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RE: "Big Column and small beam" Rule

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Thank You for your comments. It is very enlightening. I have a follow up 
question. If the beam is connected to a RC slab,  then part of the slab width 
 could be considered as part of the beam- ( T-beam or half T-beam for exterior 
 frames). How could a hinge form in the beam with the RC slab connected to 

Thanks again.

Alex Nacionales
Vancouver, BC

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Rizwan Mirza Sent: March 28, 2015 8:14 AM
To: seaint-seaosc(--nospam--at)
Subject: Re: [SEAINT-SEAOSC] "Big Column and small beam" Rule

Following is my humble opinion:

a) The presence of a strong diaphragm just means that all members of the 
vertical structural sub-system (columns and shear walls) would undergo the 
same deformation in the horizontal plane (the plane of the slab, or the rigid 
 diaphragm, as it would be called). The result would be that the lateral 
load would be resisted by the various members of the vertical structural 
sub-system in the proportion of their stiffness. The principle that we must 
have strong columns and weak beams does not flow from here and has no relation 
to the presence or absence of a rigid diaphragm.

b) For gravity loads, if you increase the stiffness of the columns the support 
 moments would increase while the span moments would decrease. This would 
continue to happen till such time that the support moments are equal to w 
L^2/12. But at this value of moment, the columns is likely to have a fairly 
 large cross-sectional depth for resisting the applicable bending moments.

c) Suppose you do do not wish to achieve such large column cross-sections, 
you would have end-moments less than w L^2/12, as computed from elastic 

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