Strategies for rapid seismic hazard mitigation in sustainable infrastructure systems

Abstract

The goal of this study is to design and evaluate economic and rapid seismic retrofit strategies for relatively small rehabilitation projects for steel structures consistent with the tenets of sustainable design. The need to retrofit existing structures in earthquake prone regions may arise directly from the problem of aging and deteriorating conditions, recognition of the vulnerability of existing infrastructure, from updates in seismic code requirements, or changes in building performance objectives. Traditional approaches to seismic hazard mitigation have focused reducing the failure probabilities, consequences from failures, and time to recovery. Such paradigms had been established with little regard to the impact of their rehabilitation measures on the environment and disruptions to occupants. The rapid rehabilitation strategies proposed here have sustainability benefits in terms of providing a more resilient building stock for our communities as well as minimizing environmental and economical impacts and social consequences during the rehabilitation project. To achieve these goals, a unique approach to design supplemental systems using tension-only elements is proposed. In this design approach undesirable global and local buckling are eliminated. Two rapid rehabilitation strategies are presented. The first is a bracing system consisting of cables and a central energy dissipating device (CORE Damper). The second is a shear wall system with the combined use of thin steel plate and tension-only bracing. Analytical studies using both advanced and simplified models and proof-of-concept testing were carried out for the two devices. The results demonstrated stable, highly efficient performance of the devices under seismic load. Preliminary applications of the CORE damper to the retrofitting of a braced steel frame showed the ability of the system to minimize soft story failures. Both techniques can be implemented within a sustainability framework, as these interventions reduce the seismic vulnerability of infrastructure, are low cost, utilize materials and fabrication processes widely available throughout the world, can be handled by unskilled labor and carried out with minimal disruptions to the environment. The approach taken in this study can provide a road map for future development of sustainability-based rehabilitation strategies.