Bamboo Structure Research Articles

Cyclic behaviour of exterior bamboo scrimber beam-to-column connections

With the advance in manufacturing technology, hot-pressed bamboo scrimber has been produced and widely utilised in construction practices in China. However, no design methods are available for bamboo scrimber members at present. Even though design equations for glulam structures are often used for bamboo scrimber members and connections, significant differences exist in the mechanical property of glulam and bamboo scrimber, which might lead to inaccurate estimations of the behaviour of bamboo scrimber structures. This paper describes the cyclic behaviour of exterior bamboo scrimber connections connecting I-beams and box columns. Four beam-to-column connections with welded steel angles and T-stubs were studied under reversed cyclic loading, and the influence of connection type and the number of bolts on the beam flange was considered. The load-displacement curve, failure mode, load capacity, ductility, stiffness degradation and viscous damping coefficient were obtained from the experimental results. Test results showed that connections with steel angles generally developed better ductility than those using T-stubs connecting the beam and column. When the number of bolts on the beam flange was increased, the energy dissipation of connections could be significantly increased. Besides, the shear resistance, distortion and strain of panel zones were studied, which could gain insight in the shear design of exterior connections. The contributions of the beam, column and panel zone to the total deformation of connections were analysed. Design recommendations were developed finally for application of bamboo scrimber beam-to-column connections in building structures. The experimental study provides valuable data for the design and practical application of this type of beam-column connection in building structures.

Experimental Study on the Flexural Behavior of I-Shaped Laminated Bamboo Composite Beam as Sustainable Structural Element

Laminated bamboo (LB) is considered a promising environmentally friendly material due to its notable strength and advantageous lightweight properties, making it suitable for use in construction applications. LB I-beams are a prevalent component in bamboo structures due to their ability to fully utilize their material properties and enhance efficiency when compared to beams with rectangular solid sections, while the characteristics of connections should be further studied. This paper presents an experimental investigation of the flexural behavior of I-shaped LB beams that are connected using self-tapping screws and LB dowels. Compared with glued beams of the same size, the findings of the study reveal that the primary failure modes observed in those two types of components were characterized by the separation of the component and web tensile fracture. The screw beam and dowel beam exhibited a reduced ultimate capacity of 43.54% and 30.03%, respectively, compared to the glued beam. Additionally, the ultimate deflections of the screw beam and dowel beam were 34.38% and 50.36% larger than those of the glued beam, respectively. These variations in performance can be attributed to the early breakdown of connectors. Based on design codes, it can be observed that the serviceability limits were in close proximity, whereas the ultimate strains of the top and bottom flanges were significantly lower than the ultimate stresses experienced under uniaxial loading conditions. As a result of the slip and early failure of connectors, the effective bending stiffness estimated by the Gamma method achieved better agreements before elastic proportional limit. Therefore, in future investigations, it would be beneficial to enhance the connector and fortify the flange as a means of enhancing the bending characteristics of an I-shaped beam.

Numerical Design and Analysis of Advanced Roof Systems in Architecture with Environmentally Friendly Low-Carbon Materials

This research explores the viability of bamboo as a green replacement for timber in building practices. Bamboo’s advantages lie in its renewability, sustainability, and resilience to disasters, despite possessing mechanical properties similar to timber. The study proposes using Finite Element Analysis (FEA) simulations, a potent instrument for designing and analyzing intricate structures under varying loads. The research explicitly employs FEA simulations to examine the application of bamboo in complex rooftop systems, using two commercial 3D CAD software—Rhino7 and Strand7. Rhino7 is responsible for 3D model creation and the member’s division into minuscule elements, whereas Strand7 is used to assign material properties, establish boundary conditions, carry out simulations, and analyze the outcomes. This research includes case studies of bamboo grid-shell structures and implements the suggested methodology. The study’s objective is to augment the scarce engineering data and to analyze bamboo as a material and the impact it can have on construction. The study’s results underscore the potential of eco-friendly, low-carbon materials, such as bamboo, in the construction industry. It also illustrates the effectiveness of FEA simulation in analyzing elaborate structures.

