Any idea of
methods used in Guam?
Michel Blangy, P.E.
Thanks for the reply. As far as why not just use hurricane clips,
it's a matter of supply. I live and work in Palau, and that's an awful
long ways from you guys which makes shipping things VERY expensive.
Another big part of it is that the construction industry here is still "old
school". We don't get a whole lot of typhoons (unlike Guam to the
north), no appreciable seismic activity either, and we haven't had a true
building boom as of yet. All this added together means that contractors
pretty much use the same method of doing things that they have for the past 30
years. Metal connectors are just beginning to make an appearance here,
and if they do get carried by the local stores then I will specify them.
Otherwise, it is useless to specify something that they cannot obtain and
course, I could always start importing them...
look over your email and see what I can do. I'm glad you mentioned the
splitting problem - that was my first thought when I saw the connection.
I need to figure out a different way of doing that, since I don't relish the
thought of clambering up on the roofs of all of these houses to check the
entire thing for split 2x3 purlins.
Terangue *Tiger* Gillham, PE
I believe you have to use the nail capacity
value from NDS for the plywood truss connections. Reduce the value by
0.9 for dead loads. Use the tables with a side board of whatever
the plywood thickness is and whatever the wood species is as the
side material. Or you can use the NDS formulas to calculate
the nail value. Check the actual nail size by pulling a few and check
embedment depth too. If the values come even close to what the truss
demand is, you may be in the ballpark and can check it by a more detailed
method if necessary. Of course, you need to do the truss analysis to
know the demand.
For the 2x2 holdown connections, again, check
the nail capacities by NDS. If the 2x2 is end-nailed, the nail value
goes way down, per NDS. If the small wood members are split by
the nailing then the nail may have no value. Check all parts of the
connection. You can ask for a mock-up of the connection in a frame or
jig that you can test with dead weights. You can design a test rig to
test the connection. Is the factor of safety for nail connections
around 8? If so, divide the average breaking strength by 8 to get a
useable design value. Why not add the hurricane straps
----- Original Message -----
Sent: Monday, June 12, 2006 5:50
Subject: Wood Truss and Purlin
Does anyone know of a source for reference tables
describing allowable loads for nailed plywood truss connections? I
am being called upon to do a lot of house plan reviews for local banks and
this material would be useful in cutting down my time spent on
A second question regarding the use of 2x2 for
holdowns at roof purlin-rafter connections. Is it fairly
common to place a 2x2 vertically, top nailed to a 2x3 purlin
(flatwise) running across the top of the rafter, 2x2 is butted up against
sideface of rafter and nailed in? I saw this detail for the first
time yesterday on a house that I had Simpson type hurricane clips
specified for use, and I need to ensure that the holdown connections will
As far as wind loads go, we use 100mph winds,
1994 UBC, so the loads aren't that bad.
Any comments from those that do a lot of wood
design would be much appreciated.
Terangue *Tiger* Gillham, PE