Abstract: In this paper the result of an investigation using finite element model (FEM) of a simple bamboo pin joint as commonly used in many types of structures especially in plane and space structures is presented. The nonlinear pressure distributions at the contact area of a steel pin in a bamboo circular hole were analyzed considering the anisotropy and heterogeneity of the functionally graded material. In turn the obtained results of the analysis are compared with those based on simplified constitutive models assuming isotropic and homogeneous representations for bamboo. The experimental results are compared with the results obtained from both methods. The assumption of the bamboo as an orthotropic material presented more reliable design method of bamboo structures Although the different maximum forces applied in each case, local stress are relatively high on both cases, showing that this type of connection depends on local reinforcements to be a safe connection. Finally the suggestion that bamboo joints at the hole can be improved by reducing the stress concentration factors, through applying reinforcing elements such as natural fiber straps composites close to the hole.
Abstract: The results of many successfully realized Research and Development (R&D) concerned with non-conventional materials and technologies (NOCMAT) in developing countries including Brazil have not been used in large scale in practice. This is due to the lack of selection and evaluation criteria and concepts from planning and designing to implementation programs by governmental agencies and private organizations concerned with the newly developed sustainable materials and technologies. The problems of selecting and evaluating R&D innovation outputs and impacts for construction are complex and need scientific and systematic studies in order to avoid the social and environmental mistakes occurred in industrialized countries after the Second World War. This paper presents a logical framework for the implementation of pertinent indicators to be used as a tool in R&D of NOCMAT projects selection and evaluation concerned with materials, structural elements and technologies of bamboo and composites reinforced with vegetable fibers. Indicators, related to the efficiency, effectiveness, impact, relevance and sustainability of such projects are considered and discussed.
Abstract: The present worldwide socio economical system created the actual situation where almost two third of world population lives under the minimum living conditions which have been established by the United Nations criteria. To overcome these deficiencies, there is an urgent need to establish a new paradigm for promoting conservation and environmental sustainability. This paper presents the evaluation criteria for this major concern. The main variables considered are: sufficient availability, renewability, adequate physical-mechanical characteristics, cost efficiency, easy access, simple production, local technology adapted to local conditions, and durability. The non-conventional materials and technologies (NOCMAT) minimize adverse impacts into the environment and also provide adequate products for a market increasingly competitive. Thus, very strict norms and clean technologies should be implemented. Positive results in Brazilian research institutions have been developed on the use of NOCMAT (bamboo, vegetable fibers, bio-composites, recycled conventional materials, etc.) since 1979 at the Pontifical Catholic University of Rio de Janeiro (PUC-Rio, Department of Civil Engineering). Nevertheless, these NOCMAT are not yet sufficiently disseminated and employed in the country due to the lack of sufficient investments. Thus, government incentives and private initiatives must be increased substantially to change this panorama in Brazil.
Abstract: There are more than one thousand of bamboo species around the world, but in some areas the most common is the Bambusa vulgaris. Comparing with other species used in construction, it is more susceptible to insect attack and its strength is slower. This work shows some studies made using culms of this bamboo with the aim to improve its durability and mechanical properties by impregnation of polymeric resins into their vases. Some information about Bambusa vulgaris microstructure is done. The percentage of vases, fibers and parenchyma was measured using an optical microscope. The absorption of this species in liquids with different viscosities was determined. Using an equipment to force the liquid into the vases, time of penetration of fluids with different viscosity was measured. Results show that the fluids penetrate most easily in the internal vases, where the diameter is greater than that close to external face of the culms and confirm that it is possible to fill the bamboo vases with viscous fluid as oil or polymeric resins. The attack of insect was eliminated when a impregnation with a resin made by 80 % de styrene + 20 % de metilmetacriyate was applied to Bambusa vulgaris culms.
Abstract: Glubam is a new construction material and glubam bolted joints have been developed in modern bamboo structures. To observe the performance of bolted joint, two major groups of glubam-single-bolted-joint specimens with double steel side plates are tested. Bearing strength and failure mode are analyzed and discussed. It is shown that specimens with tension parallel to bamboo fiber always yield by shearing out and showed higher bearing strength as well as better ductility, while specimens with tension perpendicular to bamboo fiber will fail by net tension. Results of bearing strength are evaluated by the 5% off-set method. At the end, equations obtained from test data and analysis about yielding strength of glubam bolted joint was obtained for following study and project design.
