pre cast technology

7/29/2019 pre cast technology

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Cast Insitu

Precast


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FLOW OF PRESENTATIONFLOW OF PRESENTATION

1 NEED FOR INNOVATION IN CONSTRUCTION

2 COMPARISON OF CONVENTIONAL AND PRECAST TECHNOLOGY

3 PRECAST TECHNOLOGY

4 CASE STUDIES

5 DESIGN ASPECTS OF PRECAST CONCRETE CONSTRUCTION

6 SUSTAINABLE GOALS

7 RISK MANAGEMENT
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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION--Shortage of skill & ExpertsShortage of skill & Experts

Construction industry employs approx 49 million personnel.

Sharp decline in skilled workers and engineers.

The table below shows statistics from Planning Commissions 11th five year

plan (2007-2012).

SR NO. DESCRIPTION NOS. IN 1995(IN 1000S) % WITH TOTALNOS. NOS. IN 2005(IN 1000S) % WITH TOTALNOS.

1 ENGINEERS 687 4.71 822 2.65

2 TECHNICIANS &

FOREMAN

359 2.46 573 1.85

3 CLERICAL 646 4.4 738 2.38

4 SKILLED WORKERS 2,241 15.34 3,267 10.57

5 UNSKILLED WORKERS 10,670 73.08 25,600 82.45

6 TOTAL 14,600 100 31,000 100


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51.0

52.0

53.0

54.0

55.0

56.0

57.0

58.0

59.0

60.0

61.0

0

100

200

300

400

500

600

2011 2012 2013 2014 2015

Supply

Demand

Gap(%)

Demand for affordable housing in top seven cities is likely to outstrip

supply by 2015, according to global consultant Cushman & Wakefield. Total demand of 3.94 million units of residential property in the next five

years at CAGR of 11%.

Source: Cushman & Wakefield Research

HOUSINGUN

ITS

(IN

THOUSAN

DS)

YEAR

GAP(

%)

1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION--Demand & SupplyDemand & Supply


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Estimated supply by the use of conventional methods is expected to be

approximately around 1 million units from top 7 cities. Demand for the top 7 cities is forecasted as 2.3 million units indicating a

shortfall of 1.3 million units.

Source: Cushman & Wakefield Research

HOUSING UNITS (IN THOUSANDS)

0 200 400 600 800

Mumbai

Pune

Hyderabad

Kolkata

NCR

ChennaiBangaluru

Supply

Demand

Gap

Demand Supply Projections 2011-2015

1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION--Demand & SupplyDemand & Supply


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Simple adaptation of western ideas for processes does not supporthousing solutions for low-income parts of society.

Use of designs that are appropriate to the economic, social, cultural

and natural conditions of each community are of vital importance.

Outflow of currency to purchase machinery and raw material for local

production should be stopped.

Standards and rules from developed world make housing unavailable

in third world and developing countries.

1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTIONPRINCIPLES IN AFFORDABLE HOUSINGPRINCIPLES IN AFFORDABLE HOUSING


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CONCLUSION: TechnologyCONCLUSION: Technology

"When compared to any other discipline of building construction,

civil construction is conventional in it's approach. We need to

breakaway from the convention to meet the demand and de riskcritical construction activities. One such technology proven

elsewhere in building construction is Precast

-Innovations in other discipline

High speed lifts Automation

Censors to control usage of electricity and water


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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION--Cost AnalysisCost Analysis

37%

18%

45%

Concrete Yard set up/Erection

28%

63%

2%

5%

2%

Land

ConstructionDesign Fees

Marketing

Admin9%

51%

21%

7%

2%10%

Cost analysis for structure

Sub structure super structure

Architecture PHE

FPS Electrical

Cost analysis for Precast

Margin

25%

Project

Cost75%

Yard

40%

Erection

60%

Project Costs

Selling Rate

75%

4.5%

Rebar


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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION-- PROJECT MANAGEMENTPROJECT MANAGEMENT

