Relationship Between Story Drift Angle of Steel Frames and Maximum Edge Strain of Steel Beams

In performance-based seismic design， the maximum strain developed in energy-dissipating components must be calculated and checked against specified limits. To investigate the relationship between the maximum strain in steel beams and the story drift angle of steel frames， a stress-strain curve including the strain-hardening stage was adopted， and the shear deformation of steel beams was taken into account. Given the specified maximum strain at the beam-end section， the displacement ductility factors of the beam end were calculated for four types of steel. It was pointed out that the strength ratio computed from the nominal minimum strength specified in design codes led to inaccurate ductility factors of steel beams. After incorporating the deformation of columns， the story ductility factor of the frame was evaluated. Curves relating the story drift angle to the maximum strain at the beam end were presented， and an approximate formula was proposed. Furthermore， for shear-type energy-dissipating coupling beams， the maximum strain corresponding to a story drift angle of 1/50 was given when such beams were treated as flexural members.