| 摘要 |
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. |
