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Construction Methods & Technology

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Page 1: Construction Methods & Technology
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Introduction

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Construction Application of Computers

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Application of Computers in Construction Technology

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Site Investigations

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Trial Pits and Hand Auger Holes

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Site Layout Considerations

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Excavator

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Bulldozer

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Scraper

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Roller

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Dump truck

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Solve this Example

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Equipments

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ier operation

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Machine.

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Production Estimation for Hydraulic Excavator

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FIGURE 3-6. Hydraulic shovel. (Courtesy of Kobelco Construction Machinery America LLC)

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FIGURE 3-7. Components of a hydraulic shovel.

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in the bucket by tension on the dump cable.

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FIGURE 3-26. Large crawlermounted lattice-boom mobile crane. (Courtesy of Manitowoc)

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FIGURE 3-27. Crane with ring attachment. (Courtesy of Manitowoc)

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Tower crane

Tower cranes are a modern form of balance crane that consist of the same basic parts.

Fixed to the ground on a concrete slab (and sometimes attached to the sides of

structures as well), tower cranes often give the best combination of height and lifting

capacity and are used in the construction of tall buildings.

The base is then attached to the mast which gives the crane its height. Further the mast

is attached to the slewing unit (gear and motor) that allows the crane to rotate.

On top of the slewing unit there are three main parts which are: the long horizontal jib

(working arm), shorter counter-jib, and the operators cab.

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The long horizontal jib is the part of the crane that carries the load. The counter-jib

carries a counterweight, usually of concrete blocks, while the jib suspends the load to

and from the center of the crane.

The crane operator either sits in a cab at the top of the tower or controls the crane by

radio remote control from the ground. In the first case the operator's cab is most usually

located at the top of the tower attached to the turntable, but can be mounted on the jib,

or partway down the tower.

The lifting hook is operated by the crane operator using electric motors to manipulate

wire rope cables through a system of sheaves. The hook is located on the long

horizontal arm to lift the load which also contains its motor.

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In order to hook and unhook the loads, the operator usually works in conjunction with a

signaller (known as a 'dogger', 'rigger' or 'swamper'). They are most often in radio

contact, and always use hand signals. The rigger or dogger directs the schedule of lifts

for the crane, and is responsible for the safety of the rigging and loads.

The average fee to rent a 150-foot (46 m) crane is $60,000 for assembly and

disassembly and an additional $15,000 per month.

It is often claimed that a large fraction of the tower cranes in the world are in use in

Dubai.

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FIGURE 3-27. Tower crane on a building site. (Courtesy of Manitowoc)

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FIGURE 3-29. Major types of tower cranes.

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ASSIGNMENT-II(23/10/2010)

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Compressibility

In thermodynamics and fluid mechanics, compressibility is a measure of the relative volume change of a fluid or solid as a response to a pressure (or mean stress) change.

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COMPACTION EQUIPMENT AND PROCEDURES

Types of Compaction Equipment

Principal types of compaction equipment include tamping foot rollers, grid or mesh

rollers, vibratory compactors, smooth steel drum rollers, pneumatic rollers,

segmented pad rollers, and tampers or rammers.

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FIGURE 5-4. Walk-behind vibratory plate compactor. (Courtesy of Wacker Corp.)

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FIGURE 5-6. Small vibratory rammer. (Courtesy of Wacker Corp.)

FIGURE 5-7. Walk-behind vibratory roller with remote control. (Courtesy ofWacker Corp.)

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FIGURE 5-10. Compaction equipment selection guide.

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Example

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Igneous rocks

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Sedimentary rocks

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Rock handling SystemsThe process of rock moving may be considered in four phases:

1. Loosening

2. Loading

3. Hauling, and

4. Compacting

Table 6-1. Principal rock-handling systems

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Table 6-2. Typical characteristics of rock drilling equipment

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FIGURE 6-7. Rotary blast hole drill. (Courtesy of Ingersoll-Rand Company)

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A. Sawdust (or any other type of absorbent material) soaked in nitroglycerin. B. Protective coating surrounding the explosive material. C. Blasting cap. D. Electrical cable (or fuse) connected to the blasting cap.

Dynamite

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Detonator

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FIGURE 6-12. Types of electric blasting circuits.

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Function of piles

Piles are columnar elements in a foundation which have the function of transferring load

from the superstructure through weak compressible strata or through water, onto stiffer

or more compact and less compressible soils or onto rock.

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Historical

The driving of bearing piles to support structures is one of the earliest examples of the

art and science of a civil engineer.

In Britain, there are numerous examples of timber piling in bridge works and riverside

settlements constructed by the Romans.

In China, timber piling was used by the bridge builders of the Han Dynasty (200 BC to

AD 200).

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The carrying capacity of timber piles is limited by the girth of the natural timbers and the

ability of the material to withstand driving by hammer without suffering damage due to

splitting or splintering.

Thus primitive rules must have been established in the earliest days of piling by which

the allowable load on a pile was determined from its resistance to driving by a hammer

of known weight and with a known height of drop.

Knowledge was also accumulated regarding the durability of piles of different species of

wood, and measures taken to prevent decay by charring the timber or by building

masonry rafts on pile heads cut off below water level.