Abstract: Glubam is a kind of environmentally friendly and energy efficient composite material in civil engineering developed in recent years. But the mechanical performance after subjected aging under the outdoor conditions is a blank of research field. In this paper, a new artificial accelerated aging test method and equipment for glubam have been presented by authors. The basic material performance, including deformation changing, tensile properties, compressive properties, bending properties and internal bonding strength, are tested according to the equivalent aging duration of 120 days, 240 days, 480 days and 960 days. The failure mode of specimens shows that delamination of glubam caused by dry wet circulation is the main reason for mechanical properties degradation. All test results present monotone decreasing trend and the internal bonding strength is the most sensitive to aging duration. Aging influence factor β, internal bonding correlation coefficient η and internal correlation coefficient θ can be used to evaluate aging performance of glubam, but the accuracy of evaluation results need further research.
Abstract: This paper presents the experimental results of an on-going study investigating the buckling capacity of single-culm and multiple-culm bamboo column elements. Four single-culm columns of species Bambusa Stenostachya were tested to obtain single-culm column capacities as well as control tests to determine the behaviour of short-doweled end-conditions. Three multiple-culm columns were then tested in order to investigate the ultimate capacity and buckling behaviour of these elements. Specifically of interest wasthe effect of bamboo stitching on improving column behaviour in the bamboo culms. Experimental values were compared with theoretical predictions for buckling capacity using the Euler equation. The behaviour of multiple-culm columns was shown to exhibit load redistribution and to mimic the sum of individual culm capacities rather than composite column behaviour. Stitching was shown to be beneficial in enforcing column geometry yet detrimental through introduction of lateral loading to culms. Finally, the apparent effective length factor K was shown to be closer to K=1 than to the value obtained from control tests of the designed end condition.
Abstract: Standardization, and thereby acceptance of any construction material requires years of testing and analysis. For structural bamboo, prototype model standards, in the form of the International Organization for Standardization (ISO) documents on bamboo design, testing and construction are available. While these provide useful guidelines, an important and often overlooked consideration in developing test methods is that these must be usable and reliably repeatable in the environment in which they are most expected likely to be used. The present work investigates the potential for adopting the relatively simple-to-conduct edge bearing test as an indirect means of obtaining the critical, although otherwise difficult-to-obtain transverse material properties. Expanding previous studies on transverse material properties, the research explores the effect of through-culm-wall fiber gradation on the edge bearing, or diametric compression, strength of full-culm bamboo. The test method utilizes a full culm section cut into two or three concentric annular sections. Tests results for each ring provide a measure of through thickness transverse properties. The objective of this work is the development of practical test methods for field assessment of bamboo material properties.
Abstract: As other natural materials used in construction, Bamboo Guadua is affected by different factors that can modify its strength. One factor is the equilibrium moisture content, which is a physical property related to temperature and relative humidity of the area where the material is used. Several studies have shown that the material strength to different load requirements decreases as moisture content increases. Samples from three different regions of the Republic of Colombia (Coffee region, Valle del Cauca and Cundinamarca) were taken to study the variation of the tensile strength parallel to the fiber of bamboo Guadua Angustifolia Kunth in function of the moisture content. Ten culms were taken from each region and three sections from different parts of each culm (bottom, middle and top) were selected. At least seven samples of each section were extracted and tested (so the samples taken from the same piece of bamboo have similar characteristics). The natural moisture content of each sample was modified to determine the strength with different moisture content. The method to vary the moisture content used in the research guaranteed that each group of samples, with similar characteristics, had a moisture-controlled variation. Colombian Technical Standard NTC 5525 "Methods for testing the physical and mechanical properties of Guadua Angustifolia Kunth were followed to determine the tensile strength parallel to the fiber, as well as to determine the material moisture content. Tensile tests were performed after immersing the specimens in water for about 72 hours, when the material showed a pronounced variation in moisture content. Finding that tensile strength did not show an obvious decrease, the range of moisture content was reduced to less than 35%. In order to have all the information with samples with moisture content below of that percentage, the tests were carried out during a 3-hour range of time. Results showed that tensile strength of parallel fiber does not decrease as the moisture content of the material was increased in the moisture content range where the material is used as a structural element.