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Re: Wood: Conventional Framing opinions needed from otherstates -Reply -Reply

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Frank Lew, I see that you are ready to defend both conventional framing
provisions and Thoreau. For the sake of better discussion, allow me to
add to some of your comments.

Frank, you write  " But for houses, and that's about the only type of
occupancy that conventional framing provisions are used on, the
records on injuries and deaths don't demonstrate that greater story
strength would have any benefits". 

UBC Section 2326.1 allows the use of conventional framing provisions
for all standard occupancies. With my experience as plan reviewer, I
have seen them used for commercial projects including assembly up to
300 persons. This is part of the problem.

Frank, you write"Then your records must be more comprehensive than
the file I've compiled, which started with Anchorage.  I'm not aware of
any occurrences, and would appreciate specifics if you have them. "

My point is that ALL damaged buildings comply with conventional framing
provisions. This follows from recognizing that all engineered structures
provide more story strength than conventionally framed structures. If
stronger buildings are damaged, won't the weaker ones be also? 

Frank you write, "  For the two houses that slid downhill in the Northridge
event and caused fatalities, ground failures contributed to the load  path
failures."

The City of Los Angeles added Section 1634 Seismic Provisions for
Hillside Buildings because the failure in these structures was primarily
caused by shear wall systems that complied with conventional framing
provisions. Few ground or foundation failures occurred.
 
Frank, you state "Consistency is the hobgoblin of small minds".  If the
present conventional framing provides provide adequate safety, why
raise them for the sake of consistency?"

If conventional framing provisions work, engineered standards should be
lowered to meet them. They do not work and therefore the provisions of
they should be raised to meet or exceed engineering standards.
Consistency  provides equal treatment which means equal dollars.

I believe that conventional framing provisions have a place. That place is
for one and two story dwellings with regular configurations on level or
nearly level  grades. The prescriptive lateral force provisions should
always provide the same or better performance than engineered
structures. This means that they have to be CONSERVATIVE to account
for small uncalculated differences.  

When conventional framing provisions follow this pattern, engineered
designs can be more economical. When they are not, who gains? The
owner of an large apartment building in Reseda complained in 1982 that
the engineer wanted to cover his structure with plywood sheathing. This
same owner had little complaints when the building stayed 100%
occupied following the Northridge Earthquake. Especially, since the two
neighboring apartment structures were demolished. you get what you
pay for.

The total cost of housing, policing, feeding, nursing and relocating
earthquake damage victims is astronomical. These costs are higher than
increased construction costs. Its cheaper for society to build residential
structures that maintain occupancy than pay for all of the assistance
later to help even 5% of them. This is the big picture. 

Respectfully,

Tim McCormick, PE
City of Los Angeles