Ship tracking showed 8.5kn when the power failed and slowing to 7.5kn just before impact. There are not many structures that could withstand that kind of direct impact.
Which option makes them calc out to 99.9% stress? Seriously, there was no extra capacity in those old panelized roofs. I probably get called out to develop a fix for a cracked 4x14 once a month here in the Southwest.
Take a look at the particular UL assembly you are using, the reductions should be outlined there. If you are using IBC prescriptive fire requirements, take a look at Table 721.1(2), foot note 'm'.
It looks the actual derailment caused the collapse of the single span and then dragging one of the derailed cars caught the ties on fire further across the bridge. Its a riveted steel bridge constructed in 1912.
I recently had Seattle require an SE for a TI, where we traditionally maintained a CE. They considered the stairs to be a 'major structural item'. The time to get reciprocity kinda threw a monkey wrench in things.
Part of me is glad that are starting to go this direction with the SE...
The NY times is reporting sensors and warning lights that would detect faulty AoA vanes are sold as extras. Neither of the crashed airplanes had them installed:
Link
On one of our 5 floor wood over 2 floor parking/podium projects, the contractor used a weighted base tower crane and then shored down the levels to foundation. Doubt that would work for a free standing tower crane to 12 floors. Can you attach the crane at the upper floors?