04 Scaffolding (Gg)

SCAFFOLDING

CONSTRUCTION TECHNOLOGY IV

1

CONTENTIntroduction Basic forms of Scaffolding Other forms of Scaffolding Slung Scaffold Truss-out Scaffold TrussSuspended Scaffold Mobile Tower Scaffold Birdcage Scaffold Gantries System ScaffoldCONSTRUCTION TECHNOLOGY IV 2

INTRODUCTIONDefinition: Definition: Temporary erections, constructed to support a number of platforms at different heights to enable workmen to reach their work and to permit the rising of materials.


3

FUNCTION As a working platform

- so that the worker can stand on the platform do the work easily & safely As a platform for placing material & logistic needed by the workers to carry out their job As a platform and walking passage - scaffolding support the platform that been used by the worker as their walking path to transport the material & logistic

TypesTubular metal Woods Bamboo Metal frame

Bamboo ScaffoldingUse by Chinese (almost 5000 years!) Is a slender structure of bamboo pieces 2 general types: single layered and double layered Single layered : working scaffolds, use for light duty works Double layered: finishing scaffold,

STEEL SCAFFOLDSteel tubes are nearly 3 times heavier than aluminium alloy tubes but are far stronger. Longer span can be used since it deflection is approximately 1/3 of aluminium alloy tubes. There 2 types that is: - Galvanized steel tubes - Ungalvanized steel tubes that need special care (painting, varnishing or oil bath after use)

Steel Scaffolding

ALUMINIUM SCAFFOLDS Need protective treatment when they are to

be used in contact with materials such as damp line, wet cement & sea water to prevent corrosion to the tubes. Coating the tube with bitumastic paint before using it would be a suitable protective treatment.

Aluminium Scaffolding

TIMBER SCAFFOLD Extensively used in the developing country Members are lashed together with wire or

rope instead of the coupling fittings used with metal scaffolds.

Timber Scaffold

A Scaffold should:Be stable Have a firm base Have properly constructed standards, ledgers, standards, ledgers, transoms and bracers Have a suitable working platform Have guard rails in place Be inspected where required Be constructed so that the public are not put at riskCONSTRUCTION TECHNOLOGY IV 13

CrossCross-Section of Scaffolding


14

Components of scaffoldsBase Standards Ledgers Transoms Bracing Working platforms Platform width Toeboards and guard-rails guardBrickguards Means of accessCONSTRUCTION TECHNOLOGY IV 15

DOUBLE COUPLER

STANDARD

BASE PLATE

STANDARD

Base PlateA good base is essential and the ground should be leveled and rammed to give a firm surface. Timber sole plates, at least 219mm wide and 35mm thick should be laid to support the base plates for standards. Wherever possible, a sole plate should support at least two standards, to ensure that the load carried by each standard is distributed over a fairly large area.


18

Base Plate


19

Base Plate


20

StandardsThe independent tied scaffold has two vertical rows of standards. These are an inner row about 325mm from the building, - to give a working clearance near the wall and an outer row in line with the inner standards to provide a platform of the width required. Any joints necessary in standards to reach the required height should be staggered and occur near ledgers.CONSTRUCTION TECHNOLOGY IV 21

LedgersThe standards in each row are kept equal distance and strengthened by ledgers, fixed horizontally on the inside of standards with right angle couplers.


22

Ledgers


23

TransomsTransoms, keeping the inner and outer rows of standards evenly apart, are set on top of ledgers at right angles to them and to the building. Horizontal distance between transoms at working platform level is determined by the thickness of boards to be used. Ledgers and transoms should not protrude more than is necessary beyond the general outline of the scaffold. At lower level - danger to pedestrians or passing vehicles and it is good practice to use safety caps on the open ends.


24

BracingBracing is essential to stiffen the structure.


25

Bracing


26

Working PlatformsThe minimum width of a working platform is 600mm. The surface of the working platform should be even to prevent anyone tripping. Each board should have at least three supports unless its thickness or span is enough to prevent any sagging under load. All boards should be marked with their maximum span. The maximum span should be 1.2m between supports. All boards should be laid closely together along their length. Standard boards are nominal 225mm wide x 38mm thick.


