Need a book? Engineering books recommendations...

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

Re: Base plate design forces in SDC D

[Subject Prev][Subject Next][Thread Prev][Thread Next]

Ravi,

Some quick thoughts.  Unless your piperack is over 65 feet tall I would use an OMF with R = 3.5 (see footnote c) for the transverse direction and an OCBF with R = 3.25 (see footnote b) in the longitudinal direction.  Typically the R = 1.0 for connection design is one method of complying with the code where you are allowed to design for "The maximum load effect, indicated by analysis that can be transferred to the ....".  The thought being that the largest load that can be transferred by the system is the largest load that can be delivered to the structure (i.e. the largest seismic load being R = 1.0).

Thomas Hunt, S.E.
Fluor



"Vasu, Ravi" <Ravi.Vasu(--nospam--at)jacobs.com>
01/07/2010 01:14 PM
Please respond to seaint
To
<seaint(--nospam--at)seaint.org>
cc
Subject
Base plate design forces in SDC D





List,

I am designing a Piperack(R = 2.5) base plate & Anchor bolt in SDC 'D'.  Per AISC 341-05, section 8.5(given below), I am getting very large design forces  

I am not sure whether this is the general procedure, other engineers follow.

Section 8.5 a.  - AXIAL FORCE

 Need to follow section 8.3, that is, the force should be lesser of the following:

 a.  amplified seismic load comb. & other load comb per code.

 b.  1.1Ry*(Area of column)

 Section 8.5 b.  - SHEAR

 The critical force should be lesser of the following:

 a.  amplified seismic load comb. & other load comb per code.

 b.  1.1Ry*(Area of column)/H.    

 H = Height above & below of the column considered.

 Section 8.5 c.  - Flexural Strength  (for column fixed base?)

The critical force should be lesser of the following:

 a.  amplified seismic load comb. & other load comb per code.

 b.  1.1/1.5Ry*(Fy * Zx)    

 

Per discussion with AISC, I am using R = 1 for beam moment connection & comparing with 1.1RyFy*Z (design per AISC design guide # 4) to get the design force.

I think for other connections(base plate/anchor bolt/bracing) also,  using R =1  gives big forces but not as huge as section 8.5.

Can you pl. give any input in this design forces?

Thanks

 

Ravi Vasu

 

------------------------------------------------------------
The information transmitted is intended only for the person 
or entity to which it is addressed and may contain 
proprietary, business-confidential and/or privileged material.  
If you are not the intended recipient of this message you are 
hereby notified that any use, review, retransmission, dissemination, 
distribution, reproduction or any action taken in reliance upon 
this message is prohibited. If you received this in error, please 
contact the sender and delete the material from any computer.  

Any views expressed in this message are those of the individual 
sender and may not necessarily reflect the views of the company.  
------------------------------------------------------------