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RE: Connection Design per 5th Ed PCI Design Handbook

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I am interested to find information on using reinforcement perpendicular to a concrete anchor to resist tension perpendicular to the reinforcement. 


I had a local building official tell me when you use horizontal reinforcement to resist concrete pop-out with shear friction, that the tension is perpendicular to the reinforcement.  He also said the shear friction only resists the component of force parallel to the failure plane of the concrete and there is still a force component perpendicular to the failure plane of the concrete that requires additional reinforcement perpendicular to it.


This is can be an issue in wood frame buildings in high seismic areas with small tiedown anchors because the code says the anchor needs to fail in ductile yielding and not concrete failure.




From: Jim Getaz [mailto:jgetaz(--nospam--at)]
Sent: Tuesday, November 14, 2006 10:10 AM
To: seaint(--nospam--at)
Subject: Re: Connection Design per 5th Ed PCI Design Handbook



                        You’re absolutely right. If you decrease the distance of the shear towards the free edge from 120”, the result will be the same – or only slightly different – until the free edge distance is comparable to the side distance in a 16” column.

                        The rules are entirely different, now, though. Have a look at ACI 318 Appendix D or the PCI Design Handbook, 6th Edition. Side distances are even more important, and shear towards a free edge is changed, too. Also see the article starting on page 54 of March 2004 Concrete International.

If the concrete does not provide sufficient anchorage, these days, you may assign all the load to shear-friction reinforcing that crosses the anchorage failure plane and is fully developed on each side of that plane. I do not know of a place where this is stated in print, but it is what designers are doing.

            Jim Getaz

            Precast Concrete Engineer