Abstract
The fundamental equations estimating the compressive load-carrying capacity of reinforced concrete columns with tie and/or spiral reinforcements are used all over the world, based upon the ultimate limit state design, but the common equations include both the elastic term and the plastic one; so, there is no unification concept of the ultimate limit state. In recent years, the high-strength type reinforcement (SBPD type) has been used frequently in the RC column and beam in Japan. Now, the common equations can not apply to the case of the high-strength primary reinforcement of the RC column. This paper describes the improvement of the concrete's sharing capacity, the application range of the common equations and the generalized practical equation for the ultimate limit state load-carrying capacity considering the buckling effect of the primary rebars.
