Experimental study on dynamic characteristics and seismic performance of semi-rigid steel frame with eccentric brace

Semi-rigid steel frame with eccentric brace is a new type of seismic structural system.In order to study its dynamic characteristics and seismic performance,four three-story space frame specimens were tested.Dynamic test results show that,with the reduction of rotational stiffness of beam-column connections,the natural frequency of frames decreases,and the vibration period and damping ratio increase.Cyclic loading test results show that the stiffness and strength of beam-column connections have a significant effect on the hysteretic behavior of the eccentrically braced frame.The higher the connection stiffness and strength are,the better the hysteretic behavior is.Eccentrically braced frame with lower connection stiffness should not be used in seismic zones.Eccentric brace can increase the lateral stiffness of the semi-rigid steel frame significantly,and reduce the effect of the connection stiffness on the frame stiffness.But eccentric brace can also reduce the frame ductility.The plastic deformation of structures is mainly from panel zones,links and beam-column connecters.The lateral deformation of multi-story eccentrically braced frame is shear type and the yield drift angle is relatively large.