편심지속하중을 받는 철근콘크리트 기둥의 시간의존적 변형

Time-Dependent Deformation of RC Columns Subjected to Sustained Eccentric Loading

Long-term deformation due to creep and shrinkage of concrete may affect the structural performance of reinforced concrete members and structures. In particular, in the case of columns and walls subjected to sustained axial load with eccentricity, both shortening by axial compression and curvature (or lateral displacement) by bending moment continue to increase over the sustained duration. In the present study, a sustained load test on reinforced concrete columns was carried out to investigate long-term shortening and lateral displacement. Column specimens were subjected to axial compression load either with or without eccentricity for a duration of 64 days. A test set-up using post-tensioning was introduced for the sustained load test. Test results showed that long-term deformations of columns such as axial shortening and lateral displacement continued to increase but the increasing rate rapidly decreased. The long-term deformations increasing with time were predicted by using the creep and shrinkage models of ACI 209. The predictions correlated relatively well with the test results. Reinforcement had substantial effect not on the long-term axial shortening, but on the long-term curvature (or lateral displacement).