Mito City Civic Centre was officially opened to the public in July 2023 and has since emerged as the new community hub of the city. We provided structural design services for this new building after winning the design proposal with Toyo Ito, a laureate of the Pritzker Architecture Prize.

Spanning approximately 23,000m², the new civic centre boasts an array of facilities designed to cater to the diverse needs of citizens and the provision of retail space. These facilities include a 2,000-seat main theatre, a 482-seat medium theatre, a versatile small hall, conference rooms, exhibition rooms and various rentable spaces.

First-of-its-kind timber design in Japan

The main feature of this building is the extensive use of fire-proof structural timber, totaling 1,500m³, which has been employed for beams, columns and an innovative truss system. It is essential for the primary structural elements of a building of this scale and purpose to have a one-hour fire rating. While various fire-proof timber materials have been developed in Japan, this project marks the first time such elements have been utilised to construct large truss structures spanning over 20m.

Ensuring exceptional seismic performance and sound insulation

Given the innovative nature of this fire-resistant timber technology, there are limited precedents regarding its applications and connection details. Therefore, to connect the beams at different levels with eccentric intersection across the column, we developed new steel connectors for both the beams and the truss system. Also, considering the lessons learned from the damage caused by the 2011 Tohoku earthquake, we implemented a concrete core structure surrounded by timber and steel beams and columns. This combination ensures exceptional seismic performance while effectively providing sound insulation.