Ikuta Church in Kanagawa / Ryue Nishizawa

Completed in 2014, the Ikuta Church was designed by Japanese Architect Ryue Nishizawa (SANAA) on the hillside of Kanagawa, Japan. The building has been designed to achieve the optimal structural design.

Ikuta Church in Kanagawa Technical Information

Architect: Ryue Nishizawa of SANAA | Works of SANAA
Engineer: SAPS/Sasaki and Partners
Typology : Religious Architecture / Church
Project Year: 2014
Location: Kanagawa, Japan
Photo Credit: SANAA + SAPS/Sasaki and Partners
Via : Chikara-inamura.com + Esna

To design the structural system and calculate the ball park figure of the overall sizing of each structural elements is critical to achieve the optimal structural design in the country like Japan where the lateral load from the seismic forces takes greater deal of the incoming forces, typically 30% of the gravitational load.

– Chikara Inamura

Ikuta Church in Kanagawa

Text by the engineers

This two-story church complex sits on the hillside of a Kanagawa, Japan. The building is comprised of three buildings: the main building that houses the church, the administration building, and the entrance hall. Each building is roofed with HP: Hyperbolic Paraboloid with a set of linear elements. The primary structural system for the superstructure is steel, and the substructure is a direct foundation of continuous footing.

The interesting fact of this building is that the entire structural system is designed by hand using a simple desktop calculator. In the age of modern computation technology with an abundance of sophisticated FEM software, this seemingly counterproductive design method is proven to be critical as a design engineer in order not to yield one’s design decision to the black box of the software.

This ability to design the structural system and calculate the ballpark figure of the overall sizing of each structural elements is critical to achieving the optimal structural design in the country like Japan, where the lateral load from the seismic forces takes a more significant deal of the incoming forces, typically 30% of the gravitational load. Once the decision is yield to the black box, the design becomes reactive, and most often the case, the design will not achieve the optimal solution.

This is the primary principle of engineering in the office of Sasaki and Partners. Therefore, all the project in this office is designed and calculated by hand during the preliminary stage. Once the design enters the schematic phase, the FEM is used to ensure the accuracy of the hand calculations in the preceding phase.

The first decision as an engineer to design the structural system is based on how to design the lateral load distribution within the overall system.
The two basic systems for the lateral load resistance are the rigid framing and the braces. In the case of the reinforced concrete structure, the latter is replaced with the shear walls.

What determines the choice of material for the primary structural system is the loading capacity of the soil and the cost. This church sits on a relatively softer soil of a loamy layer, whose loading capacity is about 50 kN/m2, and therefore, the steel structure is deployed to minimize the overall weight of the superstructure.
For the lateral load-bearing system, the church deploys a one-directional rigid frame and one-directional bracing.

This decision of whether to deploy two-directional rigid framing, two-directional bracing, or one and one depends on the architectural requirement for the transparency and opacity per direction, as well as the span between the columns. Regardless of the system of choice for the lateral load bearings, it is crucial to keep a clear system and not mix them arbitrary so that maximum loading conditions can be correctly examined and maximum safety can be assured.

In principle, each building is equipped with self-sufficient rigidity against the lateral load to ensure the rigidity as a whole. The bracing are allocated in strategic locations to ensure the minimum eccentricity of the building as a whole.