Design of tension structures and shells using the Airy stress function

Discontinuities in the Airy stress function for in-plane stress analysis represent forces and moments in connected one-dimensional elements. We expand this representation to curved membrane-action structures, such as shells and cable nets, and graphically visualise the internal stresses and section forces at the boundary necessary for equilibrium. The approach enhances understanding of the interplay between form and forces and can support design decisions related to form-finding and force efficiency. As illustrative examples, the prestressing needed for three existing cable nets is determined, and its influence on the edge-beam bending moment is explored.

Investigation of tape flexures for space borne deployable structures

Space exploration arises the demand for launching large size structures to satisfy the need of high bandwidth telecommunication, earth observation and deep space interplanetary missions. Launching of these monolithic structures of sizes 3 m or more are not feasible due to limited launch fairing space of state-of-the-art launch vehicles. Therefore, the development of innovative deployment mechanisms is need of the hour. Deployment process of space borne deployable systems is the process of transition from mechanism to structure which is one of the unreliable stage due to existence of many conventional rotary joints which causes loss of energy due to backlash, friction and misalignment. An investigation study is presented in this paper for churning out a solution of flexible hinges using tape springs in state-of-the-art space deployable configurations which eliminates the factors causing loss of energy. Analytical and experimental methods are evaluated for investigating the bending behaviour of tape flexures. Tape flexures demonstrate to be a suitable candidate for compliant deployable configuration. The proposed configuration with combination of two tape flexures mounted in such a way that concave curve of each tape faces each other are structurally analysed for desired rotation angle. A comparison study is carried out for various material options of single and double layered tape flexures proposed for a flexure hinge. Practical feasibility of the proposed configuration is also demonstrated successfully on space borne deployable structures.

Bias deployable grids with horizontal compound scissor-like elements: A geometric study of the folding/deployment process

Bias deployable structural units are two-way structures arranged in a rotational pattern with respect to the edges. They have interesting advantages such as robust three-dimensional operation with supports around their entire base perimeter and the exclusive use of load-bearing scissor-like elements (SLEs). However, they do not have edge trims and their resistance to angular distortion is limited. This article proposes a series of deployable bi-stable structures that address these problems and incorporate new, resilient features. A method of analysing the incompatibilities of the structural unit is developed based solely on the geometric study of the deployment process, which allows the level of incompatibility of the proposal to be graduated, varying from stress-free structures to bi-stable structures. A kinematic model of one of the proposals allows the research undertaken to be contrasted.

The optimization process leading to the tessellation of the first geodesic dome structure, the first Planetarium of Jena

The tessellation of the first built geodesic dome structure (the first planetarium of Jena, designed by Walther Bauersfeld, built 1922–23) has been unknown until recently. While original documentation of the tessellation has been published, the concept behind it has not been uncovered. This article presents the evolution of the final tessellation based on Bauersfeld’s hand-written notes found in the Zeiss Archives in Jena. Bauersfeld contemplated various methods of subdivision and performed detailed calculations and optimality analysis on them—preceding the theoretical studies on the tessellation of geodesic domes by almost 30 years. His key findings, relevant and comparable with later studies are highlighted. The concept of the presumably final tessellation is revealed to be the equal-area triangulation of the sphere—which has to the author’s knowledge not been considered ever since for geodesic domes. The remarkably simple algorithm applied did not result in a theoretically exact solution (well known to Bauersfeld), but as shown in this article in engineering terms it got sufficiently close. Moreover, it is concluded that the resulting tessellation excels in terms of important parameters (e.g. edge length ratio, number of different edges) compared to existing practical and theoretical solutions.

Generation of elastic geodesic gridshells with anisotropic cross sections

Geodesic gridshells are shell structures made of continuous elements following geodesic lines. Their properties ease the use of beams with anisotropic cross-sections by avoiding bending about their strong axis. However, such bending may arise when flattening arbitrary geodesic grids, which forbids their initial assembly on the ground. This study provides a process to design elastic geodesic gridshells, that is, gridshells that minimise bending moments in both formed and near-flat configurations. The generation process first brings a target geodesic network onto a plane by maintaining arc lengths. The flat mesh is then relaxed to minimise its main curvatures and hence bending moments in its members. The result is an elastic geodesic gridshell that can be assembled flat on the ground and then lifted up into its target surface. The method is applied to the design of six geodesic gridshells made of reclaimed skis.

