Structural engineering
Due to the presence of buried cultural properties, excavation of the site was not possible. Instead, a steel plate was laid on top of the ground and a concrete foundation was constructed. To address drainage needs, an innovative above-ground drainage system was implemented.
To expedite the construction process, early-strength cement, capable of achieving the specified strength within approximately three days of casting, was utilised. Since concrete was only used for the foundation, horizontal braces were strategically positioned to stabilise the roof surface and transfer seismic and wind pressures to the earthquake-resistant structure.
The roof tip was designed to extend 4m with plantings on top. The structure is a one-storey, braced steel frame, assembled from transportable parts that can be bolted together without on-site welding, enabling a swift construction process. The centre of the roof is thickened to provide ample soil depth for planting trees over 5m tall. This ‘bowl’ shape also facilitated the design of a lightweight roof, thin at the edges, with low eaves at the front, and upturned at both ends. This allowed for a curved ceiling in the worship hall, mirroring the shape of the roof.
The roof is mainly covered with evergreens, including camphor trees, a symbol of the Tenmangu Shrine. Shrubs, flowers and colour-changing plants, along with deciduous varieties such as autumn leaves, cherry blossoms and plum blossoms are incorporated to create a seasonal ambiance. The roof hosts a diverse array of 66 plant species, with the soil depth adjustable to suit each plant.