svbit project.docx

8/14/2019 SVBIT Project.docx

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Chapter 1

Introduction


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General

Civil Engineering:

"Civil engineering is a vital art, working with the great sources of power in

nature for the wealth and well-being of the whole of society. Its essential

feature is the exercise of imagination to engineer the products and processes,and develop the people needed to create and maintain a sustainable natural

and built environment. It requires a broad understanding of scientific

principles, knowledge of materials and the art of analysis and synthesis. It also

requires research, team working, leadership and business skills".

Or

"Civil engineering is field of engineering sciences, related to design,

construction and maintenance of buildings, dams, bridges, tunnels, highways

and other structures by the use of physical laws, mathematical equations and

theories of mechanics".

Different part of civil engineering are as follow:

Structural Environmental Water resources Geotechnical Construction Transportation Surveying

Material used in construction

Adobe:A sun dried brick derived from a yellow silt or clay depositedby rivers.

Brick:A block of clay hardened by drying in the sun or burning in akiln. Bricks come in numerous shapes and sizes. Bricks come in

numerous densities and hardness depending on the baking process,

parent material and the material mixed with it for hardening (pebbles,

hay, grass, twigs etc).


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Earth, Rammed: Soils with high clay contents are pulverizedmoistened and dumped into frames or formed into walls. Compaction

is created by ramming. These buildings are allowed to sun dry.

Structurally sound and weather resistant, these buildings survive for

several hundred years or more.

Metal Sheet: Thin sheets of metal including gold, copper, bronze,steel and aluminum or others, used for siding or roofing in

architecture. This includes corrugated metal. Sheet metal is used to

protect exposed surfaces or for aesthetic reasons, rather than load

bearing.

Stone:Limestone, marble, granite, sandstone and other durable rocksare used for construction. These rocks are altered and polished for

specific needs and come in almost any shape imaginable. They are

load bearing and durable often lasting thousands of years or more.

Stone is used as facing, for internal support and augments or is

augmented by brick and timber constructions.

Timber: The most widely used material for building. It is light,durable, strong and easily managed. Woods range widely in density

and durability.

Concrete: Concrete is a composite material composed of coarsegranular material (theaggregate or filler) embedded in a hard matrix of

material (the cement or binder) that fills the space among the

aggregate particles and glues them together.

Concrete is widely used for making architectural structures,foundations, brick/block walls, pavements, bridges/overpasses,

highways, runways, parking structures, dams, pools/reservoirs, pipes,

footings for gates,fences andpoles and evenboats.

Material used in concrete

Cement: Cement is binding material . It is used to bind sand andaggregate. It consists of a mixture of oxides of calcium, silicon and

aluminum.Portland cement and similar materials are made by heating

limestone (a source of calcium) with clay and grinding this product
https://en.wikipedia.org/wiki/Composite_materialhttps://en.wikipedia.org/wiki/Construction_aggregatehttps://en.wikipedia.org/wiki/Cementhttps://en.wikipedia.org/wiki/Architectural_structurehttps://en.wikipedia.org/wiki/Foundation_%28engineering%29https://en.wikipedia.org/wiki/Concrete_masonry_unithttps://en.wikipedia.org/wiki/Sidewalkhttps://en.wikipedia.org/wiki/Overpasshttps://en.wikipedia.org/wiki/Parkinghttps://en.wikipedia.org/wiki/Damhttps://en.wikipedia.org/wiki/Reservoirshttps://en.wikipedia.org/wiki/Foundation_%28engineering%29https://en.wikipedia.org/wiki/Fencehttps://en.wikipedia.org/wiki/Utility_polehttps://en.wikipedia.org/wiki/Boathttps://en.wikipedia.org/wiki/Calcium_oxidehttps://en.wikipedia.org/wiki/Silicon_dioxidehttps://en.wikipedia.org/wiki/Aluminium_oxidehttps://en.wikipedia.org/wiki/Limestonehttps://en.wikipedia.org/wiki/Limestonehttps://en.wikipedia.org/wiki/Aluminium_oxidehttps://en.wikipedia.org/wiki/Silicon_dioxidehttps://en.wikipedia.org/wiki/Calcium_oxidehttps://en.wikipedia.org/wiki/Boathttps://en.wikipedia.org/wiki/Utility_polehttps://en.wikipedia.org/wiki/Fencehttps://en.wikipedia.org/wiki/Foundation_%28engineering%29https://en.wikipedia.org/wiki/Reservoirshttps://en.wikipedia.org/wiki/Damhttps://en.wikipedia.org/wiki/Parkinghttps://en.wikipedia.org/wiki/Overpasshttps://en.wikipedia.org/wiki/Sidewalkhttps://en.wikipedia.org/wiki/Concrete_masonry_unithttps://en.wikipedia.org/wiki/Foundation_%28engineering%29https://en.wikipedia.org/wiki/Architectural_structurehttps://en.wikipedia.org/wiki/Cementhttps://en.wikipedia.org/wiki/Construction_aggregatehttps://en.wikipedia.org/wiki/Composite_material


