Pressure coefficient distributions for the design of hypar membrane roof and canopy structures

Membrane structures are used in the built environment as roof or canopy and must therefore be designed to resist the external conditions. Nonetheless, the topologies of membrane structures are not covered by existing wind load standards and relevant wind load distributions for the basic shapes of these structures are almost not available. To have a realistic analysis of the wind loading, wind tunnel tests can be performed for each design. However, due to the lack of resources or time, for many projects the wind analysis will be based on rough approximations by relying on conventional shapes in the Eurocodes, with applying very high safety factors or designing unsafe structures as risk. Therefore, this paper presents a study of the orientation and curvature dependency of the wind load distributions over hypar roof and canopy structures. This study is performed with a numerical wind tunnel, using CFD with Reynolds averaged Navier Stokes equations. The outcomes are summarised in pressure coefficient distribution plots for most important wind orientations for hypar roofs and canopies with different curvature. The presented pressure coefficient distributions can be used in line with the Eurocode to derive more relevant wind load estimations for hypar membrane structures. These wind load estimations will give the engineer information about the average response of these structures under wind loading and will facilitate more reliable wind design of membrane structures

(Un)folding the membrane in the deployable demonstrator of contex-t

The paper presents a system, made out of foldable ‘kinked’ beams and a membrane skin, based on a concept referring to origami. The anticlastic curvature of the membrane is obtained by transforming flat triangular parts into space. The following research question is considered: can the foldable system be stable in intermediate configurations? To obtain a well-tensioned membrane in the intermediate positions, the belts connecting the membrane to the frame can be released or increased in tension. A full scale ‘demonstrator’ has been built within the frame of IP-project Contex-T8. Although the deployment - rotating the ‘kinked’ beams about the central axis - was feasible, the tensioning and structural behaviour of the membrane, attached in the nodes of the frame, was not yet thoroughly examined. For that reason one single unit has been analysed. Forces and deformations in the membrane are verified for different opening angles using integrated models including the membrane, connecting belts and ‘kinked’ beams (for the frame). The results of the experimental investigations and numerical models are compared and occurring discrepancies are clarified

Numerical investigation of the structural behaviour of a deployable tensairity beam

This paper investigates numerically the load bearing behaviour of a deployable Tensairity beam. More precise, it studies the influence of the cables that connect the upper and lower strut of the deployable Tensairity beam on its load bearing behaviour. Finite element analysis shows that these cables are pretensioned when the airbeam is inflated. When both diagonal and vertical cables are present, only the vertical cables become tensioned. These tensioned cables are able to take compressive forces, by the same amount as their initial pretension. This has as result that these cables avoid the hinges to deflect under compression. Or in other words, the pretensioned cables ‘block’ the hinges. Once the external load has reached the value whereby the value of the pretension becomes zero in at least one cable, the hinge is not blocked or supported anymore by this cable. The hinge will experience larger displacements and the stiffness of the deployable Tensairity beam decreases

Implementation of bending-active elements in kinematic form-active structures - Part I : design of a representative case study

Due to their low self-weight and their inherently high flexibility, technical textiles offer great possibilities for the integration in kinematic structures. Furthermore, the implementation of active bending in a transformable design creates new challenging perspectives. The paper describes an integrated approach for transformable textile hybrids where an improved design is obtained through a parameter study, performing a structural analysis in the different phases of the deployment. The studied parameters include (i) the form-finding position, (ii) the prestress (ratio), (iii) the used materials and sections (including the fibre directions) and (iv) the number of bending-active elements. This research confirms the feasibility of realizing kinematic form-active structures with integrated bending active elements, where both the membrane and the supporting structure are stable in the different configurations. Due to the high interaction between the bending-active supporting system and the pretensioned membrane, the different parameters influence each other significantly. In a next step, an experimental verification of the designed pringle-shaped textile hybrid is carried out in order to both confirm the possibilities and reveal the remaining challenges

Implementation of bending-active elements in kinematic form-active structures - Part II : experimental verification