Strong and fire-resistant bamboo enabled by densification and boron nitride/graphene oxide nanocoating

Bamboo is an abundant and fast-growing nature material, which has been used in furniture and buildings. Its strength and fire-resistance are two critical issues for its wide applications. Herein, a high-strength and flame-retardant structural bamboo is obtained by constructing a boron nitride (BN)/graphene oxide (GO) composite nanocoating on the surface of delignified and densified bamboo (D-bamboo), abbreviated as BN/GO@D-bamboo. The two-dimensional BN nanosheets can form a layered structure on the surface of bamboo, providing bamboo with thermal dissipation and physical barrier for significantly improving its fire resistance. As a result, compared with natural bamboo and D-bamboo, the ignition time of BN/GO@D-bamboo is prolonged by 67% and 49%, the maximum heat release rate and total heat release are reduced by 59% and 40%, respectively, the smoke generation is also significantly reduced, showing an excellent flame retardancy and smoke suppression. On the other hand, GO in the composite nanocoating can form hydrogen bonding with the cellulose of bamboo, which in turn endows the coating with strong adhesion (5 B grade). Consequently, the axial tensile strength, bending strength and radial compressive strength of the BN/GO@D-bamboo are significantly improved compared with natural bamboo. Given the excellent flame retardancy and mechanical robustness of BN/GO@D-bamboo, it is expected to be a new generation high-performance sustainable structural material.

Evaluation of Tre Gai bamboo (Bambusa spinosa) bending strength perpendicular-to-fibre along the culm length

The continued need to decarbonize buildings has led to a deeper exploration of the use of bamboo culms in building systems. For the design and use of full culm bamboo structures, the bending strength perpendicular-to-fibre has received little comprehensive study along the length of commercially produced bamboo poles. We intensively measured the bending strength perpendicular-to-the-fibre for both node and internode sections along the length of commercially purchased Tre Gai (Bambusa spinosa) culms. Eight culms, each four meters long, were sectioned to measure the bending strength terms including tension and compression strengths in both the N-S (top/bottom) and E/W (left/right) directions using ISO 22157 procedures. Digital scanning was used to measure the inner and outer diameter of each section. Node strength was approximately 2.64 times greater than the internode strength. The performances of perpendicular-to-fibre strength terms were related to the primary tissue strength rather than the bamboo fibre strength within the culm. Based upon observations and measurements, the fmT,NS and fmC,EW strengths had greater values with lower variability, and were less sensitive to changes in length. Implications of perpendicular-to-fibre strength design in building elements are discussed.

A straightforward and efficient gradient pressure method for bamboo flattening: Strain and multi-scale deformation

Flattening is an environmentally friendly and efficient processing technique that transforms arc-shaped bamboo strips into regular rectangular ones, greatly expanding bamboo's application potential. However, the current method of bamboo flattening requires softening the strips in a high-temperature and high-pressure environment, followed by continuous roller flattening. This process consumes significant energy and does not allow real-time monitoring of the bamboo strips during the process. This study devised a straightforward and efficient gradient pressure method to flatten naturally arc-shaped bamboo strips into rectangular ones within 30 min, all while preserving the complete culm wall structure without any cracks. The analysis of the deformation characteristics during the process revealed that the outer side of the bamboo strip was subjected to compressive stress, while the inner side was subjected to tensile stress. The parenchyma and vessel cells underwent wrinkling and shrinking due to moisture loss and external pressure. Flattening generated horizontal, vertical, and shear strains in bamboo strips, with horizontal strain being predominant, reaching a maximum negative horizontal strain of approximately −0.131. Besides, significant differences were detected in strain among different parts of the bamboo strip. The overall strain exhibited an obvious left-right symmetrical distribution. For the first time this work analyzed the strain distribution and deformation characteristics during the flattening process of arc-shaped bamboo strips while preserving the intact bamboo culm wall structure. The findings of this research provide a novel option of bamboo culm flattening, enhancing the utilization of raw materials and expanding the application of bamboo as engineering materials.

