Eccentically Load Pad Footing Design
Eccentically Load Pad Footing Design
(OP)
In many design examples from the ACI318 Design Handbook (for footing strength design for Vu, Mu), the values of W or E is given in terms of a concentrically load P and subsequent q is derived (with proper load combinations) yielding a simple q=P/A. This q is then used to evaluate Vu and Mu and subsequent As and Av.
My question is how can I derive the q in these terms when I have an overturning moment at the footing and essentially an eccentric P? In some cases, applying 0.9D+E or 0.9D+1.6W, yields 'e' larger than the width of the footing (far beyond B/2) and yet q < Q allowable when evaluating stability of footing.
Should I just give up trying to figure out what q is and use whatever allowable Q given by the soil engineer or by code since it's a sin to go beyond the Q.
I'd greatly appreciate your thoughts.
My question is how can I derive the q in these terms when I have an overturning moment at the footing and essentially an eccentric P? In some cases, applying 0.9D+E or 0.9D+1.6W, yields 'e' larger than the width of the footing (far beyond B/2) and yet q < Q allowable when evaluating stability of footing.
Should I just give up trying to figure out what q is and use whatever allowable Q given by the soil engineer or by code since it's a sin to go beyond the Q.
I'd greatly appreciate your thoughts.





RE: Eccentically Load Pad Footing Design
Brad
RE: Eccentically Load Pad Footing Design
for calculating q you have to derive stress equation as following:
q=P/A+MyX/Iy+MxY/Ix. by using this equation you can calculate q in any point and can draw shear and moment diagrams. now you can design footing by calculated stresses. recently i have deisgned a footing which belongs to very big elevated tank and i had the same problem. please let me know if you could not solve your poblem.