27

Platforms WidthPlatforms should be wide enough to permit freedom of movement and to accommodate whatever materials need to be stored for short periods.


28

Toeboards and Guard-Rails GuardToeboards and guard-rails are required at the guardoutsides and ends of all working platforms from which men and materials can fall more than 2m. Toeboards and guard-rails should be fitted on the guardinside of standards to prevent outward movement. Toeboards should rise at least 150mm and the main guardguard-rail must be at least 910mm above the working platform. There must be an unprotected gap of more than 470mm in height in the means of protection against a fall of a person from the working platform. In practice therefore, either an intermediate guard-rail guardor other form of effective barrier example brickguard frames must be filled.CONSTRUCTION TECHNOLOGY IV 29

BrickguardsBrick guards are constructed of wire mesh with three hooks at the top that will be hung over the top rail of the scaffold. The lowest part then hands inside the toe board and this prevents a person or material from falling through the space between the top handrail and the working platform.CONSTRUCTION TECHNOLOGY IV 30

Means of AccessAccess to the scaffold must be by the use of a secure ladder. Under no circumstances should a person be allowed to climb up the scaffold tubes to gain access. The safety issues in the use of ladder have been covered in previous note.


31

ConnectorDouble Coupler - the only real loadbearing fitting used in scaffolding - used to join ledgers to standards Swivel Coupler - Composed of 2 single coupler riveted together so that it is possible to rotate them & use them for connecting 2 scaffold tubes at any angle. Putlog Coupler - use solely for fixing putlogs/transoms to the horizontal ledgers.

Putlog Coupler

Double Coupler

Swivel Coupler

Base Plate For Scaffold

SCAFFOLD TYPE AND SELECTIONSelecting a Scaffolding System The safe and efficient use of scaffolding depends, first of all, on choosing the right system for the job. If the scaffolds basic characteristics are unsuited to the task, or if all the necessary components are not available, proper erection and use is compromised. Selection of scaffolding and related components requires an understanding of site conditions and the work to be undertaken. The employer must consider the following: Basic Considerations: the weight of workers, tools, materials and equipment to be carried by the scaffold system (safe work load) site conditions (interior, exterior, backfill, concrete floors, type and condition of walls, access for the equipment, variations in elevation, anchorage points, etc)CONSTRUCTION TECHNOLOGY IV 37

height to which the scaffold may be erected (overhead power lines, tie-backs) tie type of work that will be done from the scaffold (masonry work, sandblasting, painting, metal siding, mechanical installation, suspended ceiling installation) duration of work weather conditions, including wind and ice buildbuild-up requirements for pedestrian traffic through and under the scaffold area means of access to the scaffold configuration of the building or structure being worked on special erection or dismantling circumstances. CONSTRUCTION TECHNOLOGY IV 38 hoarding

BASIC FORMS OF SCAFFOLDPutlog Scaffold single row of uprights or standards set outside the perimeter of the building & partly supported by the structure Independent Scaffold two rows of standards set outside the perimeter of the building not dependent on building support.CONSTRUCTION TECHNOLOGY IV 39

Putlog Scaffold


40

INDEPENDENT SCAFFOLD


41

INDEPENDENT SCAFFOLD


42

OTHER FORMS OF SCAFFOLDSlung Scaffolds: Scaffolds: Suspended by means of wire ropes or chains and are not provided with a means of being raised or lowered by a lifting appliances. Main use: for gaining access to high ceilings or the underside of high roofs.


43

Slung ScaffoldsAt least six evenly spaced suspensions wire ropes/ chains should be used and these should be adequately secured at ends. Working platform is similar to conventional in access of 2.400 x 2.400 plan size.


44

TrussTruss-out scaffolds:A form of tied scaffold, which rely entirely on the building for support. Used where it is impossible to erect a conventional scaffold from ground level. The supporting scaffolding structure which projects from the face of the building is known as truss-out. truss-


45

TRUSS OUT SCAFFOLD


46

Suspended Scaffolds:Consist of working platform suspended from supports such as outriggers, which cantilever over the upper edge of building. As a temporary means of access to the face of a building for the purpose of cleaning and light maintenance work. Cradles may be single units or grouped together to form a continuous working platform; if grouped, they are connected to one another at their abutment ends with hinges which form a gap n.e 25mm wide.CONSTRUCTION TECHNOLOGY IV 47

Suspended Scaffolds


48

Mobile Tower Scaffolds:Used mainly by painters and maintenance staff to gain access to ceilings can be easily & readily moved to a new position. A square tower constructed & mounted on wheels and fitted with brakes. Inclined ladders or vertical ladder fixed inside or outside the tower - must be secured with wire lashing & provided with bottom transom support.


