Presented by: Ricardo Brown SCAFFOLDING Presented by: Ricardo Brown

What is a scaffold? A scaffold is a temporary structure specifically erected to support access or working platform. Scaffold are commonly used in marine & offshore construction work so that workers have a safe, stable platform on which to work when work cannot be done at ground level or on a finished floor

HAZARDS Scaffolding collapse Eletrocution ( Work near over head electric lines) Mixing components from different scaffold systems. Falls from heights Falling objects Manual tasks Bad planking

Assessing the risk The type of scaffold to be used The height of scaffold to be erected The scheduling of scaffolding work The layout of the workplace, including proximity to public areas The surface on which the scaffold will be erected The number of people involved Local weather condition Exposure that might occur( radiation , gases)

Controlling the risks Usage of mechanical aids if required Use fall protection devices, proper construction Safe system of work Providing proper personal protective equipment

Types of scaffolds Birdcage scaffolds A birdcage scaffold is an independent scaffold that consists of more than two rows of standards in both directions and is connected by ledger and transoms. It is mainly used for work that is to be carried out on a single level such as ceilings

Tower scaffolds A tower scaffold is an independent scaffold consisting of four vertical members connected longitudinally & transversely Construct with modular frame or tube and coupler scaffolding. Use alternative height to base ratios or extra support if the scaffold is sheeted, loaded with heavy equipments, supporting a ladder For eg: height of tower outside the building height to base ratio is 3.5:1

Mobile scaffolds A mobile scaffold is a tower scaffold that is mounted on castors. Manufacturers and suppliers must provide information regarding the safe use and erection of mobile scaffolds Where adjustable castors are used, the slope of the surface should not exceed 5 degrees. Castors fitted to standards should be locked Before moving, check any power lines or other overhead obstruction, ground should be firm & level, never move the scaffold in windy condition, ensure guardrail , mid rail, & toe boards are installed on all working platforms

Tube & coupler scaffolds(Modular) So named because they are built from tubing connected by coupling devices. Due to their strength, they are frequently used where heavy loads need to be carried, or on structures with unusual design, shape & locations.yhe versatility of tube and coupler scaffolds enables them to be assembled in multiple directions in a variety of settings. When using tube and coupler scaffolding consideration should be given to the diameters and strength of the tube and components being used to form the scaffold. Steel tubes & Aluminium tubes should not be mixed in the one scaffold, except for guard rails, mid-rail or other member that are not structural members

A modular scaffold mainly consists of: Standards : they come in a variety of length & have performed connectors welded at fixed distances along their length. Ledgers : they are in varying lengths with connectors welded to each end. Transoms : they are generally made to support scaffold board and structures. Bracings : bracings in each direction are made to fit the different bay sizes. Scaffold boards :they are also called stagings and come in a variety of lengths, thickness & widths.

Ties : ties are generally formed in tube and fittings. Adjustable base plates : they are essential and care should be taken to establish their safe working loads and weather they are designed for heavy or light duty use.

Frame scaffold Frame scaffold is a scaffold assembled from prefabricated frames, braces & accessories. Frame scaffolds such as ‘A’ & ‘H’ frame trestle scaffolds are commonly used by painters and for general fit out & finishing work. Frame scaffold should be erected and dismantled by a competent person in a progressive manner to ensure both the installers safety and the stability of the overall structure and braces should be attached to the frames. Frame scaffold should be stable & erected on a suitable foundation to ensure it can adequately carry & distribute the loads such as materials and workers evenly to each frame

Hung scaffold Hung scaffold is an independent scaffold that hangs from another structure, but is not capable of being raised or lowered when in use. The hung scaffold should be designed by a competent person. All vertical hanging tubes are to be provided with check couplers at the suspension points and underneath the platform. Standards on a hung scaffold should be tension spliced

Suspended scaffolds A suspended scaffold incorporates a suspended platform that is capable of being raised or lowered when in use. Ensure a rescue and retrieval procedure is developed before starting work Suspended scaffolding components should be inspected foe damage, wear & cracks in before use. Ensure safe access to and egress from the cradle.

Trestle scaffold Trestles are a simple working platform used in pairs to support scaffold boards or proprietary staging and are intended for light work only. They must be sited on firm, level ground and be fully open. They must not be used where anyone can fall more than 4.5 m The top third of trestles must be above the working platform, scaffold must be at least two boards wide-430mm It is available in lengths of up to 7.3 m and has a standard width of 450mm. Toe boards & guard rails are required when persons are liable to fall more than 2 m

Cantilever scaffolds A cantilever scaffold is a scaffold that is supported by cantilever load bearing members. Design & position cantilever beams in accordance with the engineers requirements and the scaffolding plan Ensure a competent person certifies that the supporting structure can support the cantilevered scaffold. Fix the beam to the floor below using a positive fixing Use counterweights on the beam Install props to the top of the beam and to the underside of the floor above. Ensure the props are fixed to prevent dislodgement

Base plate

Couplers

Planning scaffolding work Scaffolding work should be carefully planned before work starts so that it can be carried out safely. Planning involves: Identifying the hazards. Assessing the risks & determining appropriate control measures in consultation with all relevant persons involved in the work The scaffolding plan should include a site layout plan and detail the elevations sections of the scaffold. Its to be made available for inspection at the worksite

The scaffolding plan should address the following issues Basis of design Foundations The weight bearing capacity of the surface where the scaffold is to be erected. Size & weight of the scaffold Supporting structure Access & egress Bracings Type of scaffold Edge protection Barricade , symbols & signs

Safe work method statements Identify the type of high risk construction work being done. Specify the health & safety hazards and risks arising from that work Describe how the risks will be controlled Describe how the control measures will be implemented, monitored & reviewed. Be developed in consultation with workers and their representatives who are carrying out the high risk construction work SWMS is required if the scaffold is erected near energized electrical lines or if there is a risk of a person falling more than 2m during the erection & dismantling

Loadings A scaffold should be designed for the most adverse combination of dead , live & environmental loads that can reasonably be expected during the period that the scaffold is in use. Consider environmental loads, particularly the effects of wind & rain on the scaffold. Dead loads relate to the self-weight of the scaffold structure & components including any working, catch or access platforms, stairways, ladders, scaffolding hoists or electrical cables.