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(calledclinker)with a source ofsulfate (most commonlygypsum).

Water: Combiningwater with a cementitious material forms a cementpaste by the process of hydration. The cement paste glues the

aggregate together, fills voids within it, and makes it flow more freely.

Lower water to concrete ratio yields a stronger, more durable concrete,

while more water gives a free-flowing concrete with a higher slump.

Impure water used to make concrete can cause problems when setting

or in causing premature failure of the structure.

Aggregates: Fine and coarse aggregates make up the bulk of aconcrete mixture. Sand, natural gravel and crushed stone are used

mainly for this purpose. Recycled aggregates (from construction,

demolition and excavation waste) are increasingly used as partial

replacements of natural aggregates, while a number of manufactured

aggregates.

The presence of aggregate greatly increases the durability of concrete

above that of cement, which is a brittle material in its pure state. Thus

concrete is a true composite material.

Reinforcement: Concrete is strong in compression, as the aggregateefficiently carries the compression load. However, it is weak intension

as the cement holding the aggregate in place can crack, allowing the

structure to fail.Reinforced concrete adds eithersteel reinforcing bars,

steel fibers, glass fiber, or plastic fiber to carrytensile loads.

Sand: Sand is a naturally occurring granular material composed offinely dividedrock andmineral particles. The composition of sand is

highly variable, depending on the local rock sources and conditions,

but the most common constituent of sand in inland continental settings

and non-tropical coastal settings is silica (silicon dioxide, or SiO2),

usually in the form ofquartz.

Stages of concreting

Formwork:Formwork is an ancillary construction, used as a mouldfor a structure. Into this mould, fresh concrete is placed only to harden

subsequently. The construction of formwork takes time and involves
https://en.wikipedia.org/wiki/Clinker_%28cement%29https://en.wikipedia.org/wiki/Sulfatehttps://en.wikipedia.org/wiki/Gypsumhttps://en.wikipedia.org/wiki/Waterhttps://en.wikipedia.org/wiki/Workabilityhttps://en.wikipedia.org/wiki/Sandhttps://en.wikipedia.org/wiki/Crushed_stonehttps://en.wikipedia.org/wiki/Compression_%28physical%29https://en.wikipedia.org/wiki/Tension_%28physics%29https://en.wikipedia.org/wiki/Reinforced_concretehttps://en.wikipedia.org/wiki/Rebarhttps://en.wikipedia.org/wiki/Tension_%28physics%29https://en.wikipedia.org/wiki/Granularhttps://en.wikipedia.org/wiki/Materialhttps://en.wikipedia.org/wiki/Rock_%28geology%29https://en.wikipedia.org/wiki/Mineralhttps://en.wikipedia.org/wiki/Tropicalhttps://en.wikipedia.org/wiki/Coastalhttps://en.wikipedia.org/wiki/Silicahttps://en.wikipedia.org/wiki/Quartzhttps://en.wikipedia.org/wiki/Quartzhttps://en.wikipedia.org/wiki/Silicahttps://en.wikipedia.org/wiki/Coastalhttps://en.wikipedia.org/wiki/Tropicalhttps://en.wikipedia.org/wiki/Mineralhttps://en.wikipedia.org/wiki/Rock_%28geology%29https://en.wikipedia.org/wiki/Materialhttps://en.wikipedia.org/wiki/Granularhttps://en.wikipedia.org/wiki/Tension_%28physics%29https://en.wikipedia.org/wiki/Rebarhttps://en.wikipedia.org/wiki/Reinforced_concretehttps://en.wikipedia.org/wiki/Tension_%28physics%29https://en.wikipedia.org/wiki/Compression_%28physical%29https://en.wikipedia.org/wiki/Crushed_stonehttps://en.wikipedia.org/wiki/Sandhttps://en.wikipedia.org/wiki/Workabilityhttps://en.wikipedia.org/wiki/Waterhttps://en.wikipedia.org/wiki/Gypsumhttps://en.wikipedia.org/wiki/Sulfatehttps://en.wikipedia.org/wiki/Clinker_%28cement%29


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expenditure up to 20 to 25% of the cost of the structure or even more.