A computation design method for architectural artifacts adapted from traditional Kagome bamboo basketry techniques

This study is a digital form-finding and manual fabrication experiment in woven architectural design, with one traditional weaving style, Kagome, used to scale the craft up into an architectural-scale bamboo woven artifact. Kagome is a trihexagonal pattern employed in traditional bamboo basketry as a triaxial weaving system, resulting in an object with a self-bracing capacity without the use of fasteners owing to its interlacing lattices. Although existing studies and tools have addressed triaxial weaving design and representation, the current consideration of the advantages of weaving with bamboo is insufficient. To address this research gap, this study develops a computational design method based on studies on bamboo basketry. This allows for the representation and exploration of design geometries using combinations of regular triangular meshes for the fabrication of Kagome woven bamboo artifacts. A full-scale mock-up was fabricated to evaluate the effectiveness of the method. The mock-up demonstrated the self-bracing properties of Kagome, but there were discrepancies between the mock-up and the design. Factors affecting bamboo weaving on an architectural scale have been identified within this study to inform future research on woven bamboo structures.

Microscopic and nanoscale mechanical properties of tonkin cane bamboo measured by advanced AFM methods

Bamboo is a natural composite material with a high strength-to-weight ratio traditionally used in various consumer products as well as in building and modern advanced and sustainable manufacturing technology. While its macroscopic mechanical properties are well known, nanoscale studies of the mechanical properties of the hierarchical structure of bamboo at the level of individual cells and cell walls are lacking. Here we use different AFM-based methods to analyse the mechanical properties of individual bamboo fibres that are the foundation of the hierarchical structure at the nanoscale. The elastic modulus of the fiber in the outer region varies from 7.5 to 8.9 GPa, while that of the inner fiber ranges between 4.1 and 6.1 GPa. The results demonstrate that the fibre stiffness varies in nanoscale regions between fibre interior and the fibre wall and strongly depends on the position of the individual bamboo fibre within the culm. Outer fibres with high cellulose fibril density and low lignin level show low adhesion interaction force (13.5%) in the interface between cellulose and lignin/hemicellulose matrix, hence, resulting in low plastic deformation energy release during mechanical deformation. The implications of the interrelation of plasticity, lignin level, and adhesion force are discussed for the application of bamboo as a high-performance, renewable, and sustainable material.

Mechanical properties of aged glue laminated bamboo for structural members

This research experimentally investigates the mechanical properties of aged unidirectional engineered bamboo (EB) laminate, pivotal in constructing glued laminated bamboo (glubam) structures. Investigations encompassed both outdoor exposure and artificial accelerated aging tests. In particular, outdoor exposure spanning three six-month intervals from July 2019 to December 2020. Complementarily, the Boil-Test (BT) method, as per the BS EN1087–1 standard, was employed for accelerated aging. The research examined tension, compression, bending, and shear mechanical characteristics of the aged bamboo samples. Notably, failure modes were predominantly influenced by fiber, matrix, and interfacial lamination layers. Findings revealed the superior anti-aging capacity of bamboo fibers compared with than that of bamboo matrix and lamination layer. Bamboo fibers maintaining over 75% of their original tensile strength. The BT accelerated aging method gave conservative estimations compared to outdoor exposure tests. Conclusively, the research yielded a novel tri-linear stress-strain model for analyzing the bending performance of glubam structures under varying aging conditions. This model incorporated strength reduction factors derived from the experimental data obtained from the corresponding compression and tension tests.

Estrutura populacional e distribuição espacial de Guadua weberbaueri Pilg. em florestas nativas e antropizadas da Amazônia Ocidental brasileira

ABSTRACT Brazilian forestry laws do not provide specifications for the management of bamboo-dominated forests. This study aimed to characterize the bamboo population structure, its spatial distribution and the effects of shoot density on the diversity and density of dominant tree species in the southwest of the Amazon Rainforest. An inventory was carried out in forest with and without anthropogenic interference, and the height and diameter at breast height of the trees were measured, as well as the diametrical, vertical and spatial distribution of the shoots. The bamboo diametrical distribution presented an irregular behavior in the two areas under study and the vertical distribution behaved irregularly in the forest without anthropization, in an asymmetric negative way when compared to the forest that suffered anthropogenic disturbance. The bamboo spatial distribution did not show changes in its aggregate pattern between the studied environments, and its density did not present a significant correlation with the density and diversity of tree species.

