Steel in the News
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Posted by Tasha Weiss on September 6, 2013 at 5:25 PM.
An internal steel mast, designed by Pennoni Associates structural engineers, provides the lateral support for the tallest Lego structure ever built. The 11-story creation stands at 112 ft, 11 3/4 in. high and is made up of more than 500,000 interlocking plastic bricks, which were assembled by students of Delaware’s Red Clay School District. Contractors volunteered to place the segments together last month using cranes and lifts. (Click on the photo for a full view of the structure.) Photos: Courtesy of Pennoni Associates
Guinness World Records has certified Delaware’s Red Clay School District’s 112 ft, 11 3/4-in. high tower as the tallest tower constructed of interlocking toy bricks. And it’s supported by steel.
In preparation for setting the new record, Pennoni Associates volunteered to design the internal steel mast that would provide the lateral support required to prevent the tower from toppling over. The tower, constructed of Legos, was required to be freestanding and therefore could not be supported vertically from the steel mast. However, lateral support of the tower was required due to the forces from wind gusts that could easily cause the tower to collapse.
“When it comes to a tower this tall, Lego bricks are much more than child’s play and we were fortunate to have professionals, including Pennoni Associates, to make sure the tower was safe and successful,” said the district’s Assistant Superintendent Ted Ammann.
The steel mast was designed as a series of steel HSS ranging in size from 6 in. in diameter at the base to 3 in. at the top of the tower. The frame was built in 20-ft sections and engineered to slide into one another to make erection and disassembly easier. At each section, a 1/4-in.-diameter tensioned guy-wire was attached to a gusset plate welded to the HSS to provide support for the HSS itself.
Six guy-wires were installed in each cardinal direction to brace the HSS for wind loads in any direction, for a total of 24 guy-wires in all. Four large concrete mass anchors were cast into the ground 60 ft from the tower base in each direction to anchor the guy-wires to the ground. A large concrete foundation was also cast at the base of the tower to support both the steel mast and the Lego tower itself.
The theory behind the design is that the steel mast and guy-wire assembly is a self-supporting stable structure. The Lego tower was built in sections and placed around the steel mast, with careful consideration and planning so that the tower did not touch the mast at any location. Voids were left in the tower at the gusset plate locations to allow the guy-wires to connect to the steel mast without touching the Lego tower itself. As wind blows on the Lego tower, the structure will deflect until it makes contact with the steel pipe inside the tower, which will resist the loads caused by the wind, and prevent the tower from toppling. As the wind calms, the tower will restore to its original shape.