Older Buildings Most Vulnerable to Quakes

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#1

Originally Posted By: gromicko
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Older Buildings Most Vulnerable to Quakes


(December 24) -- With yesterday's earthquake in California, attention is once again being focused on buildings' stability. Sites that are most in danger of a potential collapse or major structural damage are those built prior to 1971. Such buildings were not required to meet the strict seismic codes that have been enforced ever since. Specifically, many older buildings lack steel reinforcements to help them withstand the violent shaking of quakes. Reinforced brick buildings will still shake, but they are considered more durable. A quick survey of buildings throughout San Luis Obispo County found that most of the newer buildings, such as the VAS Entertainment headquarters in San Luis Obispo, performed as designed. While retrofitting older buildings will make them safer, such variables as strength of quake and distance from epicenter also play a role in how each will perform under seismic stress. Monday's earthquake measured at 6.5 on the Richter scale.

Source: Contra Costa Times (12/23/03); Rowlands, Katherine Ann

#2

Originally Posted By: roconnor
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Very informative post Nick … eusa_clap.gif


FYI ... older masonry buildings do not perform well since most of them are unreinforced masonry (plus inadequate roof/floor attachments too) ... a lot of weight that easily cracks and comes apart in tension ... not a good thing in an earthquake.

Also, older wood frame buildings don't perform too well either (but not as bad as unreinforced masonry). They may have missing/undersized connections of the roof/floor framing to the walls, inadequate wall sheathing (shear panels), and maybe also inadequate wall anchorage to the foundations to boot ...

Same basic principals apply in hurricane prone regions, except the lighter wood frame buildings perform worse than masonry buildings (weight helps hold things down). Also, a lot of the more stringent high wind provisions came about after hurricane Andrew ripped through the South.

Some important things to be aware of when inspecting older homes/buildings in earthquake/hurricane prone regions. Understanding current local/model building code provisions really helps in this area.

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

#3

Originally Posted By: Bill
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How could anyone possibly understand what previous earth tremors have done to older buildings? If you have large visible cracks, that’s one thing, what if these cracks are “normal”

#4

Originally Posted By: jonofrey
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Are wise cracks considered normal?


BTW - She's my girl, Bill.

--
Inspection Nirvana!

We're NACHI. Get over it.

#5

Originally Posted By: roconnor
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Damage assessment is beyond a basic inspection or anything that could be easily explained here, as it involves engineering evaluation.


Just "observe and report", and where necessary recommend further evaluation. Other topics here discuss identifying structural issues ... such as cracking, anchorage, and bracing. Here are a few examples:

http://www.nachi.org/bbsystem/viewtopic.php?t=817&start=0
http://www.nachi.org/bbsystem/viewtopic.php?p=20081#20081

For older existing buildings, a lot will not be visible and you have to go mostly by the type of construction, the age of the building, and how the structure has performed so far. Hope that helps.

--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong