Space Frames - Structural Types.

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. 

MERO node connector
Fig. 5.15 MERO node connector

NODUS node connector
Fig. 5.16 NODUS node connector

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.

Exploded view of 2.4m square section of Space Deck
Fig. 5.17 Exploded view of 2.4m square section of Space Deck

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 110m and a minor axis of 70m 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.

Novel method of dome erection
Fig. 5.18 Novel method of dome erection

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