Given the importance of modularity in structural design, understanding the performance of modular shell structures is essential for improving both circularity and construction efficiency in spatial structures. To enhance sustainability and aesthetics, timber gridshells can be used to integrate sustainable building materials with complex pattern topologies. Modularity not only contributes to circularity of building materials, but also eases assembly, reducing both cost and construction time. By investigating different segmentation strategies, their impact on structural behaviour and buildability can be identified. This knowledge supports the optimisation of modular gridshells, leading to more efficient construction solutions.

This research aims to explore optimal segmentation strategies for timber gridshells, considering structural behaviour, element reusability and the efficiency of production, assembly and transport. A timber geodesic gridshell dome serves as a case study, but the findings contribute to modularity of gridshells in general. The main research question is: How can the modular segmentation of timber gridshells be designed to optimise their structural and construction efficiency?

For this research a method is developed to generate modular gridshells and optimise their design by evaluating both structural performance and construction efficiency. The modular designs consist of pinned splice joints that longitudinally connect two beams of different modules. Various modular designs are created by defining the location of these intermodular joints, thereby determining the overall modular geometry in the structure. A structural analysis gives understanding of the structural behaviour and the required material use. A construction analysis provides insight into reusability and efficiency of production, assembly and transport. A multi-objective comparative analysis is conducted to identify the most favourable designs based on project goals and stakeholder preferences.

Findings show that this modular approach improves assembly efficiency and the reusability of elements. It is particularly advantageous to choose a modular gridshell over a classic one when the primary design objective is reusability. However, the modular segmentation method negatively affects structural performance and increases material usage, primarily due to the use of pinned splice joints, which reduce overall stability. Additionally, applying modularity results in lower production and transport efficiency.

The results further indicate that larger modules improve structural stability and reduce the required material, due to fewer splice joints. Larger modules also result in higher assembly efficiency and reusability. However, increasing module sizes may exceed maximum transport size limits. It could also lead to a higher number of module types, reducing production and assembly efficiency. Furthermore, the module shape significantly influences the number of splice joints, underlining the importance of careful geometric consideration to minimise joint quantity. Additionally, increasing the rotational stiffness of splice joints could improve the structural performance.

In conclusion, it is crucial to consider project objectives and stakeholder interests in the structural design of a gridshell. Moreover, this research concludes that modular gridshell designs perform best when:
• Module sizes are maximised within transport constraints;
• Module shapes are designed to minimise the number of splice joints;
• An increase in module size comes with a minimisation of number of module types.