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The practice of confined masonry construction started in Chile in the 1930’s after the 1928 Talca earthquake (Magnitude 8.0) that affected a significant number of unreinforced masonry buildings. Subsequently, the 1939 earthquake (Magnitude 7.8) that struck the mid-southern region of the country, revealed very good performance of confined masonry buildings (Moroni et al., 2004).
Earthquake Performance
The earliest reports describing the earthquake performance of confined masonry buildings date back to the 1939 earthquake (magnitude 7.8) in Chile. In Chillán, where a modified Mercalli Intensity (MMI) of IX was reported, over 50% of all inspected confined masonry buildings sustained the earthquake without any damage, whereas around 60% of unreinforced concrete buildings either partially or entirely collapsed, resulting in a death toll of 30,000. Subsequently, the 1985 Llolleo earthquake (magnitude 7.8) with an epicenter in the central part of Chile, caused the collapse of 66,000 dwellings and damage to another 127,000 dwellings (the affected dwellings were mostly of adobe construction). Out of 84,000 housing units surveyed after the earthquake, around 13,500 were of confined masonry construction. These buildings ranged from one to four storeys in height. Out of all inspected buildings, the most damage was inflicted to medium-rise buildings (3-to-5-storeys high); around 22% of these confined masonry buildings sustained severe or heavy damage. Low rise buildings sustained very limited damage; only 2% of two-storey buildings were damaged, while none of the single-storey buildings were damaged. Overall, a large majority (76%) of the confined masonry buildings were undamaged (Moroni et al., 2004). Damage to confined masonry buildings was mainly due to the absence of tie-columns placed at wall intersections or around the openings; this again stresses the importance of tie-columns in ensuring the seismic resistance of confined masonry buildings.

Guidelines, Standards, and Codes


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