Rodgers et al. 2008
The ultimate goal of seismic design is for structures to be able to withstand large earthquakes with minimal or zero damage. This paper discusses a new approach to damage avoidance in the design of connections. In order to avoid damage and strength degradation at the beam-column connections, plastic hinge zones were localized in RC structures to provide ductility. These zones are able to dissipate energy resulting from seismic events. The DAD connections can also provide energy dissipation during seismic events by undergoing inelastic hysteretic response without significant structural damage. Experimental tests are conducted on a 10-story frame to confirm this assumption. This paper started with the introduction of the system. After that, experimental investigation for RC connections and steel connections were explained with results and discussions.
System Concept
The high force to volume devices used a bulged central shaft. This shaft induced a plastic flow of lead during shaft motion to provide a resistive force. Emerging high force to volume damping devices could provide equivalent or higher forces than yielding steel fuses. The device response was repeatable on successive cycles and did not show any stiffness or strength degradation. Moreover the devices were not subject to any low cycle fatigue issues and also compact to allow placement directly into structural connections.
Experimental Study, Results and Discussion
A 10-story RC frame building was used to experimentally investigate the response of three different types of RC connections: an exterior post-tensioned RC connection, a corner exterior post-tensioned connection, and an exterior steel connection. The same structure was designed according to DAD principles and keeping all variables constant. Precast beams and the columns were connected via a post-tensioned system.
Displacement amplitudes were gradually increased throughout the test. It was found that if the resistive force provided by the dampers exceeded the post-tensioning force, the joint could be at risk of losing the ability to self-center following an earthquake. For corner joints, hysteresis loops were asymmetric and overall joint hysteresis loops were substantially larger when the dampers were presented. Using steel joints, hysteretic loops were stable and no strength degradation was observed.
Reference
Rodgers, G.W., Dhakal, R.P., Chase J.G., Mander J.B., MacRae G.A., Mander T.J., and Solberg, K.M. (2008). “Investigation of Rocking Connections Designed for Damage Avoidance with High Force-to-Volume Energy Dissipation,” Proceedings of the 14th World Conference on Earthquake Engineering 2008, Beijing, China, October 12-17.