Abstract

Abstract

Design, Modeling, and Nonlinear Response of Linked Column Frame with Multiple Links under Crustal and Subduction Zone Earthquakes

Avik Dhar

To mitigate the economic loss in the aftermath of seismic events, researchers required the development of low-damage seismic force resisting systems. As such is the Linked Column Frame (LCF) with backup moment resisting frame (MRF). The fundamental advantage of the LCF system is its tri-phase response: elastic, rapid return to occupancy (low residual drift), and collapse prevention.
Dusicka and Iwai (2007) developed the LCF system with single link (LCF-S) and multiple links per floor (LCF-M). Then, Malakoutian (2012) refined the design methodology for the LCF-M system using design provisions for Eccentrically Braced Frame (EBF) according to ASCE 7 and Lopes (2016) conducted experimental tests. Vayas et al. (2013) analysed different types of links acting as flexural beams and pins. However, the effect of subduction zone ground motions on the nonlinear seismic response of LCF buildings was not investigated and a design methodology complying with NBC and CSA S16 standard requirements was not proposed.
The main objectives are:

• Propose a forced-based design method for the LCF system with single and multiple links per floor using the current NBC 2015 and CSA S16-14 standard requirements.

• Develop a numerical model of LCF system in OpenSees environment that is able to show accurate nonlinear behavior of links from yielding to failure, and consider a low-cycle fatigue model to trigger the failure of MRF's beams.

• Assess the seismic performance of the LCF-M system versus the traditional EBF system

employed to brace a low-rise building subjected to crustal and subduction zone ground motions using nonlinear time history analysis and incremental dynamic analysis.
To fulfill the research objectives, the design methodology for LCF-M system was proposed and numerical models of a 4-storey building located on Site class C in Vancouver B.C. was developed in OpenSees. It was found that at design level (2% in 50 years probability of exceedance), the LCF-M prototype building showed lower residual interstorey drift than 0.5%, which is the reparability threshold, and lower link rotation than 0.08 rad., while the MRF beams were on the verge of hinging. The analysis also found that compared to EBF prototype building, the LCF-M with perimeter backup MRF provided larger margin of safety under both sets of crustal and subduction ground motions. In addition, LCF-M buildings enable rapid repair following earthquakes.