Recently, the limit state design method for the reinforced concrete structures in used in the most of countries, because it is more rational than th allowable stress method. And also in Japan. Association's specification for concrete structures has adopted the limit state design method. Under such circumstances, the design method for reinforced concrete structures in port facilities is strongly required to adopt the limit state desgin method.
　This paper presents an outline of the limit state design method and the obstacles when it is applied to port structures, that is, the characteristic values and safty factors.
　We confirm the adequacy of the characteristic values and safty factors to desgin the caisson type composite breakwaters using the limit state design method and allowable stress method.