Design of these temporary structures is made to economic expenditure.

The operation of removing the formwork is known as stripping.

Stripped formwork can be reused. Reusable forms are known as panel

forms and non-usable are called stationary forms.

A group of elements and parts designed to impart the required form to

cast concrete or reinforced-concrete structures erected at a construction

site. Selection of the type of formwork is determined by the nature of

the buildings or structures for which concrete is being poured and the

relationship of their geometric dimensions, the production technology

used, and climatic conditions.

The preparation of concrete: Concrete is made by mixing naturalmaterials without heating: cement, aggregate (sand and chippings),

water and perhaps additives. This mixture hardens after a few hours.

The placement of concrete: The placement of concrete is a veryimportant operation, which largely determines the success of a

structure and its durability. Particular care is therefore necessary and

all the technical and climatic parameters must be considered.

There are a number of different phases between the time when

concrete leaves the mixer and the finished structure: transport, pouring

into formwork or a mould, vibration, maturing, form removal and

curing.

The vibration of concrete:Vibration is essential to obtain compactconcrete with good mechanical and physical characteristics.

Applying vibration to fresh concrete helps the packing of the particles

in the concrete (the grains interlock leaving as little empty space aspossible).

During vibration, concrete behaves like a viscous liquid, which means

it fills the formwork more completely and coats the reinforcement

effectively.

This is of two main types:
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Internal vibrators, in which vibration is caused by a needle (consisting

of a tube containing a rotating eccentric mass) that acts directly on the

concrete.

External vibrators, which act indirectly on the concrete via the

formwork or a beam.

Concrete curing: Curing involves protecting the surface of theconcrete from drying out and making sure the concrete achieves

satisfactory maturation.

When concrete hardens, particularly during adverse weather conditions

(wind, sun, low humidity) it is important not to allow the water it

contains to evaporate before all the cement grains have been hydrated.

Curing is particularly important in the case of slabs and pavements

whose large surface area encourages evaporation.

Formwork:

Definition: "Formwork is a die or a mould including all supporting structures,

used to shape and support the concrete until it attains sufficient strength to

carry its own weight. It should be capable of carrying all imposed dead and

live loads apart from its own weight."

Types of formwork

Timber formwork Steel formwork Plywood formwork Hardboard formwork Aluminium formwork Plastic formwork

Timber formwork:Timber is required for practically all jobs of formwork.The timber bring used for formwork must satisfy the following requirements:

It should be durable and treatable. It should have sufficient strength characteristics. It should be light weight and well seasoned without warping. It should be easily workable with nails without splitting. It should be free from loose knots.
http://www.planete-tp.com/en/concrete-curing-a249.htmlhttp://www.planete-tp.com/en/concrete-curing-a249.html


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Advantages of using timber forms:

It is economical for small construction jobs It is design flexible and easy to erect It has good thermal insulation which makes it useful to be used in

colder Regions

It can easily be made into any shape or sizeSteel Formwork: This consist of panels fabricated out of thin steel plates

stiffened along the edges by small steel angles. The panel units can be held

together through the use of suitable clamps or bolts and nuts. The panels can

be fabricated in large number in any desired modular shape or size. Steel

forms are largely used in large projects or in situation where large number

reuses of the shuttering is possible. This type of shuttering is considered most

suitable for circular or curved structures.

Advantages of steel formwork over timber form:

Steel forms are stronger, durable and have longer life than timberformwork and their reuses are more in number.

Reuses can be assumed to vary from 100 to 120 wares timber variesfrom 10 to 12.

Steel can be installed & dismantled with greater ease & speed resultingin saving in labor cost.

Excellent quality of exposed concrete surface obtained. Thus saving inthe cost of finishing the concrete surface.

Steel formwork does not absorb moisture from concrete. Steel formwork does not shrink or warp.

Plywood Formwork: Resin bonded plywood sheets are attached to timber

frames to make up panels of required sizes. The cost of plywood formwork

compares favorably with that of timber shuttering

Advantages:

It is possible to have smooth finish in which case on cost in surfacefinishing is there.