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Types of pile

Classification of piles

The British Standard Code of Practice for Foundations (BS 8004: 1986) places piles in

three categories. These are as follows:

Large displacement piles comprise solid-section piles or hollow-section piles with a

closed end, which are driven or jacked into the ground and thus displace the soil. All

types of driven and cast-in-place piles come into this category. Large diameter screw

piles and rotary displacement auger piles are increasingly used for piling in

contaminated land and soft soils.

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How it is doneA thick-walled steel casing is made watertight with a steel baseplate, including a seal. This casing is driven into the ground with a pile hammer, completely displacing the ground. Once the driving criteria or the required driven depth is achieved, the reinforcing cage is installed and the casing is filled with concrete. Following placement of the concrete, the casing is withdrawn.

Driven Piles Cast In Place

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Screw Pile

A screw piling is a circular hollow steel pipe section (shaft) with one or more tapered steel plates (helixes) welded to the shaft.

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Rotary displacement auger Pile

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Small displacement piles are also driven or jacked into the ground but have a relatively

small cross-sectional area. They include rolled steel H- or I-sections and pipe or box

sections driven with an open end such that the soil enters the hollow section. Where

these pile types plug with soil during driving they become large displacement types.

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Replacement piles are formed by first removing the soil by boring using a wide range

of drilling techniques. Concrete may be placed into an unlined or lined hole, or the lining

may be withdrawn as the concrete is placed. Preformed elements of timber, concrete or

steel may be placed in drilled holes. Continuous flight auger (CFA) piles have become

the dominant type of pile in the UK for structures on land.

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Types of piles in each of the BS 8004 categories can be listed as follows:

Large displacement piles (driven types)

(1) Timber (round or square section, jointed or continuous)

(2) Precast concrete (solid or tubular section in continuous or jointed units)

(3) Prestressed concrete (solid or tubular section)

(4) Steel tube (driven with closed end)

(5) Steel box (driven with closed end)

(6) Fluted and tapered steel tube

(7) Jacked-down steel tube with closed end

(8) Jacked-down solid concrete cylinder.

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Precast concrete Piles

Prestressed Concrete Piles

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Large displacement piles (driven and cast-in-place types)

(1) Steel tube driven and withdrawn after placing concrete

(2) Steel tube driven with closed end, left in place and filled with reinforced concrete

(3) Precast concrete shell filled with concrete

(4) Thin-walled steel shell driven by withdrawable mandrel and then filled with concrete

(5) Rotary displacement auger and screw piles

(6) Expander body.

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Small displacement piles

(1) Precast concrete (tubular section driven with open end)

(2) Prestressed concrete (tubular section driven with open end)

(3) Steel H-section

(4) Steel tube section (driven with open end and soil removed as required)

(5) Steel box section (driven with open end and soil removed as required).

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Replacement piles

1. Concrete placed in hole drilled by rotary auger, baling, grabbing, airlift or reverse

circulation methods (bored and cast-in-place)

2. Tubes placed in hole drilled as above and filled with concrete as necessary

3. Precast concrete units placed in drilled hole

4. Cement mortar or concrete injected into drilled hole

5. Steel sections placed in drilled hole

6. Steel tube drilled down.

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Composite piles

Numerous types of piles of composite construction may be formed by combining units in

each of the above categories or by adopting combinations of piles in more than one

category. Thus composite piles of a displacement type can be formed by jointing a

timber section to a precast concrete section, or a precast concrete pile can have an H-

section jointed to its lower extremity. Composite piles consisting of more than one type

can be formed by driving a steel or precast concrete unit at the base of a drilled hole or

by driving a tube and then drilling out the soil and extending the drill hole to form a bored

and cast-in-place pile.

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Composite piles

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Ductile Iron Pile +

Additional compressive strength is provided by the concreting or grouting of the bore, to form a composite pile.

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Function of piles1. As with other types of foundations, the purpose of a pile foundations is to transmit a

foundation load to a solid ground to resist vertical, lateral and uplift load .

2. A structure can be founded on piles if the soil immediately beneath its base does not

have adequate bearing capacity.

3. If the results of site investigation show that the shallow soil is unstable and weak or if

the magnitude of the estimated settlement is not acceptable a pile foundation may

become considered.

4. Further, a cost estimate may indicate that a pile foundation may be cheaper than any

other compared ground improvement costs.

5. In the cases of heavy constructions, it is likely that the bearing capacity of the

shallow soil will not be satisfactory, and the construction should be built on pile

foundations. Piles can also be used in normal ground conditions to resist horizontal

loads.

6. Piles are a convenient method of foundation for works over water, such as jetties or

bridge piers.

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•There was a world-wide increase in the construction of heavy foundations in the period

from 1950 to the 1970s as a result of developments in high office buildings, heavy

industrial plants and shipyard facilities. The same period also brought the major

developments of offshore oilfields.

•A high proportion of the heavy structures required for all such developments involved

piled foundations, which brought about a great acceleration in the evolution of piling

equipment.

