On the design and construction of elastic gridshells with irregular meshes

International audienceDespite the time and cost advantages by the manufacture, transport and assembling of elastic gridshells, high material stresses are induced on the structures during their shaping process. An optimisation of the grid arrangement in order to reduce the curvature of the grid profiles and with it the initial bending stresses is therefore crucial when considering the stress reserves under subsequent external loading.To be able to deploy and bend the structure as a whole grid and thereby accelerate their construction process, elastic gridshells usually exhibit constant mesh size (regular gridshells). However, this condition makes the optimisation of regular gridshells only possible until a certain level. In this paper, several double-curved gridshells have been optimised allowing variation on the mesh size (irregular gridshells), so that a further reduction of the profiles' curvature and lower concentration of stresses could be obtained.By the construction of irregular gridshells, the grid profiles are normally independently bent in an incremental process, generally more time-consuming than by regular gridshells. Nevertheless, if the bending stiffness of the grid profiles is low enough, large deformations can be induced on the irregular meshes and the structures can be built by bending the whole grid. The stresses generated during the construction process must be previously controlled, e.g. using numerical simulation. For this paper, the erection process of an elastic hemisphere with irregular mesh and 10m diameter has been analysed by means of finite element modelling and tested on a 1:1-prototype. The comparison of the resulting geometry and load-bearing behaviour between the modelled and real structures are presented