Bamboo-like nitrogen-doped carbon supported chlorine-doped Fe2P as an antibacterial oxygen reduction catalyst.

Bio-inspiration and biomimetics offer guidance for designing and synthesizing advanced catalysts for the oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). Herein, a chlorine-doped Fe2P supported by nitrogen-doped carbon (Cl-Fe2P/NC) catalyst was designed and prepared based on imitating the bamboo structure. The electronegative chlorine captured the electron transfer from Fe2P and transferred it to NC through carbon nanotubes (CNTs). The antibacterial chlorine inhibited the cathode biofilm formation to enhance the ion transport. Cl-Fe2P/NC achieved a half-wave potential of 0.91 V and an onset potential of 0.99 V versus a reversible hydrogen electrode. After 500 h of reaction, the MFCs assembled by the Cl-Fe2P/NC cathode achieved a maximum power density of 1505 mW m-2. This work provides insights into the design of advanced materials through bio-inspiration and biomimicry.

Analyzing the structure of bamboo culms using computer vision and mechanical simulation

Abstract Bamboo culm is a natural material characterized by a graded structure of vascular bundles in the radial direction and a regular distribution of bamboo nodes in the axial direction. To investigate the adaptation of bamboo culm structure to its natural environment, the bamboo culm structure was analyzed using a vascular bundle identification model, complemented by mechanical simulations. The results showed a certain pattern in the macroscopic dimensional characteristics of bamboo from the base to the top: the outer diameter decreased linearly; the internode length initially increased before decreasing; the length-to-diameter ratio gradually increased; and the wall-to-cavity ratio initially decreased before increasing. In response to external forces, bamboo exhibited strong stability, which was attributed to the thin and hollow wall as well as parabolic distribution of bamboo nodes. Along the axial direction, vascular bundle numbers linearly decreased, while the ratio of fiber sheath tissue and the distribution frequency of vascular bundles increased from the base to the top. In the radial direction, the length and area of vascular bundles tended to increase before decreasing, while the width tended to increase, leading to a decreasing length-to-width ratio. Overall, the radial variation pattern of vascular bundles showed nonsignificant variations at different heights.

Out-of-plane characteristics of cross-laminated bamboo and timber beams under variable span three-point loading

Given the exceptional mechanical properties of cross-laminated bamboo and timber (CLBT) and its ability to efficiently utilize bamboo and timber resources, CLBT holds considerable potential for applications in modern sustainable timber and bamboo structures. CLBT panels, when used as floors or roofs, typically experience out-of-plane loads. This study investigates the out-of-plane bending and shear characteristics of 5-layer CLBT and cross-laminated timber (CLT) specimens using the variable span three-point loading test method. The results indicated that the developed CLBT exhibited superior mechanical properties compared to CLT, offering a preliminary demonstration of its value in engineering applications. In addition, factors such as the span and outermost lamination influenced the failure modes, vertical deflections, strain distributions, ductility indices, and energy absorption characteristics of CLBT and CLT specimens. This study provides a foundational reference for using CLBT as floor and roof panels subjected to out-of-plane loads and lays the foundation for further research.

Study on the elastic stiffness calculation method of single-bolted steel-bamboo scrimber-steel shear connections

Bolted steel-bamboo scrimber-steel (SBSS) connections are commonly employed in composite bamboo structures, but their equivalent stiffness in the elastic phase is difficult to determine. This study develops a novel theoretical formula for estimating the equivalent stiffness in the elastic phase of single-bolted SBSS shear connections considering various failure modes. Specifically, the method focuses on calculating the contact stiffness between the bolt and the pre-drilled hole wall, as well as the shear load applied to the bolt end by the steel plate. The method uses the double-shear yield mode, which is included by European Yield Modes (EYM), and the beam on elastic foundation theory (BEFT), and considers the bamboo scrimber embedment stiffness, bolt diameter and steel plate strength class. The method is tested by conducting experiments on single-bolted SBSS connections with varying load and fiber direction (LFD) angles, bolt diameters, steel plate thicknesses and strength grades. The results show that the connection stiffness increases with bolt diameter and steel plate strength grade, decreases with LFD angle, and is not affected by steel plate thickness. The parameter μ, which is important in the theoretical equations, is also calibrated based on the experimental data. The proposed method is validated by comparing it with existing test results of single-bolted SBSS connections. This paper provides a simple and reliable model for predicting the equivalent stiffness in the elastic phase of bolted SBSS connections in bamboo scrimber structures and offers useful insights for their design.