•There were increases in the size and height of piling frames, in the weight and

efficiency of hammers, and in the capacity of drilling machines to install piles of ever-

increasing diameter and length.

•The development of higher-capacity machines of all types was accompanied by

improvements in their mobility and speed of operation.

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The development of piling equipment proceeded on different lines in various parts of the

world, depending mainly on the influence of the local ground conditions.

Examples

1. In Northern Europe the precast concrete pile continued to dominate the market and

this led to the development of light and easily handled piling frames. These were

used in conjunction with self-contained diesel hammers and winches, with the

minimum of labor and without the need for auxiliary craneage, steam boilers, or air

compressors.

2. The stiff clays of the Midwestern states of America and the Great Lakes area of

Canada favored large-diameter bored piles, and mobile rotary drilling machines were

developed for their installation.

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Equipment Standards

All piling equipment should comply with the requirements in BS EN 996: 1996 Piling

equipment – Safety requirements and BS EN 791: 1996 Drill rigs – Safety.

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Piling frames

The piling frame has the function of guiding the pile at its correct alignment from the

stage of first pitching in position to its final penetration. It also carries the hammer and

maintains it in position co-axially with the pile.

The essential parts of a piling frame are the leaders or leads, which are stiff members of

solid, channel, box, or tubular section held by a lattice or tubular mast that is in turn

supported at the base by a moveable carriage and at the upper level by backstays.

The latter can be adjusted in length by a telescopic screw device, or by hydraulic rams,

to permit the leaders to be adjusted to a truly vertical position or to be raked forwards,

backwards, or sideways.

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Where piling frames are mounted on elevated staging, extension leaders can be bolted

to the bottom of the main leaders in order to permit piles to be driven below the level of

the base frame.

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Piling hammers

The simplest form of piling hammer is the drop hammer, which is guided by lugs or jaws

sliding in the leaders and actuated by the lifting rope.

The leads acts as guides for the drop weight and the pile.

The drop hammer consists of a solid mass or assemblies of forged steel, the total mass

ranging from 1 to 5 tonne.

The height of drop or fall most frequently used varies from about 5 to 20 ft.

The maximum recommended drop height varies with the pile type, 15 ft for timber piles

and 8 ft for concrete piles.

When a large energy per blow is required to drive a pile, it is better to use a heavy

hammer with a small drop than light hammer with a large drop.

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FIGURE 10-5. Drop hammer pile driver.

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Advantages of drop Hammers1. Small investment in equipment

2. Simplicity of operation

3. Ability to vary energy per blow by varying the height of fall

Disadvantages of drop hammers1. Slow rate of driving piles

2. Danger of damaging piles by lifting a hammer too high

3. Danger of damaging adjacent buildings as a result of the heavy vibration caused by a hammer

4. Unable to use directly for underwater driving

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The Single-acting hammer is operated by steam or compressed air, which lifts the ram

and then allows it to fall by gravity.

BSP single-acting hammers of the type range in mass from 2.5 to 6 tonne with a

maximum height of fall of 1.37 m; a solenoid system can be used to control the drop of

the hammer to avoid the operator fatigue of manual operation.

The single-acting hammer is best suited to driving timber or precast concrete piles, since

the drop of each blow of the hammer is limited in height and is individually controlled by

the operator.

The single-acting hammer is suitable for driving all types of pile in stiff to hard clays,

where a heavy blow with a small drop is more efficient and less damaging to the pile

than a large number of lighter blows.

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The ram of hydraulic hammers is raised by hydraulic fluid under high pressure to a

predetermined height, and then allowed to fall under gravity or is forced down onto the

pile head.

The hammer then falls freely under gravity and repositions the piston rod for the next

stroke. Using a remote control panel these hammers can deliver an infinitely variable

stroke and blow rate within the limits stated.

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Advantages of Single acting drop hammer1. The greater number of blows per minute permits faster driving

2. The heavier ram falling at lower velocity transmits a greater portion of the energy to driving piles.

3. The reduction in the velocity of the ram decreases the danger of damage to piles during driving

4. The enclosed types may be used for underwater driving

Disadvantages1. They require more investment in equipment such as a steam boiler or air compressor

2. They are more complicated , with higher maintenance cost

3. They require more time to set up and take down

4. They require a large operating crew

5. They require a crane having a greater lifting capacity

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Double-acting (or differential-acting) hammers are steam- or air-operated both on the

upstroke and down stroke, and are designed to impart a rapid succession (up to 300

blows per minute) blows to the pile.

Double acting hammers are lighter than single acting hammers of same capacity.

Double-acting hammers have their main use in driving sheet piles and are not used for

bearing piles in preference to diesel hammers.

However, unlike the diesel hammer they can operate underwater, provided that the ram

is fully enclosed.

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Advantages of double acting hammer compared with single- acting hammers

1. The greater number of blows per minute reduces the time required to drive piles

2. Piles can be driven more easily without leads

Disadvantages of double acting hammer compared with single- acting hammers

1. The relative light weight and high velocity of the ram make this type of hammer less

suitable for use in driving heavy piles in to soils having high frictional resistance.

