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RE: Closer look to Building rigid moment frame Design

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If you are using MBMA as the design code, I would chose MBMA 96 to take advantage of design improvements since 86.  Snow drift design has changed among other things.  One of the Appendices (sp) contains recommend drift requirements.  H/375 sounds heavy but could be required due to details for wall connections.  Other things such as cranes, etc. can also affect the required drift critreia.  To help lighten frames to handle h/375 you might want to fix the top connection on the interior columns... another possibility is to fix the base of the columns (frame $$ down, foundation $$ up).
 
L/180 looks reasonable as long as slope is greater than +- 1/2:12 or 1:12.
 
Might be more economical if owner allows 54m w/ 2 columns i.e., 3 modules @ 18m or even 3 Columns, 4 modules @ 13.5m.
 
If snow loads exist then consider snow loads along edge of monitor building.
 
Technically you should use the following combinations for ASD design (per MBMA 96):
1) Dead + Live
2) Dead + Snow
3) Dead + Auxiliary (i.e., crane loads, etc.)
4) Dead + Wind, Stress increase allowed... be sure to consider wind in each direction.
5) Dead + %Snow + Auxiliary
6) Dead + 1/2 Wind + Auxiliary, Stress increase allowed
7) Dead + Snow + 1/2 Wind, Stress increase allowed
8) Dead + 1/2 Snow + Wind, Stress increase allowed
9 & 10) Seismic Load combinations if applicable (sounds like no considerable seismic on this building)
 
Typically for sidesway deflection calcs involving wind use a 10 yr wind (i.e. 0.75 * 50 yr Wind Pressure).
 
HTH
Greg Effland, P.E.
 
 
 -----Original Message-----
From: namvy [mailto:namvy(--nospam--at)hcm.vnn.vn]
Sent: Monday, May 07, 2001 12:57 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Closer look to Building rigid moment frame Design

 
 Correct our own mistakes in :
 
- Load comb: ASD-89 (  I decreased load by 33%)
(DL + LL)
(DL + WL)*0.75
your reply are all highly expected
I'm waiting for Any comments or advice from you on documents possible to archive through the internet, specific websites also??
thanks
----- Original Message -----
From: namvy
To: Sent: May 07, 2001 5:29 AM
Subject: Closer look to Building rigid moment frame Design


It will be my deep gratitude if can anyone briefly show me the followings.:
 
Project ongoing:
Building rigid moment frame:(tapered sect. column+rafter)
 
- width : 54m w/ mid span column , i.e.. 27+27 = 54m,
(assumed this mid span col is pinned connection to rafter at ridge)
-bays :           8@9 m
- EaveHeight: 8m
- Monitor roof along Bldg length
- block works side walls ( as per esthetics architectural req.)
- 2 gabble-end-wall frame will be a RC casted.
 
I am considering the MBMA 86 as governing design code.
- lateral deflection at eaveheight : I am taking account  as = EH /375 ( due to block works attch to steel  )
- vert. deflection of rafter : Span / 180 = 27000/180
- Load comb: ASD-89 (  I decreased load by 33%)
(DL + LL)*0.75
(DL + WL)*0.75
no seismic load applied
 
I spent a certain time on it and thought i just need your valuable experienced specialist out there.
Any different advice also be appreciated.
Thanks and regards
Ce. NAM