Index Temporary Works: No.Subject 1Timber Trenches 2Timber Scaffolding

Trenches

During excavation, shoring systems provide safety for workers in a trench and speed excavation. In this case, shoring should not be confused with shielding. Shoring is designed to prevent collapse where shielding is only designed to protect workers when collapses occur. Concrete structures shoring, in this case also referred to as false work, provides temporary support until the concrete becomes hard and achieves the desired strength to support loads. Trenches consists of a temporary arrangement of timber planks or boards and struts to provide support to the sides of trenches.

Stay bracing when the trench soil is firm and the depth of excavation does not exceed 2.0m, this method is used for supporting the sides of trench. In this method, the vertical sheets called sheathing or polling-boards are placed on both the sides of trench, which are held in position by one or two rows of horizontal struts. The vertical sheets are placed at an interval of 2m to 3m. And they extended to the full height of the trench. The sheets may be 200mm., wide and 40to50mm thick. The horizontal struts may have size of 100x100mm to200x200mm., depending upon the width of the trench

Box sheeting When the trench soil is loose and the depth of excavation does not exceed 4.0m., this method is used. In this method, the box like structure is formed by providing vertical sheets near to each other or touching each other and two rows of horizontal Wales or rafters to keep them in position. The horizontal Wales are supported by the struts. In another system, the sheet are provided longitudinally touching each other and are supported by vertical Wales. These Wales are further supported by horizontal struts. If the depth of trench is more, the braces are provided along with struts.

Scaffolding

The height of the wall or other structural member of the building exceeds about 1.50m., a temporary structure, usually of timber planks and bamboos, is erected close to the work to provide a safe working platform for the worker, which is known as scaffolding. It is use full in construction, Demolition, maintenance or repair works.

Components of scaffolding Standards:- These are the vertical members, supported on ground. Ledgers:- These are the horizontal members, running parallel to the wall. Braces:- These are the diagonal members fixed on standards. Putlogs:- These are the transverse members which are placed at right angles to the walls with one end supported on ledgers and other end on the wall. Transoms :-These are the putlogs whose both ends are supported on ledgers. Bridle:- This is member used to bridge a wall openings, supported one end of putlogs at the opening.

Types of Scaffolding Brick layer scaffolding [Single Scaffolding] Masson’s scaffolding [Double scaffolding] Cantilever or needle scaffolding. Suspended Scaffolding. Trestle Scaffolding. Steel scaffolding. Patented Scaffolding..

Brick layer’s scaffolding This type of scaffolding consist of vertical members called standards firmly in ground at 2.4 to 3.0m intervals. The standards are connected to each other by longitudinal horizontal members called ledgers at 1.20 to 1.50m. The putlogs are the traverse horizontal members lashed on the ledgers at one end and into holes in the wall at the other end. Putlogs are 90cm. In length and are spaced at 1.20m. Apart. They are provided to support the working platform.

Masson’s scaffolding In stone masonry, it is difficult to leave the holes to provide bearing for the putlogs. In Masson's scaffolding, two frames of standards, ledgers, and braces are used. The first frame is placed close to the wall and the other frame is placed at 1.0 m from the first one. Thus, the Masson's scaffolding is entirely independent of the stone wall.

Cantilever Scaffolding When the scaffolding is to be provided on the side of a busy street, where the erection of the scaffolding will be obstruct the traffic on road, the needle scaffolding is used. The scaffolding may be single type or double type. In case of single type scaffolding, the standards are supported on serices of needles taken out through opening or through holes in the wall. In case of double type scaffolding, the needles or projecting beams are strutted inside the floors, through the openings.

Reference Books [A.S. Kotadia, Rangwala] Wikipedia. Britannica encyclopedia. Google images

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