The salbullah piles shall be painted with two coats of hot coal tar before driving. The timbers used for bridge works shall be seasoned and treated with preservatives such as ASCU or creosote oil. 50 mm × 50 mm deck stiffeners are also fixed at the bottom of decking planks for the same purpose. thick timber planks are longitudinally placed on both sides of the centre line of the transverse deck for distribution of live loads (wheel loads) over a few decking planks. Wooden sleepers are used as wheel guards on both sides of the carriageway. While the decking planks are fixed on to the timber beams directly by nails, an intermediate packing timber piece is fixed by countersunk bolts over the RSJ for the facility of nailing the decking timber over this timber piece.
channel is placed on the top of the piles and RSJ are seated on these channels. When RSJ used over double rows of pile trestle for longer spans, one m.s. Timber beams are used for 3.0 m span superstructure and these beams are seated on single pile trestle by m.s. 18.1 and double rows for 4.5 m and 6.0 m span as in Fig. The piles may be in single row for 3.0 m span as in Fig. These driven depths shall be below the bed level taking into consideration of the possible scouring of the bed if any. diameter driven to 3.0 m for 3.0 m span bridges and 4.5 to 6.0 m for 4.5 m and 6.0 m span bridges. The pile trestle is composed of a cluster of piles usually 200 mm.
Timber bridges are generally constructed on salbullah pile trestle as sub-structure and foundation and timber decking over timber beams or over RSJ as superstructure. Callender-Hamilton (Unit Construction) Bridge 4. This article throws light upon the five main types of low cost bridges.
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