Design and construction of gridshells

Since 2004

The gridshells built by the Navier laboratory are made of a flat composite grid deformed elastically to obtain the shape desired. The design of the gridshell is based on many numerical simulations and on experience acquired during the fabrication of several full-scale prototypes.

Description of the research

The gridshells built by the Navier laboratory are made of a flat composite grid deformed elastically to obtain the shape desired. The design of the gridshell is based on many numerical simulations.

Design of a gridshell

At the beginning, a desired rounded shape is proposed by an architect. A first reflexion is necessary, to know if the shape proposed is suitable with the gridshell technology. If it is, the design can start. The surface proposed by the architect is drawn in a modelling software. The surface is extended and two intersecting curves are drawn on the surface. The compass method can be performed to get a primary grid. The grid is then trimmed to get a geometrical primary gridshell. This process is explained in details in [Gridshells in composite materials : construction of a 300 m² forum for the Solidays’ festival in Paris – O. Baverel et al. (2013)].

The following step is the relaxation of the grid. An algorithm based on dynamic relaxation makes possible the investigation of the final natural shape of the gridshell. From a purely geometric grid obtained through compass method, the relaxation of the pre-stressed beams provides a grid which has a real mechanical meaning: the grid reaches its mechanical equilibrium. Once a satisfactory shape is obtained, the structure is numerically studied in response to the loads.

Construction of the prototype

The primary grid is assembled on the ground. The connections have a rotational degree of freedom in the plane of the grid so the quadrangles forming the grid can deform easily in the plane of the grid. Then, the erection of the grid is done, for example with the help of cranes. Each beam located on the edge of the grid is brought to its correspondent anchorage. The grid is then braced with a third layer of beams which confers its high stiffness.