Influence of Column Strength and Stiffness on the Inelastic Behavior of Strong-Column-Weak-Beam Frames

Abstract

The design philosophy of strong-column-weak-beam (SCWB) in which plastic deformation is predominantly allowed to occur in beams while columns remain essentially elastic is commonly adopted in seismic design codes for moment-resisting frames. Practical design of SCWB frames is employed by using the beam-to-column-joint ratio, which is mainly done to prevent formation of plastic hinges in columns without consideration of the global inelastic behavior of the SCWB frame. This paper investigates the inelastic behavior of SCWB frames with different distributions of beam and column plastic strengths at different ductility demand levels. Midrise 9-story steel frames were designed as SCWB frames with the same lateral strength but with different column strength and stiffness relative to those of the beams. Nonlinear static and dynamic analysis results indicate that the relative plastic flexural capacities of the beams and column bases have a significant effect on the structural deformation and seismic response of SCWB frames. The structural response and beam-to-column-joint demand strongly depend on the column strength and stiffness. The results indicate that a global parameter may be used in addition to the beam-to-column-joint ratio to control the inelastic response behavior of strong-column-weak-beam frames.