Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: Factored Load Combinations with Cranes

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Daryl, 
I agree completely.
Gary

On 14 Jan 2005 at 20:01, Daryl Richardson wrote:

> Rich,
> 
>         I am not familiar with the code you are referring to, Rich.  I
>         am, 
> however, familiar with crane usage.  I can show you service type
> operations and factories running two shifts with service cranes. 
> These people would not like to be told that they can not use their
> cranes when they have a full snow load on the roof!
> 
>         If your code permits the load reduction combination factors
>         you have 
> listed it may be legally correct to do so.  But I would suggest that
> you think carefully about the crane service before you do.
> 
>         I would personally not use reduced load combinations factors
>         if I 
> were designing a new facility.  For upgrading a crane, or for adding a
> crane where none existed before, you do what you have to do; but make
> sure that you have your disclaimers clearly stated and that your
> client and the local building authority are on side.
> 
> Regards,
> 
> H. Daryl Richardson
> 
> 
> ----- Original Message ----- 
> From: "Rich Lewis" <sea(--nospam--at)lewisengineering.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Friday, January 14, 2005 4:32 PM
> Subject: RE: Factored Load Combinations with Cranes
> 
> 
> > I'm not sure if you have looked at the load combinations lately.
> >
> > Eq. 16-2 has 100% crane and 50% roof.
> > Eq. 16-3 has 100% roof and a reduce live of 50%
> > Eq. 16-4 has 100% wind and a reduce live of 50%
> > Eq. 16-5 has 100% seismic and a reduce live of 50%
> >
> > I think the crane load is accounted for in Eq. 16-2
> >
> > Rich Lewis
> > Lewis Engineering
> >
> >
> >
> > -----Original Message-----
> > From: Daryl Richardson [mailto:h.d.richardson(--nospam--at)shaw.ca]
> > Sent: Friday, January 14, 2005 12:36 PM
> > To: seaint(--nospam--at)seaint.org
> > Subject: Re: Factored Load Combinations with Cranes
> >
> > Fellow engineers.
> >
> >        Do not reduce crane loads as part of load combinations!!! 
> >        Crane
> >
> > operator very often overload the cranes; in some cases
> > substantially.
> >
> >        About two years ago I was called on to check out a Five (5)
> >        Ton
> > crane because "it broke and they dropped the load".  Fortunately
> > they were lifting a dumpster of scrap metal; and, even more
> > fortunately they didn't drop it on anyone or on anything of value.
> >
> >        They were pretty upset.  They had been disposing of the scrap
> > metal
> > this way for years and nothing like this had ever happened before! 
> > (But
> >
> > then we have all heard the "We always done it that way before."
> > argument, haven't we?)
> >
> >        The final failure was a broken cable.  I also recommended
> >        that
> > they
> > strip it down and check the bearings, several sets of which needed
> > replacement.
> >
> >        The real cause of failure: the dumpster weighed ELEVEN (11)
> > TON!!!!
> >
> > Regards to all,
> >
> > H. Daryl Richardson
> > ----- Original Message ----- 
> > From: "Paul Ransom" <ad026(--nospam--at)hwcn.org>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Friday, January 14, 2005 10:00 AM
> > Subject: RE: Factored Load Combinations with Cranes
> >
> >
> >>> From: "Rich Lewis" <sea(--nospam--at)lewisengineering.com>
> >>
> >>> Are there factored load combinations recommended for design in a
> >>> one story building with a crane supported by the steel framing?  
> >>> IBC
> >>
> >>> I ask this for foundation design load combinations.
> >>
> >>
> >>> From: "Scott, William N." <William.Scott(--nospam--at)veco.com>
> >>
> >>> A crane is an equipment load. The load should not be reduced.
> >>
> >> IBC 2003 is very explicit about the application of crane loads
> > including
> >> impact. Crane loads are defined as Live Loads and therefore subject
> >> to the permissible reductions in combinations.
> >>
> >>> The loading should be based on crane capacity with impact factors.
> >>
> >> I disagree that vertical "impact" loads are a foundation issue for
> >> a typical overhead crane building.
> >>
> >>
> >>> From: "Rich Lewis" <sea(--nospam--at)lewisengineering.com>
> >>
> >>> IBC 2003 states that for occupancy loads of 100 psf or more you
> >>> can't reduce it.  It says for all other live loads it can be
> >>> reduced. ASCE 7-02 basically states the same thing except it
> >>> infers it is for occupancy loads, which is not equipment.
> >>
> >> Floor loads are different creatures with different probabilities.
> >> IBC 2003 says, "The crane live load shall be the rated capacity of
> >> the crane." Only include impact for certain elements. I don't know
> >> where they include the crane mechanism (bridge and trolley). I
> >> think that
> > Gail
> >> needs to chase these guys, too.
> >>
> >>> PEMB designers use some different load combination factors for ASD
