This paper presents a method to determine values for material factors, load factor and structure factor for designing reinforced concrete members on limit state design method. In the proposed method, structure safety is evaluated with probability of failure using probabilistic treatment on load, concrete strength and steel strength. And furthermore, economy is evaluated with Fuzzy Set in order to determine the range of a variety of reinforced concrete members designed by applying same set of values for safety factors. As every value for the factors shown in this study is near standard values shown in some design codes, this method is considered to have reached the stage for practical use.