49

Mobile Tower Scaffolds:To ensure stability, the height to working platform of the tower should not exceed three and a half times its least base dimension for internal work. Three times its least base dimension is the maximum for external work. The maximum overall height is 9.6m, unless tied to the structure.CONSTRUCTION TECHNOLOGY IV 50


51

Birdcage Scaffold:Used to provide a complete working platform at high level over a large area and consist basically of a two-directional arrangement of standards, twoledgers and transom to support a close-boarded closeworking platform at the required height. To ensure stability, standards should be placed at not more than 2.400 centers in both directions and the whole arrangement braced.


52

Birdcage Scaffold


53

GantriesUsed primarily as elevated platforms over a public footpath where the structure under construction or repair is immediately adjacent to the footpath. Can served as a storage and accommodation area as well as providing staging from which a conventional independent scaffold to provide access to the face of the building can be erected.CONSTRUCTION TECHNOLOGY IV 54

System ScaffoldBased upon the traditional independent scaffold instead being connected by a series of loose couplers & clips used integral interlocking connections. Easy to erect, adaptable & can be assemble and dismantle by a semi-skilled operatives. semiAdvantage the elimination of internal cross bracing, giving a clear walk through at all levels even though facade bracing is required.


55

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Foundation: Foundation: Ensure the ground is suitable well compacted and free from irregularities caused the sole board unstable. Use base plate for scaffold pitched on soil, pavements, and floor surfaces- mosaic, marble. surfacesSole board to hard ground (min.); 219mm square x 35mm thick.


56

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Ditto to medium ground; 219mm wide x 480mm long x 35mm thick. Ditto to soft ground; 219mm wide x 750mm long x 35mm thick. Good practice to use one length of board to support two standards. For heavy loads concentration or double standards, double thickness boards or larger timbers may be required.


57

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Basing Out: The following maximum bay centers should not be exceeded for independent, putlog or birdcage scaffolds:Very duty light Birdcage scaffold Light Duty General Purpose Heavy duty Heavy duty (bkwk) (masonry)

2.7m

2.5m

2.4m

2.1m

2.0m

1.8m


58

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Maximum 1500mm on lift height Maximum 200mm on bay length +/- 20mm in 2m lift with a maximum of 50mm deviation over full height.

+/- 20mm in 2m bay with a maximum of 50mm deviation over full length

Erection Tolerances: Plumb and level all standards and ledgers progressively as erections of scaffold proceeds.


59

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Lift Heights: For base lifts where access under is required, a maximum lift height of 2.7m is allowable. For general walkthrough access on upper lifts, a maximum lift height of 2.0m should be maintained.


60

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Ledgers: Ledgers: Jointing should be made preferably with sleeve couplers but where expanding joint pins are used, they should be positioned as close to the ledger/ standard connection as possible but not more than 1/3rd. All joints should be staggered in adjacent lifts. Connect ledgers to standards with right angle couplers.


61

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Transoms & Putlogs: Putlogs: Should be fixed to the ledgers with right angle or putlog couplers. For unboarded lifts, transom should be positioned within 300mm of the standard and connected to the ledgers with right angle couplers.


62

ERECTION NOTES COMMON TO ALL SCAFFOLDS: Standards:All standards should be pitched on base plate. Joints in standards should be made with sleeve couplers or expanding joint pins staggered in adjacent bays. Where tension is developed in a standard then the jointing should only be made with sleeve couplers or parallel laps.