2. This hammer is more complicated

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Diesel hammers

1. Diesel hammers are suitable for all types of ground except soft clays.

2. They have the advantage of being self-contained without the need for separate

power packs, air compressors or steam-generators.

3. They work most efficiently when driving into stiff to hard clays.

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Principle of Operation

1. The hammer is started by lifting the ram(B) with the crane hoist line (A).

2. The trip mechanism (C) automatically releases the ram at the top of the cylinder.

3. As the ram falls , it actuates the fuel pump cam (D), causing fuel to be injected in to

the fuel cup in the anvil (E) at the bottom of the cylinder

4. As the ram continues to fall , it blocks the exhaust ports (F), compressing the fuel-air

mixture.

5. When the ram strikes the anvil, it imparts an impact blow to the pile top and also

fires the fuel-air mixture.

6. As the cylinder fires , it forces the body of the hammer down against the pile top and

drives the ram upwards to start a new cycle.

7. Operation of the hammer is stopped by pulling the rope (G), which disengages the

fuel pump cam (D).

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Advantages and Disadvantages of Diesel Hammer

1. Diesel hammers are compact, light, and economical and can operate in freezing

weather.

2. However, they may fail to operate in soft soil, where hammer impact may be too

weak to fire the fuel-air mixture

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Piling vibrators

Vibratory hammers drive piles by a combination of vibration and static weight.

Vibrators consisting of pairs of exciters rotating in opposite directions can be mounted

on piles when their combined weight and vibrating energy cause the pile to sink down

into the soil .

The two types of vibratory hammers, either mounted on leaders or as free hanging units,

operate most effectively when driving small displacement piles (H-sections or open-

ended steel tubes) into loose to medium-dense granular soils.

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FIGURE 10-7. Hydraulically powered vibratory driver/extractor. (Courtesy of MKT Manufacturing, Inc.)

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Selection of type of piling hammer

The selection of the most suitable type of hammer for a given task involves a

consideration of the type and weight of the pile, and the characteristics of the ground

into which the pile is to be driven.

Single and double-acting hammers, hydraulic and diesel hammers are effective in all soil

types and the selection of a particular hammer for the given duty is based on a

consideration of the value of energy per blow, the striking rate and the fuel consumption.

The noise of the pile-driving operation will also be an important consideration in the

selection of a hammer.

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A knowledge of the value of energy per blow is required to assess whether or not a

hammer of a given weight can drive the pile to the required penetration or ultimate

resistance without the need for sustained hard driving or risk of damage to the pile or

hammer.

Present-day practice is to base the selection of the hammer on a derivability analysis

using the Smith wave equation to produce curves of the type shown in Figure 3.17.

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Example:

1. The falling ram of a drop hammer used to drive a timber pile is 5000 lb. The free

height during driving was 19 in., and the average penetration for the last eight blows

was 0.5 inch per blow. What is the safe rated load using the Engineering News

equation?

2. If the hammer in the above problem had been a single acting steam type what will be

the safe rated load using the Engineering News equation?

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Procedure in pile installation

Each class of pile employs its own basic type of equipment and hence the installation

methods for the various types of pile in each class are the same.

Driving timber piles

Timber piles are driven by drop hammer or single-acting hammer after pitching them in a

piling frame, in crane-suspended leaders or in trestle guides.

The Swedish piling code requires the hammer to weigh at least 1.5 times the weight of

the pile and helmet with a minimum of 1 tonne.

Diesel hammers, unless they are of the light type used for driving trench sheeting, are

too powerful and are liable to cause splitting at the toe of the pile.

The heads of squared piles are protected by a helmet of the type shown in Figure 3.20.

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Introduction

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Some practical considerations in proportioning Concrete Mixes

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Air entrainment is the intentional creation of tiny air bubbles in concrete. The bubbles

are introduced into the concrete by the addition to the mix of an air entraining agent, a

surfactant (surface-active substance, a type of chemical that includes detergents). The

air bubbles are created during mixing of the plastic (flowable, not hardened) concrete,

and most of them survive to be part of the hardened concrete. The primary purpose of

air entrainment is to increase the durability of the hardened concrete, especially in

climates subject to freeze-thaw; the secondary purpose is to increase workability of the

concrete while in a plastic state

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Water

The water that is mixed with cement to form a paste and to produce hydration must be

free from all foreign matters.

Organic material and oil may inhibit the bond between hydrated cement and aggregate.

Required water properties are cleanliness and freedom from organic material, alkalies,

acids and oils.

In general water that is acceptable for drinking can be used for concrete.

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Aggregates

To produce concrete of high quality

1. Aggregates should be clean, strong, hard, durable and round or cubical in shape.

2. The aggregates should be resistant to abrasion from weathering and wear.

3. Weak, friable, or laminated particles of aggregate, or aggregate that is too

absorptive, are likely to cause deterioration of concrete.

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FIGURE 7-8. Truck mixer. (Courtesy of Kenworth Truck Company)

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Assignment-3( 29/11/2010)

1. Ready Mix Concrete

2. Precast Concrete

3. In-Situ Concrete

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Concrete Pump

A concrete pump is a tool used for transferring liquid concrete by pumping. There are

two types of concrete pumps.

