Sigrid Adriaenssens

Tensegrity spline beam and grid shell structures

This paper considers a class of tensegrity structures with continuous tubular compression booms forming curved splines, which may be deployed from straight by prestressing a cable bracing system. A free-form arch structure for the support of prestressed membranes is reviewed and the concepts are extended to a two-way spanning system for double layer grid shell structures. A numerical analysis based on the Dynamic Relaxation (DR) method is developed which caters specifically for the form-finding and load analysis of this type of structure; a particular feature of the analysis is that bending components are treated in a finite difference form with three degrees of freedom per node rather than six. This simplifies the treatment of sliding collar nodes which may be used along the continuous compression booms of deployable systems.

Shell Elements of Textile Reinforced Concrete Using Fabric Formwork: A Case Study

Innovations in formwork solutions create new possibilities for architectural concrete constructions. Flexible fabric replaces the stiff traditional formwork elements, and takes away a limiting factor for creative designs. Combined with textile reinforcement, the production of a new range of curved and organic shapes becomes possible without the intensive labour for formwork installation. Besides a general introduction about the concepts of fabric formwork and textile reinforcement, this paper focuses on the production and structural evaluation of doubly curved shells. Creating a very interesting type of element from a structural point of view, the shape flexibility of both the fabric formwork and textile reinforcement make a perfect match to overcome practical production issues for thin shell elements. The application of shotcrete and the integration of non-metallic reinforcement allowed first of all the production of very thin concrete shell elements based on the design approach of the textile architecture. Comparing a shell structure with traditional reinforcement and one with textile reinforcement, a case study evaluates furthermore both the design and the structural performance of such a shell structure.

Structural Optimization of Deploying Structures Composed of Linkages

AbstractDetermining the global shape of a deploying structure and the section profiles of its members is a challenging design problem. Geometry, meaning the lengths and relative angles of members, is critical to achieving stable deployment to a desired span, while the design must also satisfy structural capacity demands at each stage of deployment. This paper explores the potential role of formal structural optimization in designing feasible and structurally efficient deploying steel structures composed of linkage elements. Both stochastic search and gradient-based algorithms are used to explore the design space and identify minimum weight solutions that satisfy kinematic and structural constraints. The proposed methodology is tested on the case study of a deploying pantograph. This strategy has the potential to be implemented for a wide range of deploying structures, including retractable roofs, rapidly expandable shelters, deploying space structures, and movable bridges.

Finding the Form of an Irregular Meshed Steel and Glass Shell Based on Construction Constraints

AbstractIn the context of the search for an efficient structural shape to cover the Dutch Maritime Museum courtyard in Amsterdam, Netherlands, the authors briefly discuss the driving design factors that influenced the earliest glass roof coverings. The trends that emerged during the late 20th and early 21st century in the design of skeletal steel glass shells are exposed. These design developments range from sculptural to geometric and structural intentions. The discussion of the competition design development of the Dutch Maritime Museum steel glass shell roof shows the quest for a structurally efficient catenary form based on a poetic geometric idea. This paper presents a construction-driven design methodology that slightly adapts the numerical form found catenary shape with the objective of achieving planarity in all the triangulated, four-sided and five-sided mesh faces. The challenge of facet planarity is gracefully solved by an analytical origami approach and presented. This approach is compared wit...

A unified stochastic framework for robust topology optimization of continuum and truss-like structures

In this article, a unified framework is introduced for robust structural topology optimization for 2D and 3D continuum and truss problems. The uncertain material parameters are modelled using a spatially correlated random field which is discretized using the Karhunen–Loève expansion. The spectral stochastic finite element method is used, with a polynomial chaos expansion to propagate uncertainties in the material characteristics to the response quantities. In continuum structures, either 2D or 3D random fields are modelled across the structural domain, while representation of the material uncertainties in linear truss elements is achieved by expanding 1D random fields along the length of the elements. Several examples demonstrate the method on both 2D and 3D continuum and truss structures, showing that this common framework provides an interesting insight into robustness versus optimality for the test problems considered.

Feasibility Study of Medium Span Spliced Spline Stressed Membranes

This papers examines the feasibility of 3 medium span (16m – 32m) spliced spline stressed membranes. Medium span slender arch systems have been used for canopy structures of stadia cladding such as the Gottlieb-Daimler Stadium. Lateral bracing by the membrane means that the arch can be slender and flexible. Flexibility and lightness fit in well with the design of pre-stressed structures that are themselves flexible and adjust to applied loads. The presented membrane structures are designed bearing in mind their deployability (as necessary for temporary tents) and offer a good simple alternative to medium span high maintenance pneumatics covering squash courts or swimming pools.

