Issue 48

M. Estrada et alii, Frattura ed Integrità Strutturale, 48 (2019) 348-356; DOI: 10.3221/IGF-ESIS.48.33 349 Venezuela in bamboo forests concentrated in the Andean region [1,2]. Although bamboos have proven to be appropriate materials for the construction of civil structures, their mechanical behavior remains a subject of research. Recently, researchers [3–6] have contributed to determine the mechanical properties, such as stiffness and strenght, of guadua in round and laminated configuration, finding that it has an extraordinary structural performance and great potential in the construction of civil works. Moreover, studies have been carried out on the anatomy and microstructure of different bamboos in the world [7–9] and some specifically on the guadua [10–13]. These latest investigations have revealed that this plant is a composite and functionally graded material. Despite all efforts to use guadua in the construction of buildings and to investigate its mechanical properties, there are not enough studies about the detailed description of the mechanical behavior of this plant. Consequently, a constitutive model, proposed from a theoretical point of view, that simulates the mechanical behavior of elements and structures manufactured with laminated guadua is presented, taking into account the composite character of this material, without being limited by the geometry, the size or the loads applied. The mechanical behavior of the composite material is determined by the constitutive models of each of its components and by the microstructure of the material, that is, the distribution and orientation of the fibers in the matrix. The constituents, matrix and fibers, are considered isotropic materials, whose behavior is defined by constitutive models of damage and plasticity, respectively. Figure 1 : Round and laminated bamboo: (a) general parts, (b) culm parts, (c) culm wall detail; (d), (e), (f) and (g) lamination process. M ATERIALS : B AMBOO AND L AMINATED BAMBOO he main parts of the bamboo are the rhizome, the culm (or stem), the branches and the leaves (Fig. 1-a). For practical purposes, the culm is a bar with a circular hollow cross-section, which is divided into the parts indicated in Fig. 1-b. While the bottom parts are especially suitable for the construction, the upper parts of the culm tend to be used for the manufacture of furniture and handicrafts. Figs. 1-b and 1-c show an important characteristic for the formulation of the numerical mechanical model: long fibers are aligned with the longitudinal axis of the culm, which makes it a material reinforced in one direction. Slats with rectangular cross-section are extracted from bamboo culms (Fig. 1-d). Laminated bamboo is a composite material formed by bamboo slats, which preserve the same orientation fibers and the adherence with each other (Figs. 1-e, 1-f, and 1-g). This material allows to manufacture with prismatic bars with a T