[=FPS=Cutlass]

Bridge are civilian constructions. I think that a 250 kg bomb should destroy all bridge types in a direct hit.
The most important is to prevent blast damage for light and medium bomb (50, 100, 250 kg, 500 kg)

The Photo 3.45. The Result of the bombing the railroad tracks hugh-explosive mi авиабомбами FAB-250. The Amunition has fallen into full tilt of the bridge. Kareliskiy pe-решеек, May 1940 (the photo from meeting document RGAE).

But here is as specialists described the result of the using FAB-250 on bridge the most simplest design . Aviabomba burst (the photo 3.45) in 4 m from corner stone vertical abutment railway bridge in point, marked on picture v2 , and in two metres from farm D on the other hand bridge. The Blast has formed the crater by diameter 9 m and depth 1,4 m, has wrested two stairwells wooden выстилки пешеходной of the track, laid on beem с-с , and has damaged the beem C . Meantime prevent motion a train not to manage, and railway bridge could function without correction of the ways .