The first type of concrete pump is attached to a truck. It is known as a trailer-mounted

boom concrete pump because it uses a remote-controlled articulating robotic arm (called

a boom) to place concrete with pinpoint accuracy. Boom pumps are used on most of the

larger construction projects as they are capable of pumping at very high volumes and

because of the labour saving nature of the placing boom. They are a revolutionary

alternative to truck-mounted concrete pumps.

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Trailer-mounted boom concrete pump

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The second main type of concrete pump is either mounted on a truck and known as a

truck-mounted concrete pump or placed on a trailer, and it is commonly referred to as a

line pump or trailer-mounted concrete pump. This pump requires steel or rubber

concrete placing hoses to be manually attached to the outlet of the machine. Those

hoses are linked together and lead to wherever the concrete needs to be placed. Line

pumps normally pump concrete at lower volumes than boom pumps and are used for

smaller volume concrete placing applications such as swimming pools, sidewalks, and

single family home concrete slabs and most ground slabs.

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Precast Concrete

Reinforced concrete can be classified as precast or cast in-situ concrete.

Precast concrete

Precast Concrete is a construction product produced by casting concrete in a reusable

mold or "form" which is then cured in a controlled environment, transported to the

construction site and lifted into place.

In contrast, standard concrete( Cat in–situ concrete) is poured into site-specific forms

and cured on site.

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By producing precast concrete in a controlled environment (typically referred to as a

precast plant), the precast concrete is afforded the opportunity to properly cure and

be closely monitored by plant employees.

Advantages of precast concrete over Cast-in-situ concrete

1. The production process for Precast Concrete is performed on ground level which

helps with safety throughout a project.

2. There is a greater control of the quality of materials and workmanship in a precast

plant rather than on a construction site.

3. Financially, the forms used in a precast plant may be reused hundreds to thousands

of times before they have to be replaced which allows cost of formwork per unit to be

lower than for site-cast production.

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Quality assurance for Precast concrete

Many states across the United States require a precast plant to be certified by either the

Architectural Precast Association (APA), National Precast Concrete Association (NPCA)

or Precast Prestressed Concrete Institute (PCI) for a precast producer to supply their

product to a construction site sponsored by State and Federal DOTs.

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Brief history of Precast Concrete

1. Ancient Roman builders made use of concrete and soon poured the material into

moulds to build their complex network of aqueducts, culverts and tunnels.

2. Modern uses for pre-cast technology include a variety of architectural and structural

applications featuring parts of or an entire building system.

3. In the modern world pre-cast panelled buildings were pioneered in Liverpool,

England in 1905. A process was invented by city engineer John Alexander Brodie,

whose inventive genius also had him inventing the football goal net.

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Precast Concrete Products

The following is a sampling of the numerous products that utilize precast/prestressed

concrete. The majority of precast/prestressed products can fall under one or more of the

following categories:

Agricultural Products

Precast concrete products can withstand the most extreme weather conditions and will

hold up for many decades of constant usage.

Products include bunker silos, cattle feed bunks, cattle grid, agricultural fencing, H-

bunks, J-bunks, livestock slats, livestock watering trough, feed troughs, concrete panels,

slurry channels and more.

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Bunker Silo

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cattle feed bunks

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Building and Site Amenities

Precast concrete building components and site amenities are used architecturally as

fireplace mantels, cladding, trim products, accessories, and curtain walls. Structural

applications of precast concrete include foundations, beams, floors, walls and other

structural components. It is essential that each structural component be design and

tested to withstand both the tensile and compressive loads that the member will be

subjected to over its lifespan.

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fireplace mantels

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cladding

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Retaining walls

Precast concrete provides the manufacturers with the ability to produce a wide range of

engineered earth retaining systems.

Products include: commercial retaining wall, residential retaining walls, sea walls,

mechanically stabilized earth (MSE) panels, modular block systems, segmental retaining

walls, etc.

Retaining walls have 5 different types which include: gravity retaining wall, semigravity

retaining wall, cantilever retaining wall, counterfort retaining wall, and buttress retaining

wall.

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Sanitary and Stormwater

Sanitary and Stormwater management products are structures designed for

underground installation that have been specifically engineered for the treatment and

removal of pollutants from sanitary and stormwater run-off.

These precast concrete products include stormwater detention vaults, catch basins and

manholes.

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Manhole

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Transportation and Traffic Related Products

Precast concrete transportation products are used in the construction, safety and site

protection of road, airport and railroad transportation systems.

Products include: box culverts, 3-sided culverts, bridge systems, railroad crossings,

railroad ties, sound walls/barriers, Jersey barriers, tunnel segments, precast concrete

barriers, TVCBs, central reservation barriers and other transportation products. Used to

make underpasses, surface-passes and pedestrian subways, so that traffic in cities is

disturbed for less amount of time.

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Utility Structures

For communications, electrical, gas or steam systems, precast concrete utility structures

protect the vital connections and controls for utility distribution. Precast concrete is

nontoxic and environmentally safe.

