When Cranes Fly
When New York City space constraints limit crane construction options, set your sights sky-high By Jon Skinner, PE
A monumental crane lift to support Tiffany & Co.’s iconic flagship retail store renovation took place to expand the landmark 1940 Art Moderne building on Fifth Avenue. The luxury brand, currently under - going a holistic, multi-year upgrade, sought to replace a former 1980s vertical rooftop expansion that housed three levels of office space with a new tri-story modern addition. Designed with double-height and column-free spaces wrapped in two different glass facades, the newly constructed addition would create more interest from the street while maintaining energy efficiency. However, constructing this in the heart of the congested City would require innovative solutions to configure crane space that would not take a large footprint and minimize road closures for the duration of the build. Taking space, time, and budget into consideration, McLaren Engineering Group’s construction team turned to unconventional methods of crane engineering to figure out how to work within NYC’s tight building constraints. The solution was as iconic as the retail brand itself: a crane would pick up another crane and fly it atop the Tiffany & Co. building in the heart of Midtown where it would commence work on the build. The lift of an LTM 1130 mobile crane was engineered onto the roof of Tiffany’s utilizing a giant 500-ton Liebherr LTM 1500 crane. The fully assembled LTM 1500 (utilizing the y-guy superlift kit) required eight trucks delivering over 363,800 lbs of counterweight. As a result, McLaren also provided the crane engineering for a Tadano TR450XL that assisted in putting the LTM 1500 together. With speed and cost in mind, the team provided crane plans, permitting, and the structural engi - neering necessary for the lift itself and to support the crane once placed. The LTM 1130 weighing approximately 205,000 lbs, fully counter - weighted, was lifted seven stories over the streets of Manhattan to begin work on the new three-story (8th, 9th, and 10th-floor) glass-walled ad - dition that sits atop the existing historic limestone-and-granite building. During the pre-bid process, McLaren worked with the contractor, Or - ange County Ironworks (OCI) vetting a geometry and capacity checks concept for the cranes and then a preliminary look into building reserve capacity. This solution saved several months on the project schedule, allowing OCI to work around the clock through Holiday Embargo. New York City prohibits cranes and work in the streets in most areas starting the week before Thanksgiving until after the beginning of the new year. Getting the rooftop crane in place allowed Orange County Ironworks to continue uninterrupted through the holidays, saving time and millions of dollars on the project. This heavy lift required the construction engineering team to put to - gether a total of 7 different crane plans (5 CN Applications with NYC DOB) for the project, design rigging to lift the crane, design rooftop
dunnage to support the crane on the roof, and to analyze the building for imposed loads. This additionally led to reinforcement design of a couple of existing building columns. Construction topped out in March of 2021, and the smaller crane has since been safely returned to the ground. Tiffany & Co. has temporarily relocated its flagship to an adjacent storefront at 6 East 57th Street until completion of the construction project, which is planned for Spring 2022. JON SKINNER, PE, McLaren Engineering Group Vice President of Construction Engineering, is an nationwide leader revolutionizing the industry by providing specialized services and innovative solutions to assist developers, contractors, fabricators, and erectors from design to completion. From crane engineering services to construction support, his team determines optimal and cost-effective means and methods for building construction, provides the design of temporary support, bracing, and construction sequencing, the conventional design of steel structures and connections, the design of delegated primary and secondary structural elements and everything in between.
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csengineermag.com
DECEMBER 2021
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