Atlantinsilta, Helsinki: 2022 Bridge of the Year

The new Atlantic Bridge (Atlantinsilta) added an impressive finishing touch to Helsinki’s transportation network in the area of Jätkäsaari. In addition to linking various transportation routes, this structure in the maritime part of the city has become a spectacular landmark.

WSP was responsible for designing the bridge, seawalls and observation deck. The design work started in 2016 and construction began in October 2019. The bridge opened to traffic in May 2021.

In recognition of the project’s high-quality design and WSP’s construction expertise, Atlantinsilta was recently named 2022 Bridge of the Year by the Bridges and Special Structures Technology division of RIL (Finnish Association of Civil Engineers). The competition’s theme focused on the rail transportation environment.

“This bridge captures the spirit of the place and achieves the quality objectives set for the new district,” said Ville Alajoki, jury chairman for the 2022 competition.

According to the jury, the bridge is elegant and lightweight, despite its imposing size. The singular aesthetic appeal of the Y-shaped pillars attests to WSP’s uncompromising design approach.

“After reviewing the various options, we finally selected a reinforced concrete perimeter slab bridge, which made the deck as thin as possible. This minimized the impact on the landscape,” said WSP’s Niklas Gordin, the principal designer. He added: “Building a civil engineering structure of this complexity requires many bridges of communication between all those involved. I would like to pay tribute to the valuable professional contributions made by everyone who worked on this demanding project.”

WSP's bridge design expertise has been recognized over the years both at home and abroad. The 2021 Bridge of the Year award went to WSP's Sudentassu in Sipoonkorpi National Park, near Helsinki.

Atlantic Bridge will serve residents of the fast-growing Jätkäsaari area, as well as tourists arriving at the West Terminal (Port of Helsinki). Overlooking the Gulf of Finland, the bridge closed off the Ahdinallas district, which will be surrounded by a high-quality maritime urban environment in the coming years.

The project also unified the city’s previously fragmented tramway network. In addition to three different tram lines, the bridge carries high traffic volumes. Wide pedestrian and cycle lanes also run along both sides.

Passers-by are also invited to admire the maritime landscape. The bridge’s observation deck offers unobstructed views of the sea, including telescopes for spotting ocean-going vessels and yachts.

Inspired by water’s diversity

The bridge and its embankments reflect water’s diversity. The maritime theme is reflected in the design, materials and colour choices. The concrete deck was streamlined to form the simplest possible wave shape, supported by sculptural pillars. The colour scheme is enhanced by the use of concrete and ball-blasted stainless steel.

The waves, tides and movement of the water are also reflected in the design of the sloping seawalls. A 3D wave pattern is molded into the surface of the precast concrete wall, which can be admired at close range from a track under the bridge. At night, the bridge and its embankments are illuminated by LED lights. 

“A continuous string of lights is integrated into the railings of the bridge and the seawalls. All the lighting units are connected to a control system that can be used to create different scenes in the surrounding environment. The maritime atmosphere is enhanced by the evening lighting, which highlights the pattern of the wall and brings out the crests of the wave, even after dark," said lighting designer Teemu Skogberg. 

The linear design is echoed in the bridge's Y-shaped pillars, which posed structural design challenges of their own. The slope of the columns initially caused internal horizontal forces on the deck. These were overcome by increasing the deck’s pre-stressing.  

“The shape and design of the bridge piers was the subject of much deliberation. Our designers had several potential design versions on the table. In addition to precise calculations, we needed to consult with various concrete suppliers to ensure that the dimensions and materials met the requirements,” said Niklas Gordin.  

Atlantic Bridge was designed using 3D data modeling. Using shared building information modeling (BIM) facilitated not only the design, but also the implementation of this complex project. 

When working in older port areas, special attention must also be paid to foundation design.

"Atlantic Bridge is built on top of fill soil. Over the years, clay was dredged from the seabed and replaced by dredged earth from a barge. It was impossible to compact the fill in the sea, so the piles were driven through the fill and into the rock," explained Juha Auvinen, geotechnical engineer. 

The foundations are solid—and for good reason. At each bridge support, the piling types and soil fill have a significant impact on structural performance. During construction, 2,600 metres of soil were bored and 3,500 metres of driven piles were used.  

"The design was made more challenging by the old quay structure on Melkin Pier, behind which mixed fill was brought in during construction. In particular, the bridge’s longitudinal movement had to be restricted to avoid stressing the old quay structure. The solution was to develop a rigid concrete slab that would apply weight to hold the piles back if they started to move," added Juha Auvinen.