## How to calculate radius of gyration for a channel caps on I beam?

## How to calculate radius of gyration for a channel caps on I beam?

(OP)

For an I beam with a channel cap attached to compression flange, are we supposedly to use the same formular (F4-10) in page 16.1-51 of AISC-13th to calculate its radius of gyration?

If it is the same formular of (F4-10) as for an I beam without channel cap, then for item bfc in the formular, should we consider channel web as part of the flange components in flexural compression?

Seems AISC-13th does not put it clearly? Any thoughts?

Thanks for your help.

If it is the same formular of (F4-10) as for an I beam without channel cap, then for item bfc in the formular, should we consider channel web as part of the flange components in flexural compression?

Seems AISC-13th does not put it clearly? Any thoughts?

Thanks for your help.

## RE: How to calculate radius of gyration for a channel caps on I beam?

Hope it helps.

JWB

## RE: How to calculate radius of gyration for a channel caps on I beam?

Thank you for your response.

I know this description under Eq.(F4-11), but it does not make me clear, does this description mean that we only need consider the I beam flange and do not need take the web of the channel into consideration (which is attached to the I beam flange)? say if a S12x35 with a C8x11.5 cap, could you please show me how rt is calculated?

Thanks.

## RE: How to calculate radius of gyration for a channel caps on I beam?

## RE: How to calculate radius of gyration for a channel caps on I beam?

ash060,

firstly AISC-13th Table1-19 to Table1-20 only listed part of the W and S Beam Shapes with Cap Channels. For example, in these two tables, no S12x35 beam with Cap channel was listed.

secondly, in these two Tables, it only listed rx and ry, no rt value was listed.

## RE: How to calculate radius of gyration for a channel caps on I beam?

what I do is take the channel depth and set it as a top flange width, then determine an equivalent flange thickness based on the combined areas of the channel and beam top flange.

then run your calcs based on 1/3rd of the area above n.a. or whatever it is

## RE: How to calculate radius of gyration for a channel caps on I beam?

what I do is take the channel depth and set it as a top flange width, then determine an equivalent flange thickness based on the combined areas of the channel and beam top flange.

then run your calcs based on 1/3rd of the web area above n.a. or whatever it is

## RE: How to calculate radius of gyration for a channel caps on I beam?

See linked sketch. That's my interpretation of 1/3 the compression web area...

I'd use AutoCAD to draw the shapes, create a region, then use MASSPROPS command to give me I and A. r = sqrt(I/A)

I suppose one could break the shape into "simplified" rectangles and triangles and calculate I and A of the individual pieces. I use the phrase "simplified" lightly though!

## RE: How to calculate radius of gyration for a channel caps on I beam?

## RE: How to calculate radius of gyration for a channel caps on I beam?

PMR06,

Thank you very much. Your sketch descrcribed the procedure of how to calculate rt very clear.