huangyhg

lightgage truss to concrete bearing wall attachment
what is the typical detail for attaching the two? continuous embed plate? plain concrete and they drill in a tapcon. assume there's some uplift on the truss connection but no more than 400 lbs.
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it depends on whether the truss is placed on top of the wall or is attached on the inside face with a parapet wall extending above the truss.
i would usually try to get the truss on top of the wall and avoid the eccentricity and messy shear connection.

yes, i'd do the same, but my question is how they actually attach the truss to the top of wall. do they prefer to see a metal bearing plate or concrete? or doesn't it matter?
usually - a 2x4 or 2x6 treated (flat) is anchored to the wall and the trusses anchored to that. you can use anchor bolts grouted in or epoxied bolts or drop in anchors to grout. the trusses are connected with nails or a simpson or equal type clip - size the clip depending on loads.
but for steel trusses there are also clips that go directly from concrete wall to truss. go to simpsons or usp web sites.
some local codes have minimums - you better check.
if you use treated wood, follow the new guidelines to prevent corrosion of metal in contact with it.
usually i avoid using wood top plates with steel trusses, as there is usually a fire rating limation with the wood. in general, light gage trusses are strapped down to the top of the wall with a light gage strap or bent plate. it can either be wet-set into the tie beam or tapcon'd in after the beam is cast.
however, i typically no longer call out these connections, as there are so many proprietary truss profiles out there (c-shaped, u-shaped, tubes) that it is impossible to know what type of strap or clip to use, as you have no idea what the shape of the truss chord will be, unless you are designing the truss out of standard stud shapes.
so whenever i delegate the design of light gage trusses (which is almost always), i also delegate the design of the conenction of the truss to the tie beam. that way, the truss manufacturer can use his standard details, and i don't have to guess at something which may not work.
just show the embedded 1/4" x 5" wide continuous metal plate ast the top of the wall.
chances are that the contractor will want to change it anyway.
mike mccann
mmc engineering

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