Half-PC 보와 현장타설 콘크리트의 경계면에 배근된 비인장 강연선의 부착응력-슬립 모델 및 정착길이

The purpose of this research is to obtain development length and bond slip relationship of the untensioned wire strand, applied to the precast concrete beam-column joint system developed recently. For this the pull-out tests were performed, in which the main test parameters are diameter of strands (9.3㎜, 12.7㎜, bundle), embedment length and distance from the precast concrete surface to the strand. A estimation equation of the development length was proposed based on test result. Herein 5% fractil value with 90% reliability was considered. The development length estimated by the proposed equation is comparable with that of the untensioned wire strand suggested in CEP-FIP Model Code 1990. Half-Precast concrete and topping concrete interface was proposed as an additional new bond condition for the strand location coefficient ŋ₂ in the equation of MC-90. Additionally a bond stress-slip model was established by means of a numerical algorithm applying the strand strain obtained from the pullout tests mentioned above. The development length obtained by numerical analysis using this bond-slip model agrees with the test result. This shows the validity of the bond-slip model developed in this research.