Use of rigging triangle eases repeated handoffs of concrete bridge beams

May 12, 2020
Use of rigging triangle eases repeated handoffs of steel bridge beams

When railroad tracks through Columbus, Indiana, were upgraded to accommodate larger and faster trains, it was a boon for the local economy, but created a challenge for area motorists. Train traffic was expected to triple, with trains also becoming significantly longer. The result would be frequent delays for car travelers at a major intersection connecting the east and west sides of the city.

The solution was to construct a new vehicle overpass, elevated 23 ft above the railroad tracks and nearby Highway 11.

To set the concrete beams for the new bridge, Milestone Construction chose Central Rent-A-Crane, a member of the ALL Family of Companies, to provide lift equipment for the work. A total of four cranes were needed to complete setting the beams—two for the part of the bridge over the railroad tracks and two for the part over Highway 11. Two days were scheduled for each part, for a total of four days.

Each beam weighed 160,000 lb and was 131 ft long. A total of 26 beams were needed to complete both parts of the job, and in each of those 26 lifts, cranes were to hand off the beam to one another. A little-used rigging tool would become crucial to accomplishing the task.

On days one and two, for setting beams over the railroad tracks, Central provided a 900-USt Liebherr LTM 1750-9.1 and a 600-USt Liebherr LTM 1500-8.1. “Milestone wanted to perform these lifts without having to move the crane locations,” said Lynn Johnson, special projects estimator for Central Rent-A-Crane. “That meant we needed the muscle these two units could provide at a wider lift radius.” Using smaller units would have added a day for teardown and reassembly to reposition the cranes.

The LTM 1500 was positioned above the railroad tracks on the bridge embankment. The LTM 1750 was below, on the ground by the tracks. The LTM 1750 was configured with 167.5 ft of main boom at 45.6 degrees, guyed with a Y-frame at 10 degrees. It had a 116-ft lift radius at 360 degrees and 450,000 lb of counterweights. The LTM 1500 was configured with 121 ft of main boom at 54.2 degrees, a 71-ft lift radius, and 231,500 lb of counterweight. Both cranes had outriggers at 100%.

Central provided a 600-USt Liebherr LTM 1500-8.1 and a 500-USt Liebherr LTM 1400-7.1

Picking the beams required an unusual rigging approach that was aided by a handoff triangle, a relatively small steel triangle that is specially designed to make handoffs between cranes faster and easier without compromising safety.

The handoff triangle rented from LGH Industrial is approximately 26 in. across. During a beam lift, the first point of the triangle faces down and is connected to the beam, the second point is where the first crane attaches, and the third point is left open for the second crane to eventually connect.

The LTM 1750 moved the beam approximately 50 ft over the railroad tracks below. The second crane, the LTM 1500, then swung its boom into position. A Milestone worker was lifted in a 60-ft man basket and connected the second crane to the triangle, disconnecting the first crane. The first crane, once free of the beam, swung back to the closest point of the beam, picked it, and the two cranes worked in tandem to set the beam in position for the bridge.

Although it required many steps and intricate planning, the use of the triangle significantly reduced lift times. It is how Central was able to place more than two dozen precast concrete beams in just four days.

The process, except for the use of the triangle, was repeated on the third and fourth days, when beams were set above Highway 11. These picks required a smaller lift radius, allowing the use of smaller-capacity cranes. Milestone provided their own Link-Belt 218 HSL with a 110-ton capacity, configured with 80 ft of main boom and a 20-ft lift radius. Central supplied a 220-USt Liebherr LTM 1200-5.1 with 88 ft of main boom, a 40-ft lift radius, and 158,700 lb of counterweight.  

The use of handoff triangles is still relatively novel. Johnson says this project is just the third time in his 25+ year career he has used them.

The LTM 1500 moved the beam approximately 50 ft over the railroad tracks below

Editor's Note: Scranton Gillette Communications and the SGC Infrastructure Group are not liable for the accuracy, efficacy and validity of the claims made in this piece. The views expressed in this content do not reflect the position of the Roads & Bridges' Editorial Team.

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