The use of rocking walls in confined masonry structures : a performance-based approach

Excessive economic loss and large social impact, due to extensive damage and operational problems in aseismic structures, has been observed following recent earthquakes. This situation is leading to the formulation of a new design paradigm in seismic-engineering. Performance-based design, addressing life-safety, damage-control and functionality issues, is expected to supersede in the near future the current prescriptive serviceability/life-safety approach. In this context, the observed extent of damage in masonry structures, as a consequence of recent moderate and strong earthquakes, seems to disqualify this traditional material in a performance-based environment. Masonry-structures with low density of lateral-force-resisting masonry-walls are among the buildings most likely to be damaged by moderate and strong earthquakes. The use of rocking walls is proposed here as an alternative to improve the seismic performance of these kind of buildings without having to give up the masonry as an integral part of the structure. It was found that rocking confined-masonry walls with hysteretic-energy-dissipators at their base can be reliably designed to match target drifts, which are closely correlated to the extent of the damage in a building. It is shown in this thesis that hysteretic-energy-dissipators can provide a reliable energy-dissipation source that allows the seismic design of this sort of structures with any of the new methodologies proposed to meet seismic performance-objectives. A design procedure adapted from the Direct Displacement Method is developed in the core of this thesis. A prototype structure is designed with the proposed method and a reduced-scale model is built and tested dynamically in a shake table. The experimental results confirmed that rocking walls can be successfully adapted to confined masonry structures. A numerical analysis is also conducted here, with good matching of the experimental results, providing a new tool to deepen the understanding of this system