes and shapes of cross-section, to observe its nonlinear behavior. Analytical results clarified the behavior of size effect in long-term deflection and demonstrated the decreasing of ambient influences when member size increases, due to drying shrinkage keeps the same tendency of above. This means that on larger structural sizes, the influence of drying shrinkage on long-term deflection tends to decrease, reducing the risk of excessive deflections. Also, the decreasing influence of drying shrinkage implies that on larger structures, the effect of creep becomes the only dominant time-dependent deformation phenomena. 
In other words, the size effect reduces the risk of long-term serviceability from time-dependent deflection when structural size becomes larger, which is opposite to tendency assumed on failure strength criteria.