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Scaffolding
Scaffolding is a temporary structure used to support people and material in the construction or repair of buildings and
other large structures. It is usually a modular system of metal pipes or tubes, although it can be from other materials.
Bamboo is frequently used in some Asian countries, Such as Honk Kong.
Scaffolding in the ancient world
The Berlin Foundry Cup depicts scaffolding in ancient Greece (early 5th century BC). The ancient Egyptians, Micheal Korsoutlet (http://michealkorsoutlet0.blogspot.com) Nubians and Chinese are also recorded as
having used scaffolding-like structures to build tall buildings. The ancient Africans have also used wooden scaffoldings to support mosques.
Scaffolding in the modern day
This European Standard specifies performance requirements and methods of structural and general design for access and working scaffolds.
Requirements given are for scaffold structures that rely on the adjacent structures for Michhealkors Outlet (http://michhealkorsoutlet.blogspot.com) stability.
In general these requirements also apply to other types of working scaffolds.
The purpose of a working scaffold is to provide a safe place of work with safe access suitable for the work being done.
This document sets out performance requirements for working scaffolds. These are substantially independent of the materials of which the scaffold is made.
The standard is intended to be used as the basis for enquiry and design.Thus the requirements of BS EN 12811-1.
TG20 is largely based on BS 5973 with extracts taken directly from the old code,
it also uses permissible stress design method. However, TG20 received a mixed response from the UK industry and as a result TG20 is being re-written
and the new version is due for release sometime in 2008. This is the reason for the 'limbo' situation. Until the release of the revised TG20 the HSE continue
to allow scaffold to be built in accordance with BS 5973.
Basic scaffolding
The key elements of a scaffold are standards, ledgers and transoms. The standards, also called uprights, are the vertical tubes that transfer the entire mass of the
structure to the ground where they rest on a square base plate to spread the load. The base plate has a shank in its center to hold the tube and is sometimes pinned
to a sole board. Ledgers are horizontal tubes which connect between the standards. Transoms rest upon the ledgers at right angles. Main transoms are placed next to the
standards, they hold the standards in place and provide support for boards intermediate transoms are those placed between the main transoms to provide extra
support for boards. In Canada this style is referred to as "English". "American" has the transoms attached to the standards and is used
less but has certain advantages in some situations. Since scaffolding is a physical structure, it is possible to go in and come out of scaffolding.
As well as the tubes at right angles there are?cross braces?to increase rigidity, these are placed diagonally from ledger to ledger, next to
the standards to which they are fitted. If the braces are fitted to the ledgers they are
called ledger braces. To limit sway a?facade brace?is fitted to the face of the scaffold every 30 meters or so at an angle of 35°-55°
running right micheal kohrs outlet (http://michealkohrsoutlet5.blogspot.com) from the base to the top of the scaffold and fixed at every level.
Of the couplers previously mentioned, right-angle couplers join ledgers or transoms to standards, putlog or single couplers join board bearing transoms to
ledgers - Non-board bearing transoms should be fixed using a right-angle coupler. Swivel couplers are to connect tubes at any other angle.
The actual joints are staggered to avoid occurring at the same level in neighboring standards.
The spacing of the basic elements in the scaffold are fairly standard. For a general purpose scaffold the maximum bay length is 2.1 m, for heavier work the bay
size is reduced to 2 or even 1.8 m while for inspection a bay width of up to 2.7 m is allowed.
The scaffolding width is determined by the width of the boards, the minimum width allowed is 600?mm but a more typical four-board scaffold would be 870?mm wide
from standard to standard. More heavy-duty scaffolding can require 5, 6 or even up to 8 board's width. Often an?inside board?is added to reduce the
gap between the inner standard and the structure.
The lift height, the spacing between ledgers, is 2 m, although the base lift can be up to 2.7 m. The diagram above also shows a kicker lift,
which is just 150?mm or so above the ground.
Transom spacing is determined by the thickness of the boards supported, 38?mm boards require a transom spacing of no more than 1.2 m while a 50?mm board can
stand a transom spacing of 2.6 m and 63?mm boards can have a maximum span of 3.25 m. The minimum overhang for all boards is 50?mm and the maximum overhang is
no more than 4x the thickness of the board.
