VARIOUS TYPES OF
1 FIRST GROUP OF LIGHTWEIGHT ROOF STRUCTURES
The dead weight of large span cover
can be an important part of the total design load of a structure. That
is why various forms systems of tension-strut structures have attached
consideration of engineers and architects. Very spectacular type of the
system, called as cable dome has been developed by an American engineer
David Geiger, Geiger (1986). Roofs of two main halls of the Olympics in
Seoul in Korea were built in this system. In this place one should necessary
mention about the roof of the Hall "Spodek" in Katowice, in Poland, which
designed by Waclaw Zalewski and erected in early 70s of the 20th
century, Robbin (1996). Typical forms of these structures have to be suitably
pre-stressed and almost all of them need application of a compression ring
located along the perimeter of a roof cover. The force distribution between
components of an engineering structure should provide the whole system
with an equilibrium. That is why the arrangement of component parts of
the structure plays a significant role. The symmetric positions of these
parts are easy to observe in numerous types of tension-strut structures
proposed by the author, Rebielak (2000, 2002,
2003a, 2003b, 2003c).
Figure 1: Schemes
of two chosen modules of tension-strut structures,
Figure 2: General
views of exemplary dome covers designed by means of,
These two examples of systems, which
are shown in Figure 1 and in Figure 2, are formed by means of the tetrahedron
modules. The spatial modules are symmetrically arranged around the triangular-hexagonal
grid of bars. The grid is located in the middle layer of the structure.
Tetrahedron modules are spaced over triangular fields of this grid and
the half number of them are placed above this grid and the second half
is placed beneath it. Top vertices of the tetrahedrons are connected together
by means of suitably arranged sets of tension members by means of which
the whole structure has to be pre-stressed. Roof structures designed by
means of these structural systems can obtain optional shapes, they can
be spaced over each form of the base projection and therefore they do not
need the application of the perimeter compression ring.
2 SECOND GROUP OF TENSION-STRUT STRUCTURES
Typical forms of the cable domes
consist of concentric hoops, which are connected together by means of suitable
tension members. The author has developed a numerous family of tension-strut
structures, which are composed of especially formed spatial concentric
hoops. The morphological aspects of the complex form of spatial tension-strut
systems require the applications of symmetry rules in all the processes
of shaping of these types of structural systems. The symmetry is easy noticeable
not only in the patterns of these structures but also in the shapes of
the computing programs defining their numerical models in a programming
language. Examples of some chosen forms of these structures are presented
in Figure 3 and in Figure 4.
Figure 3: a,b) Schemes
of the VU-TensO tension-strut structure,
Figure 4: General
schemes of the complex forms of the tension-strut structures,
Roof structures designed by means
of the proposed systems can be the lightweight structures capable to be
applied as the main support structures of large span covers. They can obtain
interesting and individual architectonic views. The numerical models of
these structural configurations will be very helpful in the further and
comprehensive analyses of all the shapes of the proposed structural systems.
Robbin, T. (1996) Engineering a New Architecture, Yale University Press.
Rebielak, J. (2000) Special forms of structural systems proposed for cable dome, Proceedings of the Third International Conference on Mobile and Rapidly Assembled Structures – MARAS III, Madrid, June 21-23, 2000, eds F. Escrig & C.A. Brebbia, WITPRESS, Southampton, UK, 93-99.
Rebielak, J. (2002) New structural proposals of tension-strut systems for lightweight roofs, Space Structures 5, eds. G.A.R. Parke and P.Disney, Vol. 2, Thomas Telford, London, England, 2002, pp. 1179-1188.
Rebielak, J. (2003a) Tension-strut shaped by means of polyhedron modules, Structural Membranes - International Conference on Textile Composites and Inflatable Structures, Universitate Politectica de Catalunya, Barcelona, Spain, 30 June – 3 July, 2003, 402-407.
R?bielak J. (2003b) The concept of the triangular-hexagonal tension-strut structure, IASS-APCS International Symposium on New Perspectives for Shell and Spatial Structures, Taipei, Taiwan, October 22-25, 2003, Extended Abstracts, 184-185.
Rebielak J. (2003c) Chosen types of tension-strut systems proposed for lightweight roofs, IASS-APCS International Symposium on New Perspectives for Shell and Spatial Structures, Taipei, Taiwan, October 22-25, 2003, Extended Abstracts, 236-237.