Performance of Multi-Phase Passive Control Systems in Steel Structures

Abstract

Earthquake resistant buildings can experience significant damage during an event. A multi-phase passive control system (MPCS) was developed to reduce structural damage, repair costs, and downtime of buildings subjected to large earthquakes by limiting the main damage to the replaceable elements. Previous research investigated multi-phase behavior in single degree of freedom (SDOF) systems to identify the factors affecting structural response. An overall improvement has been detected by the multi-phase system when compared to a baseline system consisting of a dual lateral force resisting system. In this study, the multi-phase system was implemented in a multi degree of freedom (MDOF) model. The multi-phase behavior is created by adding a gap element with multilinear elastic properties to a dual system that consists of a moment frame and buckling-restrained braced frame. The gap element has a lock-out mechanism that creates a transition phase when the slip displacement is reached. After the gap locks out, the buckling restrained braces (BRB) will become effective. The transition phase created by the gap allows the buckling restrained braces (BRBs) to yield before the moment frame because the BRBs are replaceable and easier to replace. Dynamic response history analyses of 3-story and 6-story steel frames were performed for a suite of scaled ground motions. The comparison between the multi-phase systems and the baseline systems was based on the story drift, story accelerations, moment frame plastic hinge rotation, and cumulative BRB ductility response. Superior behavior was achieved by the multi-phase system on certain aspects.