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Permit Requirement Questions

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Lew, Ernie, Dennis, Roger, Neil, Tom and others interested;

To add to your list, I am told that the City of El Segundo has recently 
decided that it will no longer accept any deferred submittals.  As far as 
Ernie's comment about "reasonable" building departments, El Segundo is a UBC 
city, and its building official is aware of 1994 UBC Sec. 106.3.4.2, but has 
decided on the administrative level that its provision will not apply in his 
jurisdiction.  In theory, this decision requires the concurrance of the City 
Council, since they adopted the entire UBC, but in practice most building 
officials are given broad administrative powers by local legislative 
authorities.  I haven't talked to him about the requirement, but assume that 
he is driven by the concerns Roger and Ernie mentioned in their postings.

Much of the discussion of this issue on the list has focussed on 
pre-fabricated wood trusses.  In re concerns Ernie and Tom express for making 
sure such trusses, typically designed by others, have adequated lateral 
bracing designed AND installed -- this is a real problem we all need to take 
seriously.  I assisted the design architect in participating in forensic 
studies after the collapse of the Music Auditorium at California State 
University Long Beach about ten years ago (lead structural engineer in the 
investigation for the University was SEAOSC's own Lynn Bockemohle of Robert 
Englekirk's office, who I think spoke to one of our dinner meetings about the 
findings, and who would be the guy to talk too if anyone wants details beyond 
those below).

That building's roof consisted of long span (I think it was about eighty feet) 
open web Trus-Joist products supported on tilt-up concrete bearing walls.  
There was a heavy plaster ceiling and a layer of "non-structural" concrete on 
top of the plywood roof diaphragm for acoustical reasons.  The roof collapsed 
on a warm summer day under no unusual load.  Essentially the entire area over 
the auditorium came down on its seats and stage in a few seconds -- air 
pressure blowing shattered glass from lobby windows a hundred feet or more out 
on to the surrounding lawns.  It is unlikely that any person in the auditorium 
could have survived the collapse, but the orchestra practice session scheduled 
in the building that afternnon had been cancelled because cracks in ceiling 
plaster and creaking noises from above made the professor nervous (I hope he 
got a medal).  No one was injured, but the economic loss was more than four 
million dollars.

To make a long story short and at the risk of oversimplifying (there turned 
out to have been more than one straw on the camel's back) the critical factor 
leading to the collapse was the absence of bottom chord bracing.  Trus Joist 
had specified a modular erection technique in erection drawings and called for 
several transverse lines of bridging to stabilize the bottom chords of its 
trusses.  Their erection scheme called for groups of trusses to be plumbed and 
trued to line on the ground and then to have plywood nailed across their tops 
and bridging/bracing installed before being lifting as a unit and placed on 
the structure.  The contractor said that he understood this scheme to be 
optional.  He instead used a "stick" erection scheme, placing the trusses on 
the building individually.  Unbraced top chords twisted off line under 
erection stresses before the plywood was nailed, creating a tendency for the 
trusses to roll.  Bottom chord bridging was omitted even though the trusses 
had factory installed bridging clips on them to receive it.  There was, 
incidentally, a full time resident inspector for the University, but no record 
of what he did.

My understanding of Lynn's conclusion was that the collapse was initiated by 
the failure of a single truss whose compression chord crept far enough off 
line to create a destabilizing eccentricity.  The member, lacking the intended 
bracing, rolled gradually out of vertical, probably over a period of years, 
its effective depth being decreased and chord stress proportionally increased, 
until it finally snapped, immediately overloading its neighbors and 
precipitating a rolling collapse that progressed down the length of the 
auditorium, taking out the structural elements like dominoes.

