Experimental Evaluation of Cyclic Behavior of Concrete Filled Steel Battened Columns

Steel battened columns have been widely used in semi-rigid frames in last decades in some countries including Iran. In past earthquakes, severe failure under lateral actions was observed in residential and industrial buildings with such structural system. Many retrofitting or repairing methods have been proposed including adding some steel plates to the columns in order to change their section to a box. These methods are not only expensive and hard but also did not strengthen the columns at the connection with beams. Therefore, this paper has focused on a new innovative method; filling the battened columns with concrete, which has been previously applied for steel tubes. In this experimental and analytical program on seven specimens, axial load level and batten spacing intervals were considered as the key variables. The obtained results showed that the concrete filled battened columns can provide a stable cyclic response with enhanced lateral strength, higher dissipated energy and ductility, in comparison with the hollow one; the average improvement in the lateral strength and energy dissipation were recorded as about 30% and 300%, respectively, in comparison with the hollow ones. Furthermore, it is shown that capacity modification factor of a concrete-filled specimen is up to 47% higher than that of the similar hollow one. Regarding that filling with concrete raises both the ductility and strength. This method is highly recommended to strengthen fragile hollow battened columns.