advanced scaffoldings

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ADVANCED SCAFFOLDINGS

Shoring

In multistory work, the shoring which

supports freshly placed concrete isnecessarily supported by lower floors which

may not yet have attained their full strength,

and which may not have been designed to

carry loads as great as those imposed during

construction. Construction loads may

exceed design loads by an appreciable

amount. Therefore shoring must be

provided for enough floors to develop the

needed capacity to support the imposed loads without excessive stress or deflection. Whether

permanent shores or reshores are used at the several required lower floor levels depends on ob

plans for reused of materials as well as the rate of strength gain in the structure. There are several

types of adustable individual shores.

!caffold"Type !horing Tubular steel form scaffolding was first designed to support loads

imposed by the workers getting to the work area. !ince the system of acks in the tubular steel

scaffolding makes it easy to adust and level elevations, it is often used as a support for

formwork. !ince it is a modular assembly, it makes it an attractive option for rapid utili#ation for

formwork support.

The word $scaffolding% refers to any raised platform or ramp used for ingress and egress forpedestrian movement and&or the passage of building materials. !ince the mid"'()*s the concept

of using steel pipes fastened together with metal"form or cast clamps +couplers instead of poles

and ropes was introduced.

-luminum alloy pipes and couplers were developed for their lighter weight and speedier

construction. -luminum alloy is only two"thirds as strong as steel, but it is only one"third to one"

half its weight. ecause of the higher initial cost, aluminum is restricted mostly to building

maintenance scaffolds and suspended platforms.

General Design Considerations

It is a common practice to use a minimum factor of safety of four in the design of all

scaffoldings, meaning that scaffolds and their components can support four times the maximum

design load without experiencing failure. /or this reason, the design load is multiplied by a factor

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of ?, before and determining limiting strength and yield stress of the metal used in the

engineering design of scaffolds and their components.

Tube and Coupler Scaffolds

Tube and coupler scaffolds are assembled from threebasic structural elements@ the uprights, or posts, which

rise from ground or other solid support the bearer,

which supports the work platforms and & or provide

transverse hori#ontal connections between the postsA the

runners, which attach to the posts directly below the

bearers and provide longitudinal connections along the

length of the scaffold.

2iagonal bracing is used to stiffen the structure as necessary, most important in the longitudinal

direction. racing is generally connected to the posts

with $adustable% or $swivel% couplers which have the

facility of adusting a full B*D. 2iagonal bracing should

always be attached to the posts as closely as practical to

the $node% points formed by the runner"bearer

connections. -nother important structural element is the

building tie which connects the scaffold to the wall or

structure and is needed to provide rigidity and anchorage

of the scaffold in the transverse direction. !caffolds need

to be laterally supportedA otherwise, they are unstable

because of their height"to"width ratio and have low

strength to resist wind and other lateral forces.

Tube and Coupler !caffolds@ -EE1IC-TI73

Tube and coupler scaffolds can be assembled in many different ways because of the

flexibility of their assembly dimensions in the hori#ontal and vertical planes. Tube and coupler

scaffolds are more adaptable since they are not restricted by frame width in the transversedirection or by brace length in the longitudinal direction or by frame height in the vertical

direction +unlike sectional frame scaffolds which is going to be discussed later in this lesson.

Therefore for cases of irregular dimensions and contours, such as churches or old auditoriums,

tube and coupler scaffolds become the preferred option since it makes access to the work place

easier.

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Tube and Coupler Scaffolds !ASIC CONFIG"#ATIONS

The basic configurations are as follows@

'. Double $ole. 2ouble Eole or Independent Eole !caffold is a scaffold supported from the base

by a double row of uprights, independent of support from the walls and constructed of uprights,ledgers, hori#ontal platform bearers, and diagonal bracing.

). Single $ole%!ingle Eole !caffold is a platform resting on putlogs +putlog is a scaffold member

upon which the platform rests or crossbeams, the outside ends of which are supported on ledgers

secured to a single row of posts or uprights and the inner ends of which are supported on or in a

wall.

B% To&er Scaffolds. These consist of one or few bays in either hori#ontal plane, constructed to

required height for access to ceilings or for speciali#ed load support requirements not

conveniently achievable with sectional frames.

Sectional Scaffolding

!ectional scaffolding is available in many frame configurations. =ost frames are available in

the widths of ), B, and 9 feet. !ome special purpose frames are available in ? and feet widths

+"ft frames are used in sidewalk canopies. !tandard frame heights are B, ?, 9, , and .9 feet

high for sidewalk canopies. The frames are also available in heights of F.9, G, and '* feet.

