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- To: <seaint(--nospam--at)seaint.org>, <light_framing(--nospam--at)structuralist.net>
- Subject: Simpson CCO or ECC connection in Concrete Column
- From: "Dennis Wish" <dennis.wish(--nospam--at)verizon.net>
- Date: Mon, 16 Oct 2006 20:39:29 -0700
I have not been able to get a fast answer from Simpson today – it appears everyone is in meetings. I am designing a Patio Cover that is to extend from the face of a CMU building being converted into a restaurant. The Patio cover is 2x8 framing with stucco on the lower side and anodized steel roofing on top – slight 2% pitch. The open front is carried by two columns supporting a 5.125x12” 24F-V8 GLB that has an 8-foot cantilever on one end – 17.5 feet between columns and a 2-foot cantilever at the other end. The lateral load to the open front is 2-kips; 1-kip per column at 6’-6” above finished slab (bottom of GLB connection to top of column).
I’ve been discussing the columns with Scott Maxwell privately as it is a pre-manufactured “modular ledgestone” column that has the stone embedded into a 21-inch square x 4.5” substrate to create a 12-inch square cavity. The manufacturer is sketchy on the design for lateral load resistance and Scott asked a good question – whether or not I was designing the core as masonry or concrete. The manufacturer uses the term grout synonymously with concrete, but my intent was to use an aggregate mix concrete and have designed a 12-inch square column that is lap spliced with (4) #6 rebar and a #3 rectangular cage that is embedded into a 24-inch square x 4’-0” deep post hole foundation. I’ve used an R of 2.2 according to the 97 UBC and the lateral weight of the open structure is 37% of the weight of the roof and columns. This works out to be 4-kips lateral – 2Kips at the front and 2Kips at the CMU wall that is roughly 90% solid.
I believe I have a handle on the design of the column, but could use any suggestions if what I am describing seems off base or less than conservative. If you care to see the manufacturers concrete surrounds follow the column links at www.eastweststone.com as well as the installation guide for their modular ledgestone columns.
The top of the column is capped with a 21-inch square x 2-inch thick cap stone. I would like to weld two 24” long threaded rods (A307) to the bottom of the Simpson CCO connectors and pre-drill the cap stone to allow me to drop the column cap into wet concrete with a dry pack for level on top between the connector and the cap stone.
I mentioned that the beam develops a moment at the column location where it connects to the CCO cap. However, it has been my experience to oversize the holes in the GLB and not tighten down the column caps until all roofing materials and stucco are in place. This allows the beam to settle in on the moment at the point of bearing. The slight oversize of the hole will also provide for some rotation based on weather conditions (we are dry Desert here as low as 5% relative humidity in the summer but can be wet in the winter although rare). I’ve worked with curved GLB’s before and have always kept the bearing plate connections loose until the dead loads are in place – then I wait until they are ready to add exterior finishes before tightening down the beam / bearing plate connections.
Does anyone see a problem with welding on the two A307 rods to the CCO connector and then setting them through the cap stone onto a dry pack level to level the GLB?
Thanks in advance – please feel free to e-mail me directly if you do not care to post to the list.
Dennis S. Wish, PE
Structural Engineering Consultant
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