63

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Couplers: Can be classified into two categories: Load bearing couplers Right angle couplers Swivel couplers 5KN Brace coupler Sleeve coupler Adjustable Fork Heads Adjustable Base Plate/jack

NonNon-load bearing Putlog couplers couplers Expanding Joint Pine Toe board clipsCONSTRUCTION TECHNOLOGY IV 64

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Bracing: Bracing should be remain in position at all times for stability. Types of bracing: Ledger bracing: bracing:Dog leg bracing fixed from ledger to ledger with right angle or 5KN brace couplers, or from standard to standard with swivel couplers at alternate pairs of standards on every lift for full scaffold height.


65

ERECTION NOTES COMMON TO ALL SCAFFOLDS: One way bracing; fixed from ledger to ledger with bracing; right angle or 5 KN braced couplers at alternate pairs of standards on every lift for full scaffold height. Where clear access is required on base lifts, ledger bracing may be omitted on the base lift provided the lift height does not exceed 2.7m. Where clear access is required on any working lift bracing at every pair of standards may be inserted from inside ledger to guardrail to increase clear access way.CONSTRUCTION TECHNOLOGY IV 66

DOG LEG BRACING

ONE-WAY BRACINGCONSTRUCTION TECHNOLOGY IV 67

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Facade Bracing: All scaffolds should be faade braced either with zig-zag bracing from bottom zigto top or by continuous long bracing from bottom to top, each brace assembly must occur along the scaffold at intervals not exceeding 30 m.CONSTRUCTION TECHNOLOGY IV 68

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Plan Bracing : Not normally required on access scaffolds unless there is a point or level on the scaffold where some lateral loading may be applied, such as loading platform or a lift where no ledger bracing can be placed plan bracing should be placed under the ledger line and be connected from standard to standard with right angle or 5KN brace couplers.CONSTRUCTION TECHNOLOGY IV 69

ERECTION NOTES COMMON TO ALL SCAFFOLDS:Boarded Lifts: All boarded lifts should be closed boarded.Thickness of board Max. Max. between transoms span Minimum overhang Max. Max. overhang

38mm

1.5m

50mm

150mm


70

SAFETY PRECAUTION Standard must be on the same level and

vertically straight on the base plate. The supporting platform wood must be supported properly. Working platform must been equipped with safety elements such as hand rail. Scaffold must be inspected at certain times. Use safety tools such as safety boots, safety helmet and etc when using platform.

Supervision of scaffold erection & progress

/safety reports are undertaken by a suitable experience & qualified person that normally occurs: a) within the preceding 7 days b) after adverse weather conditions that may have affected the scaffolds strength or stability c) whenever alterations / additions are made to the scaffold

The report made after inspection must consist : Location & description of scaffold Date of inspection Result of inspection, stating the condition of scaffold Signature & office of the person making the inspection Badly assembled & neglected scaffold have been a significant contributory factor to the high accident rate associated with the construction industry.

PREVIOUS EXAM QUESTIONSThe Department of Occupational Safety and Health (DOSH) has come out with a standard guideline to ensure the performances and safety of scaffold while installation being done. Explain briefly these safety measures in conjunction to the following aspects:Foundation Lift Heights Erection tolerances


74

PREVIOUS EXAM QUESTIONSDemolitions give rise to the need for temporary support and to some extent cause consequences to the adjacent structure/building. Explain with the aid of sketches, THREE (3) situations that may justify the use of each of the following in relation to demolition works. You are to make necessary assumptions where appropriate. Shoring Scaffolding


75

PREVIOUS EXAM QUESTIONSExplain FIVE (5) factors influencing the choice of selection for the type of scaffolding to be use.


76

PREVIOUS EXAM QUESTIONS (APRIL2005)Scaffolding is a temporary structure which is constructed to support workmen and materials to be reach at different heights. List all the basic components of scaffold and explain briefly with the aid of sketches, the characteristics of two (2) of these components to fulfill its functionality adequately. (15 marks)


77

PREVIOUS EXAM QUESTIONS (NOV2005)Scaffolding is a temporary structure which is constructed to support workmen and materials to be reach at different heights. Explain briefly two (2) basic forms of scaffolding: Putlog Scaffold Independent Scaffold (15 marks)CONSTRUCTION TECHNOLOGY IV 78

YOUR TASKPlease update the notes with the required sketches/ drawings or photographs....


79

Documents

04 Scaffolding (Gg)