Author: Esteban Morales – Eco-materiales y estructuras
Bamboo, often referred to as the ‘gift of the gods’ of our era, is capturing the imagination of architects and engineers worldwide. With its remarkable strength-to-weight ratio, flexibility, and sustainability, bamboo is a fascinating alternative to traditional construction materials.
When it comes to innovative structures, bamboo is no exception—it needs a robust foundation of research and structural analysis. The Luum Temple is a living example. Developed using cutting-edge finite element mathematical models and specialized software like SAP2000 V.14, this structure has garnered widespread attention and admiration since its completion in 2019.
Navigating the complexities of structural bamboo in Mexico, where regulations are still taking shape, was a challenge that led us to lean heavily on current technical literature and global standards. The custom structural analysis procedure was developed by lead engineer Esteban Morales, highlighting the project’s role as a milestone in the bamboo engineering landscape.
Basis of the Structural Analysis
Studying in depth the work of the legendary Mexican architect and engineer Felix Candela, we developed a structural system consisting of the intersection of five hyperbolic paraboloids composed of main arches holding four layers of bamboo split joists arranged at 90° and 45° angles. These are connected through a roof diaphragm composed of crossed layers of bamboo mats and dried palm leaves (Zacate).
To input the architectural model into the engineering software required for structural analysis, a wireframe AutoCAD 3D geometry was generated and then exported to the specialized software SAP2000 V.14.
The structure was divided into four main element types to orient the design process:
- Arches, spanning in the edges of the structure and radially from the center;
- Joists, spanning in layers and connecting the main arches over several layers;
- Roof diaphragm, conformed by the rigid surface resulting from several layers of joist triangulation and split weaving below the roof.
The maximum internal forces found in the most stressed arch, joist, and roof diaphragm elements were considered for the design of the structural elements.
In terms of load magnitudes, considerable seismic loads and 250km/h hurricane wind loads governed the design. These were combined to dead loads and live loads obtain the design internal forces of the structure. For this, the allowable stress method was employed, complying to the most adequate approach for structural bamboo design. The loads were then multiplied by the prescribed load coefficient for each of the required load combinations.
As the loads on the foundation are concentrated, a detailed analysis was carried out to determine the mechanical connection to the base. The connection of the bamboo arches to the base is hinged, thus allowing rotation between the arch and the foundation, preventing bamboo elements from having to resist shear and bending forces, which they are not adequately suited for. The goal is for the bamboo elements to mostly work in tension and compression parallel to the fibres.
The connections were designed according to the M-10 Mechanical Connections chapter of the National Design Specification® for Wood Construction 2012 from the AMERICAN WOOD COUNCIL and Eurocode 5. The computational programs used in the design of the connections were SAP2000, WoodWorks® Connections, SFS Timber Work, and APF Wood Joint.
The Documented Process: An In-depth Resource
The experiences and learnings from the Luum Temple project were profound. To make this information public and bridge the knowledge gap in practical bamboo engineering, the structural design procedures were documented in a new publication in collaboration with Rodrigo Istchuk: “A Step by Step Guide to Engineering Split Bamboo Spatial Gridshells”.
Unlock the Potential of Bamboo Structures
For those serious about pioneering the next wave of green construction and understanding the practical aspects of using bamboo as a structural material, the “Bamboo Structures” eBook series can be an essential guide. This recent publication dives deep into methodologies, design details, and example applications, serving as an invaluable resource for both novices and experts in the field. Developed based on the structural calculation methods used for the Luum Temple project, this first volume addresses a long-awaited resource gap, offering a clear lens into bamboo structural design for the wider audience.