LIGHTWEIGHT STRUCTURES

LIGHTWEIGHT STRUCTURES

The smaller the ratio between a structure’s dead load and the supported live loads, the “lighter” the structure (Schleicher, S., Lienhard, J., Fleischmann 2010). Designing and forming lightweight structures is not an easy task due to the small ratio of the structure's self-weight to the live load compared to traditional structures where the ratio is much higher. Each part is clear and useful and relies on the proper functioning of all parts. From an ecological, social, and cultural perspective, lightweight structures have never been more contemporary and necessary than today. Moreover, lightweight structures can bring beauty and elegance to the space, and they are seen in various forms, shapes, sizes, and variations in a wide range of applications. They transform the space through their unconventional solutions, unique shape, as well as subtle and elegant quality. Lightweight structures, in place of stiffness of the material, derive their resistance from their shape and may therefore be denoted as shape active. One of the main design steps of lightweight constructions is therefore the design of a shape that is controlled by the required stress state. According to their characteristics, lightweight structures can be divided into several subgroups, one of them being tensegrity systems. Physical models of bridges in Fig. 1. and Fig. 2. a,b, and c are nice examples showing the relation between art and structural engineering. The advantage of lightweight structures is that all forces are nicely visible. Forces are a mechanical concept useful for engineers who want to size their structures and they are by nature visible. By differentiating cables and struts, the model of the footbridge provides information on whether tension and compression are present. Therefore, the dimensions of the components such as tubes and size, and the arrangement of cables depend upon the material properties as well as on the level of tension resp. compression state. As seen in the figures, lightweight tensegrity structures are fascinating as the gravity seems to be absent and the structure looks as if floating in the air. The stability of the entire system ensures that the whole is in equilibrium which ensures its stability. The potential of lightweight structures in the future for designers is very significant, so the tensile integrity structure as it is called tensegrity is of great importance for construction under tension. And that is why we were dealing with parametric models in this section that we expressed the benefits of this system for pedestrian bridges. In general, a tensile structure is a type of construction involving the use of elements in which tensional forces are implied, with no compressive forces action, or bending, giving it great construction advantages. That is the quality that offers possibilities of large spanning and utilizing a variety of free-standing forms.

We attempt to create light and slender structures quickly set a high standard for structural design. Steel and prestressed concrete enabled us to embody the lightweight ideal in structural design. This type of parametric bridge is a wonderful example of this. The structural system of the cable-stayed bridge or suspension bridge is well suited to this desire: by decreasing the distance between the cable supports, the deck can be made slenderer as the bending moments are reduced. Therefore, the structural designer's greatest goal was to make the deck as slender as possible. Cable-supported bridges, which can be built in a great variety of forms and with considerable elegance, have undisputed potential.

Fig. 1. Pedestrian Tensegrity Bridge (Shawkat, 2019)

Fig. 2a. Pedestrian Tensegrity Cable-stayed Bridge (Shawkat, 2019)