Troll A – The Tallest Structure Ever Moved By Mankind


When was the last time you moved something heavy? Was it heavy enough to make you think you moved a mountain? Think twice, if not a mountain, there exists something equivalent has already been moved by humanity. Still wondering what could it be? Troll A. It is a natural gas platform built in the year 1995. It was placed in the North Sea owned and operated by Statoil. Troll A was one of the complex engineering feats that were achieved by the humanity. Overlooking the blue ocean at 472 meters (1,549 ft) from the ground above, it has no match at the sea. The platform weighs as much as 683,600 tons (1.2 million tons with the ballast included). This colossal towering giant was towed 200 km from the village of Vats to its resting place in the North Sea in the year 1996. The entire event was televised as it was one of an iconic engineering feat.

Troll A – The Tallest Structure Ever Moved By Mankind
Image Courtesy: olavolsen

The platform rests on the sea floor that is 303 meter (994 feet) below the surface. The legs of the platform are a continuous hollow slip made of concrete. They have channels installed to mobilize the imports and exports from the bottom to the surface. It also has an elevator installed that takes 9 minutes to reach the floor from the surface.

The Walls of the Troll’s towering legs measure a meter thick. It is heavily reinforced with high-grade steel and concrete in one continuous fill (slip forming). Each joint (composed of several conical cylinders) is attached with mathematical precision. The width of the legs dilate at the bottom, thus giving greater stability to the structure itself, and it flares out gracefully from the surface to the floor. Troll A’s concrete legs are designed to withstand the forces of the sea. It is designed to withstand the pressure of the water below. Hence, continuous flow concrete is used to design the structure. To fill the frame of this structure using a continuous flow took 20 minutes to fill out every 5 cm area.

The construction of the Troll A platform began in the year 1991 by the Norwegian contractors for an oil company named Norske Shell for a whopping $650 million USD. The construction began in phases where the deck and the base were separately built. The entire structure was joined in the year 1995 after partially submerging the base. The gargantuan base is a Condeep gravity structure that is built from highly reinforced concrete. Its final resting place is just 80 kilometers (50 miles) from the northwest of Bergen, Norway. It took just seven days to haul such a colossal structure over the sea.