Institute for Lightweight Structures and Conceptual Design
Address: Pfaffenwaldring 7, 70569 Stuttgart
Telephone: (0711) 685-66227
Fax: (0711) 685-66968
Prof. Dr.-Ing. Werner Sobek
Prof. Dr.-Ing. Balthasar Novák; Telephone: 0711-685-66227
Dr.-Ing. Walter Haase; Telephone: 0711-685-68310
Fields of activity
In its research and teaching the ILEK combines the dominant aspects of architecture, namely design and form, with the primary responsibilities of civil engineering – the fields of analysis and construction, as well as material technology. Using a targeted and interdisciplinary approach, the institute undertakes the conceptual and material development of all manner of construction methods and structural systems. The scope ranges from modern building techniques employing textiles and glass to advanced possibilities with traditional reinforced and prestressed concrete. From the individual details to the overall system the aim is to optimize form and structure with regard to material and energy expenditure, durability, reliability, recyclability, and environmental compatibility. The results are published either in the institute’s own bilingual book series (IL) or in separate research reports on special subjects.
The individual research areas are described in further detail below.
Lightweight construction involves foils, fabrics, nets, ropes and rods, made of synthetic, metallic and natural materials, and may take such forms as tents, pneumatic elements, cable nets, grid shells, tree columns and hybrid systems. These systems may be permanent or temporary and for stationary, convertible, or mobile use. The ILEK carries out architectural and structural design, analysis, form-finding, and manufacturing using experimental and computer-aided methods. Structures in nature serve as a strong inspiration for processes and principles of form generation, and the field of bionics is also drawn upon for use in architecture. In addition to its primary research, the institute also conducts feasibility studies and consulting, and collaborates with international organisations of architects and engineers.
Adaptive Building Envelopes:
- Adaptive Multilayer Textile Building Envelopes: A principal area of current research at the ILEK is the development of multilayer textile facade systems to fulfill present and future requirements for high performance building envelopes. Primary objectives include translucency, light weight, and flexibility of form, while simultaneously meeting the increasingly critical requirements of energy efficiency and facade performance. The concepts developed should enable maximum architectural freedom for the future development of membrane structures.
- Switchable Glazing: Transparency is the most important property of glass. The ability to alter this transparency instantly and at any time is a highly-sought goal for future glazing systems. By regulating the transmission of incident radiation, either in general or selectively by wavelength, the amount of heat and light entering a building can be actively controlled, allowing for significant energy savings as well as improved user comfort. Research being carried out at the ILEK is making significant progress towards adaptive glass building envelopes. A major advance has been the development of a switchable liquid crystal system, carried out in conjunction with the Chair for Display Technology. In contrast with other switchable glazing approaches, the light transmission with this system can be regulated instantly and smoothly, with no steps in intensity. The maximum transmissivity as well as the range of transformation can be adjusted through boundary conditions of the system design.
- Vacuumatics: Possibilities are being investigated and developed for facade and support structures using vacuum-stabilized construction. New approaches in engineering are being explored with respect to structural behaviour, insulating properties and sound suppression. The new opportunities in design vocabulary offered by these approaches are also being examined from an architectural standpoint.
- Adaptive Building Envelopes: This research area deals with the development of components and systems using different materials (eg. textiles, glass, plastics) which through chemical or physical modification or manipulation (self-acting or controlled) enable the building envelope to adapt to changing exterior conditions. Light transmission, temperature balance, as well as properties of ventilation, acoustics and colour may be influenced to optimize the interior climate and energy balance, and to match utilization requirements.
Adaptive structures are intelligent systems equipped with sensors and actuators and directed by an electronic control system which react to changing exterior stresses by modifying the rigidity and/or the length of individual members. This approach allows weight to be minimized by actively influencing the flow of forces depending on the static or dynamic load-bearing requirements..
- Concrete Structures
Research at the ILEK in concrete structures focuses on the design of reinforced concrete, prestressed concrete and masonry structures using high-performance, self-compacting, and fibre-reinforced concrete in the form of highly-integrated building elements. Applications include high-rise buildings, towers, storage tanks, bridges, shells and hybrid systems. A primary area of research is the development and investigation of new methods of construction with regard to load-bearing behaviour and structural dimensioning (using CAD and FE methods). The institute also performs consulting duties, advises on code committees, and collaborates with international organisations in the area of concrete construction.
