A Triangular grid-shell greenhouse inspired by the Sydney Opera House

Theme                                  Greenhouse for Jørn Utzon’s house
Location                               Hellebæk, Denmark
Semester                             2nd semester of master’s (Mini project in course Performance Aided Design)
Year                                       Spring 2019
Group/Individual                Individual project
Project Description
The concept for the greenhouse is inspired by Jørn Utzon’s Sydney Opera House in Australia. The idea was to form three shells in a triangular grid structure, which were placed on top of each other. The structure allows for different spatial experiences and gives the greenhouse a light expression. 

The structural system & stability

The structural concept allows for a high flexibility in creating different geometric shapes by the use of only timber struts and simple joints. By using the triangle, known as the most stable geometrical shape, the triangular grid structure for the shells become kinematically stable and will impose a high stiffness in every element. A load calculation has been made for the project, showed at the digram below. 

Important to notice is, the wind load is divided in two areas according to negative (suction) or positive pressure; and the snow load has only been added to joints where the inclination angle would be higher than 60 deg. 

Robot Analysis

The structure was made in Rhino/Grasshopper 3D and then exported to Robot Structural Analysis to analyse the structure for deformation and buckling. The analysis showed an extreme deformation in the system as well as local buckling. By redefining the joints, the issues were solved. 

The Joint

The joints used in the structure can be categorized as hinges. They have been designed to ensure the necessary flexibility for adjusting to every node on the structure, and create a locking property, making sure the struts will stay in their proper position. The joints are made with an inner center ring, to where the struts are attached, and a free-floating outer collar, through which the struts are inserted and locked.
Joint 1

Rhino 3D visualisation – built up with Grasshopper 3D

Physical Models

As part of the final exam, a model in 1:20 were made of the smallest of the three shells, as well as a 1:1 model of the joint. The shell was made with small 3mm sticks, while the joint was made of timber strusses and the two rings, which had been 3D-printed.