Effects of Sustained Load on Concrete-Filled Hollow Structural Steel Columns

Abstract

The use of concrete-filled hollow structural steel (HSS) columns has become widespread in the past few decades. However, these members are subject to static long-term behaviors under sustained loading, a common phenomenon in concrete structures. Such a problem has not been addressed satisfactorily by design codes. The present study is an attempt to predict the time-dependent behavior of concrete-filled HSS columns by means of a model that is proposed by ACI 209R-92. Tests on the behavior of concrete-filled HSS columns with square sections under long-term sustained loading are performed, in addition to proposing further tests on the static ultimate strength of the composite columns. A theoretical model of analysis to account for shrinkage and creep effects on concrete-filled HSS columns under sustained loading is presented. A comparison of results calculated using this model shows good agreement with test results. Finally, formulas for the calculation of the ultimate strength of the concrete-filled HSS columns subjected to long-term sustained loads are presented.