Products include: hand holes, hollowcore products, light pole bases, meter boxes, panel

vaults, pull boxes, telecommunications structures, transformer pads, transformer vaults,

trenches, utility buildings, utility vaults, utility poles, controlled environment vaults (CEVs)

and other utility structures.

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Water and Wastewater Products

Precast water and wastewater products hold or contain water, oil or other liquids for the

purpose of further processing into non-contaminating liquids and soil products.

Products include: aeration systems, distribution boxes, dosing tanks, dry wells, grease

interceptors, leaching pits, sand-oil/oil-water interceptors, septic tanks, water/sewage

storage tanks, wetwells, fire cisterns and other water & wastewater products.

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In-Situ Concrete

Concrete which is deposited in the place where it is required to harden as part of the

structure, as opposed to precast concrete.

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Rolled structural shapes are produced by passing hot blooms, billets or slabs of steel through a series of grooved rolls.

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Lifting Equipment

1. The mobile crane and tower crane are often used for handling steel and lifting it in to

final position.

2. There are also a number of other lifting devices which are often used in steel

construction.

3. The gin pole is one of the simplest types of powered lifting device.

4. The guy derrick is probably the most widely used lifting device in high-rise building

construction.

5. Stiffleg derricks may be mounted on tracks to facilitate movement within a work area.

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there are many types of trusses, some of the more common types roof trusses are

illustrated in Figure-11-13

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Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for

egress, commonly at each end.

A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal.

Some tunnels are aqueducts to supply water for consumption or for hydroelectric

stations or are sewers.

Other uses include routing power or telecommunication cables, some are to permit

wildlife such as European badgers to cross highways.

In the United Kingdom, a pedestrian tunnel or other underpass beneath a road is called

a subway. In the United States that term now means an underground rapid transit

system.

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Geotechnical investigation

1. A tunnel project must start with a comprehensive investigation of ground conditions

by collecting samples from boreholes and by other geophysical techniques.

2. An informed choice can then be made of machinery and methods for excavation and

ground support, which will reduce the risk of encountering unforeseen ground

conditions.

3. In planning the route the horizontal and vertical alignments will make use of the best

ground and water conditions.

4. In some cases conventional desk and site studies yield insufficient information to

assess such factors as the blocky nature of rocks, the exact location of fault zones,

or the stand-up times of softer ground. This may be a particular concern in large

diameter tunnels.

5. To give more information a pilot tunnel, or drift, may be driven ahead of the main

drive. This smaller diameter tunnel will be easier to support should unexpected

conditions be met, and will be incorporated in the final tunnel.

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Tunnel Construction

Tunnels are dug in types of materials varying from soft clay to hard rock.

The method of tunnel construction depends on such factors as the ground conditions,

the ground water conditions, the length and diameter of the tunnel drive, the depth of

the tunnel, the logistics of supporting the tunnel excavation, the final use and shape

of the tunnel and appropriate risk management.

There are three basic types of tunnel construction in common use:

1. Cut and cover tunnels, constructed in a shallow trench and then covered over.

2. Bored tunnels, constructed in situ, without removing the ground above. They are

usually of circular or horseshoe cross-section.

3. Immersed tube tunnels, sunk into a body of water and sit on, or are buried just under,

its bed.

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Cut-and-cover

Cut-and-cover is a simple method of construction for shallow tunnels where a trench is

excavated and roofed over with an overhead support system strong enough to carry

the load of what is to be built above the tunnel.

Two basic forms of cut-and-cover tunneling are available:Bottom-up Method1. In the cut-and-cover bottom-up or caisson wall method, a drilling rig is used to install caisson

walls down to the existing bedrock.

2. Once the caisson walls are in place, soil between the walls is excavated to a depth below the

tunnel floor.

3. The tunnel floor, a slab, is poured, followed by the sidewalls of the tunnel from the bottom-up.

4. After the walls of the tunnel are completed, the roof is constructed and the roadway or ground

on top of the tunnel restored.

5. Materials used to provide the structure and support in the construction of the tunnel may

include concrete, pre-cast concrete, pre-cast arches, or corrugated steel arches.

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Top-down method:

In the cut-and-cover top-down or diaphragm wall method, the opposite process takes place in

constructing the tunnel.

A trencher or trench cutter is typically used to dig a trench out of the the ground first before

concrete walls are built.

This processes consists of using a slurry mixture to build a slurry wall. The slurry wall provides

temporary support to the sides of the trench before concrete is poured for a permanent wall

structure.

Once the concrete walls of the tunnel are completed, the roof of the tunnel is constructed and the

surface roadway restored.

Excavation of the tunnel is then carried out through openings in the tunnel roof top-down to the

tunnel floor.

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Boring machines

1. Tunnel boring machines (TBMs) and associated back-up systems are used to highly

automate the entire tunneling process, reducing tunneling costs.

2. Tunnel boring in certain predominantly urban applications, is viewed as quick and

cost effective alternative to laying surface rails and roads.

3. Expensive compulsory purchase of buildings and land with potentially lengthy

planning inquiries is eliminated.

4. There are a variety of TBMs that can operate in a variety of conditions, from hard

rock to soft water-bearing ground.

