Abstract

Concentrically braced frames, CBFs, are the most popular systems used in seismic areas in Canada, due to their large stiffness. However, after braces buckle in compression, their stiffness is significantly reduced and their hysteresis response, displayed in terms of force-displacement, shows an asymmetric behavior. To overcome this drawback, researchers proposed to add fuses that were conceived to be installed either in braces or brace-to-frame connections. The purpose of these fusses is to dissipate the earthquake input energy, while preserving braces to respond in elastic range. In this thesis, a new type of fuse, designed to be installed in brace-to-frame connections, is proposed. This device is labeled dissipative pin connection. Depending on the level of axial tension/ compression force that has to be transferred from the brace to the connection, this device can be manufactured in single-pin, double-pin and multi-pin configurations.
The objective of this thesis was two-fold: i) to develop design rules for double-pin connections displayed in-line and in-parallel and ii) to study the seismic response of a 4-storey CBF building with and without dissipative connections, located in Victoria, BC.
In this thesis, the computations were carried out by means of OpenSees (open system for earthquake engineering simulation). The numerical model developed for single-pin connection was calibrated based on experimental tests carried out at the Technical University of Lisbon. Similarly, the double-pin connection was calibrated using the same approach. Based on experimental test results conducted on single pin connections, design rules were proposed. It was concluded that by doubling the pin member and employing the parallel configuration, the load-carrying capacity of the dissipative connection increases two times, while the deflection is similar to that experienced by an equivalent single-pin device.
The second part of this thesis emphasizes comparative results, in terms of seismic response of a 4-storey CBF building with and without dissipative connections. Building design was conducted according to S16-2009 and NBCC 2010 provisions. The seismic response was studied under two sets of ground motions that are representative for Victoria, BC: crustal and subduction events.
The results have shown that forces generated in structural members were reduced due to an increase in building period and system ductility. Thus, by lowering the axial force developed in the CBF columns, a reduction of foundation size can be achieved which implies reduction in the overall building cost. The effect of earthquake type on the building response is also discussed. However, to prove the efficiency of double-pin connections displayed in-line and in-parallel, further experimental tests are required.