Development of a Minimal-Disturbance Rehabilitation System for Sustaining Bidirectional Loading

Abstract

A light-weight and rapid seismic rehabilitation technique, named biaxial minimal-disturbance arm damper (biMDAD), is developed to upgrade steel buildings that are weak for seismically-induced force in two orthogonal frame directions. The components of biMDAD behave similarly to the original device, named minimal-disturbance arm damper (MDAD), in each frame direction. The biMDAD configuration is designed to increase the deformation capacity of steel buildings by reducing the deformation demand at all fracture-probable beam ends without directional dependence. To investigate the performance of the biMDAD, quasi-static tests and shaking table tests are conducted on a shaking table with the same setup and its component-level behavior is examined under bidirectional and dynamic loadings. The test results show that load-resisting components placed orthogonally behaves independently and that out-of-plane drifts have no significant influence on in-plane behavior. Furthermore, the original and new configurations are applied to the rehabilitation of a 4-story steel moment-frame building considering the same cost in terms of installation time and labor. The numerical results demonstrate that the new biMDAD configuration is efficient in reducing the demand of plastic rotations at the beam ends and increases the drift and peak ground acceleration (PGA) capacity of the building while retaining the global collapse mechanism.