methodology for staging

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Temporary Structures CMCM

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Shoringand

Scaffolding

Lecture 7




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Shoring In multistory work, The shoring which

supports freshly placed concrete isnecessarily supported by lower floorswhich

may not yet have attained their theirfull strength,

and which may not have beendesigned to carry loads as great asthose imposed during construction

Construction Loads may exceed designloads by an appreciable amount!"ef# $rundy % &abaila, 'CI (, )ec *+, pp 7-./7+01




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ShoringTherefore shoring must be provided

for enough floors to develop theneeded capacity to support theimposed loads without excessive

stress or deflection2hether permanent shores or

reshores are used at the several

re3uired lower floor levels dependson 4ob plans for reused of materialsas well as the rate of strength gain

in the structure




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ShoringThere are several types of ad4ustable

individual shores

The simplest ofthese, is basedon clampingdevice whichpermits the

overlapping oftwo -x5members




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Shoring

' portable 4acking tool is usedto make vertical ad4ustments

6etal shore 4ack fittings areavailable to fit over the end of5x5 or *x* wood shore, thustransforming the piece oflumber into an ad4ustable

shore These devices are capable of

varying the shore height asmuch as - in




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Shoring

' number of patented shoringsystems have been developed withad4ustable legs which eliminatecutting, close fitting, and wedging




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Scaffold-Type Shoring2hen tubular steel frame

scaffolding was first introduced, itwas designed to support therelatively light loads involved in

getting workers to the work areaLater contractors began to try out

the scaffolding as a support for

formwork because of the apparentadvantages of its modular assemblyand system of 4acks for leveling and

ad4usting elevations




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Scaffold-Type Shoring nd frames assembled with diagonal braces

to form typical shoring 8tower9




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2alk/through/typeframes used by masons

Scaff olding

Scaffolding has beenused for :;;; years toprovide access areasfor building and

decorating structurestaller than people whowork on them




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Scaffolding

The word 8scaffolding9 refers to anyraised platform or ramp used foringress and egress for pedestrian

movement and<or the passage ofbuilding materials

Since the mid/.-;s the concept of

using steel pipes fastened togetherwith metal/form or cast clamps!couplers1 instead of poles and ropeswas introduced




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Scaffolding

'luminum alloy pipes and couplerswere developed for their lighterweight and speedier construction

'luminum alloy is only two/thirds asstrong as steel, but it is only one/third to one/half its weight

=ecause of the higher initial cost,aluminum is restricted mostly tobuilding maintenance scaffolds andsuspended platforms




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ScaffoldingGeneral Design Considerations

Commonly, all types of scaffold haveincorporated in their design a minimum safetyfactor of 5

This means that scaffolds and theircomponents shall be capable of supportingwithout failure at least 5 times the maximumintended load

To comply with this re3uirement, multiply thedesign load by 5 and derive the limitingstrength of the component from the yieldstress of the metal in accordance with

acceptable engineering criteria and practices




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ScaffoldingDesign Loads

In accordance with >S?' and '@SI criteria and

common practice for many years, design loadratings for scaffold platforms are as follows#

Light-Duty Loading -: lb<ft- maximum workingload for support of people and tools !no

e3uipment or material storage on the platform1 Medium-Duty Loading :; lb<ft- maximum working

load for people and material restricted not toexceed this rating, often described as applying to

bricklayersA and plastersA work Heavy-Duty Loading 7: lb<ft- maximum working

load for people and stored material oftendescribed as applying to stone masonry work

OSHA: Occupational Safety Health Administration/ ANSI: American National




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ScaffoldingDesign Loads

These ratings assume uniform loaddistribution

2ith the exception of the weight of stored

materials, scaffold loads most oftenconsist of personnel, both stationary andtransitory

