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Steel Designers' Manual - 6th Edition (2003)
182 Other structural applications of steel
Three-way grid domes are formed from three principal sets of members arranged
to form a triangular space lattice. This member topology is ideally suited to both
single-layer and double-layer domes, and numerous beautiful large-span steel threeway
domes have been constructed throughout the world.
The steel lamella dome is formed from a number of ‘lozenge’-shaped lamella units
which are interconnected together to form a diamond or rhombus arrangement.The
spectacular Houston Astrodome is an excellent example of this type of construction.
This impressive steel double-layer dome was constructed from lamella
units 1.52 m deep and has an outside diameter of 217 m with an overall height of
63.4 m. Figure 5.14 shows the four main dome configurations now in prominent use
worldwide.
5.2.3 Special features
The inherent characteristics of steel skeletal space frames facilitate their ease of
fabrication, transportation and erection on site. There are two main groups into
which the majority of space frames may be classified for assembly purposes: the
particular structure may be assembled from a number of individual members
connected together by purpose-made nodes or alternatively may be constructed by
joining together modular units which have been accurately fabricated in a factory
before transportation to site.
There are numerous examples of ‘chord and joint’ space frame systems available
for immediate construction. These systems offer full flexibility of member lengths
and intersecting angles required in the construction of skeletal dome structures.
Many jointing systems are available; Figs 5.15 and 5.16 show a typical spherical node
used in the MERO system and a cast steel node used in the NODUS system.
The ‘modular’ systems are usually based on pyramidal units which are prefabricated
from channel, angle, circular hollow section or solid bars. The individual
units are designed to nest together to facilitate storage and transportation by
road or sea. Most manufacturers of modular systems hold standard units in stock,
which greatly enhances the speed of erection. Figure 5.17 shows typical details of
the prefabricated steel modular inverted pyramidal units used in the Space Deck
System.
Steel space frames are generally erected rapidly without the use of falsework.
Double-layer grids of substantial span can be constructed entirely at ground level
including services and cladding and subsequently lifted or jacked up into the final
position. Dome structures can be assembled from the top downwards using a central
climbing column or tower. A novel approach adopted for the erection of a dome
with a major axis of 110 m and a minor axis of 70 m involved fabrication of the dome
on the ground in five sections, which were temporarily pinned to each other. The
central section was then lifted and the remaining segments of the dome locked into
position as shown in Fig. 5.18.