- Strut-and-Tie Models and Shear Behaviour
Research in this area centres on the analysis of reinforced and prestressed concrete using strut-and-tie models as well as theories and examples of calculation in zones of discontinuity. Such zones include areas of local load application or corbels and similar supports in precast elements. The shear behaviour of reinforced concrete with and without shear reinforcement is also a focus of investigation, both theoretically and experimentally. The results of this work are collected in an experimental database. Related consulting work is also performed.
- Ultra-High-Performance Concrete (UHPC)
This area of research arose from the design of economical solar heat storage systems for short-term as well as seasonal needs, including new types of hot water storage tanks. The continuing study involves experiments with UHPC and theoretical investigation to examine the size effect under combined axial load and bending, as well as the influence of fibre orientation.
- Modular Thermal Ceilings and Roofs
The goal of this research is the development of an intelligent roof system which offers reduced costs and improved insulating properties through structural optimization and material savings.
- Built Structures Management System
Research into the management of structures involves the development of a networkbased expert system to monitor the state of federal engineering structures and to provide a prognosis about future maintenance requirements and the most appropriate rehabilitation strategies. This includes the development of components such as material-based damage models, systems to determine required intervention times, catalogues of maintenance measures and strategies, as well as techniques to optimize object-based maintenance.
- Functionally Graded Materials
Functionally graded materials (FGMs) are materials constructed with smoothly varying properties through their cross-section. These variations enable the specific local material characteristics of a given component to correspond to specific local design requirements. The particular properties being investigated are variations in porosity and density, fibre concentration and alignment, as well as composites of different materials. This study endeavors to explore the relationship between material and form. Many forms are defined by the properties of materials; it is now time for material properties to be re-defined by form.
- Building with Glass
This area concentrates on the fundamentals and the applications of glass as a structural material for plane and spatially curved building forms. This includes the development of appropriate load-bearing structures, detailing and fastening techniques for prestressed, laminated and reinforced types of glass, investigation into post-breakage residual strength, and exploration of the appearance of glass structures in architecture.
- Flat to Form: Rapidly-Deployable Grid-Shell Domes
In 1975, the construction of the Mannheim Multihalle demonstrated that a large open span can be constructed by assembling a flat orthogonal grid of overlapping materials which are subsequently erected into a structurally optimized form known as a grid-shell. The final form of a grid-shell minimizes the presence of bending forces, allowing the use of a range of possible construction materials, but the erection process places specific demands on the grid’s internal joinery. During this process the joints must allow rotation in the plane of the grid, but upon the shell’s completion these same joints must bear all bending and torsion loads without deformation. The purpose of this research is to simplify and accelerate the construction process of grid-shell structures through the manipulation of the flat assembly grid, allowing a simplification of the internal joinery. Working with conventional off-the-shelf materials joined with common cable-ties, this investigation endeavors to understand the geometric relationship between pre-deflected flat grid patterns and the structural potential of the resulting erected forms.
Cell-based Structural Systems
In order to generate bone tissue in vitro similar to that found in vivo, an understanding of the influence of mechanical stress components on the structural formation of tissues is essential. An apparatus was therefore developed at the ILEK in combination with the Institute of Anatomy in Tübingen with a three-dimensional visualization capability, enabling the investigation of cell morphology behavior under mechanical loading in real-time.
Branding in Industry – the example of the Automotive Sector
This research investigates a number of manufacturing plants as potential brand icons of the automobile industry. The central focus explores how the architectural appearance of a company contributes to its brand awareness and thus has an impact on the behaviour of consumers. This analysis is conducted on the basis of approaches taken from typology, marketing, social sciences and manufacturing.
The facilities of the institute include experimental test equipment for the form-finding of structures; an intranet connected to the University Computing Centre with software available for form generation, structural analysis, word-, graphics- and image-processing; a library with approximately 8600 volumes, including a comprehensive archive of photographs and literature on lightweight and concrete structures in architecture, civil engineering, technology and nature; studio equipment and a darkroom for photography; and a model-building and mechanical workshop (at Location 2).
The Central Laboratory manufactures specimens and prototypes and plans and executes tests of structural members and assemblies for the verification of structural analyses as well as for official approvals and permits. Computerized test and measuring installations are used for the collection, evaluation and presentation of data.
Target groups include civil engineers, architects, specialized experts, public and private clients and user groups, project developers, investors, and contractors for concrete structures, and manufacturers of lightweight structures, including materials and components.