It is important to remember that the >S?'and '@SI load/rating system is intendedfor guidance of field personnel in theconstruction and use of nonspecifically

engineered scaffolding applications




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Tube and Coupler Scaffolds

Tube and coupler scaffolds are assembledfrom three basic structural elements#

the uprights, or posts, which rise fromground or other solid support

the bearer , which supports the workplatforms and < or provide transversehoriBontal connections between the posts

the runners, which attach to the postsdirectly below the bearers and providelongitudinal connections along the lengthof the scaffold




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Tube and Coupler Scaffolds These three elements are usually connected

with standard or fixed couplers which provide a.;° connection in two places

The threeelements!uprights,

bearer, andrunners1 formthe basicstructure




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The basic assembly and components of tube and coupler scaffolds





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Tube and Coupler Scaffolds )iagonal bracing is used to stiffen the

structure as necessary most importantin the longitudinal direction

=racing is generally connected to the

posts with 8ad4ustable9 or 8swivel9couplers which have the facility ofad4usting a full +*;°

)iagonal bracing should always beattached to the posts as closely aspractical to the 8node9 points formed bythe runner/bearer connections

CCM




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'nother important structural element isthe building tie which connects thescaffold to the wall or structure and isneeded to provide rigidity and

anchorage of the scaffold in thetransverse direction

Scaffolds need to be laterally supported

otherwise, they are unstable because oftheir height/to/width ratio and have lowstrength to resist wind and other lateralforces

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Tube and Coupler Scaffolds 6ethods of stabiliBing against a building

!a1 2all tie and

anchorage

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Tube and Coupler Scaffolds 6ethods of stabiliBing against a building (cont’d)#

!b1 2indow reveal tube

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Tube and Coupler Scaffolds 6ethods of stabiliBing against a building (cont’d)#

!c1 "eveal between

pilasters

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Tube and Coupler Scaffolds APPLICATION

Tube and coupler scaffolds can be assembled innumerous ways because of the flexibility of theirassembly dimensions in the horiBontal andvertical planes

Dnlike sectional frame scaffolds they are notrestricted by frame width in the transversedirection, by brace length in the longitudinaldirection, or by frame height in the vertical

direction Conse3uently, they are preferred for access to

workplaces having irregular dimensions andcontours, eg, churches, old auditoriums, etc

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Tube and Coupler ScaffoldsBASIC CONFIGURATIONS

The basic configurations are as follows#

Double Pole 'lso called 8independent9 wallscaffolds, these are used for access to vertical surfacesfor construction, alterations, or surface finishing andrepair They consist of repetitive pairs of posts along

the length, connected by bearers and runners- Single pole 'lso called 8putlog9 wall scaffolds, theseare used for the construction of masonry walls Theyconsist of single posts + to : feet away from the wallsurface spaced at regular or varying intervals along the

wall The different feature of this type of scaffold is thatthe inside ends of the bearer are supported at 4oints orcourses in the wall being built instead of the insideposts

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+ Tower Scaffolds These

consist of one or few bays ineither horiBontal plane,constructed to re3uired heightfor access to ceilings or forspecialiBed load supportre3uirements not convenientlyachievable with sectionalframes They may be mountedon casters and become mobile

scaffolds or rolling towers 'n application of tower

scaffolds is to provide stairaccess to to unusual structuressuch as cooling towers

Tube and Coupler ScaffoldsBASIC CONFIGURATIONS

Rolling scaffold

with stand-offladder

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The construction principle of sectional

scaffolding is shown below

Sectional Scaffolding

=asic assembly

of sectional

scaffolding

Temporary StructuresCMCM




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Sectional Scaffolding The most common material used in the

fabrication of steel frames is :<0/in

>)tubing with a wall thickness between ;;0*and ;;: in

The most common grade of steel used for

this purpose is 'ISI designation ';:;, ahigh/carbon alloy having a minimum yieldstress of :;,;;; psi with a correspondingultimate stress of over 7:,;;; psi

The higher carbon steel is generallypreferred because its lower ductility andgreater rigidity make it more resistant todamaging and bending of the members and

because it has greater strength

methodology for staging

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