Four Potain MDT tower cranes become integral part of famous Minneapolis bridge’s history — and also its structure

• 由于各种原因，传统的起重机解决方案已经被淘汰, restoration of the historic Minneapolis Third Avenue bridge called for an innovative new approach. 
• Potain MDT吊车安装在桥墩上, 因为传统的锚定解决方案需要太多的空间.
• The solution is working so well that the contractors plan to take it into consideration right from the start of future bridge projects — even where more typical solutions would fit.

When a host of awkward access and structural issues meant it would be impossible to adopt traditional go-to lifting solutions for the restoration of the downtown Minneapolis Third Avenue bridge, a handful of Potain topless cranes were the novel answer — and were literally built into its foundations to save the day.

这座具有重要历史意义的大桥上著名的s形曲线, 1918年开业, was the result of a design decision enforced by difficult foundation conditions resulting from its proximity to St. Anthony Falls spillway — two factors that made the use of tried-and-tested barge crane solutions a non-starter. And because the bridge was built using the old-fashioned Milan arch technique — a steel skeleton clad with concrete arches — the use of standard all-terrain or crawler cranes would have been too risky due to concerns over load-bearing and stress. Finally, the surrounding historic parkland and cobbled streets would have made delivering these cranes with a fleet of large trucks difficult for a variety of reasons.

Fortunately, 艾姆斯建筑公司的天才们, 桥梁工程总承包商, 和芬利工程集团, 艾姆斯的工程分包商, 想到了使用波特塔式起重机的好主意. 但他们典型的锚地对于可用空间来说太大, an even more innovative plan was dreamed up — the existing bridge piers would be used to support each crane.

“我们以前从未尝试过. 我们之间的互动非常紧密, Ames, 我们的起重机供应商, ALL塔式起重机,克雷格·芬利说, FINLEY工程集团首席工程师. “我们必须找到最安全的地方, 换句话说，最有效的方法就是把塔扔到桥墩上, 在箱形柱中嵌入一段桅杆, 然后像往常一样把塔吊的其余部分固定好.”

新的解决方案

计算出在5号码头安装MDT - 389, 再加上3台MDT 368塔式起重机安装在2号到4号桥墩上, 能否充分处理所需的负载, 然后，ALL工程师就可以向FINLEY提供每台起重机的反应情况, 最大允许移动量, 起重机锚凳图纸.

“Our main point of coordination with the FINLEY team was the interface where the equipment leaves the grillage and becomes the crane,山姆·莫耶解释道, ALL塔吊总经理.

Following thorough investigation into how the tower bases could be mounted without damaging the bridge due to the slight deflection of the crane as it handles a load, the column walls were reinforced so as to avoid undue stress on the towers or the pier walls. 甲板的一部分被移除, 柱子的空心部分一直延伸到基座, where a section of mast was installed before being secured with concrete and rebar.

今年1月，道斯·索具 & 起重机租赁公司建造了三艘MDT 368, MDT 389于8月加入其中. 作为MDT 368的继承者, 这被选择用于码头5由于它的新, improved Crane Control System (CCS) that ensures securer work around nearby obstructions by virtue of its Top Site geofencing function.

虽然这两种型号提供的最大潜在高度下钩超过300英尺, 在这个项目中，高度从72英尺到120英尺不等, 由于镐的水平性质. Likewise, 最大臂长可达246英尺, the MDT cranes in use in Minneapolis operate configured to avoid overlapping with their neighbors. 从他们的安全, 战略位置, 他们在桥面上搬运各种重型建筑材料, accompanied by a fleet of small Grove rough-terrain cranes that are light enough to avoid causing damage to the deck or bridge structure.

一座重建的桥

“对于组装这些装置的道斯团队，我怎么评价都不为过,Jerry Volz补充道, 艾姆斯建筑公司桥梁和结构副总裁. “Within days, and in the midst of a Minneapolis winter, the cranes were erected and operational.”

Once the Minneapolis Third Avenue bridge renovation is complete and the tower cranes have been disassembled, 每个部分都将在桥内不被看到, 成为它隐藏历史的另一部分. And their successful implementation on this project is likely to mean that more tower cranes will be employed as secret weapons in future — even where the traditional choices could be easily adopted.

“We quickly learned to love the towers’ ability to work 180° and out to the midpoint of the span — all of a sudden, 它改变了我们看待塔楼的方式,芬利透露道。. “这对我们来说是第一次，我做这个已经超过35年了. 在未来，我们将在第一轮谈判中提出这个想法. 这是个好主意，效果甚至比我们想象的还要好.”

“This project surely opened our eyes to the fact that Potain tower cranes can be even more advantageous than barge-mounted cranes. 我们肯定会在未来的项目中考虑到这一点，”Volz同意道.

CONTACT
Amy Crouse
Manitowoc
T +1 717 593 5960
amy.crouse@practicaldrilling.com