Temporary, Trailered Tower atop Precast Garage

[azcats]

I have an existing, precast concrete parking garage that was built in the late 70's. Two parking levels above grade. Double Tees, spandrel beams, beams & columns w/ precast shear walls. It appears to be generally in good condition and there is no snow/salt/ice here. It is also unoccupied, as the site is under complete redevelopment.

Telecom company would like to place a temporary (likely a couple years though, so semi-permanent), tower site atop this garage. It's a guyed, telescopic tower that rides in on a 2 axle trailer. Tip the tower up, and extend it vertically and guy it back to the base level. Trailer weighs about 12,000 lbs. and also has 4 outriggers in addition to the tires.

Still awaiting drawings on the garage, but I'm digging into the loading and seeing what kind of reactions I'm getting.

Normally, when these setups are installed on grade the bring in concrete blocks for anchoring the guys. At first glance, I'm not so keen on that.

Anyway, I don't have a lot of experience with precast, but it appears that depending on the governing code the live load ranges from 40 to 50 psf and the concentrated tire loads are from 2000 to 3000 lbs over a 4.5" square.

Any of you with precast experience have any initial words of advice or caution? I'll have some leeway with regard to placement of the trailer and guys. Also wondering about anchoring the guys to existing columns that poke into the top level. Initial worries are loading just getting trailer into place with tire loads and then in the final condition how the guy forces are resolved and then combined with the weight for some pretty large reactions at the trailer & outriggers.

Thoughts welcome. I'll update as I move thru analysis.

 

[dhengr]

Azcats:
Take all the junk, tool boxes, control panels, etc. off the trailer and save a few thousand pounds. Take the support frame and tower off the trailer and bolt them to a couple 24’ long WF’s, with some cross bracing, which will distribute the load (maybe WF’s = trailer wt.) over three or four double tees. Study placing the stl. beams directly over a conc. beam line or over top of a column, for best weight distrib. to member, or members with most reserve cap’y. Counter weights may not be so bad, 3 or 4 bolted together, the weight of a car, in one parking space. Broken down to 3 or 4 makes them more transportable.