Abstract: An elongate support member of the type generally used to span a pair of horizontally spaced supports is stiffened by pivotally attaching thereto at spaced points along its length at least two posts which extend in the same general direction and generally transverse to the length of the support member, and by pivotally attaching tension members or ties to a point at or near each end of said member and the free end of the nearer post and from at or near the free end of a post to the pivotal connection of the next adjacent post to the member, whereby the tension members or ties cross each other between adjacent posts. This form of stiffening allows bending moments and deflections arising as the result of loads applied to the member to be reduced and rendered positive.

Abstract: A framework in particular an arch comprising at least one frame member and wherein the framework extends in at least two dimensions, a linkage system associated with the framework and attached thereto at at least three non-collinear positions on the framework, said linkage system embodying two tension members, one of which extends from each of the two outer positions of said three non-collinear positions to the central position thereof where the tension members are each attached to one of two spaced points on a swivel member which is at least swivelable in the plane of the framework and is attached to the framework at the said central position by a connection operable in use, to allow at least limited rotation about a point offset from the line of the tension members and thereby ensure that a change in tension in one of said tension members results in a rotation of the swivel member which causes a change in tension in the other tension member.