Beyond Ductility: Parametric Testing of a Jointed Rocking Beam-Column Connection Designed for Damage Avoidance

Abstract

Despite their good performance in terms of their design objectives, many modern code-prescriptive buildings built in Christchurch, New Zealand, had to be razed after the 2010–2011 Canterbury earthquakes because repairs were deemed too costly due to widespread sacrificial damage. Clearly, a more effective design paradigm is needed to create more resilient structures. Rocking, posttensioned connections with supplemental energy dissipation can contribute to damage avoidance designs (DAD). However, few have achieved all three key design objectives of damage-resistant rocking, inherent recentering ability, and repeatable, damage-free energy dissipation for all cycles, which together offer a response that is independent of loading history. Results of experimental tests are presented for a near full-scale rocking beam-column subassemblage. A matrix of test results is presented for the system under varying levels of posttensioning, with and without supplemental dampers. Importantly, this parametric study delineates each contribution to response. Practical limitations on posttensioning are identified: a minimum to ensure static structural recentering and a maximum to ensure deformability without threadbar yielding. Good agreement between a mechanistic model and experimental results over all parameters and inputs indicates the model is robust and accurate for design. The overall results indicate that it is possible to create a DAD connection where the nonlinear force-deformation response is loading history independent and repeatable over numerous loading cycles, without damage, creating the opportunity for the design and implementation of highly resilient structures.