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For the nodular systems mostly circular or square hollow tubes are used as the main structural members. However, in some cases channels were also used (such as in the Unistrut System). Spherical, cylindrical and folded plate shape components have also been used as connectors (or nodes). The members are secured to their connectors by bolting or interlocking into pre-drilled holes or slots.
Systems using spherical nodes are the most common and aesthetically pleasing, which are also called ‘Ball Joint Systems’. The nodes can be solid or hollow. The solid spheres are generally drilled with threaded holes at specific angles for connecting members. The attachment surfaces are also machined for better bearing. Members are attached to the connectors through a single bolt. The most common example of this connector is the ‘Mero System’.
The other variations of these systems are: ‘Plate Joint Systems’ such as Unistrut, Tridimatec, Octatube; ‘Slot Joint Systems’ such as Triodetic; ‘Shell Joint Systems’ such as ‘Nodus’, and ‘Socket Joint Systems’ such as Tuball.
The Plate Joint System consists of members, joints (in the form of plates) and nuts and bolts to connect the members to the connectors. Unlike the Ball Joint or Socket Joint systems for which the member axial forces are transmitted to the connectors through bolts in tension or compression, the bolts in the plate joint system generally transmit forces through shear. Also, the Plate Joint Systems are usually made of members that are not tubular shapes.
In Slot Joint Systems, the node is made of an
aluminum cylindrical component (hub) with slots around its periphery which are used to insert the coined (crimped) ends of the tabular members made of steel or aluminum. No direct bolting or welding is required in this system.
Socket Joint Systems consist of connectors or nodes from which bolts are inserted and screwed to the members.
The members of nodular system can also be welded to each other. This type of spatial structure is usually used to support heavy loads and is considered custom-made.
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