Spotlight Rigging
Tilt Wall and Steel Erection
The finished performing arts center is a highlight of Carlsbad, New Mexico. Its construction was complicated by buildings on three sides, including a high school just 15 feet away.
That was no small task for a crane whose crawler base measures 39 feet 1 inch long by 33 feet 10 inches wide, and whose counterweight tailswing is 28 feet seven inches.
One consideration was that the crane’ s counterweight tailswing would need to pass above the stage, which sat 12 feet above the seating area’ s floor, but the LR 1750 has only about 7 feet of clearance under its counterweights, so the crane would have to be raised about 6 feet above the floor.
“ We needed to pile up about 6 feet of dirt to provide an elevated and level surface above the sloping, already-poured finished floor,” said Ortiz.“ To make sure the floor stayed safe and the crane sat level, we topped the dirt with two layers of Sterling 700 mats, which also helped disperse ground-bearing pressure.”
Panel Placing
To erect each panel, the Alliance crew attached rigging to eight double picking points, and connected the rigging to a spreader suspended from the crane’ s load block.
Cordova explained,“ You could pick an 80-foot-tall panel pretty easily with 16 individual pick points, but we used eight double pick points instead. Doing that eliminated one tier of rigging, which saved us a lot of headroom and weight. As a result, we could boom down much farther to reach longer radii.”
As each tall panel around the stage was set into place, Alliance connected four temporary braces to hold the panel upright
After the LR 1750 had set three 120-foot-long trusses, the Magni telehandler and Liebherr LTR 1100 teleboom crawler crane set the rest of the structural steel, roof decking and catwalks from inside.
until it was locked into place permanently by structural steel.
Each of those extra-long braces for the tall walls weighed from 1,000 to 1,600 pounds, far too much to be manhandled.
So Alliance lifted each brace into position using the Magni RTH 6.35 rotating telehandler equipped with a winch.
As the LR 1750 picked and placed the concrete wall panels, the Magni rotating telehandler and the 110-ton capacity LTR 1100 teleboom crawler crane set perimeter structural steel and columns.
When panel placement and perimeter steel erection had been completed on all but the close-out panels, the LR 1750 crawled out of the building and set up on a crane path, from which it reached over the building to set three trusses, each 120 feet long and weighing 35,513 pounds with rigging.
When the three trusses were in place, the LTR 1100, the Magni RTH 6.35, and the Merlo P120.10 all worked to erect the rest of the structural steel, as well as roof decking, four catwalks and a grand stair.
After that, the interior fill was removed, the crane and telehandlers exited the building, and the final close-out panels were cast and lifted into place.
Alliance Riggers & Constructors’ success on this project earned the company a 2025 Project of the Year award from the Steel Erectors Association of America.
30
July 2025 • www. cranehotline. com