"nderpinning

0nderpinning is the installation of temporary or permanent support to an existing foundation to

provide either additional depth or an increase in bearing capacity. There are several existing

conditions which may lead to the need for underpinning. They are

Construction of a new proect with a deeper foundation adacent to an existing building

!ettlement of an existing structure

Change in use of a structure

-ddition of a basement below an existing structure

!ettlement of existing structures in many cases is caused by lowering of the water table due to

tidal fluctuations, wells for a water district, etc. This lowering of the water table can cause the

tops of timber piles to decay over time and will require remedial underpinning. With certain soil

profiles, rising of the water table can effect a decrease in bearing capacity of the soil causing

settlement and require underpinning. Construction of structures on unsuitable bearing material or

over compressible layer +peat, organic silts, or poorly compacted backfill may cause settlement.

Deter'ining the need for underpinning

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0nderpinning is the direct support of an existing building foundation. It provides the opportunity

to preload +i.e., acking to limit settlement and improve poor foundations. When a structure

starts showing signs of settlement or distress, it is of utmost importance to precisely monitor the

settlement or movement by a professional on a daily, weekly, or monthly basis, depending on the

severity of the movements. Elotting these readings will indicate if the movements are decreasing

or increasing, and by analy#ing the results, a decision can be made whether or not underpinning

+or other measures are required to safeguard the structure.

Erior to the start of excavation for a new structure, it is advisable to have a professional examine

all structures in close proximity to the construction site, to determine whether or not

underpinning is necessary.

"nderpinning (ethods

Temporary support with =aintenance Hacking

1ight structures +for example, wood"frame garages that fall within the influence line of the

adacent excavation and which do not warrant the expense of an underpinning installation may

me supported on timber or concrete mats.

0nderpinning =ethods " racket Eile 0nderpinning

When both the existing and future structures belong to the same owner, the use of bracket piles is

very economical +most municipal building codes do not allow a building to be supported on the

foundation that is located on someone elses property. The steel bracket piles are driven or

placed adacent to the future structure in pre"augured holes which are then backfilled with a lean

sand"cement mix. The load is transferred from the structure into the pile through a steel bracketwelded to the side of the pile.- combination of steel plates, wedges, and drypack is installed to

ensure a tight fit between the structure and the bracket.

ADVANCE FO#()O#*S

(ultifor' Shoring S+ste'

,% The =ultiform !ystem was designed to withstand the maximum concrete pressure

possible stated in the -CI and ! codes for form"work design, )*** psf +(F k3&=) forwalls and B*** psf +'?9.9 k3&=)for columns. In construction field language, the

allowable fresh"concrete height is unrestricted by the forms

-% -s a Table"!ystem with a soffit si#e of ') ft x G ft +B.*m x ).??m supported by two

foldable heavy"duty frames spaced at G ft +).9*m c&c., the system is capable of supporting

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a solid slab up to B(in. +'***mm thick, and ?( in. +')9*mm thick hollow

.% - reduction in erection and dismantling time by as much as 9*J which will result in hugesavings on labour and a faster construction cycle

/% The =ultiform !horing !ystem was designed to support the main system. 0ser"friendly,simple and rapid"shoring system, its allowable load capacity is double that of the widely

used systems. The estimated allowable loading of the multiform shoring system is 'G.*

>IE! +G*,* k3 per leg. 6owever, besides the foldable, fully"braced upon opening,double"frame system, the multiform shoring system includes heavy"duty single frames to

be used in heavy construction proects such as bridges, etc.. 2epending on frame si#es and

tower heights, the safe working loads of this system varies form 'G,* to 'B,* >IE!+G*,* to

9G,* k3 per leg

Soldier S+ste'

Target soldier systems designed to cover wide

ranges of construction and to withstand the high

pressure exerted while pouring concrete

members. The soldier which is produced in

many lenghts, can be assembled in combination to

suit any heights of pouring.

Single Sided )all Shuttering

" 7ne"sided wall form is strong, and flexible. The

distance between elements is calculated according

to the height of the wall and the concrete pressure.

The form is plumbed using acks at the base.

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!upporting elements transfer the forces through the anchors embedded in the concrete and the

rear pressure ack on the bracket.

Single Sided )all For'

Tied and 4anged 7ne"sided /orms -tlas provides

wall form equipment as described in the 4anged Wall

/orm !ection along with Weld brackets which are

mounted to the soldier beams supporting shoring to

the basement excavation typically at G ft. centers.

Concrete placement rates at 9&hr. can generally be

accommodated, while still maintaining 9 ft. vertical

spacing of ties.

!tandard inventory, snub"nosed coil taper ties are included as part of the system package,

allowing both rapid installation and stripping of forms.

Tunnel for's

Tunnel form is a formwork system that allows the

contractor to cast walls and slabs in one operation in a

daily cycle. It combines the speed, quality andaccuracy of factory&off"site production with the

flexibility and economy of in"situ construction and is

recognised as a modern method of construction

+==C.