Uniformly varying load

Live load on standards will vary for different bays & platforms Live load on standards will vary for different bays & platforms. To calculate the live load on a standard, assume that each standard in that bay supports one third of the duty live load on each platform in each adjoining bay. This is to allow for off center loading of platforms and concentrated loads placed closer to a standard. For eg: consider a medium duty scaffold The live load on any one standards based on the worst possible loading in adjacent bays (4.4kn) =4.4KN(450kg)/(2/3)=2.9kN(300kg) Assume that the dead load-3.5KN(350KG)+2.9KN=6.4KN Assume that ground capacity 2500kg/m2 , timber plank 225mm wide Soleboard length=[650kg/(2500kg/m2)]/0.225m=1.16m

Scaffold working platforms are generally rated as Light duty-up to 225kg/bay. Examples include painting, electrical work, many carpentry tasks and other light tasks. Platform should be at least two planks wide (approx:450mm) Medium duty-up to 450kg/bay. This is suitable for general trades work. Platform should be at least four planks wide (approx:900mm) Heavy duty-up to 675kg/bay. This is what is needed for bricklaying, concreting, demolition work and most other work tasks involving heavy loads or heavy impact forces. Platform should be at least five planks wide( approx:1000mm) Special duty- has a designated allowable load as designed

Safe erection of scaffold After enough components of the scaffold have been erected to support it immediately install: A platform at least 450mm wide along the full length of the section of scaffold. Edge protection across the space between the uprights forming the outer frame of the scaffold at the level scaffold has reached. A means of access to the level the scaffold has reached A section of platform may be left open to allow the passing of planks or other scaffolding components between the levels

Scaffold fittings & other connections should be securely tightened. All scaffolding components should be installed as the scaffold is erected Obtain certification from a competent person Limit the number of workers on a scaffold at anyone time. Do not climb on guard rails to gain extra height. Implement measures to control the risk of fall by edge protection, additional scaffold planks to minimise the size of the internal gap.

Scaffold load & size calculation Dead load : The dead load(G) shall include the self weight of the scaffold structure. Environmental loads : wind loads , snow loads , rain & ice loads , earthquake loads in accordance with NZS 4203 Live loads (Q): the weight of the persons, materials & debris, tools & equipments & impact forces

Duty live loads Light duty- a load of 2.2 KN/bay, that includes a single concentrated load of 1 KN. Medium duty- a load of 4.4 KN/bay that includes a single concentrated load of 1.5 KN Heavy duty- a load of 6.6 KN/bay that includes a single concentrated load of 2 KN Special duty- the largest intended load but not less than heavy duty For design purposes, the single concentrated load shall be assumed in the most adverse position within the bay

Inspection of scaffolding materials Sufficient material should be provided for and used in the construction of scaffolds Scaffolding material should be free from defects. The boards & planks used should be unpainted so that defects should be visible Timber scaffold boards should comply BS 2482 or other equivalent international standards All scaffolding components should comply with BS 1139, BS EN 39 ,BS EN 74, BS EN 1004, & BS EN 12810 Hot dipped galvanized, or unprotected tube may be used in scaffolding . Tubes end should be free from distortion, corrosion, splits ,undue rust. Where tubes have become split at the ends, these should be cut off, cut should be perpendicular to the axis

The safe working loads for individual couplers & fittings should comply with bsen12811 Special attention should be paid to the use of joint pins. All couplers & fittings should be free from rust & distortion, worn threads & damaged bolts & should be maintained in lubricated condition The nuts should be run on their bolts to ascertain that they have free-running fit . Spanners & podgers should have length as recommended by the coupler manufacture

Dismantling of metal scaffolds The dismantling work shall be done by trained workmen under the immediate supervision of a competent person. Sufficient time should be allowed for the dismantling work to be conducted safely. The scaffold to be dismantled should be checked for its strength & stability beforehand. Dismantling sequence should be planned and that sequence of dismantling sections of the scaffold should be logical and determined with due consideration of the scaffolder’s safety. Dismantling work should be carried out according to the plan. Because changes may have been made in a scaffold structure during its work, its not safe to assume, to dismantle it in reverse order. If the scaffold is defective ,it should be made good before dismantling commences.

Scaffold should not be dismantled in vertical sections from one end towards the other unless special consideration is given to ties & bracings Safe access to & egress from the place of work should be provided for the scaffolders The scaffold to be dismantled should be fenced off at the ground level/public area to prevent persons entering the work area and warning notices should be posted up in the vicinity Steps shall be taken to ensure that scaffolding materials are not thrown, tipped or shot down from height, properly lowered in a safe manner by means of a lifting appliance or lifting gear. Every scaffolder involved in the dismantling should have all safety equipments. All the trades on the site should coordinate and collaborate closely among the members