By use of large size panels it is possible to effect saving in the labourcost of fixing and dismantling.


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Numbers of reuses are more as compared with timber shuttering. Forestimation purpose, number of reuses can be taken as 20 to 25.

Hardboard forms: Hardboard is a board material manufactured of wood

fiber, which is then refined or partly refined to form a panel having a density

range of approximately 50 to 80 pounds per cubic foot.

Hardboards are standard / non-tempered or tempered.

Advantages

The tempered one being used for formwork. Tempered hardboard issolid or perforated hardboard panels impregnated with resin under

high pressure to make them stronger and more resistant to moisture

and abrasion.

The boards available in large sheets have a hard, smooth surface thatproduces a concrete whose surface is relatively free of blemishes and

joint marks.

The thin sheets can be bent to small radii, which is an advantage whencasting concrete members with curved surfaces.

Aluminum formwork: Forms made from aluminum are in many respects

similar to those made of steel.

Advantages:

Because of their lower density, aluminum forms are lighter than steelforms, and this is their primary advantage when compared to steel.

As the strength of aluminum in handling, tension and compression isless than the strength of steel, it is necessary to use large sections.

The formwork turns out to be economical if large numbers of reusesare made in construction.

Disadvantage:

No changes can be made once the formwork is fabricated.Plastic formwork:These forms have become increasingly popular for casting

unique shapes and patterns being designed in concrete because of the

excellent finish obtained requiring minimum or no surface treatment and

repairs.


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Different types of plastic forms are available like glass reinforced plastic, fiber

reinforced plastic and thermoplastics etc. Fiberglass-reinforced plastic is the most

commonly used.

Advantages:

The material allows greater freedom of design. Unusual textures and designs can be molded into the form. It allows the contractor to pour structural and finished

concrete

Simultaneously. Because sections can be joined on the job site in such a way so as to

eliminate joints, there is no size limitation.

If carefully handled, a number of reuses are possible making it highlyEconomical.

It is lightweight and easily stripped.Disadvantages:

It does not lend itself to field fabrication Hence, the design andplanning of this form must be carefully carried out.

Care must take not to damage the plastic by the heat applied foraccelerated curing of the concrete.

Type of formwork

Traditional formwork Climbing formwork Sliding formwork or slipping formwork Special formwork

Traditional formwork

This usually consists of standard framed panels tied together over theirbacks with horizontal members called waling.

The waling is provided with the basic function of resisting thehorizontal force of wet concrete.


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One side of the wall formwork is first assembled ensuring that it iscorrectly aligned, plumbed and strutted.

The steel reinforcement cage is then placed and positioned before theother side of the formwork is erected and fixed.

Plywood sheet in combination with timber is the most commonmaterial used for wall formwork.

The usual method is to make up wall forms as framed panels with theplywood facing sheet screwed on to studs on a timber frame. This

allows for the plywood to be easily removed and reversed and used on

both sides so as to increase the number of reuses.

The wall forms are susceptible to edge and corner damage and must becarefully handled.

Special attention must be given to comers and attached piers since theincreased pressures applied by wet concrete could cause the abutments

to open up, giving rise to unacceptable grout escape and a poor finish

to the cast wall.

Climbing formwork

Method of casting walls consists of a climbing formwork, the climbingof which may be manual or crane assisted.

It employs a common set of forms used in a repetitive manner forcasting walls in set vertical lifts.

After each casting the forms are removed and raised to form the nextlift until the required height has been reached.

These forms are widely used in the construction of industrialchimneys, silos, high rise towers & building cores, bridge piers &

pylons, airport control towers, telecommunication, towers etc.

Advantages

Staged construction process allows balance of site resources. Anchor accessories can be reused after each pour, reducing material

costs on current and future construction programs.

In case of trolley mounted formwork, the panel retracts from the face,providing space for cleaning and fixing of concrete.


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Formwork & access platforms lifted as one, minimizing crane support,reducing labour and material costs.

Fine adjustments of the form face can be made during construction,providing accurate alignment of the form face vertically & laterally.

Sliding formwork or slipping formwork:

Slip form means a continuously moving form, moving with such aspeed that concrete when exposed has already achieved enough

strength to support the vertical pressure from concrete still in the form

as well as to withstand lateral pressure caused by wind etc.

