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Re: Fwd: Positive connection

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My head is spinning! Doesn't all of this boil down to: does it work or not?
I don't think the structure will know what definition we use....

On Mon, Apr 21, 2014 at 1:01 PM, Joseph Gmail <jrgrill55(--nospam--at)gmail.com> wrote:

> So, after reading all that, would you consider the shear key a "positive"
> attachment?
> 
> Joseph Grill
> 
> On Apr 21, 2014, at 11:49 AM, Steve Gordin <sgordin(--nospam--at)sgeconsulting.com>
>> wrote:
>> Good morning,
>> 
>> The question arose during a plancheck for one of my designs, and was
> related
>> to the issue of whether a concrete shear key (or similar component)  can
>> be classified as a positive connection for a pedestrian bridge - even
>> though it is not a steel attachment and allows some movement.
>> 
>> I got the reply from AISC Solution Center (below) this morning.
> Apparently,
>> they did quite a research…
>> 
>> At the end of the day, the term appears to directly correlate to the
>> Merriam-Webster's definition of "positive:" formally laid down or
> imposed;
>> fully assured;
>> independent of changing circumstances;
>> relating to or constituting a motion or device that is definite,
> unyielding,
>> constant, or certain in its action; not fictitious;
>> directed or moving toward a source of stimulation.
>> Evidently, some smart engineer once coined the term - but forgot to
> define
>> it...
>> 
>> They way I see it now, the definition for the positive connection should
>> be something like: "A structural connection against all applicable forces 
>> that is fully assured without the consideration of friction."
>> 
>> Have a good week,
>> 
>> Steve
>> 
>> ______________________________
>> V. Steve Gordin PhD
>> Licensed Structural Engineer
>> SGE Consulting Structural Engineers
>> 2081 Business Center Drive #105
>> Irvine CA 92612
>> 949-552-5244
>> sgordin(--nospam--at)sgeconsulting.com
>> 
>> Begin forwarded message:
>> 
>>> From: "Solutions Center" <Solutions(--nospam--at)aisc.org>
>>> Subject: RE: Positive connection
>>> Date: April 21, 2014 5:38:02 AM PDT
>>> To: <sgordin(--nospam--at)sgeconsulting.com>
>>> 
>>> 
>>> Steve,
>>> 
>>> 
>>> It does not appear that the AISC Specification, or the IBC define
> “positive
>>> connection”.  In fact, the only place that I found that provided a
>>> definition is in the FEMA E-74 document “Reducing the Risks of
> Nonstructural
>>> Earthquake Damage, Section 6.6.1 Positive Connections.  There it states: 
>>> “The objective of nonstructural anchorage or restraint details is to
>>> provide what engineers refer to as a positive connection between the
> item
>>> and a hard attachment point, such as a structural wall, braced
> partition,
>>> concrete floor, or built-in countertop. Positive connections generally
>>> consist of some combination of screws, bolts, cables, chains, straps,
>>> steel angles, and other steel hardware that transfer seismic loads to
>>> structural framing. Positive connections do not rely solely on the
>>> frictional resistance produced by the effects of gravity. Frictional
>>> resistance between the base of an object and the floor or mechanical
>>> friction connections such as C-clamps or thumbscrew clamps are not
>>> considered positive connections. The most common nonstructural
> connection
>>> details for wall attachments, floor or ceiling attachments, countertop
>>> attachments, and attachments between adjacent items are discussed below. 
>>> GENERAL INTEREST SIDEBAR Earthquake Forces Keep in mind that although
>>> heavy objects are hard to move by hand, their weight (mass) interacts
>>> with the shaking (accelerations) of an earthquake to produce large
> inertial
>>> forces. Those forces mostly act sideways to make the object slide or
> tip,
>>> and there are also vertical motions in earthquakes that temporarily
>>> "lighten" an object and reduce frictional resistance.” You can find
>>> this online at <http://cirrus.mail-list.com/seaint-seaosc/09421005.html> 
>>> 
>> 
>>> Also, the term positive connection is sometimes used in relation to the
>>> OSHA regulations related to rigging and lifting, though I was unable to
>>> find a definition supplied by OSHA or even the use of this exact term 
>>> in the regulations – though I may have missed it. It can be inferred 
>>> from the context in which the term is used that a positive connection 
>>> is one which cannot accidentally become disengaged (i.e. slide off). For 
>>> 
> instance
>>> OSHA seems to deem a shackle through a lifting lug to be a positive
>>> connection, but a sling around a trunnion is not a positive connection.
>>> I suspect the term is typically not used in conjunction with the
> regulations
>>> related to steel erection since bolts provide a positive connection and
>>> regulations relative to their use in steel erection are pretty explicit. 
>>> This definition of positive connection is also used informally in other
>>> applications. The term positive connection can also refer to electrical
>>> continuity and is also used this way in OSHA documents.” I hope this
>>> helps.  Please let me know if you have any additional questions.
> Sincerely,
>>> Carlo Lini, P.E., LEED AP BD+C Staff Engineer American Institute of
> Steel
>>> Construction 866.ASK.AISC lsm/eng How did we do? Your opinion matters 
>>> to us: www.aisc.org/TellAISC for your chance to win a free Steel
> Construction
>>> Manual! This document has been prepared in accordance with information
>>> made available to the American Institute of Steel Construction at the
>>> time of its preparation. While it is believed to be accurate, it has not 
>>> been prepared for conventional use as an engineering or construction
>>> document and should not be used or relied upon for any specific
> application
>>> without competent professional examination and verification of its
> accuracy,
>>> suitability, and applicability by a licensed engineer, architect or
> other
>>> professional. AISC disclaims any liability arising from information
>>> provided by others or from the unauthorized use of the information
> contained
>>> in this document.

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