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RE: Anchorage to concrete

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It would appear that the additional safety factor would be required for
anchor bolts connecting to footings, where the bolts are in tension due
to uplift, or moment transfer.  In these situations, the uplift or
moment transfer would most likely produce tension in the top of the
footing under the base plate.

Charles F. Espenlaub, III, P.E.
Martin-Espenlaub Engineering

-----Original Message-----
From: Rex Donahey [mailto:rdonahey(--nospam--at)]
Sent: Thursday, December 02, 1999 1:28 PM
To: seaint(--nospam--at)
Subject: RE: Anchorage to concrete

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
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
an unfavourable influence on the loadbearing behaviour of the

The paper includes figures showing beams loaded in flexure and with
fasteners in the resulting cracked region.  Since the German studies are
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
the tension in the fasteners themselves.  That tension zone will exist
any fastener installation, no mater where the fasteners are located in
element.  However, if the fasteners are located in a building element
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

Eligehausen, R.,Fuchs W., Lotze, D., und Reuter, M., "Befestigungen in
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
in Section 1909.2 shall have a multiplier of 3 if special inspection is
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.