철근콘크리트 단순보의 유효 단면2차모멘트에 대한 모멘트 분포 형상의 영향 분석

Abstract

Dept.of Architectural Engineering, University of Seoul, Seoul 130-743, KoreaABSTRACT The concept of the effective moment of inertia has been generally used for the deflection estimation of reinforcedconcrete flexural members. The KCI design code adopted Branson's equation for simple calculation of deflection, in which a rep-resentative value of the effective moment of inertia is used for the whole length of a member. However, the code equation for theeffective moment of inertia was formulated based on the results of beam tests subjected to uniformly distributed loads, which maynot effectively account for those of members under different loading conditions. Therefore, this study aimed to verify the influencesof moment shapes resulting from different loading patterns by experiments. Six beams were fabricated and tested in this study,where primary variables were concrete compressive strengths and loading distances from supports, and test results were comparedto the code equation and other existing approaches. A method utilizing variational analysis for the deflection estimation has beenalso proposed, which accounts for the influences of moment shapes to the effective moment of inertia. The test results indicatedthat the effective moment of inertia was somewhat influenced by the moment shape, and that this influence of moment shape tothe effective moment of inertia was not captured by the code equation. Compared to the code equation, the proposed method hadsmaller variation in the ratios of the test results to the estimated values of beam deflections. Therefore, the proposed method is con-sidered to be a good approach to take into account the influence of moment shape for the estimation of beam deflection, however,the differences between test results and estimated deflections show that more researches are still required to improve its accuracyby modifying the shape function of deflection. Keywords : effective moment of inertia, deflection, moment of inertia of the cracked transformed section, flexural rigidity