The integration of bending-active elements in kinematic form-active structures opens new perspectives for the development of transformable architectural applications, introducing new typologies and interesting structural concepts. Structures that combine the use of membrane materials and the concept of active bending are referred to as 'textile hybrids'. The complex interaction between the bending-active boundary elements and the membrane, but also the inherent high flexibility of both the membrane material and the bending-active elements, however, complicate the structural behaviour of the studied transformable textile hybrid. Therefore, an experimental verification of the structure becomes crucial to validate the results obtained through the numerical analysis and to allow a full understanding of the structural behaviour. This paper discusses the experimental set-up and investigation of a representative case study and compares the experimental results to the numerically obtained values

A Deployable Mast for Adaptable Textile Architecture

p. 252-263Proposed here is a concept for a deployable mast with angulated scissor units, for use in adaptable temporary architectural constructions. The adaptable structure serves as a tower or truss-like mast for a temporary tensile surface structure and doubles up as an active element during the erection process. The mast consists of scissor-like elements (SLE¿s) which are an effective way of introducing a single D.O.F.(degree of freedom) mechanism into a structure, providing it with the necessary kinematic properties for transforming from a compact state to a larger, expanded state. The scissor units used here are not comprised of straight bars, but rather consist of angulated elements, i.e. bars having a kink angle. Although primarily intended for radially deployable closed loop structures, it is shown in this paper that angulated elements can also prove valuable for use in a linear threedimensional scissor geometry.De Temmerman, N.; Mollaert, M.; De Laet, L.; Van Mele, T.; Guldentops, L.; Henrotay, C.; Debacker, W.... (2009). A Deployable Mast for Adaptable Textile Architecture. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/650

Functional Grading of Mycelium Materials with Inorganic Particles: The Effect of Nanoclay on the Biological, Chemical and Mechanical Properties

Biological materials that are created by growing mycelium-forming fungal microorganisms on natural fibers can form a solution to environmental pollution and scarcity of natural resources. Recent studies on the hybridization of mycelium materials with glass improved fire performance; however, the effect of inorganic particles on growth performance and mechanical properties was not previously investigated. Yet, due to the wide variety of reinforcement particles, mycelium nanocomposites can potentially be designed for specific functions and applications, such as fire resistance and mechanical improvement. The objectives of this paper are to first determine whether mycelium materials reinforced with montmorillonite nanoclay can be produced given its inorganic nature, and then to study the influence of these nanoparticles on material properties. Nanoclay–mycelium materials are evaluated in terms of morphological, chemical, and mechanical properties. The first steps are taken in unravelling challenges that exist in combining myco-fabrication with nanomaterials. Results indicate that nanoclay causes a decreased growth rate, although the clay particles are able to penetrate into the fibers’ cell-wall structure. The FTIR study demonstrates that T. versicolor has more difficulty accessing and decaying the hemicellulose and lignin when the amount of nanoclay increases. Moreover, the addition of nanoclay results in low mechanical properties. While nanoclay enhances the properties of polymer composites, the hybridization with mycelium composites was not successful

(Un)folding the membrane in the deployable demonstrator of contex-t

The paper presents a system, made out of foldable ‘kinked’ beams and a membrane skin, based on a concept referring to origami. The anticlastic curvature of the membrane is obtained by transforming flat triangular parts into space. The following research question is considered: can the foldable system be stable in intermediate configurations? To obtain a well-tensioned membrane in the intermediate positions, the belts connecting the membrane to the frame can be released or increased in tension. A full scale ‘demonstrator’ has been built within the frame of IP-project Contex-T8. Although the deployment - rotating the ‘kinked’ beams about the central axis - was feasible, the tensioning and structural behaviour of the membrane, attached in the nodes of the frame, was not yet thoroughly examined. For that reason one single unit has been analysed. Forces and deformations in the membrane are verified for different opening angles using integrated models including the membrane, connecting belts and ‘kinked’ beams (for the frame). The results of the experimental investigations and numerical models are compared and occurring discrepancies are clarified