Thus, the slip form concreting technique is a rapid and economicalconstruction method that can be applied with great advantage to many

types of construction projects such as chimneys, silos, water towers,

bridge-columns, lift shaft cores and shaft lining etc.

The technique is based on movable forms which are gradually lifted byhydraulic jacks.

It is a continuous process where wet concrete is added to wet concrete.Reinforcing steel and/or post tensioned cables are continuously fixed

as the normal slipping speed is 3 to 6 meters per 24 hours. The slip

form construction is designed for each project depending on the

structure of the project.

Advantages

Minimum consumption of timber and steel plates. Total elimination of traditional scaffolding Minimum requirements of carpenters for assembling. It gives a monolithic structure. The concrete surfaces can be treated and finished while concrete is

green,

Depending on the weather conditions, it is possible to achieve avertical rise to the tune of 4 to 5 m in summer and 2 to 3 m in winter.

The procedure of continuous slipping is applied to making both innerand outer walls as well as columns of a building.

Form climbs.


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Permanent formwork

Permanent form or stay-in-place formwork is one in which the form isleft as an integral part of the structure.

Permanent formwork can also be utilized as the facing materials of insitu reinforced concrete. They can be of two typesparticipating and

non-participating.

The material used for these forms must be durable and of sufficientstrength. Commonly used materials include polyvinyl chloride (pvc),

galvanized coiled sheet steel, fabricated steel, carbon/epoxy thin shell.

The high initial cost of design and installation, lack of familiarity forinstallation and maintenance and more specified form design are some

of the barriers to the use of this form.

However, there are various advantages like low cost of transportationand installation, precise form design, maximum flexibility, greater

durability with reduced long term maintenance and versatility.

Special formwork

These are those forms that are specially designed and manufactured fora particular kind of construction. The need for a special formwork

may arise due to several factors such as

when the contract demands the highest class of dimensional toleranceto be followed

Where the form work shape required becomes uneconomical orimpracticable for site fabrication

Where the formwork is required to be self-contained i.e. self propelled, Where rate of concreting, admixtures or types of concrete are such that

concrete pressure developed within forms and stresses in the forms

demand special attention where a substantial number of re-uses is

envisaged

Formwork for different element like:


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Column Beam Wall Slab

Columns

The function of column formwork is to enable the construction of columns

that have the specified surface quality and are acceptably accurate in shape

and position with good alignment to other adjacent columns, walls and

building facades . Columns are often constructed with the column

reinforcement extending well above the form. This is done so it can lap with

the reinforcement of the next column or floor to be constructed above.

The accuracy requirements for columns vary according to their position in the

building. The tolerances, which are the maximum permitted deviations, are

normally specified in the project documentation.

Column Formwork Construction

To avoid plywood joints, it is normal practice to cut the sheets lengthwise in widths to match the column faces.

Most column forming methods use plywood to form faces. The cornerjunctions of the plywood must be detailed to achieve the maximum tig

htening action from the column clamps.

The corners of the form are usually formed to have a 45 degree arris.Timber angle fillets are used to form the arris.

Care must be taken to align the fillet inside the column form.


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Erection of formwork for columns

Before erecting column formwork, apply a release agent to all internal

surfaces. If specified, fix any required edging, metal corners, arris pieces or

casted inserts.

Prior to the erection of formwork for structural members, it is important to

check the exact location of grids relating to the structural member being forme

d. The location, size of column, height, and specified finish should be clarified

from site documentation. Often hurdles restrict the positioning of grid

locations, therefore offsets may be required. It is the contractors

responsibility prior to the erection to check site documentation for the exact

position of the structural member you are working on.

Erection sequence for a column. Prior to positioning column formwork check that steel for the column

has been inspected and cleared for casting.

Position formwork for the column from predetermined grids. Plumb formwork both ways and securely support using adjustable

steel props.

The propping angle should be 45 to the floor. Ensure the steel props are safely secured to the column formwork and t

he floor, and that adjustment for pushing and pulling is operational.


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Set out the positions of column clamps from a storey rod. Transfer the column clamp. positions from the storey rod onto column formwork. Use nails to support the arms of column clamps while wedging. Position and wedge the bottom, middle and top clamps sets. Check the formwork at the top for square. Position and wedge the remainder of the column clamps. Using a plumb bob suspended from a gauge block plumb the column. When all the column formwork is securely propped a final check must

be made for plumb and column alignment before and immediately aft

er the concrete has been.

poured and vibrated.

