Unique Crane, Unique Location
Published in: Rocky Mountain Construction
Date: 9/12/2005
Jake’s Crane & Rigging employs street-legal 400-ton truck crane to erect tower gantry cranes for Hoover Dam Bypass bridge
Ever-increasing traffic congestion at Hoover Dam on the Colorado River southeast of Las Vegas, combined with post-9/11 security restrictions at the dam crossing, have led to development of the Hoover Dam Bypass Project to reroute US-93. A 3.5-mile corridor, beginning at milepost 2.2 in Clark County, Nev., crossing the Colorado River on a spectacular bridge some 1,500 feet downstream of the dam, and terminating near milepost 1.7 in Mohave County, Ariz., was ultimately selected.
The Arizona and Nevada approach segments of the project are now nearly complete, and last year construction of the 1,900-foot single-arch bridge itself was awarded to a joint venture of two Japanese firms, Obayashi Corp. and P.S. Mitsubishi Construction Co. Ltd., based on their A + B bid of $114 million.
As work got under way, Jake’s Crane & Rigging of Las Vegas was subcontracted to provide two tower cranes, one on each side of the gorge, to handle removal of material from the rock walls of the canyon to facilitate construction of the abutments and piers of the bridge, and to handle general chores in construction of the bridge.
Jake’s is well known for its use of Link-Belt tower gantry cranes with luffing booms — units which look like conventional lattice-boom cranes mounted atop tall steel towers and which have greater capacities and higher production capabilities than conventional horizontal boom tower cranes. These big TG cranes are common sights along the Las Vegas Strip, where most of the big mega-resorts have employed them during one phase of construction or another. But beyond the Las Vegas area, they are almost unknown in Mountain America. For the Hoover Dam Bypass bridge, Jake’s settled on a pair of 115-ton-capacity TG1900s, specifically refurbished for the project. The Nevada side TG1900 was also redesigned by Jake’s, employing a significantly larger operator’s station and state-of-the-art hydraulics that improve performance, ergonomics and visibility.
Erecting the TG1900s atop their towers on the Arizona and Nevada sides of the river presented something of a dilemma. Site accessibility was a problem in itself, further complicated by stringent traffic restrictions on the Nevada side that limited erection hours to 6:30 p.m. to 6:00 a.m., Mondays through Thursdays.
But Jake’s had the answer: the SL400, a street-legal 400-ton-capacity truck crane that has filled an important void in the company’s crane fleet. Designed, engineered and manufactured by Jake’s in conjunction with TransWorld Crane Co. of Minnesota, with which Jake’s has a longstanding relationship. The SL400 can perform tasks that were previously reserved for comparably sized crawler cranes. It effectively doubles the capacity of street-legal trucks cranes in many parts of the country.
On the Hoover Dam Bypass project, the mobility of the rubber-tired truck crane, as opposed to a crawler, lent itself to quick move-in over the narrow paved road from the staging area above to a cliff adjacent to where the tower gantry crane was erected. On the Nevada side particularly, traffic flow on the existing US-93 is a major financial and logistical issue. With a truck crane, Jake’s personnel were able to pause traffic and drive the SL400 from the staging area to the erection location, then allow traffic to resume.
A crawler crane would have been used for the erection chores on the Nevada side only if a viable option hadn’t been available. Assembly of the crawler crane components in the staging area, on a hairpin turn of US-93, would have blocked the highway for extended periods of time. A crawler crane would have required the use of plywood to protect the highway from damage. Further, the comparable crawler crane is about 10 feet wider than the truck crane (with its outriggers retracted), so the crawler would have taken up more of the roadway. And, with a crawler, the ground would have needed to be leveled with Type 2 soil on the cliff where the erection crane was positioned for the set. Finally, if a smaller crane had been employed, it would have required setting up on the US-93 hairpin curve, thus causing traffic delays and work stoppages. The SL400, then, was a real time- and inconvenience-saver.
Not only did the SL400 save time during move-in and move-out, it also provided the ability to assemble (and later, remove) the tower cranes in larger components, thus saving more time and labor — and more importantly, increasing jobsite safety.
The SL400 was positioned on the cliff 871 feet above the Colorado River for the Nevada side erection work and 957 feet above the river on the Arizona side.
“We drove the SL400 from the hairpin curve on the Nevada side across the dam to the Arizona side,” explains Mark Sovocool, Jake’s director of engineering and fabrication. “With outriggers, we were able to quickly level the SL400 with little ground preparation. The SL400 allowed us to set the tower cranes from an optimal point on the cliff outcropping. Without the SL400, we would have had to use our Liebherr LTM1300 or American 9490 300-ton truck crane to set the tower cranes.
“The LTM1300 and 9490 would be required to sit on the outside lane of the hairpin curve, closer to the tower, to pick the heavy pieces. This would have worsened the traffic flow, caused long traffic delays and prolonged work stoppages after each pick to allow traffic to pass.”
With the SL400, both tower cranes were set without incident — or undue traffic delays — and are now working as intended. Jake’s utilized five ironworkers and two heavy-duty repairmen in addition to the SL400 crew to erect the two TG1900s. The company is also providing three operators to operate and maintain the two tower cranes, which are currently running on two shifts.
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