Im working on an eccentric compound footing and am not sure whether i'm doing is right or wrong. I am in need of your guidance.
What we have is an 4x1.2 eccentric compound footing and have been loaded with an ulitmate (0.2mx0.3m) column load of 60KN on the left and 53KN on the right. Considering that the footing is 0.6m thk and that a concrete density of 24KN/m3 was used, the maximum pressure would be at roughly 120.5Kpa for the ultimate load. I am to check whether the footing design is sufficient enough to resist one way shear.
Here's what I did.
_______ d ____________________________
|[tab][tab]|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|[tab][tab]|
| 63KN|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|53KN|
|____|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab] |_____| 1.2meters
|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|
|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|
|____________________________________|
1. assume uniform maximum ultimate pressure (believe its more conservative); assume uniform 120.5Kpa at bottom footing
2. the highest shear force is located at d distance from the face of column load 63KN.
3. shear at d distance from the left column is (4.2-0.2-0.51) = 3.49
0.2 = column width
0.51 = 0.6 - 0.075-0.010-0.05 =0.510
cutting plane is facing the right side column
4. Vu at 3.49m = ((1.2)(120.5)(3.49)) - 53 = 451.66 KN
1.2 = width of the footing; multiplied to determine KN/m force
120.5 = scattered it all through out the entire section believed to be more conservative
53 = right side column force
5. shear force = Vu/ (phi x B x d) as per ACI code
451.66(1000)/ (0.85 x 1200 x 510) = 0.868
6. allowable shear force for 27.6 Mpa concrete = 0.875 Mpa
7. Compare 0.868 to 0.875 Vc>Vu
therefore safe?????
What are your thoughts? kindly write your comments below
What we have is an 4x1.2 eccentric compound footing and have been loaded with an ulitmate (0.2mx0.3m) column load of 60KN on the left and 53KN on the right. Considering that the footing is 0.6m thk and that a concrete density of 24KN/m3 was used, the maximum pressure would be at roughly 120.5Kpa for the ultimate load. I am to check whether the footing design is sufficient enough to resist one way shear.
Here's what I did.
4.2meters
|[tab][tab]|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|[tab][tab]|
| 63KN|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|53KN|
|____|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab] |_____| 1.2meters
|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|
|[tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab][tab]|
|____________________________________|
1. assume uniform maximum ultimate pressure (believe its more conservative); assume uniform 120.5Kpa at bottom footing
2. the highest shear force is located at d distance from the face of column load 63KN.
3. shear at d distance from the left column is (4.2-0.2-0.51) = 3.49
0.2 = column width
0.51 = 0.6 - 0.075-0.010-0.05 =0.510
cutting plane is facing the right side column
4. Vu at 3.49m = ((1.2)(120.5)(3.49)) - 53 = 451.66 KN
1.2 = width of the footing; multiplied to determine KN/m force
120.5 = scattered it all through out the entire section believed to be more conservative
53 = right side column force
5. shear force = Vu/ (phi x B x d) as per ACI code
451.66(1000)/ (0.85 x 1200 x 510) = 0.868
6. allowable shear force for 27.6 Mpa concrete = 0.875 Mpa
7. Compare 0.868 to 0.875 Vc>Vu
therefore safe?????
What are your thoughts? kindly write your comments below
