Computation design method for Statics-Responsive Grid Shells

Quadrangular Grid shells have generated interest in recent years for their application in rationalizing free form geometry in the built environment. Shell structure are efficient because their form is governed by flow of internal forces. But while discretizing shells into grid shells, instead of using flow of forces, current method follows patterns and tessellation techniques. Quadrangular grids are easier to manufacture but they are not stiff inherently compared to triangulated meshed grid, which doesn’t allow them to be used as frequently. There is a scope to improve stiffness by discretization informed by flow of forces. A workflow was developed for designing quadrangular static-responsive grid shells which are structurally efficient, homogenous and has near planar cladding, including preferences of the designer. The workflow is set up in a parametric environment in grasshopper, a plugin for Rhino 3d modelling software. It uses particle spring method for form finding a shell which has membrane like load bearing behaviour. The solid shell is discretized into a grid shell by a custom stress line generator which uses principal stress vector field derived by Finite element analysis of the shell. The grid shell is homogenised and optimized for planarity by dynamic relaxation. Multiple design alternatives are generated and stored. Design space is explored by using data analytics and visualization techniques which helps user to make informed design decisions. The workflow is applied to create a grid shell over delft bus station as a case study to protect travellers from varying weather conditions. The results are quite satisfactory in terms of structural performance when compared to methods used in state of the art in practice. Stiffness of a structure can be measure by total strain energy. The grid shell for delft bus station generated using this workflow was 32% and 49% lower in terms of total strain energy(compliance) than regular quad grid shell and diagrid quad shell respectively. The results are promising for real life application. Meaning that the workflow can be used to find a homogenised quadrangular grid shell which are stiffer than their predecessors. Grid shells are used for approximating free form geometry for various projects around the globe. Using this method can save time, money and material which was required to make a grid shells stiff by thicker beams or extra stiffening members.Architecture, Urbanism and Building Sciences | Building Technolog