Space frames

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIGS.
1 to 3 of the drawings, the chords 10 of each layer of a double-layer space frame are lengths of round-section metal tube each end of which is flattened and also deformed to a transversely stepped formation of two substantially equal adjacent parts 11 and 12.
One of these parts, when they are horizontal, is above the level of the other, the top surface of the lower part 11 being substantially in the same plane as the bottom of the adjacent upper part 12, the axis of the tubular chord being in or close to this plane.
The adjacent parts 11 and 12 are separated by a shoulder 13, and each of the stepped parts 11 and 12 is formed with a more or less central bolt hole 14.
Each chord end may be flattened, stepped and formed with its bolt hole in a single operation.
At each node of the space frame the flattened and stepped ends of the chords 10 are interfitted, the upper part 12 of each chord end overlying the lower part 11 of the next succeeding chord end.
When the chord ends are so interfitted, the upper faces of all upper parts 12 are substantially co-planar, and the lower faces of all lower parts 11 are substantially co-planar, superimposed pair of upper and lower parts 12 and 11 are brought into register.
The end edges of the stepped parts 11 and 12 of each chord 10 then, as shown in FIG.
3, abut against the shoulders 13 of the next succeeding chords, and the side edges of the stepped parts 11 and 12 of each chord bear against abutments 15, at the commencement of the flattening of the ends of the succeeding chords 10.
Four bolts 16 and nuts 17 are used to interconnect rigidly the interfitted chord end parts at the node, and also to connect the ends of oblique struts or web members 18 and to secure a load distribution plate 19.
Each of the struts or web members 18 is a length of round-section metal tube of lesser diameter than the chords 10, and has each end portion 20 flattened, bent to an angle to the axis of the strut, mitred so its sides are convergent at a right angle, and formed with a bolt hole 21