A lot more progress was made in May of 2001. After allowing the telescope
footings to cure for a couple of weeks, the forms were stripped off. Concrete
caps were poured atop the footings that will hold the steel columns that
support the rolloff roof rack. And the subfloor for the building that will
house the observing level was poured.
At the end of this bit of construction, you can finally begin to visualize
what the building is going to look like.
One of the mistakes made during the construction was that the access ramp
the excavator used to dig the basement hole was dug in the location where
we were to pour the footings for the telescope piers. These footings
should have been placed in undisturbed soil. In order to mitigate this
problem, we had to do a lot of extra work.
First, when the ramp was filled in, extra time was taken to drive the
heavy equipment over the area as each layer of dirt was dumped in, to
compact the soil as much as was practical. Now, with the footings poured,
we backfilled the hole surrounding the footings by hand, using a motorized
tamper. A few shovelfuls of earth were thrown in, wetted down, and then
tamped. All told, a day and a half was spent doing this; the footings
should be pretty solidly in place.
Once that was done, we excavated and laid rebar for the subfloor for the
observing building. Inch-thick slabs of styrofoam were placed around the
two telescope footings so that the subfloor slab would not contact these
footings. This will isolate the telescopes from building vibrations.
Simultaneously with the tamping operation, the electrician was out to
install the electrical panel in the basement. He put in a temporary
double-duplex outlet so we no longer had to run a couple of hundred
feet of extension cords to get electrical power to the building site.
This was a time of extensive planning work on my part. The steel frame
of the building would soon be erected on the subfloor slab, but the
vertical members at the north end of the building would be on top of
the stairwell walls 27" (69 cm) above the height of the slab. Additionally,
the vertical supports of the rolloff rack would be placed on their own
individual footings built on top of the basement roof.
The top of these three sets of columns all had to be exactly level with
one another; the beams on which the roof would roll would sit on top of
the columns.
First, the steelwork was sized by a structural engineer. The building
had to withstand 100 mph (160 km/hr) winds without significant flexure.
This isn't as easy as it sounds -- remember that the roof rolls off the
building, so there are no horizontal supports at the top of the walls
to hold the walls together (or apart, as the case may be).
It turned out that the skeleton of the building had to be built with
6" (15 cm) box beams, which have a wall thickness of 1/4" (6 mm).
I then sat down with a computer-aided drafting program and began to
design the steelwork that would frame the building, rolloff rack, and
roof. All of this steel had to be cut to exact lengths in Tucson;
we weren't going to be able to do this cutting on site! And it all
had to go together correctly the first time, or construction would
have to stop. I spent a lot of time learning to use the program, then
drawing, calculating, and redrawing until I was certain I had everything
exactly right. This included bracing in the corners at the top of the
walls and at the end of the roof rack to keep the building and the rack
square.
At the same time, I got the V-groove wheels on which the roof
would roll and designed brackets to attach them to the base of the roof;
then those brackets had to be fabricated. Then I had to size the angle
iron the wheels would roll on, and make sure that got onto the steel
order, too.
To keep the roof from blowing
away, C channel would be attached along the top of the building walls and
the bottom of the roof, arranged in an interlocking fashion so the
roof couldn't be lifted away. That all had to be designed in concert
with the roof eave detail so that everything would fit without interference.
I also had templates made for the bolt patterns for the baseplates
of each set of steel columns, and get the baseplates made. They would
be welded to the columns on site. The templates would also be used to
sink J-bolts into the concrete to bolt the columns down. You can see
the bolts sticking up out of the slab in the photo.
I also needed to provide
steel purlins to run horizontally between the columns of the building
skeleton; the building siding would attach to the purlins with screws.
There had to be a supply of steel rod to make cross-bracing for the
steel skeleton, and I had to get an entry door and the steel necessary
to frame it into the building's skeleton.
One more small detail: I had four square plates cut to enclose
the ends of the box beams that would form the top of the long walls and
the rolloff roof rack.
The wood rafters for the building's gable roof also had to be engineered;
in addition to holding up the roof, they had to provide support for hoists
which would be mounted in the ceiling of the observing building to help
assemble and disassemble telescopes, and move telescopes and mounts between
the basement and the observing floor.
And in my spare time, I needed to find a supplier for the residential steel
siding for the building and the roof.
As architect and general contractor, no one would be more relieved than
I when the building was finally erected. Every day there was a list of
things that needed to be done for the observatory project. One of the
primary problems was that this construction job was 175 miles from the
nearest construction supply store, so I had to make sure there were
enough supplies to keep things moving. Everything from nuts and bolts
to welding rods and wrenches had to be anticipated, procured, and brought
to the building site.