The height of safety

The Challenge

When you are building the world’s tallest freestanding broadcasting tower in one of the world’s most earthquake-prone countries, using anything but the highest quality materials and the safest construction solutions is just unthinkable.

The 634 metre high Tokyo Skytree, recognised by Guinness World Records in 2011 as the tallest tower in the world and the second tallest structure, is a marvel of modern architecture and the absolute state of the art.

But the challenges facing such a extremely tall structure are many: besides the high winds and the ever-present threat of earthquakes, the fact that its upper reaches spend much of their time enveloped in cloud and smog require that all components have the highest possible corrosion resistance.

When it came to bolt securing, the extreme height, the small spaces in which the construction workers had to operate and their varying levels of technical expertise, meant that Tokyo Skytree had very specific demands.

The Solution

Faced with these challenges, and with Tokyo Skytree’s sky-high demands on quality, Nord-Lock washers were the inevitable solution. More than 10,000 pairs of various sizes have been used on the tower, making it almost certainly – with the possible exception of the aerospace industry – Nord-Lock’s highest-altitude application. The washers have been used to secure many crucial bolted joints on this awe-inspiring structure.

To meet the customer’s exacting demands for corrosion resistance, Nord-Lock supplied washers in high-grade 254SMO® stainless steel, originally developed as a substitute for titanium for use in seawater and other aggressive chloride-bearing environments.

The Result

Tokyo Skytree, its Nord-Lock washers and other components, were subjected to an unexpected and extreme test on March 11, 2011 when a terrifying 9.03 magnitude earthquake struck off Japan’s east coast. While this earthquake and the tsunami that followed caused devastation across the country, the tower – which was then approaching completion – was undamaged, and its Nord-Lock secured bolts had not shifted.

Since its opening in May 2012, Tokyo Skytree has become one of Japan’s most high-profile buildings and a major tourist destination. But one sight that visitors to its two observation decks – at 350 metres and 450 metres – will not witness are maintenance workers scaling the tower to tighten those 10,000-plus bolts, because those are secured for good.

Tokyo Skytree is a trademark of Tobu Railway Co., Ltd. and Tobu Tower Sky Tree Co., Ltd. in Japan.