With the old city hall reduced into rubbles in an earthquake, Kashiwazaki city of Niigata Prefecture wanted a quake-resistant successor to provide the necessary space for citizens’ art and cultural activities. Hence, this multi-purpose civic centre was born, consisting of the Main Hall, the Citizen Lounge, a gallery plus functional rooms for community use.
Arup provided the structural, mechanical and electrical engineering services as well as site supervision for the project, while Japan’s Environment Design Institute is the architect. The project has also been listed as a Selected Work in 2014 by the Architectural Institute of Japan.
Seismic isolation design
Kashiwazaki city was struck by a powerful earthquake in 2007. This new civic centre is therefore erected as a vivid symbol of recovery. It is now a base-isolated building with high seismic resistance (see Details), which also means it can serve as an emergency shelter in the event of disasters.
Human comfort and sustainability
User experience is central to our indoor environment design. For instance, the air flow and air conditioning system of the Main Hall is specifically designed that the air will flow around the backrest of the seats to maintain good ventilation and even save energy. Skylights are also installed to bring natural light into the Citizen Lounge where people would gather and relax.
An effective and economic seismic design
A typical base-isolated structure requires drilling an extra layer underground for the isolators, which leads to larger soil excavation volume and higher cost than a conventional foundation system.
For this project, we proposed a more economic option by fastening the isolators directly on the pile heads. As these isolators-on-the-piles can effectively absorb the lateral forces during a major earthquake, this means far less grade beams and footing will be needed for the extra foundation work.
Cater for local circumstances
Since the seismicity in Kashiwazaki city is characterised by long-period earthquakes, the standard approach may not be able to take full advantage of base isolation. Therefore, this new city hall is designed to have an ‘extra-long’ natural period (no less than 5 seconds) to withstand such seismic force.