a reply to: JBurns
In my lifetime, I never thought I would hear someone say..."Now don't bend the building!"
And...they weren't referring to the Hush House, because those things are built like fortresses!
You see, I worked for an aerospace fabricator in Utah during the 80's and we won several contracts to build Hush Houses for the Air Force. The hush
house design (at that time) required the the above grade portion of the actual test facility to be erected with a series of single transverse steel
beams, over and under which a very specialized skin would be attached with this exotic insulation between the two layers. So, it looked like a series
of croquet wickets, all single steel members from end to end. The ones we built were about 120' wide and about 30' tall. I want to say they were
about 120' long too. The buildings had to withstand incredible forces.
So the challenge we had to figure out was how to get straight wide-flange steel beam bent into a giant upside down "U" shape. A beam which would be
120' long with a 30' arch in it. BTW...this arch I refer to is known as "camber" in steel terms. Then we had to figure out how to get this monstrous
piece of steel from Utah all the way to the base (rinse and repeat about 12 times for each building). The first one we did was at Minot AFB in Minot
Anyway, in order to induce the camber to these steel beams we had to bend them, but how do you "bend" something so big? The Engineering teams worked
with the fabrication teams and we figured out a way to use structure of one of the big fabrication shops as a counter-force. We'd roll these 20 ton
beams into the facility on these specially made dollies and chain the ends down to specially made anchor points on the floor. Then we used a series
of overhead cranes and chainfalls to start applying tension to points along the beam at different angles. As this was happening we'd apply heat along
the top flange of the beam so it would stretch. The process took a couple weeks for each of the first ones (our times improved as we learned tricks
along the way). There was so much force involved we actually had to reinforce the fabrication shop structure (I say "shop", but it was really more
like a plant) so we wouldn't crush the building from the inside. This resulted in management issuing us the directive to not "bend the building" in
the process of manufacturing these support members.
(Note - They never knew how close we actually came to really doing it! There were times when you could put a 6 foot level or straight edge on the
vertical columns of the building and actually see the building squatting down under the force!!)
One of the tricky parts was, as the camber was brought into the beam the end points (base plates) moved inward along the floor, so our anchor points
on the floor had to constantly move as the beam arched. So this meant the forces across the counter-force structure (our shop) were constantly moving
and changing. Once we got some about 15' of camber into the steel we could begin using these giant hydraulic jacks to push the ends toward the
middle, this in conjunction with the overhead cranes pulling upward (at multiple angles).
It was a pretty interesting process, and not one a lot of people in the world could have pulled off.
Transporting these beams on the custom made trailers from Utah to places like Minot was a whole other adventure. Probably should save that one for
edit on 3/29/2019 by Flyingclaydisk because: (no reason given)
edit on 3/29/2019 by Flyingclaydisk because: (no reason