STRAND JACKS

摘要

Strand jacks 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.