مطالعه تجربی و عددی رفتار سازه مدول منسوجات چوب منفرد

The present work investigates an innovative class of timber structure with potential applications in roofing, facade and bridge construction, called Timberfabric. The development of Timberfabric structures originates from the approach of harnessing the structural, modular and qualities of textiles in timber construction (Weinand and Hudert, 2010) [9]. Timberfabric structures are comprised of repetitive arrangements of one or more structural unit cells called Textile Modules. When properly designed, one obtains a modular and lightweight structure with interesting and unusual geometrical and structural qualities. This paper focuses on the single timber Textile Module. Based on the finite element (FE) method, a reliable procedure is proposed for modeling the overall assembly process of the Textile Module. For comparison, Textile Module prototypes are constructed at two different scales (large and intermediate scales) with different assembly conditions. The proposed geometrically nonlinear FE model allows evaluation of the stresses that are induced during the construction process and which may affect the structural integrity of the module. In particular, the risk of failure during assembly is identified using the anisotropic Tsai-Hill criterion. The structural behavior of the timber Textile Module is then investigated through bending tests using the constructed prototypes. During the loading procedure, the vertical deflections are measured at different locations on the prototype surface by means of external displacement transducers. Using the FE model, the corresponding deformed shapes are simulated by applying the bending loads on the pre-stressed Textile Module. Experimental displacements and FE predictions are thus compared and found to be in good agreement.

Wood is a versatile construction material that is abundant in many regions of the world. Moreover, this is a renewable resource that can be processed and assembled in energy efficient ways. Recent studies [1] and [2] indicate that the use of timber as construction material results in buildings with a better environmental performance in comparison to conventional materials. With regard to present-day concerns over globally increasing energy consumption and simultaneously decreasing resources wood holds a distinct advantage over other construction materials such as concrete or steel. This, in turn, should increase the interest of the research community in expanding the range of applications of timber structures. Examples of modern but already well-established timber architectural forms include folded plate structures [3] and [4], lattice structures (e.g. timber lattice roof for the Mannheim Bundesgartenschau) [4] and [5] and Multi-reciprocal frame structures [6] and [7]. Such forms present clear advantages over more traditional flat-surfaced roofing structures, increasing the efficiency of the structure, reducing its weight and enforcing load carrying capacity. Recently, a new type of timber structures, called Timberfabric, with particular structural properties emanating from the principle of weaving techniques has been developed at IBOIS [8] and [9]. Its development has been driven by the aim of incorporating specific textile qualities such as modularity and the mutual support of textile fabrics’ constituent elements in timber construction. Timberfabric structures have a broad potential for architectural applications due to their versatility, adaptability and their qualities, which are directly linked to their structural make-up. They are based on repetition of a structural unit cell, the Textile Module, which is depicted in Fig. 1a, and which results from bringing together textile assembly principles with timber components. The double-layered Timberfabric structure shown in Fig. 1b represents only one of many possible configurations of Textile Modules.The single Textile Module presented in Fig. 1a provides a structural shape of particular interest for this study. Briefly, it consists of two mutually supporting thin panels that become curved during the assembly process as illustrated in Fig. 2. Consequently, construction (or residual) stresses are generated during the fabrication of the module and their amplitude typically depends on the constitutive material, the size of panels as well as the assembly conditions. The use of poor quality material or inappropriately dimensioned panels or a combination of both may even cause the Textile Module’s premature failure during the assembly process. The construction stresses can be evaluated by means of a finite element (FE) model that takes into account the different fabrication stages (Fig. 2).This paper focuses on the fabrication process and structural behavior of a representative single Textile Module in a bending load configuration. The proposed approach is both experimental and numerical. It involves the fabrication of two prototypes at two different scales (intermediate and large scale) with different assembly conditions, as discussed in the first part of Section 2. The second part of the section is devoted to the bending test setup and required measurement equipment. Despite the numerous finite element (FE) models already available for braided textile composites [10], [11], [12], [13] and [14], the numerical study of the timber Textile Module requires special attention as its analysis is complicated by the particular geometry and assembly conditions encountered. Because of the large deflections and rotations undergone by the module during the fabrication stages (Fig. 2), a geometrically non-linear FE model that aims to accurately reproduce the geometrical shape of the Textile Module is developed in Section 3. It is anticipated that this model should permit a representative evaluation of the construction stresses involved in fabrication. In Section 4, vertical displacements measured at several locations of the prototype surface during the bending tests are compared to the finite element predictions. Finally, the structural behavior of the Textile Module is discussed.

In this work, a novel class of timber structures based on the logic and principles of textile techniques has been investigated. A geometrically nonlinear finite element model has been developed for the construction of a single Textile Module including pinned and so-called wedge connections for the assembly conditions. For comparison, large-scale and intermediate-scale experimental prototypes with the previous connections have been constructed. The proposed analysis aimed first at reproducing the initial shape of the structure and thus evaluating the resulting construction (initial) stresses induced during the assembly process. It was shown that the simulated shape could satisfactory fit to the experimental one at several measurement points. Moreover, the anisotropic Tsai-Hill criterion based on the maximum induced stresses allows one to select safe design parameters. It was observed that a length-to-width ratio l/w = 7.5 for the large-scale GFP panels leaded to failure during the construction while l/w = 15 was safe. For the intermediate prototype (l/w = 9.75), wedge connections comparatively lead to lower levels of construction stresses and could be adopted at larger scale. Secondly, the structural behavior of the Textile Module has been examined under bending tests. For the two considered geometries, the resulting deflections have been measured and calculated at several locations. They highlight a nonlinear bending response of the Textile Module. A good agreement is generally observed between the experimental results and the FE predictions at intermediate and large scales. Finally, the introduction of wedge elements was found to significantly improve the overall rigidity of the Textile Module.