2005 NDS SECTION 3.4-7 (C)---CONCEALED HANGERS?

[ARJ1]

THE 2005 NDS SECTION 3.4-7 SUBSECTION (C)(PAGE 17) STATES: "WHEN CONCEALED HANGERS ARE USED, THE ADJUSTED DESIGN SHEAR, Vr', SHALL BE CALCULATED BASED ON THE PROVISIONS IN 3.4.3.2 FOR NOTCHED BENDING MEMBERS. MY QUESTION IS, WHAT DO THEY MEAN BY CONCEALED HANGERS? THEY ARE NOT REFERRING TO CONCEALED FLANGE HANGERS ARE THEY? THANK YOU IN ADVANCE.

 

[JAE]

I think concealed hangers are when the member is cut with a slot in the end so that any plate connectors would fit inside the connected member to hide it...and only show the bolts on the outside of the member.

 

[ARJ1]

JAE,

That would make sense. That would explain the need for the adjusted shear formula.

Thanks

 

[RARWOOD]

JAE is correct. A common concealed hanger in the past consisted of a vertical back plate with a top flange. The back plate had a horizontal round bar about 6" long welded to it. A round dap was made in the end of the member and the member's end was routed out for the back plate. When the member was installed The steel was completely concealed.
Since the load was carried by the top of the bar the effect was similair to a beam that had the material below the top of the bar notched out.

Today it is more common to see partially concealed hangers. A common partially concealed hanger is made up with a top flange,a vertical back plate, a horizontal bearing plate with a vertical stiffner at the bearing plate centerline. A vertical saw kerf is cut in the supported memeber so that it can sit down on the bearing plate. Bolts then may go through the member and vertical stiffner plate.

With a partially concealed hanger the back plate and horizontal bearing plate are left exposed. This type of hanger can also be dapped into the end of the hanger so now steel is exposed. If the member is large enoungh the mmember may be countered bored so that the bolts may be concealed by plugging the counter bores.

 

[ARJ1]

Thanks RARSWC

 

[structuralaggie]

Check out the Simpson CJT hanger.

 

[JAE]

Here's a link to the CJT that structuralaggie mentions:

http://www.strongtie.com/products/connectors/cjt_apg.html

 

[ARJ1]

Thanks for all the comments.