Britannia bridge after rebuilding. Notice that the stone towers have been retained, and that the tubular structure has been replaced by a double-deck arrangement for trains and cars; the extra loads are carried to the towers just above the water level by the newly installed arches, fixed to the base of the original stone towers.
The under-deck arch support solution that we see in the new bridge was not possible in the original design of the bridge because of the clear height requirement for sailboats, demanded by the Britsih Admiralty.
Admitting uncertainty in a very public way:The towers were constructed high above the bridge-deck level, to allow the installation of suspension chains, if necessary.
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