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RE: "Big Column and small beam" Rule

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Yes I meant "strong column and weak beam". I am a little rusty on structural 
 systems, when analyzing Seismic loads, does this rule apply when you have 
a rigid diaphragm?

Thanks in advance.

Alex Nacionales
Vancouver, BC

-----Original Message-----
From: seaint-seaosc(--nospam--at)mail-list.com [mailto:seaint-seaosc(--nospam--at)mail-list.com] On 
Behalf Of Rizwan Mirza Sent: March 24, 2015 7:23 PM
To: seaint-seaosc(--nospam--at)mail-list.com
Subject: Re: [SEAINT-SEAOSC] "Big Column and small beam" Rule

In my humble opinion, the rule for seismic design is not big column and small 
 beam; it is strong column and weak beam. There is a difference between the 
 two.The former deals with relative stiffness while the latter with relative 
 strength.

Relative Stiffness
If you increase the stiffness of column, its capacity to restrain the beam 
end, against rotation, increases and under the gravity loading, the support 
 moments of beam increase while the span moment falls. There is no rule that 
 governs this stiffness ratio. It is, however, true that increasing the 
column stiffness has a snowball effect and the support moment may in fact 
become so large that it actually 'requires' a columns with large depth for 
strength reasons.

Relative Capacity
The strong column and weak beam theory is based on the location of hinges 
when the flexural capacities of the various members, at the connections, are 
 exhausted, as they ultimately would under seismic action. The intent of 
good design is to ensure that the hinges are formed in beams and not in 
columns. The former does not form a mechanism , leading to a collapse, while 
the

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