콘크리트충전 각형강관단주의 P-M 조합강도 예측을 위한 콘크리트 구성방정식

The plastic stress distribution method and the strain compatibility method are the two representative methods tocalculate the P-M interaction strength of RCFT (rectangular concrete filled tube) columns. The plastic stress distribution methodis approximate while the stress compatibility method should approach the exact solution if accurate constitutive relations of thematerials involved are used. Recent study by the authors pointed out that, because of lack of accurate constitutive model for theconcrete confined by the rectangular steel tube, no strain compatibility method according to the current structural provisionsprovides a satisfactory prediction of the P-M interaction strength of RCFT columns under various material combinations. Anempirical constitutive model which can capture the stress-strain characteristics of the confined concrete of RCFT columns isproposed based on analyzing extensive exisitng test database. The key idea was to define the concrete crushing strain as afunction of steel-to-concrete strength ratio and width-to-thickness ratio of steel tube. It was shown that the proposed model leadsto more accurate and more consistent prediction of the P-M interaction strength of RCFT columns under general designconditions.