Highway bridge no. GRE-35-1199 was built in Greene county, Xenia, Ohio. The project was started on October 1990. During the bridge construction, performance of the spread footing foundation that was placed on the silty sand layer was recorded. Two kinds of instruments were installed to monitor the footing settlements and wall tilts.
A laboratory experiment was also conducted to determine settlements of the footings. Two alluminum models of footing at 1/50 and 1/60 of scale were tested in a centrifuge instrument. Beside that, the settlement of the footing was computed by using several methods.
Comparing the three methods of investigations, it appears that a centrifuge experiment is reliable to determine footing settlement. To predict the settlement of footing on silty sand layer, the general equation of settlement on an elastic foundation that was modified by Bowles is available. Several empirical equations, such as proposed by Terzaghi and Peck, Peck and Bazaraa, and D'Appolonia give more economical dimensions of the footings.