The result is a cellular reinforced structure, the

surfaces of which are sufficiently high quality to require only minimal finishing for direct

decoration, while the end walls and facades are easily completed with thermally insulated units

that can be clad as required.

The system creates an efficient load"bearing structure for use in a wide variety of applications. Itis particularly effective in proects suited to repetitive cellular construction such as residential

blocks, hotels, student accommodation, barracks and prisons.

Se'i S+ste' For'&or0

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This is a more advanced formwork type than the modern

conventional type as there are pre"fabricated formwork

items. /or example there are pre"fabricated formworks

for slab panels and supports and other structural parts.

There are several types of semi system formworks and is

discussed as below@

+- /iberglass formwork@ The use of fiberglass as a

material to make forms for concrete work has increased

rapidly within the past two years. -mong the reasons

are@

K /iberglass forms provide a means of producing a concrete surface that is

architecturally acceptable without rubbing and grinding.

K !pecial patterns and designs can be readily molded into the material.

K 1arge areas or sections may be made without oints or seams.

K When repeated usage is possible, fiberglass is often the most economical form

material.

Eerhaps most important one is fiberglass forms allow the architect complete freedom of design.

7ne advantage of fiberglass forms is it is possible to eliminate the oints or seams. -lso when

special conditions dictate building a form in sections, it is

possible to oin the units in such a manner that the several

sections may later be sealed together with additional

applications of resin and fiberglass to produce a seamless

mold.

:ersatility is another advantage. /iberglass panels can be

'** percent reversible in any situation. /iberglass is also

an excellent insulating material and is impervious to

moistureA thus fiberglass forms provide built"in protection

against temperature extremes. -lthough the first cost of

fiberglass forms is relatively high, the durability of the material permits almost unlimited reuses.

Consequently, wherever it is possible to make repeated use of the same form, the cost may be

reduced substantially to a point that the material becomes the lowest cost per use of any form.

+ Elastic /ormwork@ It comes as individual structural elements like columns and walls. :arious

si#ed columns and walls are available in the market. The formwork is very easy to install and

uninstall and has a very high repetitive nature. The ease of application makes it very usefulwhere faster completion of work is a criterion.

+C /iber"reinforced polymer +/


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of a computer numerical control +C3C machine. 7n

site, the si#e and weight of the formwork required the

use of forklifts and scissor lifts for assembly. -fter the

forms were assembled and the reinforcement was

placed, self"consolidating concrete was used to

produce the required smooth, uniform finish.

Alu'iniu' $anel S+ste' For'&or0

!ystem formwork has prefabricated modular components with casting panels. The system

formwork can suit the required shape of concrete structure. The speedy and quality construction

is the biggest advantage in this type while high initial cost is the main disadvantage and hence

this is not economical to use in low"rise buildings. ut this is the most economical form of

formwork type to be used in high"rise building construction when it is having few +more that '*

typical storeys as it can be made in a single storey complete formwork set form and a faster floor

to floor construction can be achieved.

1u'p For' S+ste'to Construct Concrete Core Walls of 6igh


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Glossary

-ccess platform@ - platform that gives access to and from places of work for persons, materials

or equipment.

-nchorage@ Components cast or fixed +temporarily or permanently into the building or structure

for the purpose of attaching a scaffold tie and&or a harness system.

aseplate@ - plate of steel that is able to distribute the load from a load"bearing member to a

supporting structure.

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race@ - member fixed diagonally to two or more members of a scaffold to provide rigidity to

the scaffold.

racket@ 5ngineer designed bracket that is attached to a structure to support a scaffold.

Counter weight@ - weight or series of weights that counterbalance a scaffold against overturning.

Coupler@ - fitting that oins two tubes.

/oundations@ The support beneath a scaffold or structure that distributes the imposed loads

+ground.

4antry@ - structure that is primarily intended to support a protection deck or portable building. -

gantry can be constructed from scaffolding, structural steel or timber.

6emping@ The process of oining additional standards to the top of existing standards. -lso

referred to as topping up.

6oist@ =echanical assembly for raising and lowering personnel or materials +swinging stage

motor.

1edger@ - hori#ontal structural member that longitudinally spans between adacent standards.

Elank@ - component used to form a working platform or deck.

Elatform@ -n elevated surface.

!caffolding hoist@ - lifting appliance +manually operated or power operated through which the

suspension rope passes.

!pan@ The distance measured along a member between the centre lines of support points +e.g.,

bearers supporting a scaffold plank.

!trut@ - scaffolding member that supports a compressive force.

Whipping@ The wrapping or tying of an end of cut rope to stop fraying or unravelling.

Winch@ =echanical assembly for raising and lowering materials.

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