Papers by Author: Caori Patricia Takeuchi

Abstract: Raw bamboo is a composite graded naturally material with variable distribution of fibers in the culm wall thickness and also in height. The strength and fiber volume fraction obtained in tests of round bamboo are very variable, while laminated bamboo has more uniform properties. The fiber volume fraction was determined in two groups of specimens of laminated bamboo Guadua angustifolia and also in two groups of bamboo clapboards. Although the average values of fiber volume fraction was around 45% for all cases, it was found that the coefficient of variation in the groups of specimens of laminated bamboo guadua was 6%, while in the groups of slats was 29%.

Abstract: Laminated bamboo is a natural composite material with cellulose fibers, parenchyma cells, and vascular bundles. The mechanical characterization of this material includes not only the determination of its strength, but also of its elastic constants. Given the anisotropic nature of the laminated material, compression tests were performed on three groups of specimens. The elastic modulus in the load direction and the Poisson's ratio were determined, and the results showed that the material's physical anisotropy causes an anisotropic mechanical behavior. The average values obtained for the elastic modulus ranged from 30044 MPa for group 1 to 265 MPa for group 2. The results of the test to determine the Poisson's ratio in compression perpendicular to the fibers, ranged from 0.013 to 0.278 whereas those obtained in compression parallel to the fibers, ranged from 0.621 to 1.506.

Abstract: Specimens of laminated bamboo Guadua angustifolia do not usually fail due to fiber breakage when submitted to shear stresses. The common failure mechanism in that case is slippage in the fiber-matrix interface, accompanied by degradation of the lignin matrix (parenchyma). In this study the shear strength of laminated bamboo Guadua angustifolia specimens was determined by tension tests reducing the cross section area. The perimeter of the slipped area was determined using digital image processing. Shear stresses were calculated taking into account the load and slipped area in specimens of two different groups, depending on the orientation of the laminated boards. It was found that the average value of the shear strength on pull out tests were 2.9 MPa, which is a mechanical property of the material that is useful, for example, in the analysis of the behavior of the joints, and analysis of the fracture process.

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.

Abstract: This article presents the experimental tests results of frames made with glued laminated pressed bamboo guadua under lateral load. The tested frames had two floors with 1.40m of height each one and 2.80m of total height; the width of the frames was 2.10m. Beams and columns had square box cross-section of 0.10m side and 0.015m of wall. Three frames had bracing type K and other threes had panels. The adhesive used for the manufacture of beams, columns and braces was Urea Melamine Formaldehyde and for the elaboration of panels was Polyvinyl Acetate. The frames of glued laminated pressed bamboo guadua had elastoplastic behavior with great ductility.

Abstract: In 2008 began the research project "Design and construction of housing with structural elements of bamboo (guadua) laminated" of the research program Innovation for Guaduas productivity chain strengthening at the Rionegro province in Cundinamarca.In the first part of the project it was necessary to implement the production of laminated bamboo elements, for which, they were manufactured parallel saws for the production of slats, handheld devices for applying adhesive and a equipment for pressing. In Pacho and Ibama located in Rionegro province of Cundinamarca in Colombia two primary production sites for the production of slats were stablished. So, the bamboo was cut in the natural forest, the slats were obtained and were transported to the Universidad Nacional de Colombia (National University of Colombia) at Bogotá, where, after a selection process and machining, were pressed to obtain test samples and structural elements.After, it was performed the experimentation phase which included the testing of samples elaborated with four types of glue, under different types of solicitations, beams with four different configurations of slats density, solid and box section beams and columns, solid and sandwich panels, T-section boards and frames with two different types of panels.The last stage of the project included the architectural and structural design and construction of a housing prototype using structural elements in laminated bamboo.

Abstract: The earthquake on 1999 in Armenia city (Colombia) showed the good seismic performance of structures using bamboo guadua as main material but also the mistakes caused by improper techniques of construction and the lack of parameters design for this type of structures. This work presents the experimental methodology used for the determination of allowable stresses for the design of bamboo guadua structures, used in the project "Validation of Guadua Angustifolia as a structural material for design, by the allowable stresses methodology" financed by the Ministry of Agriculture and Rural development of Colombia (Ministerio de Agricultura y Desarrollo Rural de Colombia) and developed by National University of Colombia (Universidad Nacional de Colombia) since the year 2008 when there were no allowable stress design standards for this structures in Colombia. For the determination of the allowable stresses were carried out tests of samples in compression, tension, and shear parallel to the fiber, compression perpendicular of the fiber and bending beams with bamboo guadua from three different areas of Colombia. It was found also the flexural elastic modulus for the material.

Abstract: Steel reinforced concrete is generally used in houses structure elements. However bamboo strength properties similarly to the wood, make it an alternative concrete composite material. Load test were performed in two kinds of bamboo guadua concrete reinforced composite slabs. During the tests the slabs functioned as domestic roofing-flooring in standing houses, the slab systems tested were bamboo stem covered slab and stem free slab. Two different tests were designed to measure the deflection in the middle of the composite slab and along a single bamboo stem. In three different slab sizes and after replications, no deflection under the applied load was recorded. Therefore, bamboo composite slabs without steel reinforcing seem likely to be used in long lasting houses for middle and high class dwellings in Colombia.