Digital workflow for the accurate computation of the geometric properties of bamboo culms for structural applications

Bamboo is one of the most promising sustainable construction materials due to the large endemic natural reserves prevalent in the Southern Hemisphere. However, industrialised materials, such as concrete, steel and aluminium have overshadowed the application of natural bamboo culms, due to the high-quality assurance achieved over decades refining the production processes of structural elements manufactured from the former. As a result, the physical, geometric and mechanical properties of these industrialised structural elements are quantifiable, predictable and in agreement with international standards. This research presents the details of a digital workflow to quantify the inherent geometric variability of bamboo culms as part of a new quality assurance process for this natural structural element. This workflow relies on the use of a mid-range, commercially available structured-light 3D scanner to accurately capture a point cloud of the bamboo geometry and generate a corresponding polygon mesh. Digital models of three different bamboo species were validated through comparison with key physical measurements finding that the adoption of these digital models can significantly improve the accuracy and efficiency of manual methods due to the complex irregularities found in bamboo culms. This work demonstrates the benefits of adopting a non-destructive, reverse-engineering approach to quantify the geometric properties of bamboo compared to traditional tools and methods. Overall, this research shows the potential of digital technologies to support the adoption of this natural material allowing for the re-assessment of design workflows and providing an opportunity for bamboo to compete with industrialised materials

Digitisation of bamboo culms for structural applications

Reducing the negative environmental impact caused by the intensive manufacturing of industrialised building materials and components requires the adoption of alternative sustainable resources and the development of appropriate procedures to encourage their use in the construction industry. Bamboo in its natural form (culms or poles) is one of the most promising non-conventional sustainable building materials, endemic to most developing countries where high demand for building materials will be driven by the large-scale urbanisation predicted for the coming decades. The use of bamboo poles as structural elements poses multiple challenges starting with the need to define their inherent geometric variability to enable their inclusion in formal design and fabrication processes. This paper describes the details of a non-destructive 3D scanning and modelling workflow developed to capture and process the relevant digital information that describes the geometric properties of bamboo poles. The digitisation of over 230 poles with a combined length of 500 m was carried out confirming the accuracy of the generated geometric models. Also, a small reciprocal frame prototype was successfully developed based on the geometric information extracted from a 3D model of the structure incorporating the digitised poles. The effective digitisation of bamboo poles and its integration into modern platforms can provide the construction industry with the necessary support to design, build and maintain high quality structures that incorporate this sustainable and renewable resource

Determination of the physical and mechanical properties of moso, guadua and oldhamii bamboo assisted by robotic fabrication

The large-scale urbanisation taking place in the developing world requires the construction industry to adopt alternative non-conventional renewable materials to reduce the unsustainable level of greenhouse gas emissions associated with the production of industrialised building materials. Bamboo is one of the most promising non-conventional building materials endemic to most developing countries, but there is still insufcient consistent information on the physical and mechanical properties of the numerous species suitable for construction. This study shows the potential of robotic fabrication to accelerate testing programmes on small clear samples of bamboo required to compare physical and mechanical properties across diferent species and difering plantation management practices. This fabrication method is applied on an experimental testing programme to determine the characteristic values of density, compressive strength, elastic modulus and shear strength of Phyllostachys pubescens (moso), Guadua angustifolia Kunth (guadua) and Guadua angustifolia (oldhamii). The efcient development of comprehensive experimental datasets of clear samples of bamboo is fundamental to inform the development of future design guidelines for bamboo as a construction material

Digital analysis of the geometric variability of Guadua, Moso and Oldhamii bamboo

