Civil Engineering/footing

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footing
footing  
QUESTION: Hi Sir,

Please have a look at the picture of steel mat footing before the concrete was poured. The steel mat below the column is not equally spread on both the sides of the column bottom. Steel is little more towards the right side of the column. Does this have any impact on the overall strength of the footing ? Concrete was filled for the whole area.  Need your suggestion

warm regards
Sudarshan

ANSWER: Dear Sudarshan

I dont know what was your actual design but this system will decrease the strength of the footing compared to a symetric geometry. You should adjust the column on center of footing. But if you had increased the dimension in one side no problem because the eccentricity defficiency will be balanced with dimension increased even if allowable stress method shows you the contrary. Actually the extreme strength of the structure will not be affected.

Regards
BEH

---------- FOLLOW-UP ----------

QUESTION: Hi Dear BEH, Thank you for your inputs.

There was no change in the design. The only deviation was that steel mat which is 5 feet x 5 feet as per the design was just happen to be placed slightly more towards the right side of the column center. As I mentioned, the overall footing dimension was as per the design in terms of length, width and height. Height of the Concrete was was also filled as per the design . Need your further comments on the overall strength of the column in this case. Does this have any negative impact ?

warm regards
Sudarshan

ANSWER: Dear Sudarshan

A accidental eccentric placement will lead to a unwanted moment. This will alter the footing strngth but not the column. After all a precise calculation will clear the situation. Normally this may not have impact. An enigineer has to check the calculations.

Regards
beh

---------- FOLLOW-UP ----------

QUESTION: Thanks for the clarification.

Just wondering what did you mean by 'unwanted moment' ?

Also since the over all reinforcement is same as per the design do you think that the strength of the footing will be reduced ?

warm regards,
Sudarshan

Answer
Dear Sudarshan

An accidental eccentrencity will cause an unwanted moment. If this eccentrencity occurs in the column axis with respect to the footing axis then an unwanted moment will occur which has to be managed, calculated and checked. I dont claim it being untolerable but it must be checked.

Regards
BEH

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