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RE: Anchorage to concrete

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Some of the original work on anchors in a tension zone was conducted by
Elighausen, et al in the late 80's.  Review of the work shows that the
Betonzugzone, or concrete tension zone, was intended to be the tension zone
in a bending member.  The translated abstract of the below cited paper

"It is highly probable that fastenings arranged in the tensile zone of
reinforced concrete building components will be crossed by cracks.  This has
an unfavourable influence on the loadbearing behaviour of the fastening."

The paper includes figures showing beams loaded in flexure and with
fasteners in the resulting cracked region.  Since the German studies are the
root investigations for the current CCD method, the definition clearly
applies to your first example.
The second example is more questionable.  In my opinion, the requirement
does not apply to the local tension zone in the concrete that is caused by
the tension in the fasteners themselves.  That tension zone will exist in
any fastener installation, no mater where the fasteners are located in the
element.  However, if the fasteners are located in a building element that
is in tension because of flexural loading, that zone could be precracked
before the fasteners are loaded.  That zone is considered a tension zone
because the potential precracking will reduce the capacity of the fasteners.

Eligehausen, R.,Fuchs W., Lotze, D., und Reuter, M., "Befestigungen in der
Betonzugzone" (Attachments in the Concrete Tensile Zone), Beton- und
Stahlbetonbau 84 (1989), H.2

Rex C Donahey
Composite Technologies Corporation

-----Original Message-----
From: Jeff J. Johnson [mailto:jjohnson(--nospam--at)]
Sent: Thursday, December 02, 1999 11:42 AM
To: 'seaint(--nospam--at)'
Subject: Anchorage to concrete

Section 1923.2 of the 97 UBC indicates that

"When anchors are embedded in the tension zone of a member the load factors
in Section 1909.2 shall have a multiplier of 3 if special inspection is not
provided, or of 2 if it is provided."

I need clarification of what the "tension zone of a member" means.

If a base plate is sitting on a concrete beam directly over a cantilever
support the anchors would definately be in the member's tension zone.

Does this requirement also apply to a base plate that has a large moment
that puts some of the anchor bolts into tension (or) a base plate which
transfers uplift forces to all of the anchor bolts?

Please help clarify what type of situations this applies to.

Thanks in advance

Jeff Johnson, PE
UniField Engineering Inc.