Behaviour of Recycled Aggregate Concrete-Filled Steel Tubular Columns under Long-term Sustained Loads

Recycled aggregate concrete-filled steel tube (RACFST) causes the recycled aggregate concrete (RAC) to be in a state of protection with the outer steel tube and thus the RAC is hardly affected by harmful environmental factors (e.g. wind, rain, moist). However, shrinkage and creep are the phenomena commonly associated with concrete-related structures, so studies on the behaviour of RACFST columns under long-term sustained loads are essential for the design of structures which include RACFST members. This study is an attempt to predict the time-dependent behaviour of RACFST columns by using the age-adjusted effective modulus method. The concrete shrinkage and creep in RACFST columns were studied experimentally, and the static bearing capacity of the tested specimens was also investigated. A theoretical model to account for the effects of concrete shrinkage and creep on RACFST columns under long-term sustained loading is developed, and comparisons of the results predicted using this model show good agreement with the test results. Formulae for the calculation of the bearing capacity of RACFST columns under long-term sustained loads are suggested.