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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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