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江の島湘南港ヨットハウス内観オープンビーム; 江の島湘南港ヨットハウス内観オープンビーム;

Shonan Yacht House, Kanagawa

A wave-shaped roof with slits through which daylight penetrates into the interior

Located by the sea of Enoshima, the yacht house is highly recognisable with its unique shape and structure. The 2-storey building features a wave-shaped roof with slits introducing daylight into the interior.

Arup provided structural engineering and daylight simulation services to realise the design that is optimised for construction and fits into the surroundings.

Envisioned as ‘an open space for everyone’, the entire building is covered by a wave-shaped roof, creating a seamless continuity of the inside and outside. In line with this concept, the structure consists of thin columns like yacht masts providing an uninterrupted view of the sea and a concrete curved surface roof filtering natural light.

Various design methods were adopted to realise the complicated shape. The initial shape of the roof was defined by applying forced displacement to a steel-plate model analytically. We also designed the ‘open beam’ – inserting steel bars of 70mm thickness into the upper and lower chords and putting steel plates of 40mm thickness into the strut of the slits. This ‘open beam’ works as a string beam that enables a long-span free-form slab with columns at both ends.

A total of seven ‘open beams’ were installed throughout the 300mm thick concrete roof in accordance with the daylight simulation results. High strength concrete was used for its ability to free from and its application as a salt damage prevention measure. Two minimum cores were placed to enhance seismic performance of the building.

A 3D model was prepared for the construction and was shared with the contractor, carpenters and steel fabricators to facilitate communication and construction.

The renewed yacht house was opened in June 2014 after 13 months of construction; and it has immediately become a new icon for Enoshima, and another source of pride for the local community.