Experimental performance of concrete filled welded steel tube columns

Effectiveness of concrete filled steel tube columns in improving life quality and safety is particularly noteworthy. Assembling columns at story levels by bolted connections is the current practice in the field. Closed section tubes do not allow bolted joint designs at intermediate locations of column length. As a result of such limitation, proper fractions of steel tubes are generally used to minimize steel waste. However, considering vast variety applications of columns, it is not always possible to use proper fractions of the tubes. In order to eliminate steel material waste, lateral welding can be employed to develop intermediate joints. However, there exists limited guidance on lateral weld design for concrete filled steel tube columns. A limited number of studies on seam welded tubes are present in the literature, but the individual paper's conclusions do not reference seam weld behavior under severe compressive loading. This paper presents results of 18 tests which were undertaken to assess the performance of laterally and longitudinally welded columns. Different L/D ratios (short, medium and long columns), D/t ratios and different lateral weld locations were studied. It has been shown that seam weld failures have slight effects on capacity and failure mode. However, seam weld failures certainly reduce ductility. On the other hand, lateral welds are very successful in transmitting compression and bending effects. It can be deduced that lateral weld joints have the potential to lead reliable and economical designs for concrete filled steel tube columns.