Hello friends how are you? I hope you are all right. Now today discuss the formwork and scaffolding structure. Which is very much used in the engineering construction industry. In any type of construction, this structure is required. So friends we will get knowledge about the scaffolding and formwork structure.
Formwork ( Shuttering)
Requirements of formwork
- The material of formwork should be cheap and it should be suitable for several reuses.
- It should be waterproof.
- Its shrinkage and swelling should be minimal.
- It should be strong enough to withstand the loads coming in it.
- It should be right as possible.
- The surface of the formwork is smooth.
- It should afford easy stripping
Types of formwork.
- Timber formwork.
- Ply formwork.
- Steel formwork.
Shoring is the temporary structure constructed to support a temporary unsafe structure. These are used when.
Types of shoring
These are placed at 3.0 to 4.0 cm clc ( Canter to center) and can be single, double, triple or multiple raker format.
Suitable materials are timber or structure steel
Minimum angle of raker 40deegre maximum angle 70 deegre.
Flying shores are used to give horizontal support to two adjacent, paralleled walls which have become unsafe due to the removal of the intermediate building.
Single-flying shores are used up to 9m. And double flying shores are used for spans up to 12m.
The centerline of flying shore and struts and those of flying shore and struts and those of the walls should meet at the same floor level of the two buildings.
In the case of floors at different levels, shores should be placed either midway between the level of two floors or should be placed at the level of two floors.
The stunts should be inclined at 45 degrees not exceeding 60 degrees.
Should be spared at 3 to 4.5 m center to center.
Dead or vertical shore:
It consists of a vertical member called the dead shore.
Used to serve the following properties.
- To rebuild the defective lower part of the building.
- To build or deeper the existing foundation.
- To make large openings in the existing wall at a lower level.
A temporary rigid structure with platforms raised up as the building increases in height. It enables the mason to work safely at different stages of building and to hoist the required materials such as brick, block, mortar, etc. For immediate use at various heights.
The temporary structure constructed very close to the wall to provide the platform over which workers sit and carry on the construction is known as scaffolding.
The scaffolding should be stable and strong enough to support workers and the construction material placed on the platform.
There are various types of scaffolds that are commonly used some of them are listed and explained hereunder:
Types of scaffolding:
- Single scaffolding (Bricklayers scaffold)
- Double scaffolding (Mason’s scaffold)
- Close masons scaffold
- Steel or tubular scaffold
- Needle scaffold or cantilever scaffold
- Wooden or timber gantry
It consists of vertical members called standards normally bamboo, firmly secured in the ground at 2.4 to 3 m apart. The standards are connected to each other by longitudinal horizontal members called ledgers at every rise of 120 to 150 cm they are provided on the building side of standards and they are secured in position by rope lashings.
Transverse horizontal members called putlogs are lashed on the ledgers at one end and into the holes in the wall at the other end.
Putlogs are a minimum of 900 mm in length and are generally spaced 100 cm apart.
They are provided to support the working platform.
In high scaffolding, cross bracing is invariably used to stiffen the temporary structure. These braces consist of poles tied by rope lashing on the standards. This is known as a Bricklayers scaffold.
Since it is difficult to leave holes in the stone masonry to provide a bearing for the putlogs.
In Mason’s scaffold two frames of standards, ledger sand braces are used.
One is placed quite close to the wall and the other at a distance of 1.5 m from the first one.
Actually, Mason’s scaffold is entirely independent of the stone wall. This is termed double scaffolding.
Close masons scaffold
They are supposed to carry loads of heavy blocks of stones and the stresses produced on account of the lifting devices and hence they are made stronger by placing the standards at a fairly close distance apart.
Steel or tubular scaffold
The construction of steel scaffold is essentially similar to that of timber or bamboo scaffold. In this case, the wooden members or bamboo are replaced by 38 to 63-mm diameter steel, and instead of rode lashing, special types of steel couplets or fittings are used for connecting different members.
The steel tubes used for scaffolding for normal building construction work are of heavy class and of diameter varying from 40 to 60 mm.
In this type of scaffold, the vertical tubes are called uprights, or standards that are spaced 2.5 to 3 mm apart.
The base plate has holes so that it can be spiked to a timber concrete base thus forming a rigid foundation for the scaffolding.
Ledgers or the longitudinal tubes connecting the standards are spaced at 1.8 m vertically apart. Short tubes or putlogs are normally 1.2 to 1.8 m in length the putlogs have special ends to fit into the joints in the wall and thus no big holes are required to be left in the wall for their bearing.
Steel or tubular scaffolding has many advantages over timber or bamboo scaffolding such as rapid erection and dismantling.
Greater strength and durability and higher fire-resisting qualities and salvage value. Although it works out to be costlier initially but considering its several advantages and the increased number of reuses, it proves to be economical in the long run and hence it is extensively used nowadays.
Needle scaffold or cantilever scaffold
When scaffolding is to be provided for a building on the side of a busy street where the erection of ordinary scaffolding will obstruct the traffic on the road, then a needle or cantilevered scaffold is used. This type of scaffold is erected from window corners or string courses by means of projecting needles.
A needle is a bamboo or timber beam which cantilevers out through the holes formed in the wall.
From inside the needles are supported on sole pieces and are prevented from lifting by up vertical struts wedged between the needles and headpieces.
The projected end of the needle is supported by an inclined strut that rests on the window sill.
The joint between the raking or inclined strut and the needle is clamped by means of dogs. The arrangement provides the staging for the erection of an ordinary type of scaffold.
Wooden or timber gantry
There are two types of wooden gantries which are following:
Gantry with crane
When the stone blocks used in the wall construction are too heavy, crane travelers have to be used the framework of the gantry consists of timber standards raised on either side of the wall longitudinal members called runners are fixed on the top of the standards while at the bottom the standards are fixed to common sole pieces.
Rails are fixed on the runners to carry the traveling platform.
The traveling platform consists of trussed beams carrying lifting tackle, which can run on wheels on rails, fixed on runners. This enables the traveling platform to move parallel to the wall along its length.
In addition, the beams of the traveling platform have rails so that the lifting tackle can move in a direction perpendicular to the wall. Thus, the stone blocks can be placed in any desired direction while building the wall.
Plat form gantry
This is constructed for providing a working platform above ground level and leaving the space below free from obstruction. This variety of scaffolds is adopted in stone masonry construction as it can be used independently of the wall.
The gantry consists of vertical posts fixed to common sole pieces at its base and headpieces at the top. The headpieces support the joint on which the platform is laid.
The entire framework is thoroughly braced and logged. A 90 cm high boarding is fixed on the outside of the gantry to prevent the material on the plate form from falling down.
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