Holyhead is one the UK’s busiest ferry ports, located on the Isle of Anglesey in North Wales. Approximately 2.4 million passengers pass through the port every year. The region has wanted to turn the Holyhead town center, located near the port, more accessible to the passengers and, at the same time, to give a boost to the economy.

The final step in the development is a footbridge appropriately named Celtic Gateway. The designers of the bridge aspired to create an outstanding, aesthetically appealing and futuristic structure. The dominating feature of the bridge is its two tubular, load-bearing arches, which first curve over the deck and then swerve upward over a ramp section, joining to form a pointed end.

Photo courtesy: Cimolai

A major contribution to the design comes from a daring use of material. The arches are built out of Duplex stainless steel plate.

Duplex stainless steels have emerged as noteworthy, competitive construction materials to conventional austenitic stainless steels and even to mild steel when life cycle cost is taken into account. Duplex grades offer good corrosion resistance and high strength, which translates into considerable weight and subsequent cost savings.

Celtic Gateway’s steelwork was fabricated by the Cimolai Group of Italy, the leader in metal bridges in Italy and a powerful player elsewhere in Europe. The bridge designers selected the Duplex grade 2304 (EN 1.4362) for the arches and other load-bearing structures on view, owing to 2304’s optimal combination of corrosion resistance suitable to the environment, mechanical properties and cost.

Cimolai turned to Outokumpu for the Duplex plate. Ing. Damiano Mion of Cimolai explains that the choice for Outokumpu was initially based on Outokumpu’s track record of a number of successful bridge projects. Cimolai would, however, find further benefits from working with Outokumpu. “We were impressed with the attention that Outokumpu paid to this project,” Ing. Mion explains. “Their Italian staff were quick to visit, taking the time to listen and always looking for alternative solutions in case of complications.”
 
Celtic Gateway is Cimolai’s first large stainless steel bridge project. However, the fabrication of Duplex plates presented no problems. “Duplex is an easy material – our presses can handle it very well,” Ing. Mion says. The only challenge was the highly smooth surface finish required by the design (1K roughness – less than 0.4 micrometers), necessitating even unusual manual surface finishing on site. The project has left Ing. Mion convinced, “Duplex is the way of the future.”

Architectural design and structural engineering:

Gifford and Partners, UK