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Bridge

A bridge is a structure built to span physical obstacle such as a body of water, valley,

or road, for the purpose of providing passage over the obstacle.

Designs of bridges vary depending on the function of the bridge, the nature of the

terrain where the bridge is constructed, the material used to make it and the funds

available to build it.

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Types of bridges

There are six main types of bridges:

1. beam bridges,

2. cantilever bridges,

3. arch bridges,

4. suspension bridges,

5. cable-stayed bridges and

6. truss bridges.

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Beam bridges

Beam bridges are horizontal beams supported at each end by abutments, hence their

structural name of simply supported. When there is more than one span the intermediate

supports are known as piers.

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Cantilever bridges

Cantilever bridges are built using cantilevers—horizontal beams that are supported on

only one end.

Most cantilever bridges use a pair of continuous spans extending from opposite sides of

the supporting piers, meeting at the center of the obstacle to be crossed.

Cantilever bridges are constructed using much the same materials & techniques as

beam bridges.

The difference comes in the action of the forces through the bridge. The largest

cantilever bridge is the 549-metre (1,801 ft) Quebec Bridge in Quebec, Canada.

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Arch bridges

Arch bridges have abutments at each end. The earliest known arch bridges were built by

the Greeks and include the Arkadiko Bridge.

The weight of the bridge is thrust into the abutments at either side.

Dubai in the United Arab Emirates is currently building the Sheikh Rashid bin Saeed

Crossing which is scheduled for completion in 2012. When completed, it will be the

largest arch bridge in the world.

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Suspension bridges

Suspension bridges are suspended from cables. The earliest suspension bridges were

made of ropes or vines covered with pieces of bamboo.

In modern bridges, the cables hang from towers that are attached to caissons or

cofferdams. The caissons or cofferdams are implanted deep into the floor of a lake or

river.

The longest suspension bridge in the world is the 12,826 feet (3,909 m) Akashi Kaikyo

Bridge in Japan.

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Suspension bridge @ Sur

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Suspension bridge @ Sur

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FACTORS CONSIDERED IN DECIDING FACTORS CONSIDERED IN DECIDING BRIDGE TYPEBRIDGE TYPE

••Geometric Conditions of the SiteGeometric Conditions of the Site••Subsurface Conditions of the SiteSubsurface Conditions of the Site••Functional RequirementsFunctional Requirements••AestheticsAesthetics••Economics and Ease of MaintenanceEconomics and Ease of Maintenance••Construction and Erection ConsiderationConstruction and Erection Consideration••Legal ConsiderationsLegal Considerations

In general all the factors are related to economy, safety and aesthetics.

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Geometric Conditions of the SiteGeometric Conditions of the Site

•The type of bridge selected will always depend on the horizontal and vertical

alignment of the highway route and on the clearances above and below the

roadway

•For Example: if the roadway is on a curve, continuous box girders and slabs are

a good choice because they have a pleasing appearance, can readily be built on a

curve, and have a relatively high torsion resistance

•Relatively high bridges with larger spans over navigable waterways will require

a different bridge type than one with medium spans crossing a flood plain.

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Subsurface conditions of the soilSubsurface conditions of the soil

•The foundation soils at a site will determine whether abutments and

piers can be founded on spread footings, driven piles, or drilled shafts

•If the subsurface investigation indicates that creep settlement is going

to be a problem, the bridge type selected must be one that can

accommodate differential settlement over time

•Drainage conditions on the surface and below ground must be

understood because they influence the magnitude of earth pressures,

movement of embankments, and stability of cuts or fills

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Functional RequirementsFunctional Requirements

•Bridge must function to carry present and future volumes of traffic.

•Decisions must be made on the number of lanes of traffic,

inclusion of sidewalks and/or bike paths, whether width of the

bridge deck should include medians, drainage of the surface waters,

snow removal, and future wearing surface.

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AestheticsAesthetics•It should be the goal of every bridge designer to obtain a positive aesthetic

response to the bridge type selected

•There are no equations, no computer programs or design specifications that

can make our bridge beautiful.

•It is more an awareness of beauty on our part so that we can sense when we

are in the presence of something good.

•Aesthetics must be a part of the bridge design program from the beginning.

It can’t be added on at the end to make the bridge look nice. At that time it is

too late. From the beginning, the engineer must consider aesthetics in the

selection of spans, depths of girders, piers, abutments, and the relationship.

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Economic and ease of maintenanceEconomic and ease of maintenance

1. The initial cost and maintenance cost over the life of the bridge govern when

comparing the economics of different bridge types.

2. A general rule is that the bridge with the minimum number of spans, fewest

deck joints, and widest spacing of girders will be the most economical.

3. Generally, concrete structures require less maintenance than steel structure. The

cost and hazard of maintenance painting of steel structures should be considered

in type selection studies.

4. One effective way to reduce the overall project cost is to allow contractors to

propose an alternative design or designs.

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Construction and Erection ConsiderationsConstruction and Erection Considerations

•The length of the time required to construct a bridge is

important and will vary with the bridge type.

•Generally, larger the prefabricated or pre-cast members shorter

the construction time. However, the larger the members, the

more difficult they are to transport and lift into place.

