Today's heavy-lifting toolbox is diverse. Technology is constantly improving, making alternative lifting devices more feasible for large-scale modular construction. Below is a sampling of equipment riggers employ on these projects.
PLATFORM TRAILERS: Calling this heavy-haul device a trailer "is selling it very short—it really is a rigging tool," says Jeff Latture, senior vice president at Barnhart Crane & Rigging. Whatever you call them, these modular machines come at a steep cost. Many are imported from Germany, with prices starting at $45,000 per axle for a trailer that requires a prime mover and more than $120,000 per axle for a self-propelled unit. Introduced in the late 1980s, the latest generation of platform trailers features wider axle spacings to allow riggers to transport oversized objects by road with fewer permits. "It is one of the great tools of the last 15 to 20 years," Latture says. "If you didn't have a platform trailer, you couldn't do modular construction."
LIFTING BEAMS: Although not necessarily new to the industry, the concept of using cantilevered lifting beams is finding more widespread use as construction sites grow more complex and require creative solutions to move heavy loads into structures that are difficult to access. These under-the-hook lifting devices typically have counterweights at one end and a single hook at the other end. Riggers carefully balance the beam like a set of old-fashioned scales to make sure the device stays under control at all times as they maneuver it with the crane's boom. So-called "tip sticks" take the idea to another level by allowing riggers, using hoists and tackle, to change the center of gravity of the assembly so they can pivot the load into position.
SUPERCRANES: Marine cranes have long been able to lift thousands of tons, but not too long ago, a construction crane that could lift that much weight was unheard of. Over the past decade, however, crane capacities have climbed rapidly, enabling larger modular project lifts on land. Built by Bigge Crane & Rigging Co. and owned by CB&I, two of the world's largest heavy lifters—each has a maximum rating of about 7,500 tons and costs around $50 million—are muscling modules at the V.C. Summer and Vogtle nuclear plants in the southeastern U.S. Shown here is Mammoet's PTC-140/200, a 3,500-ton rig that stands roughly twice as tall as the Statue of Liberty.
STRAND JACKS: They are not just for post-tensioning anymore. Riggers use these highly versatile devices to lift, pull and slide heavy objects when a conventional crane is not feasible. Often placed atop towers, gantries or derricks, the jacks use hydraulic power to grab a set of cables to place bulky loads within millimeters of precision. The downside? Strand jacks sometimes need to be overhauled after a few uses, so manufacturers are designing new components that can be switched out in the field. Next month, crews building the new Milton-Madison Bridge across the Ohio River plan to slide the entire 2,400-ft-long truss into place using eight 360-ton strand jacks.