Friction magazine: The upcycling of manufacture for structural design

The growing need for new buildings and the soaring resources depletion call for a new way of considering the building material. As follows, the principle of recycling and reuse keep gaining in consideration as a pertinent strategy to address those issues, inciting the use of new materials and approaches for structural design. The present paper inscribes in this later framework and proposes a method for structural design and manufacturing out of old magazines using a broadly known physical phenomenon of friction in interleaved assemblies. The proposed method consist of a stock-based form-finding strategy for a net-like structure, based on the mechanical and fabrication-aware considerations with an integration of a geodesic constrain control for the rectilinear paper strips. In closing, a demonstration pavilion is built using the developed method and its further potential applications in construction sector are discussed.

Minimal-waste design of timber layouts from non-standard reclaimed elements: A combinatorial approach based on structural reciprocity

The use of timber allows reducing the environmental impact in the construction sector. However, as the demand for construction timber rises, the pressure on the world’s forest is increasing too. To maintain an adequate supply of timber from sustainable forests in the coming decades, the building industry must adopt practices that reduce the impact on forestry. Reuse is one of the principles of Circular Economy (CE). Among the technical challenges of reuse are the variability and the short size of the stock of elements coming either from demolition or from new construction, such as cut-offs and temporary scaffolding. This work presents a study for the design of structural configurations with short and non-regular sized elements that would normally be considered waste. The configurations are based on the principle of structural reciprocity and are generated by an optimization algorithm that allows minimizing the material waste and maximizing the stock elements use. A computational strategy based on the SPEA-II multi-objective method is employed for the investigation of optimal trade-offs between competing objective functions, such as structural lightness and optimal use of stock inventory. The goal of this work is demonstrating the feasibility of an industrial process, borrowing key elements from the Industry 4.0 paradigm, for a streamlined and economical production of standardized building components using non-standard reclaimed elements.

Stock-constrained truss design exploration through combinatorial equilibrium modeling

Reusing structural components has potential to reduce environmental impacts of building structures because it reduces new material use, energy consumption, and waste. When designing structures through reuse, available element characteristics become a design input. This paper presents a new computational workflow to design structures made of reused and new elements. The workflow combines Combinatorial Equilibrium Modeling, efficient Best-Fit heuristics, and Life Cycle Assessment to explore different design options in a user-interactive way and with almost real-time feedback. The method applicability is demonstrated by a realistic case study. Results show that structures combining reused and new elements have a significantly lower environmental impact than solutions made of new material only.

Development and evaluation of novel modules for deployable tension-strut structures

There is a growing need for new alternatives of long-span roof structures with high level of transformability and structural robustness. This led to the development of deployable cable-strut structures, which are composed of a continuous net of struts and another continuous net of cables. Subsequently, a special type of these systems was pioneered and given the term deployable tension-strut structures (DTSSs). The motivation beyond this new concept was the lack of structural efficiency and form flexibility of conventional space trusses that are usually employed for covering large spaces. Typically, DTSSs are roof structures consisting of multiple modules put together to form the roof system. This paper is mainly concerned with developing new robust modules for DTSSs. The technique that was adopted for this purpose is a form-creation methodology previously introduced in the literature. A few modules were already developed based on this shape grammar. However, its potential to develop multiple efficient modules has not been sufficiently investigated. In this current work, the afore-mentioned algorithm was utilized to form 16 new modules. A comparative study based on a nonlinear finite element technique was conducted to investigate the efficiency of the novel modules as compared to that of the previously proposed in the literature. The results show that some of the new proposed modules are far more efficient than those presented in previous researches. Based on this comparative study, the most two efficient modules among the novel ones were picked for further study. Parametric studies were conducted on these two systems under gravity loads and wind loads considering the following parameters: no. of modules, span/depth ratio, and cables’ pre-stress level. For each parameter, the optimal range of values were determined to be used as a guide for the design of such systems.