COLUMN DESIGN
COLUMN DESIGN
(OP)
In interior column design, should we consider moments from the beams (four sides) as we do for corner columns (biaxial bending) or interior columns are only subjected to axial reactions from beams?
How do we differentiate the load transfer of interior columns to exteriors as they commonly support only three beams; two being collinear and the other is perpendicular to the two?
Any reference showing the analysis of such load transfer will be a great help.
How do we differentiate the load transfer of interior columns to exteriors as they commonly support only three beams; two being collinear and the other is perpendicular to the two?
Any reference showing the analysis of such load transfer will be a great help.






RE: COLUMN DESIGN
Mike McCann, PE, SE (WA)
RE: COLUMN DESIGN
Thank you so much for giving some insight on that.
I am new to actual structural design.
RE: COLUMN DESIGN
RE: COLUMN DESIGN
RE: COLUMN DESIGN
So even with interior columns, you would have situations where alternative (odd, even, adjacent) bays are loaded, causing bending moments in those interior columns.
So it isn't just axial. ASCE 7 requires this along with other codes.
As far as references to help you understand the analysis of such frames I can't help you much. The analysis we would use would simply involve a 3D frame model using
a structural program (RISA, RAM, ROBOT, etc.) and separate the floor live loads into different cases so you can apply live loads in various patterns.
I have typically alternated about 75% of the total live loads on floors (i.e. 25%LL is uniform and constant).
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RE: COLUMN DESIGN
I am only using staad pro to cross-check my spreadsheet for finding moments and reactions on continuous beams and 2D frames. I am going to practice making some simple 3D to see the results.
Attached pic is my spreadsheet I am used to getting moments and reactions. I purposely put two bending moment signs which indicate that the bending moments from Beam A and B at the support (column) cancel out each other. So, my assumption has usually been "no dead load moment transferred to interior supports".
I am more than happy to be corrected on this particular analysis.
RE: COLUMN DESIGN
For 3D model applications - it seems to me that the code is somewhat silent on how to "alternate" the live loads - do the patterns run in strips across the building or do you use a checkerboard pattern?
For one-way continuous beam designs the correct patterns to use are:
Odd Spans only
Even Spans only
Adjacent spans (1) - i.e. spans 1, 2, 3, 5, 6, 8, etc.
Adjacent spans (2) - i.e. spans 2, 3, 5, 7, 8, 10, etc.
Adjacent spans (3) - i.e. spans 1, 3, 4, 6, 8, 9, etc.
Full uniform live load
The odd and even span arrangements get you the maximum positive moments
The adjacent span arrangements get you the maximum negative moments.
The full uniform and some of the adjacent arragements get you the maximum shears.
How you take the above arrangements and convert to a 3D bay system takes some thinking and experimenting.
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RE: COLUMN DESIGN
I am from Timor-Leste where English design books are not available. I finished my study in the Philippines and have returned home a year ago. Luckily few E-books are available with limited pages though.
I appreciate very much on the insight you share to help me doing a bit better than yesterday.