Frost Damage Risk Map Based on Local Climate Condition and Site Investigation
By Takeshi Narita, Shin-Ichiro Koyama and Hirozo Mihashi
Concrete Research and Technology
Vol. 19. No. 1. Jan. 2008 (Issue 46)
- In cold regions such as Tohoku and Hokkaido districts, many RC structures are suffered from frost damage. While a frost damage risk map produced by S. Hasegawa has been widely used to evaluate the required durability performance for concrete against frost damage, the capability of resolution is quite limited and engineers can guess only briefly the risk of the frost damage. Another shortcoming is that the correspondence of the map to the damage in existing structures is not sufficiently proved. In order to overcome the shortcoming of the currently used map of frost damage risk, the local climate condition was taken into consideration and a detailed map of the frost damage risk with 1km square mesh was produced. Based on the detailed map, it has become possible to quantity the risk of the frost damage on the site where RC structures of electric power plant are located.
On the other hand, a series of site investigation on the existing RC structures of electric power plant was carried out. Many of them were damaged by frost action, though it was difficult to clearly quantity the rank of damage by the currently used assessment diagram that is composed of five ranks determined with a set of five levels of damage development and four levels of damage extension. To avoid the shortcoming of the currently used assessment diagram, a new one was proposed in this paper. It is composed of twenty ranks, each of which is determined by a set of a single level of damage development and a single level of damage extension. Therefore the damage rank of the investigated RC structure is clearly quantified.
All data of the assessment of frost damage by the site investigation on totally 2,246 components in 176 structures were collected and also the risk of the frost damage on the site was quantified. For the sake of relating these two variables, a theoretical model developed by authors was introduced and the coefficient of a function in the theoretical model was determined by data fitting with the obtained values of two variables mentioned above. Finally a detailed frost damage risk map was produced by the obtained function.
- concrete structure, site investigation, frost damage risk, ranking of frost damage, mapping