With respect to the current topic (deferred approvals), helping to clean-up 
after the CSULB collapse taught me that quality control and structural 
observation during the erection of these types of structures are essential.  I 
have used pre-fabricated wood trusses since, including in long span 
conditions, but as engineer of record I insist that the manufacturer's design 
drawings and calculations be submitted for my review under the seal and 
signature of a qualified professional engineer.  I make sure among other 
things that bridging, bracing and/or special erection requirements are plainly 
and clearly stated, adding notes to my design drawings as appropriate, and I 
specify framing inspections.  There are no guarantees, but the standard of 
care is not in my opinion met by "fire and forget" designs that give a generic 
call-out for the joists and leave their proper design and installation to the 
manufacturer and contractor.  If any of you are still doing this I urge you to 
think again.

In general, prefabricated trusses are of course only the tip of the iceberg 
with respect to deferred approvals.  Industry standards for pre-fabricated 
metal stairs, storefronts and curtain walls also call for supplier designs.  I 
am aware of the El Segundo requirement but have not yet had it enforced on one 
of my projects.  In general, though many building departments, including the 
City of Los Angeles Department of Building and Safety and the State of 
California's Division of the State Architect, will tell you that their policy 
is to prohibit deferred approvals, such a policy is impractical and building 
officials know it.  I have run into very few instances were a reasoned 
explanation of the situation along with a commitment to timely submission of 
the deferred approval package has not resulted in an "administrative 
exception" or other device allowing the policy to be set aside.  I have had 
this experience specifically with COLA and DSA, who I think we all recognize 
as reasonably hard headed regulatory authorities.

My principal complaint about the building department policies is the fact that 
they waste my time.  I would be willing to participate in a SEAOC or SEAOSC 
effort to get the various authorities to draft appropriate and practical 
guidelines, or to draft them for them, that would allow deferred approvals 
within a framework that would reduce the risk that the follow-up would fall 
between the cracks.  Does anybody know which committee I might contact to 
volunteer?

Building officials aside, our responsibilities to those who will use the 
structures we design require that we accept our responsibility as engineer of 
record to review the design of such components at least for compatibility with 
our designs of the buildings to which they are to be attached.  I think 
Dennis' suggestion of a deferred approval list on the cover sheet is on point, 
but such a list cannot stand alone.  The trick in my opinion is to make sure 
that the construction documents, either in specifications or on drawings, 
clearly set forth the contractor's obligations with respect to supplier 
designed components, and then to follow up.  One useful device is appropriate 
notes right on your framing plans and details.  For example, everywhere you 
show a pre-fabricated wood truss you can tack a note saying something like: 

"TRUSS SIZES AND DETAILS SHOWN ARE PRELIMINARY.  DETAILED DESIGN DOCUMENTS FOR 
THE PRE-FABRICATED WOOD TRUSSES, INCLUDING BRIDGING AND BRACING REQUIREMENTS 
AS WELL AS END BEARING DETAILS ARE TO BE PREPARED BY THE SUPPLIER FOR 
SUBMISSION TO AND APPROVAL BY THE ENGINEER OF RECORD BEFORE DELIVERY OF THE 
MEMBERS TO THE SITE.  FRAMING INSPECTION BY A REGISTERED DEPUTY BUILDING 
INSPECTOR IS REQUIRED.  INSPECTORS SHALL REJECT ANY WORK IN THE ABSENCE OF OR 
NOT IN ACCORDANCE WITH THE SUPPLIER'S APPROVED DESIGN SUBMITTAL."

Such a note would probably have prevented the CSULB collapse.  Industry 
standards were different when that building was designed, and it is my 
understanding that structural design drawings were prepared by the architect 
for the signature of his structural consultant.  The detail drawings were 
however prepared and reviewed by the structural engineer of record -- they 
were simply not followed.  Good notes placed prominently are not just boiler 
plate -- they can save your building and its occupants' lives (not to mention 
your business).  Secondarily, when you meet a building official and have to 
fight for a deferred approval in order to preserve your client's schedule and 
budget, they can help to demonstrate that you intend to do things right and 
bring you a step closer to that administrative exception.

Drew A. Norman, S.E.
Drew A. Norman and Associates