Exploring bundle bamboo split technique in bending dendrocalamus asper for landscape structure

Bamboo is one of the fastest-growing natural construction materials and is locally available in most developing countries, including South America, Africa, and Asia. Bamboo is a “green gold” plant in the tropical forest. It is a fast-growing monocotyledon species belonging to the Gramineae family (Bambusoideae) and requires a short time for re-production. Bamboo’s physical strength provides builders from ancient times until today an opportunity to use bamboo as a natural and sustainable construction material for building houses and structures. Due to its capability to bend, bamboo is the most preferred material in vernacular construction and lately in Southeast Asia countries which borne new trend in building design. The built-environment professionals, namely landscape architects, architects, and engineers in Malaysia, still lack knowledge of bamboo, especially on bending capabilities, as one of the sustainable construction materials. Less concern was given to researching the capabilities of bamboo’s ability to bend, even though its strength is more than steel and provides various design opportunities compared to other sustainable materials. Different types of bamboo present different strength capacities. Therefore, the aims of this research is to compare and determine their strength capacity, bending criteria and species suitability for design and construction in Malaysia. This paper collects published literature on experimental studies on the different methods of Hot and Cold Bending Methods which allow bamboo to bend to suit designer needs and concentrate on Malaysian Dendrocalamus asper (Buluh Betung), which considered as tough and durable species, as the primary construction material for landscape structures. Bundle Bamboo Split (BBS), identified as one of the bending techniques adopted for an experimental project, using BBS of 0.8m radius, produces a prototype for a landscape structure. The findings indicate observation of works by a team of craftsmen trained by an expert in bamboo construction who used to produce bamboo structures from Bali, Indonesia, highlighted tools and procedures in bamboo construction. In short, this paper will also enhance the use of bamboo as an accessible, durable, creative and sustainable construction material that represents the local identity of Tropical Malaysia Landscape Architecture.

Bamboo Inspired Silicon Anodes with Ultrahigh Initial Coulombic Efficiency and High Capacity for the Li-Ion Batteries.

Silicon is regarded as the most promising candidate due to its ultrahigh theoretical energy density (4200mAhg-1). However, the large volume expansion of silicon nanoparticles would result in the destruction of electrodes and a shortened cycle lifetime. Here, inspired by the natural structure of bamboo, the silicon anode with vascular bundle-like structure is proposed to improve the electrochemical performance for the first time. The dense channel wall in the silicon anode can accommodate the volume change of silicon nanoparticles and the transport of ions and electrons is also enhanced. The obtained silicon anodes display excellent mechanical properties (50% compression resilience and the average peel force of 4.34N) and good wettability. What more, the silicon anodes exhibit high initial coulombic efficiency (94.5%), excellent cycle stability (2100mAhg-1 after 300 cycles) which stands out among the silicon anodes. Specially, the silicon anode with impressive areal capacity of 36.36mAhcm-2 and initial coulombic efficiency of 84% is also achieved. This work offers a novel and efficient strategy for the preparation of the flexible electrodes with outstanding performance.

Transparent Bamboo with Multiple Light Transmittance levels, Fiber Textures, and Colors Based on the Gradient Structure of Bamboo

