Slender Concrete Columns Under Sustained Load

A theoretical and experimental investigation into the effect of sustained load on the ultimate load of eccentrically loaded slender reinforced concrete columns is described. The results of short-term loading tests on 26 pin-ended concrete columns and sustained loading tests on twenty similar columns at load levels of 0.4 and 0.6 of their short-term load carrying capacities are given. The latter show significant reductions in strength in some cases when the load is increased under short-term loading conditions following the sustained load period. An analytical procedure for predicting the behavior of such columns under successive short-term, sustained, and short-term loading is described. Comparisons between experimental and theoretical results show that the behavior of columns under both short-term and sustained load can be predicted closely using the proposed analysis.