The
Triodetic System was developed in Canada in 1955. This system was originally made from aluminum components, and in 1966 steel members were also included. It uses
extruded cylindrical solid aluminum hubs (nodes) with slots and tubular aluminum or steel members with matching crimped ends. A hole is placed in the center of the hubs for placement of a through-bolt to secure the member inserted into the hub. The bolt does not carry any forces. A special press is used to flatten (or coin) the tabular member ends to match the slots in the hubs. The length and end angles of tubes are factory made with high precision, and can be painted on. The threads in the tubings are made without the removal of the material to prevent the strength reduction. This is done by flattening (coining) the tubes, which are inserted into the hubs using a soft tip hand or electric hammer. To create lightweight systems, the aluminum hubs and tubes were developed, however, aluminum hubs with steel tubes are more common. Up to 12 members can be connected to a hub at almost any angle. Six different hub configurations are available. After the members are inserted into the hubs’ slots, retaining washers are placed on both ends of the hubs, the through-bolt is inserted and tightened using a nut to secure the members connected to the joints. The Triodetic joints can resist tension, compression and combined loadings.
Tests conducted on the Triodetic System have shown that it is practical and suitable for most environments. No strength reductions due to the effects of corrosion of aluminum connectors have been found. Also, tests conducted on the system using a combination of steel tubes and aluminum hubs have shown no electrolytic problems between the two metals. Using the galvanized tubes reduces the overall maintenance costs.
This system has been used in single and double-layer grids of flat, barrel vaults, domes, hyperbolic-paraboloids, and free-form spatial structures. Spans of up to 100 ft have been used for flat double-layer grids. Triodetic System is most cost effective for square or rectangular plan structures with length to width ratios of less than 1.5. The module sizes of up to 8 ft square can be used.
The two main advantages of the Triodetic systems are: (1) the relative low cost of the connectors with the possibility of many members being connected to them in space, and (2) the low assembly and erection costs since little or no scaffolding is required in most cases. The Triodetic members are light and can be assembled in place, and the structure, in most cases, is self-scaffolding.
The Triodetic products are sold on a ‘supply-only’ and ‘supply and erect’ basis. For the ‘supply-only’ basis, a field supervisor is provided by Triodetic to direct the work of the local workers hired by the owner to assemble and erect the structure.
Assembly of Triodetic system requires very little skill as the attachments of the members to connectors is purely mechanical. Smaller structures generally require a higher man-hour per square foot ratio than the larger ones. Where labor costs are high, partial assembled units of the spatial structure are shipped instead of individual components.
