모멘트-처짐 관계에 기반한 철근콘크리트 보의 유효단면 2차 모멘트 산정식

Abstract

KCI and ACI design code adopted the equation of Branson for simple calculation of deflection, in which a representative value of the effective moment of inertia is used for the whole length of a member. However, the inadequacy of the formulation of the equation had been being pointed out through many researches till now. This study formulated a new equation of the effective inertia moment for deflection, which was formulated through a clear and simple approach using experimental data. The moment-deflection curves of a simple beam was modeled using by a bilinear curve. The straight line after formation of cracks was determined by the consideration of tension stiffening effect, which is multiplied by the moment of inertia for a cracked section. This coefficient was approximated by a regression curve estimated using experimental results of 18 specimens, in which the tensile strength and reinforcement ratio were selected as a parameter. From the bilinear model the effective inertia moment can be estimated for any level of moment. The deflections estimated using the equation from the study showed the better approximation that from ACI, and comes close to CEB-FIP MODEL CODE 1990, EUROCODE 2. The study also demonstrated statistically that the suggested equation indicated more similar experimental results rather than the domestic standard equation.