Exploring The Structural Details of a Bamboo Dome

Explore the innovative use of bamboo in architecture with a focus on dome structures. Learn about augmented reality-enhanced construction, bamboo and concrete integration, and secure bundling techniques in bamboo gridshells

In this article, we delve into the intricate world of bamboo architecture, focusing on its application in dome structures through a series of detailed illustrations that uncover the depth of this sustainable material's capabilities. Highlights of the article include:

  • Augmented Reality-Enhanced Bamboo Gridshell
  • Foundation Design: Integrating Bamboo and Concrete for Structural Stability
  • Secure Bundling Techniques for Gridshell Construction
  • Square Lashing for Bamboo Gridshell Structures

Augmented Reality-Enhanced Bamboo Grid Shell: A Pioneering Project by Kristof Crolla and Garvin Goepel

In August 2023, architects Kristof Crolla and Garvin Goepel from the University of Hong Kong Faculty of Architecture, collaborated with Bamboo U to create an innovative bamboo grid shell structure. This project, realized during Bamboo U's 11-day Bamboo Build and Design Course in Bali, leveraged augmented reality to streamline the construction process.

The construction began with the careful preparation of bamboo bundles, each comprised of three 4cm Bamboo Thyrsostachys Siamensis, known in Bali as bamboo jakarta, and a bamboo split. These bundles were methodically arranged on the ground, with the first layer laid in one direction and the second layer placed perpendicularly. Each intersection was secured using traditional square lashing, providing the necessary flexibility for the structure.

A crane then lifted the assembled grid shell into position, utilizing holo-lenses for precise placement. Once elevated, scaffolding was added to support the structure. This setup allowed for the accurate installation of the Lidi bundles, perfectly aligning with the 3D model visible through augmented reality tools.

The bamboo columns were subsequently anchored to the pre-poured concrete foundations, ensuring stability and durability. With the grid shell in place, the project advanced to the final stage: installing the bamboo roof, completing this remarkable dome structure.

This project not only demonstrates the potential of augmented reality in construction but also highlights the versatility and sustainability of bamboo as a building material.

Foundation Design: Integrating Bamboo and Concrete for Structural Stability

The foundation detail of this bamboo dome showcases a robust integration of traditional and modern construction techniques, ensuring both stability and durability. The base of the structure consists of a concrete foundation, providing a solid and level platform that evenly distributes the loads from the bamboo dome above. This concrete base is essential for preventing settlement and ensuring that the structure can withstand various environmental stresses, but also provides additional mass to counteract any uplift forces.

Source: Bamboo U
Rising from the concrete base are the main vertical supports made from bamboo petung or Dendrocalamus asper, a species known for its strength and big diameter. The bamboo columns are capped and strategically positioned, with cap holes drilled to facilitate the pouring of mortar, where steel reinforcement bars run inside the bamboo culms. This system enhances the overall load-bearing capacity of the bamboo while maintaining the aesthetic and sustainable advantages of using natural materials. The incorporation of rebar within the bamboo ensures that the columns can handle both compressive and tensile forces, making the structure resilient against dynamic loads such as wind or seismic activity.

A large river stone is embedded between the bamboo columns and the concrete base; acting as a protective barrier, which prevents moisture that could lead to bamboo degradation over time. 

This combination of materials and techniques results in a foundation system that maximizes the structural benefits of both bamboo and concrete, creating a harmonious and resilient base for the bamboo dome.

Secure Bundling Techniques for Gridshell Construction

This structural detail illustrates the method for creating continuous bamboo bundles, essential for constructing the gridshell of a bamboo dome. The bamboo culms are overlapped by one meter to ensure a strong and stable connection that can extend to the desired length. The overlapping sections are secured using bamboo pins, which are driven through pre-drilled diagonal holes. These pins provide a traditional and effective means of fastening, leveraging the natural strength of bamboo to create a seamless connection between segments.

Source: Bamboo U
To enhance the structural integrity of the bamboo bundles, stainless steel band clamps every 60cm are used to tightly bind the overlapping sections. These clamps offer a modern reinforcement technique that prevents the bamboo from separating under load. This ensures the bundle maintains its integrity over extended lengths. The use of stainless steel is crucial as it resists corrosion, which is vital for the longevity of the structure, especially in outdoor environments. This combination of bamboo pins and stainless steel band clamps results in a robust and durable connection, capable of withstanding significant tensile and compressive forces.

Source: Bamboo U
By employing this hybrid approach, architects and engineers can create long, continuous bamboo elements necessary for the gridshell of a bamboo dome. This method not only preserves the aesthetic and sustainable qualities of bamboo, but also allows reaching large spans with small diameters. The resulting structure benefits from the flexibility and strength of bamboo, coupled with the reliability of contemporary fastening methods, making it suitable for innovative and resilient architectural designs.

Square Lashing for Bamboo Gridshell Structures

This structural detail illustrates the square lashing technique used to securely tie two bamboo bundles at their intersection, forming a critical joint in the gridshell framework. The square lashing process begins by positioning the bamboo bundles at right angles to each other. A durable natural rope or cord is then wrapped around the intersection in a series of steps to ensure a tight and stable connection. The first set of wrappings goes around both bamboo bundles, binding them closely together, followed by circular frapping to lock the previous step.

Source: Bamboo U
After completing the initial wrappings, the lashing is reinforced with frapping turns to lock the previous step. This traditional lashing method permits the necessary degree of free rotation required for a grid shell structure.

Connection between columns and lidi bundle

This connection is essential for maintaining the integrity and stability of the dome structure, ensuring that the loads are efficiently transferred and distributed. At the heart of the connection is a threaded rod, which serves as a central anchoring point, holding the various components together securely. This rod runs through a central washer and nut, preventing any loosening under stress.

Source: Bamboo U
These columns are strategically positioned and secured using additional components to ensure a robust and durable connection. The bamboo columns have pre-drilled holes that align with the threaded rod, allowing them to be bolted in place with the washer and nut. The lidi bundle, composed of slender, flexible bamboo sticks. This combination of rigid bamboo columns and lidi bundles creates a synergistic effect, blending rigidity with flexibility. The connection details, including the use of washers, nuts, and threaded rods, highlight a thoughtful approach to bamboo construction, addressing both structural and assembly challenges.

Conclusion:

The exploration of bamboo in architectural design, particularly in dome structures, reveals its immense potential as a sustainable and versatile material. Projects like the bamboo dome by Kristof Crolla and Garvin Goepel in collaboration with Bamboo U illustrate the fusion of traditional craftsmanship and modern technology, resulting in structures that are both resilient and environmentally friendly. By integrating bamboo with concrete foundations, utilizing secure bundling techniques, and employing methods like square lashing, architects and engineers can create innovative and durable designs. This approach not only highlights the aesthetic and ecological benefits of bamboo but also sets a precedent for future sustainable architectural practices.

Credits:

Structural concept design, parametric modeling, and augmented reality consulting of The Dome at Bamboo U by Dr Kristof Crolla (@lead.architecture ) and Dr Garvin Goepel ( @augmentedarchitecture) from the University of Hong Kong's Building Simplexity Lab (https://bsl.hku.hk/) - constructed under their expert guidance and utilizing their provided augmented reality tools.

Illustrations: Luis Echeverria

About the author
Luis Echeverria | Management Consulting Professional

Program Manager at Bamboo U. Mexican architect with a decade of expertise in bamboo construction, winner of international architectural competitions in Hungary, India, China and Chile. Passionate about education and sustainability, integrated into modern esthetics with eco-building practices.

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