The Rail bridge was constructed of prefabricated spans, that lock together like toy railroad tracks and rest on pylons on top of high specialized bearings that stabilize movement and absorb stock.
The fire that oxidized and melted the steel of the RR tracks, burned for 5 to 7 hours and can be visually seen to ’drip” extending down the sides of at least two spans and one pylon, probably at points of connection. It is likely all three of these are badly damaged and the bearings on top of at least one pylon are fused. These will take months to replace, presuming there are spare spans and bearings at hand, as the Dutch company that ignored sanctions and colluded with the Russians to build the bridge, is unlikely to be able to do so again.
“Official” Russian sources are now saying they expect it to take 1 to 1.5 months to repair the RR bridge, that may be pushing it.