Effect of section shape on the behaviour of thin walled steel columns filled with light weight aggregate concrete: Experimental investigation

•The effect of section shape on the behaviour of steel columns filled with light weight aggregate concrete was investigated.•19 CFST columns with different cross sections and same steel area were fabricated and tested till failure.•All the CFST columns failed due to crushing of the concrete core with local buckling of the steel tube.•As the number of steel plates welded together to form the section increases, more confinement can be achieved.•As the shape becomes irregular, its ductility index decrease and vice versa.