Post-mounted flat roof substructure - has single size I=section joists bolted together into square frames with cantilever arms at each corner

摘要

The roof is fabricated using uniform length standard joists (2). These are mounted on posts (1) to a squared plan grid, and form a horizontal framework. The joists are of an 'I' section in lightweight concrete, bolted (10, 11, 13) together in sets of four to form a modular frame bay. The bay is a square with a side of half the joist length and a cantilever arm projecting from each corner. Each arm extends one side of the square, their ends being bevelled (14) in plan to sit on a post head and form a cross-tied node joint with an in situ concrete core. Post grid lines locate at square root 1.25 or 1.5 times joist length, the former siting posts on grid nodes whilst utilising a sec. joist module in oblique straight roof edges. The sec. maintains parallelism between prim. joists and edge joist of the same length, the posts sited on grid lines straddling the nodes at third points of the grid squares.