Research on cyclic behavior of welded and bolted steel frames

In order to investigate and compare the ultimate load-carrying capacity,hysteretic behavior and dynamic characteristics of welded and bolted steel frames;6 single-span two-story steel frames were tested under cyclic loading.There were 2 welded,end-plate bolted and angle bolted frames apiece.During the test,concrete floor were laid and vertical weight was applied on every floor.Triangle horizontal loads were applied to frames cyclically.Experimental results show that the welded frames with high quality connection welding have better load-carrying capacity and hysteretic behavior.The reason for the fracture is that the plastic hinges broke,and the failure is the typical ductility mode.The plastic story drifts can reach(1/25) of the height of the story. The plastic deformations are mainly caused by the shear deformation of the panel zone in beam-to-column connections,and the bending deflections of column and beam.End-plate bolted frames also have better load-carrying capacity and hysteretic behavior,while the dissipation capacity is a little lower than that of the welded frames.The plastic story drifts can reach 1/30 of the height of the story,but the end-plate welds are easy to crack.For angle bolted frames,the load-carrying capacity and hysteretic behavior are much lower than those of the welded frames.The plastic deformations mainly occur in flange angles and column feet.The flange angles are easy to cause low-cycle fatigue fracture.Dynamic characteristics tests show that the natural vibration period of steel frame can be prolonged with the reducing of connection rotation stiffness.