Column formwork construction stages

Column formwork bracing Column formwork bracing performs two functions: It must maintain the accuracy of the column form position and plumb

so that it is within tolerance.

With stand results of forces acting on either the column formwork orthe bracing. The forces may be wind or impact.

These impact forces can occur from the collision ofconcrete buckets or cranes hoisting materials.

raced column


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BEAM AND SUSPENDED SLAB FORMWORK

In a typical reinforced concrete building frame, the slabs are the primary load

carrying element. They transfer their load to secondary elements such as

walls or beams. Beams can be grouped in two categories. When located in the

interior of the structure they are usually TEE Beams and when on the

perimeter are L Beams.

Design and construction of beam formwork

Beam soffit must be thickened timber or strengthened plywood. Beam sides 18mm plywood or 25mm boards, with studs (cleats)500 to

600mm centres.

Deep beams (over 600mm) should have walers and ties. Props or false work must be placed under the head tree, or under the

bearers, and must be spaced to suit the weight of concrete.

Use angle fillets in the beam side to soffit joint where possible. Allowance must be made for height adjustment of the props or false

work.

Erection sequence for constructing beam formwork includes: Position of sole plates; Marking out and setting heights for false works;


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Assemble and position props, adjustable head jacks, false works ,bearers and Spreaders;

Construct and erect side walls and beam soffit. Position of sole plates.

The purpose of a sole plate is to transfer vertical load from one verticalsupport member to the foundation. The vertical support requires a base plate

fitted to help distribute the load to the sole plate, which is usually a sleeper. If

the sole plate is positioned on natural ground, it is important the ground is

graded and consolidated to a level surface.The objective is to achieve

maximum bearing beneath the sole plate. Once sole plates are positioned and f

irmly bedded they should be checked for level.

SUSPENDED SLABS

Suspended floor slabs can be constructed using cast in-

situ, precast units or a combination of both. Whichever method isused, it is im

portant to support the proposed method of construction using a combination of

timber or steel bearers and adjustable shoring. The spacing and type of suppo

rt system required is

determined by the load imposed during the construction process. Manufacturers provide tables to assist in the

selection and spacing of adjustable shoring systems.

The erection sequence for constructing a suspended floor slab includes:

Determining the bearer spacing; Erecting bearers and joists; Fixing the sheeting; Preparation for concrete.

Design and construction of slab formwork

As a number of collapses have occurred when pouring suspended slabs, caref

ul attention must be given to the

overall support system. Unless using a proprietary or well proven system, eng


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ineer design is required.Decking will probably be plywood sheets or shutters,

but boards and joists could be used. Thick sheets of fibre cement arealso suita

ble. Props and other falsework must be perfectly plumb at the time of pouring

the concrete.

All props and falsework must be tied together and braced. Proprietary bearers

in timber or steel are often used

as their bearing capacity is easily determined. Consideration must be given to

the order of striking, and the installation of permanent or back propping.

Determining The Bearer Spacing

To calculate the bearer spacing measure the span between the supporting wall

s. Divide the span by the

recommended bearer spacing. This will determine the number of spaces bet

ween bearers. Divide the span by the number of calculated spaces. This will

establish the centre to centre spacing of bearers.

Erecting Bearers And Joists


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Bearers

Positioning bearers for a suspended slab are the same as for a beam however: i

t is important that sole plates are firmly bedded on either compacted ground or

level concrete. Bearer supports must be adequately braced. Extra bearers may

be required to support joists and sheeting either side of major penetrations.

Check the following:

bearers are positioned and set in line and adjusted to the correct level. sole plates are bedded firmly and positioned central to the bearer. all bearer supports are plumb. bearer joins are supported. bearers are seated centrally in Uheads. supports spaced as specified and are firmly fixed at the head and bearing plate.

all supports are horizontally and diagonally braced.

Joists

The position of joists is determined by the sheet length and the centre-to-centre spacing of the intermediate joists. Check with the specifications of the s

heeting material being used. Determine the perimeter support required, laying

pattern and whether the face grain is to run parallel or at 90 degrees to

the joists. This will effect the joist arrangement.

Mark out the joist spacing on the side walls clearly identifying the joists atthe end of each sheet.

Fixing The Sheeting

If using formply for sheeting, it is important to avoid damaging the edgesof sheets.

By sealing the edges of sheets you will prevent swelling.


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Position the first row of sheeting straight and square, this will make fittingthe remainder simpler.