Transparent bamboo (TB) is a new type of biomass and light transmitting material with potential to serve as a substitute for transparent wood. However, the potential of the bamboo structure in preparing transparent composites is underexplored. Inspired by the functional gradient structure of bamboo, we used a simple and efficient two‐step strategy to prepare TB with different transmittance levels, fiber textures, and colors. We evaluated the performance of single‐ and multilayer TB with various fiber volume contents prepared using different lamination methods. We found that the optical and mechanical properties of TB differed with the fiber volume content and the lamination method used. TB composed of veneers with low fiber volume showed the highest light transmittance (44.6%), whereas TB composed of veneers with high fiber volume had the highest tensile strength (45.7 MPa). In terms of water resistance, cross lamination inhibited expansion in width (water absorption rate, 16.37–21.26%) and thickness (thickness swelling rate, 10.22–21.74%). The lamination structure and fiber volume content in the preparation of TB should be selected according to the specific application scenarios. The graded utilization of bamboo veneer with a fiber gradient can effectively realize the rational allocation of bamboo resources and promote sustainable development.This article is protected by copyright. All rights reserved.

Effects of nozzle orifice shape on jet breakup and splashing during liquid jet impact onto a horizontal plate

In some accident situations in nuclear power plants, liquid coolant is discharged from a non-circular rupture hole. Thus, to improve the understanding on the effects of nozzle orifice shape on the jet behavior, experiments were carried out on the liquid jet ejected from oval nozzles. In the experiments, water was used as the test liquid, the area-equivalent nozzle diameter was within 1.8-2.9 mm, the aspect ratio of the nozzle hole was within 2.6-4.8, and the jet velocity was varied within 0.25-11.3 m/s. At low and high liquid flow rates, the liquid jet behaved similarly to the circular jet; the jet breakup lengths and the size of the droplets formed after the jet breakup were expressed by similar dimensionless correlations as those for the circular jet. At the intermediate liquid flow rate, a bamboo leaf-like structure formed on the liquid jet dominated the jet breakup. The jet breakup length was therefore correlated using a theory for the surface tension-induced shape oscillation of elliptical fluid. These correlations enabled to estimate the liquid jet state at any distance from the nozzle. It was also confirmed that if the state of the liquid jet at the impact point is known, the splash rate and the size of the splashed droplets can be predicted satisfactorily using the available correlations based on the experimental data for the circular jet. Therefore, the present work extended the available knowledge on the liquid jet discharged from a circular nozzle to enable the prediction of the behavior of the liquid jet and the characteristics of the secondary droplets produced during liquid jet impact onto a solid surface for the oval nozzles.

A more explosion-resistant bamboo fiber reinforced composite structure through balancing bamboo anisotropy

Explosion-resistance of two kinds of bamboo composite plates with different laminated structures was investigated by in-field explosion experiments. It is revealed that both unidirectional parallel bamboo strand lumber (PBSL) plates and cross-laminated bamboo (CLB) plates can resist large dynamic elastic deformation and have good anti-explosion ability. Through balancing PBSLs’ anisotropy by cross-laminated structure, the CLB plate is far superior to the PBSL in explosion resistance. In this research, the critical scaled distance is between 1.293 m/kg1/3 and 1.086 m/kg1/3 for the PBSL, while it is significantly reduced and between 0.543 m/kg1/3 and 0.407 m/kg1/3 for the CLB. Matrix cracking penetrates the full thickness of the PBSL plate and attenuates its explosion resistance, while this shortcoming is overcome by the CLB whose main damage modes are fiber fracture and spalling. The CLB is a more explosion-resistance bamboo structure.

Eco-friendly, high-utilization, and easy-manufacturing bamboo units for engineered bamboo products: Processing and mechanical characterization

Bamboo units used for manufacturing engineered bamboo products are typically processed by breaking and planing, resulting in products with high glue content, substantial costs, and adverse environmental impacts. To address these issues, a simple and effective approach for processing standard bamboo units, based on the natural form and structure of bamboo, is proposed and tested in this study. More specifically, bamboo splits were dried at 0.05 MPa pressure and 140 °C for about 2.5 h in a pressurizing device. After drying, the bamboo splits each formed an equal-arc shaped bamboo split (EASB) in which the inner and outer radii were roughly equal. The EASB unit represents a double breakthrough of a high material utilization rate (as high as 80%) and low damage to bamboo. Additionally, the appropriate drying technique improves the dimensional stability and retains the excellent mechanical properties of natural bamboo. This work demonstrates the concept of “natural form inspired design,” and the EASB provides a basis for wider applications of sustainable engineered bamboo products.