Today marks a significant moment at the construction site of Helsinki's Kruunuvuori Bridge as the first section of the bridge's central support, or pylon base, is being cast. Following this milestone, the construction of the pylon will ascend above sea level.
The pylon serves as the central support for the Kruunuvuorensilta bridge and anchors the steel beams of the cable-stayed section.
In total, there will be 17 pairs of cables on either side of the pylon.
By 2025, when completed, the pylon will stand at a height of 135 meters. For perspective, Helsinki's Olympic Stadium tower is 72 meters tall, the tallest building in Kalasatama is 134 meters, and the Hanasaari power plant chimney reaches 149 meters. The Kruunuvuorensilta bridge's pylon will become a prominent feature in Helsinki's skyline.
The pylon is founded on bedrock, and the lower base plate is situated 9.5 meters below sea level. The lower base plate measures 18m x 18m x 4.5m and was cast in a rock-cut pit. Above this lower base plate, a slightly smaller one measuring 12m x 12m x 3.5m was cast. The lower base plate was constructed underwater, but the structures above it will be built in dry conditions. The pylon's base will rise from these base plates.
The pylon's base is a solid reinforced concrete structure up to the level of the bridge deck. Above the deck level, the structure is hollow. One leg houses maintenance stairs, while the other leg features a maintenance elevator reaching a height of 78 meters. Access to the top is provided via maintenance stairs, and at the pylon's peak, there is a "balcony" for tasks such as servicing aviation obstruction lights.
The pylon is constructed using the "climbing formwork" technique for its upper sections. After casting the concrete, the material is allowed to cure to a certain percentage of its final strength. Then, the forms are removed from the casting surface. The formwork surfaces are inspected, and the formwork "climbs" upward using rails for the next casting phase.
Tram traffic is expected to commence in 2027.