SEISMIC DESIGN OF COMPOSITE MOMENT FRAME BUILDINGS -CASE STUDIES AND CODES IMPLICATIONS

摘要

Building code seismic design provisions for steel and composite moment frames and their implications on seismic performance are examined through comparative trial designs of three six-story buildings. Using nonlinear analyses, static and dynamic contributions to inelastic force reduction are identified and compared to code-specified assumptions. The trial design study demonstrates that static overstrength is significantly larger for space frame systems compared to perimeter frames, whereas the force reduction attributable to inelastic dynamic response is fairly constant between the frame types. The trial designs are shown to meet the minimum performance implied by building code provisions, primarily due to the large static overstrength resulting from minimum stiffness requirements imposed through seismic drift limits. The study suggests that more consistent reliability can be achieved by disaggregating the R-factor into its component static and dynamic parts and that the default values of static and dynamic inelastic response factors should be reduced from those implied by current R-factors.