Structural slab members

Claim 1

In a structural member comprising: first and second spaced grid frameworks each composed of two mutually perpendicular sets of parallel, elongated framework elements with the elements of one set connected to the elements of the other set at the points of intersection of the two sets; and a plurality of elongated diagonal elements each having one end connected to a point of intersection of one framework and its other end connected to an adjacent point of intersection of the other framework, each diagonal element being inclined with respect to both sets of framework elements of each framework so that the points of intersection of one framework are offset, with respect to the plane of each framework, from the points of intersection of the other framework in the directions of both sets of framework elements and each set of framework elements Of one framework is oriented in the same direction as a respective set of framework elements of the other framework, there being two diagonal elements connected to each point of intersection of each said framework, the improvement wherein the diagonal elements connected to at least one said point of intersection comprise extensions extending from the ends of said diagonal elements which are connected to that point of intersection and projecting out of said structural member and perpendicular thereto for connecting said elements to a body of material formed around said extensions, wherein said member is made free of elements in a three-dimensional region to define a clear channel extending at least partially through said member and having a square cross section one dimension of which coincides with the area enclosed by two adjacent framework elements of one set of said first framework, said channel extending parallel to one set of framework elements of each said framework, and wherein said member further comprises two reinforcing framework elements connected on said second framework and disposed parallel to, and in line with, said two adjacent framework elements of said first framework to define therewith the corners of said channel, and reinforcing diagonal elements, each connected between one of said reinforcing framework elements, at a point of intersection of that framework element with a framework element of the other set of said second framework and that one of said adjacent elements which is at the same side of said channel, at a point of intersection of said first framework, each said reinforcing diagonal element being parallel to a plane defining one side of said channel and being inclined to said reinforcing framework elements, said reinforcing elements have a greater load bearing capacity than the other elements of said member.