Static Long-Term Effects in Short Concrete-Filled Steel Box Columns under Sustained Loading

Abstract

Concrete-filled steel columns have been widely used over the last decade, which has been brought about by a renaissance of using structural steel in construction worldwide. Considerable research efforts have been conducted on these column types into the short-term effects for strength, and other extensive research has been conducted in relation to seismic effects. However, only limited research has been conducted on the long-term performance of these columns under sustained loading. This paper presents a series of experiments designed to ascertain the creep and shrinkage characteristics of high-strength concrete in composite columns, and also those of high-strength concrete specimens. These values were compared with existing experimental results. It is shown that the creep and shrinkage characteristics of concrete inside a steel column are much lower than those for exposed concrete. The static strength after long-term loading was also determined in this paper. A predictive model based on previously developed ACI provisions for both the service load and ultimate load behavior of the concrete specimens and the composite columns is calibrated with the experiments, and recommendations for design are suggested.