확률론적 염해내구성 설계를 이용한 RC구조물의 지속가능 유지관리 시스템 구축

Abstract

During past few decades, the research of durability model was only focused on the concrete structure that exposed to sea environment directly. The research is based on deterministic service life prediction model which assumes corrosion initiation is occurred at the certain conditions and times, though the material is heterogeneous and the environment has uncertain factors. However, the most of concrete material properties are unstable depending on the chloride attacked environment. In spite of the situation, service life estimation and durability design for the structure in the sea environment was only accomplished at the level of empirical method. Since the durability design method mentioned in above has problems and limitations, it is necessary that systematic durability model in order to overcome the problem. These reason makes attentions as to probabilistic service life model for the RC structures, in addition, various probabilistic models are applied on the durability design in nowadays. The probability based service life model considers the uncertainties of environment, material and model those uncertainties are expressed by probability density function that introduced to give the range of real environment to examine. The model is getting popular during last 5 years and widespread among North American/European countries. Moreover, there is one another problem that cannot deliberated in previous researches is that they only regarded about the directly exposed structure against chloride attack. Despite of that in the most cases of chloride attacked structures are covered and/or protected by finishing material or they are maintained by maintenance strategy. The maintenance strategy is so important for both newly built and existed structures that accomplishing aimed service life. In order to delaying performance degradation and corrosion initiation, this study drew durability design procedure for idealized maintenance strategy when the RC structure in the sea environment are repaired by section restoration material. At the moment, reasonable service life was assumed by JSCE (Japan Society of Civil Engineers) model. In addition, Monte Carlo Simulation (MCS) bootstrapping method was introduced to think about uncertainties be in inward/outward of the structure. Furthermore, life cycle cost of repair was analyzed based on the probabilistic service life model mentioned above with the aim of determine economically best time for repair. At this time, the theory of lowest expected cost was used for guessing the cheapest amount between repair and risk cost. To sum up this paper, Probability (MCS) based durability design model can consider the uncertainties among inside/outside of the structure that is hardly to consider in the deterministic method. As the result of service life prediction, service lives estimated by probabilistic model are half (sometimes less than quoter) of the deterministic prediction result. The service life gaps are reasoned by the deviations of assembled parameters which have significant impacts on the corrosion initiation. When the service lives are presumed through the probabilistic durability model, it might be very available when the owner of each structure has different requirement about his/her maintenance strategies. It can fulfill the requirement of safety and economic plans of each single owner. However, the probability based service life model also has its limitations of lack of reliable experimental data. In order to be a high-reliable durability model, it is strongly recommended that considering not only chloride diffusion but also crack and corrosion process. Besides, development of evaluation tool as to environmental load such as Life Cycle Carbon dioxide emission might involved with this study to achieving goals of more advanced evaluation tool.