Fix intermediate sheeting. Nail offsheets, seal and install any bevelled trim required to external and internal corn

ers. Some specifications require surface tape to be applied over butt joints. Check that joints are sealed, level and tight. Intersections at edge beam formwork are planed flat. Sheeting is fixed as specified.

STAIR FORMWORK

Points to consider when designing stair form work Stair formwork must support the weight of concrete. The weight of the throat of the stair and the steps will have to be supported.

Because of the slope of the stair, some of the force is transmitted sideways. All

formwork must be well tied together to prevent sideway movement. Consider the finish of the stair treads and type of nosing. Space may haveto be left for purpose made nosing.


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The design of the stair must conform to the stair design regulations e.g. reside

ntial or commercial. Refer to the Building Code

D1 for stair design and regulations.

Stair Formwork construction

Sheathing can be dressed boards laid across or longitudinally or use sheet material such as plywood or particle board.

Dressed boards may have sheet material fixed on top to prevent loss of grout. Joists and bearers must be spaced to avoid undue sagging of any part of the

structure. Select timber carefully to avoid weaknesses caused by knots or cross grain.

Vertical struts must have a means of height adjustment and be very securely fixed to the bearers to prevent

Sideways movement. Place and fix riser boards accurately. For safety all steps must be the same siz

e.

Ensure that all reinforcing steel is placed exactly as shown on the drawings. Misplacing the steel, particularly in depth, can alter the strength of the finished s

tair. Ensure adequate cover on exterior stairs.

Place inserts for balusters and nosing pieces as required.


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CROSS SECTION OF STAIR FORM WORK


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Failure of formwork


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Industrial Building in Kwai Fook Rord, Kwai Chung, 1995


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A portal beam in the Ma On Shan Station of the KCR East Rail Extension


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Economy of formwork

In the design of the form-work for a concrete structure, there comes into

consideration 3 areas of cost: materials, labor, and the use of equipment

required to fabricate and handle the forms. (1) Should a practice be used that

can reduce the cost in any of these areas, or reduce the combined cost of these,

money will be saved. Since the cost of concrete is fairly static, with the

existence of ready-mixed concrete, there is little in savings to be had with the

material itself. Thus, the most obvious place for savings is within the

formwork itself.

Economy of concrete formwork includes:

Design the forms to provide the required strength but using the leastamount of materials.

When planning forms, consider the sequence and methods of strippingthem.

Using prefabricated panels as often as possible will save time andmoney.

Use the largest practical prefabricated panels that can be handled bythe men or equipment on site..

The plan of the building should imply minimum number of variationsin the size of rooms, floor area etc. so as to permit reuse of the

formwork repeatedly.

Minimum sawing and cutting of wooden pieces should be made toenable reuse of the material a number of times. The quantity of surface

finish depends on the quality of the formwork.

Need/Requirement of formwork

Containment: formwork must be capable of shaping and supportingthe fluid concrete until it cures.

Strength: formwork must be capable of safely withstanding withoutdistortion or danger the dead weight of the fluid concrete is placed on

it, labour weight, equipment weight and any environmental loadings.

Resistance to leakage: all joints in form work must be either closefitting of covered with form tape to make them grout tight. If grout


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leakage occurs the concrete will leak at that point. Leakages cause

honeycombing of the surface.

Ease of handling: form panels and units should be designed so thattheir maximum size does not exceed that which can be easily handled

by hand or mechanical means. In addition all formwork must also be

designed and constructed to include facilities for adjustments, leveling,easing and striking without damage to the form work or concrete.

Finish and reuse potential:the form face material must be selected tobe capable of consistently imparting the desired concrete finish

(smooth, textured, featured or exposed aggregate etc.) At the same

time it should also achieve the required number of reuse.

Access for concrete: any formwork arrangement must be provideaccess for placing of the concrete. The extent of this provision will be

dependent on the ease of carrying out the concrete operations.

Alignment:The formwork should be set accurately to the desired lineand levels should have plane surface.

Weight: It should be as light as possible. Material: The material of the formwork should not warp or get

distorted when exposed to the elements.

Removal of debris:Provide all formwork with special cleanout holesto allow for the removal of sawdust, shavings, and other

It should rest on firm base. Time for removal: Formwork should be such that time required for

removal of erected formwork is less.

Area:The area required by the legs of shore. Base: The formwork should rest on firm base.

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