Improvement of traditional masonry wall construction for use in low-rise / low-wall-density buildings in seismically prone regions

NZSEE 2001 Conference ABSTRACT: The current trend of designing structures to meet performance-based demands could severely limit the use of some traditional construction materials and systems. Masonry construction, used in conjunction with reinforced concrete frames, as used extensively in Latin America, is among those affected. This limitation is due to the poor performance of conventional masonry systems in past earthquakes. This paper discusses the option of using reinforced concrete frames infilled with masonry, acting together as a series of rocking walls providing a desired performance level. Such system may be used in buildings with a low density of elements where the demand expected in conventionally built masonry walls might result in structural damage in moderate earthquakes. Rocking walls can be designed to rock while ensuring no damage will occur anywhere else in the structure. During the rocking process the system has a much lower equivalent stiffness than before rocking is triggered. Most often this means that the inertial forces are reduced as the response is shifted into a less demanding region of the acceleration spectra. The softening of the system also lets other flexible elements participate in the response. Triggering of the rocking may be set for levels of excitation greater than frequent earthquakes for which the element can be designed to behave as a fixed-base wall. Rocking also allows the use of hysteretic energy dissipators at the base of the wall. It was found that these energy dissipators could add up to 20% of equivalent viscous damping to the system.