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RE: Low LOP Progressive Collapse Horizontal Ties

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Eric, I'm looking at 7-2.6, & I see where you pulled the quote from.  If you read beyond that point, you'll see it says that where peripheral tie IS located within the wall, provide horiz. ties adequate to anchor the int. ties to the periph. ties.

The intent for the internal & horiz. ties is that (1) internal ties be continuous from one side to the other (in both directions, over interior of structure), & (2) horiz. ties tie exterior cols & walls to rest of structure.

I haven't used this UFC & don't have time to digest the example problem; however, I can steer you to additional/better help.  I attended ASCE's Progressive Collapse Mitigation course about a year ago, & this UFC was a major topic.  The presenter was Brian Crowder, Naval Facilities Engineering Command, Atlantic: brian.crowder(--nospam--at)


30 Message:0030 30
From: "Eric Tompos" <etompos(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: Low LOP Progressive Collapse Horizontal Ties
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Can someone please clarify the requirements for 'horizontal ties to external
walls and columns' in UFC 4-023-03 (Progressive Collapse). The examples in
the Appendix don't seem to match the requirements.

Section 7-2.6 requires horizontal ties at "each external column and, if the
peripheral tie is NOT located within the wall." It goes on to require
horizontal ties "at each floor and roof level"

Section 7-2.4 requires internal ties "must be anchored to peripheral ties"

The result, in a bearing wall if the peripheral tie is in the wall, only
internal ties are required (no horizontal ties), as shown in in the example
in Appendix F. However, the example only addresses the top of an exterior
wall. At the bottom of the wall there is no peripheral tie in the wall, so
based on Section 7-2.6 a horizontal tie is required at the floor level. In
all of the design examples I have seen the bottom of the wall is not
addressed. Am I misreading this requirement? Is a horizontal tie required
at both the top and bottom of each exterior bearing wall?
And, if it is to be "anchored or tied horizontally" how is this being
achieved with a strap, as shown in the examples, when a strap would provide
no resistance in the horizontal direction?

Thanks in advance,
Eric Tompos, PE

Glen Pappas, Ph.D., PE, SECB
Los Alamos National Laboratory
Technical Staff Member
Phone: 505-665-1221
Fax: 505-665-4728
MS M791