(57) A portal frame structure is provided comprising a horizontal truss (10) and vertical
supports (11, 12) secured to the respective ends of the truss (10), the truss (10)
being provided with a joint arrangement (13) intermediate its end, said joint arrangement
(13) being such that outside elements (15, 16) of the truss (10) on one side of its
neutral axis (X-X) are maintained in compression in both directions of load on the
truss, and that outside truss elements (18, 19) on the other side of said neutral
access are subjected to predetermined tension, such that as the load increases in
one of said load directions the tension is reduced, and to tension exerted in the
other of said load directions. The predetermined tension may be zero, such that the
joint arrangement collapses immediately a compressive load is applied. Alternatively,
it may have a value such that it reaches zero at any point up to the maximum designed
load for a particular building application. The portal frames are for use with cladding
secured to the inner side of the frames.
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