Stability of Footing with 2 columns

[nrjdjjs]

Refer to the attached image. Column 107 has no load and 1035 has a 200 kN load. There are no external applied shears or moments on either of the columns. The footing is 0.7 m thick and its top is at grade. What is the correct way to calculate overturning and resisting moments in this footing?

 

[JoshPlumSE]

First, I tend to assume that the footing is rigid. Which means I convert the loads / moments to an equivalent load and moment at the centroid of the footing. At that point, I use the same basic calculations that we use to determine the soil bearing and Overturning / Resisting factors that we use for a single spread footing.

 

[nrjdjjs]

200 Kip load on column 1035 is a downward acting compressive load.
JoshPlumSE - Thank you for your response.
So the overturning moment would be 200*2.25 = 450 kN m
Resisting Moment from the would be (200)*0.5*6.5 = 650 kN m if footing weight is ignored?

 

[HTURKAK]

Refer to the attached image. Column 107 has no load and 1035 has a 200 kN load. There are no external applied shears or moments on either of the columns. The footing is 0.7 m thick and its top is at grade. What is the correct way to calculate overturning and resisting moments in this footing?

The size of the ftg 2.3 X 6.5 m and if the column 107 has no load , you do not need combined footing . If the attached picture is scaled , the column size should be around 1000X 1000 mm , and this column size is pretty sturdy for 200 kN load and meaningless for Column 107 which has no load.
I will suggest you ,
-provide spread ftg 2.3X2.3 m for column 1035
- provide spread ftg 1.5X1.5 m for column 107 and reduce the size around 400X400 mm ,

In your case , since the columns have not moment and shear , OT moment will not develop. The design moment , which would be calculated acc. to the soil stress distribution would be resisted by internal resisting moment of the RC footing section.