8. There Was a Temporary Gap in the Hell Gate Bridge
When it came time to close the arch of the bridge during construction, there was a 5/16th of an inch gap at the apex. Lindenthal employed 3000 ton hydraulic jacks, considered to be the most powerful in existence, to get the job done. Several massive gusset plates breaking girders were also used to secure the two sections of the arch together permanently at a staggering 280 feet above the water. The two-hinged arch actually appears to be hingeless because the design called for the hinges to be obscured by steel housing nestled close to pylons.
The hinge design was essential so that the pylons could take on some of the thrust of the chords not sending it into the ground as in other hingeless bridge designs. Even though it appears that the both upper and lower chords are exerting the thrust, in reality it is only the lower chord.