12-29-2010, 10:23 AM
It appears that additional stories are being added to the originally constructed building. There are two scenarios.
One: The building is originally planned for the additional stories. In this case, the footings will be designed for the ultimate loading, and sized accordingly. So no change in footing should be required.
Second: The additional loading was not planned in the original design. This is very tricky. Now the whole original and new building configuration needs to be looked at in detail - the columns, connection design for different building response etc. As far as footings are concerned, you also now need to look at building construction. Were the original footings on undisturbed soil, or compacted soil. How much, and what type of disturbance was caused during original construction. etc.
Also, what type of underpinning will be needed during footing resizing. This is not a simple structural issue. Do get in touch with an experienced geotech engineer for advice.
One: The building is originally planned for the additional stories. In this case, the footings will be designed for the ultimate loading, and sized accordingly. So no change in footing should be required.
Second: The additional loading was not planned in the original design. This is very tricky. Now the whole original and new building configuration needs to be looked at in detail - the columns, connection design for different building response etc. As far as footings are concerned, you also now need to look at building construction. Were the original footings on undisturbed soil, or compacted soil. How much, and what type of disturbance was caused during original construction. etc.
Also, what type of underpinning will be needed during footing resizing. This is not a simple structural issue. Do get in touch with an experienced geotech engineer for advice.