Brick Chimneys Can Be Earthquake Hazards
Great article from the LA Times about brick chimneys and earthquakes...
Earthquakes have shifted the ground beneath Libby Rose's historic Craftsman house several times in the last half-century, but still her home is standing. The chimneys, however, haven't fared as well.
When the 1989 Loma Prieta quake struck, the Roses' front chimney came tumbling down. Two weeks ago, the magnitude 6.0 Napa earthquake sent bricks from a second chimney raining into her backyard.
"They just fell all over the back. They broke the back gate," said Rose, 87. "This one was by far the worst."
Although brick chimneys have received little attention from seismic safety experts — overshadowed by more life-threatening issues such as unreinforced masonry and older concrete-frame buildings — they account for the most common form of damage during larger California quakes.
When chimneys collapse, bricks can become deadly projectiles. At least 15,000 brick chimneys were damaged in Los Angeles during the 1994 Northridge earthquake. In Napa, about half of the residential buildings damaged were due to brick chimneys.
"Chimneys are the first thing to go, we've seen it time and time again," structural engineer David Cocke said.
Older brick chimneys — generally those built before 1980 — are too stiff and brittle to withstand major shaking. The mortar holding them together can be ground down.
Full article here...