Foundations
Good foundations are essential. Often scaffold framework will require more than simple base plates to safely carry and spread the load. Scaffolding can be
used without base plates on concrete or similar hard surfaces, although base plates are always recommended. For surfaces like pavements or tarmac base plates
are necessary. For softer or more doubtful surfaces sole boards must be used, beneath a single standard a sole board should be at least 1,000?cm2 with no
dimension less than 220?mm, the thickness must be at least 35?mm. For heavier duty scaffold much more substantial baulks set in concrete can be required.
On uneven ground steps must be cut for the base plates, a minimum step size of around 450?mm is recommended. A working platform requires certain other
elements to be safe. They must be close-boarded, have double guard rails and toe and stop boards. Safe and secure access must also be provided.
Materials
The basic materials are tubes, couplers and boards.
Tubes are either steel or aluminum, although composite scaffolding uses filament wound tubes of glass fiber in a nylon or polyester matrix. If steel they are either
'black' or galvanized. The tubes come in a variety of lengths and a standard diameter of 48.3 mm. (1.5 NPS pipe). The chief difference between the two types of
tubes is the lower weight of aluminum tubes (1.7 kg/m as opposed to 4.4 kg/m) and also a greater flexibility and so less resistance to force. Tubes are generally
bought in 6.3 m lengths and can then be cut down to certain typical sizes.
Boards provide a working surface for users of the scaffold. They are seasoned wood and come in three thicknesses (38 mm (usual), 50 mm and 63 mm) are a standard
width (225 mm) and are a maximum of 3.9 m long. The board ends are protected by metal plates called hoop irons or sometimes nail plates. Timber Scaffold boards
in the UK should comply with the requirements of BS 2482. As well as timber, steel or aluminum decking is used or laminate boards. As well as boards for the working
platform there are sole boards which are placed beneath the scaffolding if the surface is soft or otherwise suspect, although ordinary boards can be used, another
design called the scaffpad is another solution as it is michael kors outlet at fremont ca (http://michaelkorsoutlets2.snack.ws/) made from a rubber base with a base plate molded inside, these are great to put on uneven ground because
they adapt to any ground where sole boards would split costing more money to replace.
Couplers are the fittings which hold the tubes together. The most common are called scaffold couplers, there are three basic types: right-angle couplers, putlog
couplers and swivel couplers. To join tubes end-to-end joint pins (also called spigots) handbag mk (http://handbagmk7.blogspot.com) or sleeve couplers are used, or both together. Only right angle couplers
and swivel couplers can be used to fix tube in a 'load-bearing connection'. Single couplers are not load-bearing couplers and have no design capacity.
Boards provide a working surface for users of the scaffold. They are seasoned wood and come in three thicknesses (38 mm (usual), 50 mm and 63 mm) are a standard
width (225 mm) and are a maximum of 3.9 m long. The board ends are protected by metal plates called hoop irons or sometimes nail plates. Timber Scaffold boards
in the UK should comply with the requirements of BS 2482. As well as timber, steel or aluminum decking is used or laminate boards. As well as boards for the working
platform there are sole boards which are placed beneath the scaffolding if the michaels kors outlet store (http://michaelskorsoutlet4.blogspot.com) surface is soft or otherwise suspect, although ordinary boards can be used, another
design called the scaffpad is another solution as it is made from a rubber base with a base plate molded inside, these are great to put on uneven ground because
they adapt to any ground where sole boards would split costing more money to replace.
Couplers are the fittings which hold the tubes together. The most common are called scaffold couplers, there are three basic types: right-angle couplers, putlog
couplers and swivel couplers. To join tubes end-to-end joint pins (also called spigots) or sleeve couplers are used, or both together. Only right angle couplers
and swivel couplers can be used to fix tube in a 'load-bearing connection'. Single couplers are not load-bearing couplers and have no design capacity.
Other common materials include base plates, ladders, ropes, anchor ties, reveal ties, gin wheels, sheeting, etc.
Despite the metric measurements given many scaffolds measure tubes and boards in imperial units. With tubes from 21 feet down and boards from 13 ft. down.
Bamboo scaffolding is widely used in Hong Kong, with nylon straps tied into knots as couplers.
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