Structural Analysis and Validation of a Smart Pantograph Mast Concept

To progress the development of deployable, lightweight infrastructure for relief and recovery efforts in the aftermath of natural and man-made disasters, this article develops a proof of concept for a smart mast that leverages the versatility of pantograph systems and ad- vances in sensor, actuator, and informatics technologies. More specifically the article addresses key design crite- ria of transportability, deployability, global stability, and site responsiveness through the development of analyt- ical expressions and control framework, and reduced- scale physical model testing. The case study, a three- tiered tetrahedral mast is composed of three connected sets of planar pantograph systems and deployed by single actuator located between two of the three mast supports. The article discusses the optimum configurations for the individual design criteria and trade-offs to be made be- tween compactness, overturning, and operational power. The design, construction, and experimentation with a 73- cm tall fully deployed physical model reinforce the feasi- bility of the presented smart mast concept.

Structural Analysis of Reinforced Concrete Folded Hyperbolic Paraboloid: A Case Study of the Modern Miami Marine Stadium

The study of historic thin shell structures shows how masterpieces of Mid-Century Modern architecture were realized without complex mathematical analysis or numerical techniques but with solid foundation in simplified yet realistic structural performance and construction practice. Historic knowledge studies how successful past designs, such as the shells of the Miami Marine Stadium, advanced in the light of limited scientific knowledge and cost restrictions. In 2009 the United States National Trust for Historic Preservation put the Stadium on the list of Americas 11 Most Endangered Historic Places. This study briefly reviews the roofs construction history, reconstructs its original structural analysis, and confirms its validity through a comparative study of four finite element models (FEMs). These models conceptualize the roof as a folded plate or a hypar shell, analyze the structural influence of stiffeners and groin thickening and investigates the connection between numerical results and physical observed crack patterns. Generally, this study allows a better constructional and structural understanding of one of the successful modern architectural masterworks, and of simplified and complex folded plate and shell analysis models. The study also demonstrates how the close link between analysis interpretation and actual structural phenomena can inform decisions about the structural integrity of historic structures.

The Piston-Stayed Bridge: A Novel Typology for a Mobile Bridge at Tervate, Belgium

The Tervate bridge, situated over the river Yser in Belgium, introduces a new type for mobile stayed bridges: the piston-stayed bridge. The design of the bridge considers the statics and kinematics as a whole and not as an accumulation of individual design issues. This design approach stems from the idea of maximum member reduction which favours the introduction of elements that fulfil more than one function. Thus, the engineering design innovation lies in the use of one single element, i.e. the piston stay, for actuation as well as support of the mobile bridge section. The bridge, designed for vehicular traffic, pedestrians and cyclists, consists of a 16 m long central mobile section, adjoined on either side by an 11 m long static section. The deck of the static bridge sections consists of a 0,25 m reinforced concrete slab spanning the two steel girders. In the mobile section, a light steel orthotropic deck spans the two steel girders. A pair of masts is situated at the hinging point of the mobile bridge section. Each of the masts is connected to the mobile section by a fixed-length stay and to the static bridge section by a variable-length piston stay. The fixed-length stay forms a non-deformable triangle with the mast and the mobile section. The piston stay powers the opening and closing mechanism, and forms a deformable triangle with the mast and the static section. In effect, the piston stay uses the mast as a lever to tilt the bridge open or closed, while the dead weight of the mobile section ensures that both stays are always in tension. The Tervate bridge is the first instance of this new mobile stayed bridge typology. (A)

Nonlinear Elastic In-Plane Buckling of Shallow Truss Arches

Abstract The available analytical methods for determining the buckling resistance of trusses typically focus on the local load capacity of individual elements and ignore global in-plane buckling behavior. In addition, theoretical expressions that describe the in-plane critical buckling load of shallow arches do not account for trusses or nonsolid cross sections. This paper investigates the nonlinear elastic in-plane buckling behavior of shallow truss arches subjected to a uniformly distributed gravity load. Adapted methods for calculating the equivalent moment of inertia and equivalent area of truss cross sections are presented first. Using these equivalent geometric properties and existing analytical expressions, a novel methodology is then presented for generating an equivalent arch model that accurately predicts the critical nonlinear elastic in-plane buckling behavior of shallow truss arches. This methodology is validated by obtaining close agreement between the nonlinear elastic critical buckling fac...