> >>> design when combining crane with live and wind forces.  Are there
> >>> any PEMB designers out there who can clarify what typical practice
> >>> is for load factor design?
> >>
> >> PEMB designers use the same load combination factors that you use,
> >> ASD or LRFD. Those who don't should not be lumped into the
> >> generalized
> > group
> >> of "designers." Unfortunately, there are PEMB manufacturers that
> >> don't know a "designer."
> >>
> >> Per IBC 2003:
> >> 1.2DL + 1.6L + 0.5(Lr or S)
> >> 1.2DL + 1.6(Lr or S) + f1(L)
> >> 1.2DL + 1.6W + f1(L) + 0.5Lr
> >> etc.
> >> where f1 = 0.5 and L includes crane loads per 1607.12, including
> > impact,
> >> and floor loads (reduced for area or not).
> >> Those are the mandatory combinations (code specific).
> >>
> >> ASCE7 is verbatim to IBC 2003 as far as I reviewed. I did note some
> >> inconsequential differences (e.g. f1 is overtly replaced with 0.5).
> >>
> >> NBCC does not permit reductions of crane loads in combination with
> > other
> >> (roof, floor) Live Loads and does require impact in the design
> >> load. I think this is a little conservative.
> >>
> >> The MBMA has put together one of the nicest crane-building design
> >> references available, in the Low-Rise Building Manual. The Manual
> >> is
> > not
> >> a code but a compilation of MBMA ->member<- manufacturers
> >> agreed-to-be-acceptable design practices ... kind of like AISC
> > manuals.
> >> So, no load combinations, just load development. Nobody has to
> >> follow this guide unless it is in the contract or in a building
> >> code.
> >>
> >> Also, see the new (free for download, pdf, http://www.cisc-icca.ca)
> >> publication by the CISC, "Guide to Crane Supporting Steel
> >> Structures" and the usual AISE TR-13, "Guide for the Design and
> >> Construction of
> > Mill
> >> Buildings."
> >>
> >> For those who have read this far, a question:
> >> What "static" load should be used for limiting crane building
> >> deflections, what should be the limiting deflections and why should
> >> it matter? Should we be concerned about lateral building deflection
> >> or
> > only
> >> rail separation as a deflection control (P-delta issues aside)? I
> > would
> >> be interested in Christopher Wright's opinions related to the
> >> dynamic effect aspects.
> >>
> >> -- 
> >> R. Paul Ransom, P. Eng.
> >> Civil/Structural/Project/International
> >> Burlington, Ontario, Canada
> >> <mailto:ado26(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>
> >>
> >> ******* ****** ******* ******** ******* ******* ******* ***
> >> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> >> *
> >> *   This email was sent to you via Structural Engineers
> >> *   Association of Southern California (SEAOSC) server. To
> >> *   subscribe (no fee) or UnSubscribe, please go to:
> >> *
> >> *   http://www.seaint.org/sealist1.asp
> >> *
> >> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you *  
> >> send to the list is public domain and may be re-posted *   without
> >> your permission. Make sure you visit our web *   site at:
> >> http://www.seaint.org ******* ****** ****** ****** ******* ******
> >> ****** ********
> >>
> >
> >
> >
> > ******* ****** ******* ******** ******* ******* ******* ***
> > *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> > *
> > *   This email was sent to you via Structural Engineers
> > *   Association of Southern California (SEAOSC) server. To
> > *   subscribe (no fee) or UnSubscribe, please go to:
> > *
> > *   http://www.seaint.org/sealist1.asp
> > *
> > *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> > *   send to the list is public domain and may be re-posted
> > *   without your permission. Make sure you visit our web
> > *   site at: http://www.seaint.org
> > ******* ****** ****** ****** ******* ****** ****** ********
> >
> >
> >
> > ******* ****** ******* ******** ******* ******* ******* ***
> > *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> > *
> > *   This email was sent to you via Structural Engineers
> > *   Association of Southern California (SEAOSC) server. To
> > *   subscribe (no fee) or UnSubscribe, please go to:
> > *
> > *   http://www.seaint.org/sealist1.asp
> > *
> > *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> > *   send to the list is public domain and may be re-posted
> > *   without your permission. Make sure you visit our web
> > *   site at: http://www.seaint.org
> > ******* ****** ****** ****** ******* ****** ****** ********
> > 
> 
> 
> 
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> * 
> *   This email was sent to you via Structural Engineers 
> *   Association of Southern California (SEAOSC) server. To 
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
> *   send to the list is public domain and may be re-posted 
> *   without your permission. Make sure you visit our web 
> *   site at: http://www.seaint.org 
> ******* ****** ****** ****** ******* ****** ****** ******** 



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********