•The availability of skilled labor and specified materials will

also influence the choice of a particular bridge type.

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General

When undertaking works such as concreting, brickwork, plastering, erection of

prefabricated members, it is necessary to install some works to carry loads temporarily

or to give access for workmen to the works. These are called temporary works.

Centering, formwork, scaffolding and shoring are the principle types of

temporary works.

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Centering

Temporary work used for construction of arches is called Centering.

Formwork or Shuttering

Temporary works used as a mould in which fresh concrete is poured for it to harden is

called formwork or shuttering.

ScaffoldingScaffolding

Temporary works erected for construction of masonry works, plastering, painting etc. is

called scaffolding.

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CONCRETE FORMWORK

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• Formwork being erected

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• Most of the pads and concrete footing poured

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• Formwork for the parkade walls is built for each pour

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• Most of the parkade walls been completed

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2 TYPES OF FORMWORK

Temporary Structure- Temporary structure required to safely

support concrete until it reaches adequate strength.

Permanent Structure

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DEFINITION: FORMWORKS FOR IN-SITU

CONCRETE WORK“ A mould or box into which wet concrete

can be poured and compacted so that it will flow and finally set to the inner profile of the box or mould.”

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Forms mold the concrete to desired size and shape and control its position and alignmentFormworks also act as a temporary structure that support:a) it’s own weight +b) The freshly placed concretec) Construction live loads (material ,

human, logistic)

FUNCTION

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Formwork is a classic temporary structure in a sense that:

a) It can be erected quicklyb) Highly loaded for a few hours during

the concrete placementc) And within a few days it is

disassembled for future use

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A good formwork would have the following characteristics that is:a) Safeb) Cost effective or economicalc) High Quality • finished concrete surface is of acceptable quality• in the correct location• able to produce the required shape and surface

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FORMWORK DESIGN

Loads include in design process are as followsa) Fresh concreteb) Rebarc) Formwork materiald) Wind and lateral loadse) Live loads due to – Formwork construction

- Reinforcing installation- Concrete placement

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MATERIAL FOR FORMWORK CONSTRUCTION

Among the material that can be used for construction of formwork: a) Timberb) Steel c) Glass Reinforced Plastic

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TIMBER FORMWORK

Timber Formwork:After Concrete Was Poured

Timber Formwork : For The Slab

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ADVANTAGES OF TIMBER FORMWORK

Among the advantages of timber formwork are as follow:

a) Easy handling because it’s light weightb) Easy to disassemblec) Damaged parts can be replaced with new

oned) Very flexible

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DISADVANTAGES OF TIMBER FORMWORK

Among the advantages of steel formwork are as follow:

a) Can’t be used for long. Have limited re-use. Can only be re-used 5 or 6 times

b) If the timber is dry, it will absorb moisture from wet concrete which could weaken the resultant concrete member.

c) Timber with high moisture content (more than 20 % moisture content), wet concrete will shrink & cup leading to open joints & leakage of grout.

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Timber formwork used for the construction of 2nd and the 3rd floor.

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ADVANTAGES OF STEEL FORMWORK

Among the advantages of steel formwork are as follow:

a) Very strong and able to carry heavy loadb) Easy to be fixedc) Uniform size and surfaced) Can be used for a very long time

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DISADVANTAGES OF STEEL FORMWORK

Among disadvantages of steel formwork are as follow:

a) Limited size or shape

b) A very smooth surface will be produced which would give problems for finishing process

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STEEL FORMWORK

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• The first floor circular columns were constructed using steel column forms. The steel column form should be oiled

before concreting.

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• After concreting to the first floor columns, the steel column forms were

dismantled easily.

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Causes of Formwork Failure

Improper stripping and shore removalInadequate bracingVibrationUnstable soil under mudsills, Inadequate control of concrete placementLack of attention to formwork details

Mudsill is a wood component that is attached to the foundation of a building.

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Inadequate bracing

More frequent causes of formwork failureInadequate cross bracing and horizontal bracing of shores is one of the factors most frequently involved in formwork accidents.

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Vibration

Forms sometime collapse when their shores/ jack are displaced by the vibration caused passing trafficmovement of workers & equipment on the formwork the effect of vibrating concrete to consolidate it

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SAFETY PRECAUTION

Among the precautions that can be taken to ensure formwork function as it

suppose to be are as follow:

Material used for the construction of formwork must fulfill the

specification.

Formwork is fixed firmly & properly

Construction area must be protected to prevent vandalism of formwork.

Warning sign must be put up at the area where the formwork is fixed

to prevent entrance of people that may damage the formwork.

The formwork must be inspected before the concrete is poured.

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Permanent Formwork

It’s a part of the permanent structure of the building. Permanent formwork is a structural element that is used to contain the placed concrete, mould it to the required dimensions and remain in place for the life of the structure.

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Permanent formwork capable of supporting

various slab thicknesses

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Use of Permanent Formwork:

1) reduce construction and maintenance costs

2) shorten construction time3) improve safety by reducing hazards

during construction.4) reduces construction waste

generation during construction.