The invention relates to a three-dimensional framework as a frame-like support structure for installations, consisting of tubular longitudinal posts (1), which are mutually spaced apart and are substantially rectangular, and braces (6a, 6b), which connect said posts to each other and are disposed horizontally and/or diagonally. The aim of the invention is to improve such a support structure and to simplify assembly. To that end, at least the longitudinal posts (1) consist of glass fiber-reinforced plastics and are connected to the braces (6a, 6b) by clamping. The longitudinal posts (1) have longitudinal slots (2) in at least two opposite walls. An elongate flat clamping element (10) which is arranged on a screw (9) by means of a screw thread, said screw extending through a bore (8a, 8b) in the brace (6a, 6b), and which is inserted into the interior of the post through the longitudinal slot (2) secures the brace (6a, 6b) and the longitudinal post (1) relative to each other. When the screw is tightened, the clamping element (10) automatically rotates into an abutment position that secures the brace (6a, 6b) in a clamping manner.