Integrating Semi-Rigid Joint Stiffness into Complex Timber Gridshell Modelling for Improved Accuracy

Student: Kaj Hasenaar
Supervisors : Arjan Habraken, Joey Janssen

The construction industry has a significant impact on the environment, primarily due to the large quantities of materials used in load-bearing structures. As construction activity continues to grow, there is increasing pressure to design structures that use less material and produce fewer CO₂ emissions. Timber is a promising material in this transition because it is renewable, stores carbon, and has a much lower environmental impact than steel or concrete. However, designing reliable timber structures remains challenging due to the material’s directional properties and long-term behaviour.

Timber gridshells are lightweight structures that can span large distances using slender elements, making them both material-efficient and architecturally expressive. Their behaviour, however, is strongly influenced by how the elements are connected and their geometry. In current digital design and structural analysis, these connections are often simplified, even though timber joints commonly behave in a semi-rigid way. This simplification can lead to inaccurate predictions of stiffness, deformation, and overall structural performance.

Shell elements with different in- and out-of-plane stiffness configurations.

This research investigates how the stiffness of semi-rigid timber joints affects the behaviour and design of unbraced quadrilateral timber gridshells. By developing a parametric digital workflow that links Grasshopper, RFEM, and Abaqus, the study connects joint-level behaviour with the global response of the structure. The research focuses on gridshells whose shapes are driven by architectural and fabrication constraints rather than purely structural optimisation, and it examines both short-term and long-term deformations.

Different expected gridshell shapes and their real deformation behaviour.

By improving how joint stiffness is represented in structural models and linking this directly to fabrication logic, the project aims to make timber gridshell design more reliable, predictable, and feasible. Ultimately, this contributes to the wider goal of enabling efficient and sustainable timber structures that can be realistically built.

To achieve this goal, the following research and sub-questions are to be answered:

How do material and geometric parameters impact the stiffness of semi-rigid timber joints, and how does this relationship influence the designed form, structural performance, and fabrication strategies of unbraced quadrilateral timber gridshells?

  1. How do variable node stiffnesses affect the behaviour of unbraced quadrilateral gridshells?
  2. What are the stiffnesses and behaviours of common timber connections found using the simulation of the joints modelled in Grasshopper?
  3. How can Python code create an efficient workflow between RFEM 6, Abaqus, and Grasshopper?
  4. How do the stiffnesses and behaviours of common timber connections affect the behaviour of unbraced quadrilateral gridshells?
  5. How can the nodes designed in Grasshopper be applied in computer-aided fabrication? 
Proposed parametric workflow, including their respective subquestions.
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