There seems to be real interest in yesterday's post so here comes some more.
A load test was carried out using gritting lorries to apply 518 tonnes to one lane over half the length of the bridge. That's almost exactly 1 tonne per m. That is just a little more than the code required in the 1960s and a half span is the worst possible. The bridge posted these two pictures.
This picture of the load in place was also posted by the Forth Road Bridge (at https://www.forthroadbridge.org/bridge-closure/images/) It's worth watching that, there is a lot to see and pictures accumulating daily.
There is more to see there than was mentioned in the Tweet so I downloaded and drew over the edges to produce this
This isn't absolutely correct, but I think it shows how the main span has gone up at the far end as well as down and how the side spans have been lifted. I think that needs explaining too so here is a sketch.
The grey lines show the original shape and the black the deflected shape. The extra tension in the cable pulls the towers closer together. That lifts the side span and allows the main span to drop. But the load at one side also causes it to sway that way and results in the deflection which is looks like a full parapet height. Since this is a cycle lane, I guess that must be 1.8m.