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Re: Fwd: Positive connection

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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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