The implementation of sustainable building materials is currently one of the principal global challenges faced by the construction industry. Natural bamboo culms are a potential alternative to tackle this challenge due to its favourable environmental credentials as well as affordability. However, the organic geometry of bamboo culms is one of the barriers that prevents them from being implemented in formal design procedures. This work presents the details of a new digitisation workflow to systematically capture the geometry of bamboo culms through the application of 3D scanning technologies and reverse engineering principles. This workflow is applied to carry out a comprehensive analysis of the geometric variability of Guadua angustifolia kunth (Guadua), Phillostachys pubescens (Moso) and Bambusa oldhamii (Oldhamii) to identify potential correlation patterns. This geometric analysis showed a wide variation in the geometric properties of all species and no particular pattern was found which could be adopted for a potential visual grading system. These results highlight the challenges that the use of bamboo culms pose for the traditional design and fabrication processes developed for manufactured structural elements. The proposed reverse engineering methodology adopted for this study can be used to quantify and manage the geometric variability of bamboo culms to support the development of new formal design and fabrication processes for this natural structural element

Non-linear behaviour and failure mechanism of bamboo poles in bending

The adoption of bamboo poles in construction can support the reduction of carbon dioxide emissions generated by the manufacture of conventional structural elements produced from unsustainable industrialised materials. This research focuses on the study of the nonlinear softening behaviour and failure mechanism of bamboo poles in bending through a series of experimental tests on Moso (Phyllostachys pubescens) bamboo and Finite Element simulations supported by digitisation techniques. The results indicate that this nonlinear behaviour is caused by the incremental development of cracks at the locations where the circumferential tensile capacity of bamboo is exceeded leading to the eventual failure of the pole. Also, the simulations in this study suggest that reinforcing bamboo poles with pretensioned stainless steel bands is ineffective in counteracting the development of significant circumferential tensile stresses and the associated longitudinal cracks. More generally, this work highlights the challenges and limitations of applying traditional methods of structural testing and design for manufactured components to a highly variable natural structural element and speculates whether modern digital technologies can be adopted to manage more effectively the effects of this inherent variability

Bimodulus bending model for bamboo poles

The building industry is currently under pressure to transit from non-renewable materials with high embodied energy towards natural and sustainable options. Bamboo poles are some of the most promising renewable structural elements, but their formal utilisation in construction requires the development of appropriate analytical models and new design tools to address their challenging natural and organic nature. Considering the composite nature of bamboo poles and the properties of their high-strength sclerenchyma fibres and parenchyma matrix, this paper presents the formulation of an analytical bimodulus model to determine the cross-sectional strain and stress distribution in bamboo poles in bending. This model was validated through full-scale experimental four-point bending tests on Moso (Phyllostachys pubescens) bamboo poles suggesting a constant tensile elastic modulus of fibres for this species

Mechanical properties of laminated bamboo under off-axis compression

To investigate the compression performance of laminated bamboo, 210 laminated bamboo specimens were tested using seven different lamination angles. Six failure types were classified. All the specimens experienced elastic stage at the beginning of the loading process and then elastic-plastic stage. At the end of the elastic-plastic stage, specimens of 15°, 30° and 45° immediately reached the ultimate bearing capacity, showing brittle failure, while other specimens entered a longer plastic stage before failure. The off-axis compression strength and the apparent elastic modulus both decreased with the increment of the angle. Two empirical formulas were proposed to predict the off-axis compression strength and apparent elastic modulus of laminated bamboo compared with several well-known failure criteria. The Poisson's ratio in A/C planes increased with the increment of the angle while in B/D planes, it increased and peaked at 30° before decreasing. Based on Ramberg-Osgood relation, the compression and shear stress-strain curves were fitted

Mechanical properties of laminated bamboo under off-axis compression

To investigate the compression performance of laminated bamboo, 210 laminated bamboo specimens were tested using seven different lamination angles. Six failure types were classified. All the specimens experienced elastic stage at the beginning of the loading process and then elastic-plastic stage. At the end of the elastic-plastic stage, specimens of °15, °30 and °45 immediately reached the ultimate bearing capacity, showing brittle failure,while other specimens entered a longer plastic stage before failure. The off-axis compression strength and the apparent elastic modulus both decreased with the increment of the angle. Two empirical formulas were proposed to predict the off-axis compression strength and apparent elastic modulus of laminated bamboo compared with several well-known failure criteria. The Poisson’s ratio in A/C planes increased with the increment of the angle while in B/D planes, it increased and peaked at °30 before decreasing. Based on Ramberg-Osgood relation, the compression and shear stress-strain curves were fitted