SEISMIC RESPONSE EVALUATION OF THE LINKED COLUMN FRAME SYSTEM
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The Linked Column Frame system (LCF) is a new structural steel frame system capable of achieving enhanced seismic performance and safely providing continued occupancy of buildings impacted by moderate earthquake events. The LCF consists of two components: a primary lateral system, denoted the linked column, which is made up of dual columns interconnected with replaceable link beams; and a secondary moment frame lateral/gravity system that is a flexible moment resisting frame with beams having fully restrained connections at one end and simple connections at the other. The linked columns are designed to limit seismic forces and provide energy dissipation through yielding of the links, while preventing damage to the moment frame under certain earthquake hazard levels. A design procedure is proposed that ensures the links of the linked column yield at a significantly lower story drift than the beams of the moment frame, enabling design of this system for two distinct performance states: rapid repair, where only link damage occurs and relatively quick link replacement is possible; and collapse prevention, where both the linked column and moment frame may be damaged. Nonlinear dynamic analyses of prototype buildings were conducted using OpenSees and the results identified how the system's parameters impact the ability of the LCF to achieve the performance objectives and the adequacy of the proposed design procedure. It was found that in general the LCF system provides collapse prevention for longer return period events and enables rapid repair following earthquakes with shorter return periods. The seismic performance factors for the LCF system, including the response modification coefficient, the system overstrength factor, and the deflection amplification factor were established following recently established procedures described in FEMA P695 (2009). These parameters are necessary for inclusion of the system in the building codes. Finally, models were developed in support of the experimental validation of the system's performance being done using hybrid simulation at the Network for Earthquake Engineering Simulation Laboratory at the University of California, Berkeley. Using the modeling techniques developed here, the numerical portion of the hybrid simulation specimen has been developed and used to predict the experimental response. The experiments are being conducted by collaborators at Portland State University.
- Civil engineering