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Re: ANCHORAGE TO CONCRETE[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: ANCHORAGE TO CONCRETE
- From: COEngineer(--nospam--at)aol.com
- Date: Mon, 15 Nov 1999 15:07:22 EST
I don't think that the CCD will address a j bolt since they do not load the concrete very evenly to provide for the typical cone assumption. However, the CCD should cover a headed bolt in a 6" stemwall with deeper embedments within reason. Remember, these calculations are based on unreinforced concrete. Once you put one little #4 through the cone, you will see great benefits in performance. We have a listing in our ICBO report for a 5/8" diameter threaded rod in a 5" unreinforced concrete stemwall with 9 inch embedment, that has an allowable tensile value of 3460 lb if you are at least 12 inches from the end of the wall. Obviously there is benefit from going deeper into the wall. Calcing that exactly can be difficult. Regards, Howard Silverman Covert Operations, Inc. (800) 827-7229 www.covertoperations.com In my original post, I was trying to justify the anchorage that so many residential contractors in this area (Tucson, AZ)use for hold down anchor bolts in a concrete stem wall for 6" stud walls. I was attempting to justify it with a simple truncated cone on a j-bolt. I now understand that the cone failure may not be very applicable for a j-bolt. In my simple analysis I was not proposing to reduce the embedment length from 12 inches to 2.75." I was only basing the failure cone to be that equal to a 2.75 inch embedment since the edge distance for a j-bolt embedded 12 inches is only 2.75 inches on each side for an 6 inch stem wall. This was not adequate to develop the published load of a Simpson HD2A with a 5/8" anchor bolt much less develop enough to ensure a ductile failure of the bolt. (All they are usually trying to develop is the 1800# uplift for the prescriptive braced wall panel required in UBC '94 2326.11.4). I was looking for justification to use more surface area of the cone failure with 12 inches of embedment; however, it appears that I need to look at a different failure mode for a j-bolt. Does the CCD method that John Silva referenced in the IBC 2000 address a smooth j-bolt (that is typically used) in a narrow stem wall. Has anyone calculated the allowable service load for a 5/8" diameter j-bolt with 12 inches of embedment in a 6 inch stem wall.
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