Which preposition to use with substructures

of Occurrences 10%

There is little doubt that the substructure of the great scene might have been very much simpler.

for Occurrences 1%

These considerations evidently precluded the construction of a central pier and double-armed swing bridge, and on the other hand they also precluded the construction of any solid masonry substructure for the turntable, either upon the quay or projected into the river.

Which preposition to use with  substructures