Transfer Force Question

[CDLD]

I've been trying to figure out the transfer forces in this braced bay of a 2 level & 2 bay building.

Does this make sense?

 

[Nick6781]

The column of this type of frame typically bends in double curvature, you should also check the shear force & moment within the column.

 

[Eng16080]

Are the braces sharing the lateral force evenly? I assume so, considering you note the force as plus or minus which I assume means one brace is in tension while the other is in compression?

Assuming the braces are sharing the lateral force equally (to be confirmed), it seems that your axial forces are too high.

 

[BAretired]

Not really.

Remove the diaphragm forces; they are not applied. Remove all the TF references. They make no sense.

The total applied loads are 2(24+44.5) = 137 kN. The horizontal component of each diagonal is 24 and 68.5 kN in upper and lower cross brace respectively.

There are some significant moments carried by the columns which are not shown on the sketch.

 

[CDLD]

I’ve shown additional loads on the outside of the frame ( which are girt reactions from the wind loads), maybe this wasn’t clear.

The total applied load is 96kN at roof level and 178 kN at the first storey.

There is 48 kN diaphragm and then 24kN X 2 wind loads from the girts at the roof.

There is 89 kN from the first storey diaphragm and then 44.5kN X 2 applied from the girts.

 

[Eng16080]

The forces seem more reasonable considering the applied loads are double what I originally thought. (It's confusing that the diaphragm and girt loads are exactly the same.) I agree with the comment above concerning the large moments acting on the columns, including at the bottom of the columns between the brace and base plate.

 

[CDLD]

Yes there are column moments, which was included in the frame design. Are the column moments really relevant to the question regarding transfer forces?