SEISMIC DESIGN AND PERFORMANCE OF DUAL MOMENT AND ECCENTRICALLY BRACED FRAME SYSTEM USING PBPD METHOD

Abstract

MOST STRUCTURAL DESIGN CODES USE ELASTIC ANALYSIS TO CALCULATE AND DISTRIBUTE SEISMIC BASE SHEAR OVER THE HEIGHT. THIS MAY LEAD TO UNSUITABLE DESIGN AND MAY CAUSE UNDESIRABLE DAMAGES TO THE STRUCTURE. TO SOLVE THIS PROBLEM, IN RECENT YEARS THE PERFORMANCE-BASED PLASTIC DESIGN (PBPD) METHOD WHICH CONSIDERS THE PLASTIC BEHAVIOR OF THE STRUCTURE, HAS BEEN PROPOSED. IN THIS STUDY, THE PBPD METHOD IS EXTENDED TO THE DUAL SYSTEM OF MOMENT AND ECCENTRICALLY BRACED FRAMES. AS A CODE REQUIREMENT, IN DUAL SYSTEMS THE MOMENT FRAME MUST BE ABLE TO RESIST AT LEAST 25 PERCENT OF THE BASE SHEAR. IN THE PROPOSED PBPD METHOD, THE SHEAR RESISTANCE OF EACH SYSTEM IS SELECTED AT THE BEGINNING OF DESIGN PROCESS AND THIS CRITERION CAN BE CONTRIBUTED TO THE DESIGN PROCESS DIRECTLY. IN THIS REGARD, THREE 6, 12 AND 20 STORY STRUCTURES ARE DESIGNED BASED ON PBPD AND CONVENTIONAL METHOD. TO ASSESS THE BEHAVIOR OF EACH SYSTEM, NONLINEAR PUSHOVER AND TIME HISTORY ANALYSIS ARE CONDUCTED. RESULTS SHOW THAT DUAL PBPD FRAMES HAVE LESS STIFFNESS AND STRENGTH THAN ORDINARY FRAMES. HOWEVER THE YIELD MECHANISM IS CONTROLLABLE AND PLASTIC DEFORMATION CAPACITY OF STRUCTURES ARE BETTER CONDUCTED TO DESIGN IN PBPD METHOD. THE RESULTS ALSO SHOW THAT THE COLLAPSE PROBABILITY OF PBPD FRAMES IS ACCEPTABLE.