Nailed girders

Nailed girders: a) with web of boards, b) with a plywood web; 1 - bottom straps, top, 2 - web of boards, 3 - plywood web, 4 - stiffening rib.

Nailed girders with an I-section shown in the drawing are made of length up to 20,0 m. The spar chords may be parallel, or the belt up may be kinked (two-fall). The mid-span height of the spar is (1/8-1/12)l (l - spar span). Girders with a broken upper flange are used in gable roofs, while girders with parallel flanges can be used in mono-pitched roofs, either as purlins or joists.

The girder consists of top and bottom planks or logs that are shelves (belts) girder, which are connected to the cross-wall - a web composed of two layers of intersecting boards. The boards are set at an angle of 45 ° or 60 ° to the bottom flange.

For a cross-brace (web) thick boards are used 19-25 mm, for belts with a cross-section from 2,5 x 20 cm do 7,5 x 20 cm. Figure b also shows a plywood girder. Diagonal wall (web) it is stiffened with ribs made of boards with a width of not less than 8,0 cm. The stiffening ribs are placed on the supports and at points of concentrated forces, i.e.. pod płatwiami i belkami. The rib spacing is 1,0-1,5 m. The number of nails and their arrangement are determined on the basis of calculations and the rules for the correct construction of elements.

The construction details of the nail girder are presented in the drawing.

Construction details of a girder consisting of two segments: a) view, b) arrangement of nails in the cross wall (web), c) arrangement of nails at the waist, d) the minimum length of nails in stripes; 1 - top chord boards, 2 - diagonal wall boards, 3 - bottom chord boards, 4 - top covers, 5 - stiffening rib boards, 6 - bottom covers.