Phase 1 Phase 2 Phase 3 Phase 4

Initiation Planning Execution Close out

Time

Cost of Making Change Curve

High

Low

Project Life Cycle

Plan Act


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Time

High

Low

Project Life Cycle

Plan Act


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Time

Value Addition Curve

High

Low

Project Life Cycle

Plan Act


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Time

Amount of Stake Curve

High

Low

Project Life Cycle

Plan Act


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Precast Concrete construction

a) Full Precast system

All elements including faade are precast

b) Precast column / walls with flat plate / flat slab

c) Precast beam and precast slab

Floor system could be

Precast hollow core slab + cast-in-situ topping

(this can be used for long span structure of 8.0m to 15.0m

Spans) Precast plank with cast in situ topping

1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTIONPRECAST SYSTEMPRECAST SYSTEM -- OPTIONSOPTIONS


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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION-- BENEFITS OF PRECAST SYSTEMBENEFITS OF PRECAST SYSTEM

Construction time can be reduced by 40%.

- Layout should be suitable for mechanization

Labour requirement can be reduced by 40%.

High Quality Finishes.

Design flexibility by maximizing repetition can reduce cost and

aids speed of construction.

Faster construction results in earlier cash flows and leads to

reduced capital costs.- Central yard can be a strategy for huge developments

Reduces Environmental impact.

Enhances Energy Performance.


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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION-- BENEFITS OF PRECAST SYSTEMBENEFITS OF PRECAST SYSTEM

Durable and require little or no maintenance to preserve theiroriginal look.

Fireproofing material is not required as Precast concrete is non-

combustible.

Acoustical isolation and vibration attenuation.

Improved air quality

Various kinds of architectural finishes can be easily incorporated

in design.


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1.NEED FOR INNOVATION IN CONSTRUCTION1.NEED FOR INNOVATION IN CONSTRUCTION-- LIMITATIONS OF PRECAST SYSTEMLIMITATIONS OF PRECAST SYSTEM

The system has certain limitations. Precast member sizes will be restricted by crane capacity

Progress depends on hoisting facilities. If it breaks down

progress of work will be affected

Lack of planning will derail the schedule. Missing of anycomponents will affect the progress of work seriously.

Proper logistic planning and inventory checks are required

Requires skilled labour for erection.

BACK


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2.COMPARISON WITH CONVENTIONAL

CONSTRUCTION


CONSTRUCTION

Sr No. Description Conventional technology Precast technology

For construction of 1 Million sq.ft. G+20 (6 bldgs).

1 Construction time 34 Months 24 Months.

2

Cost

(considering labour and

construction costs)

100% 95%

3 Labour requirement 5 Lakh man days/year 2.5 Lakh man

days/year

4 Quality

Quality control at site is

difficult owing to variable

parameters.

Factory production

ensures quality

product.

5 Safety

Safety at site requires

more attention and

comparatively more

expensive

Less safety

measures needed

when compared

with conventional.


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CONSTRUCTION


CONSTRUCTION

Accumulatedcosts/pa

yments

Design Period

Mobilization

Construction Time

Conventional

Construction

Precast

Construction

Construction Payment Schedule


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

ting of Precast Elem

Substructure

Superstructure

Finishing

Handing Over

Proposed Tentative Construction Schedule-Precast

ActivityMonth

Mobilization

Design

Precast Yard Set up

2M

3M

6 M

10M

6M

11M

11M

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Finishing

Handing Over

Proposed Tentative Construction Schedule-Conventional

ActivityMonth

DesignSubstructure

Superstructure

3M6M

25 M

20 M

1


CONSTRUCTION


CONSTRUCTION

BACK


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3.PRECAST TECHNOLOGY3.PRECAST TECHNOLOGY

Following are the two widely accepted systems suitable for Residential buildingconstruction:

1. Large Panel System.

2. Framed System.

PrecastTechnology

Large PanelSystem

Panel

System

ModularSystem

Combinationof Both

FramedSystem


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3.PRECAST3.PRECAST TECHNOLOGYTECHNOLOGY

--LARGE PANEL SYSTEMLARGE PANEL SYSTEM

Consists of large concrete walls and slab panels

Horizontal slabs acts as a diaphragm in transferring load.

Height of panels is one floor high.

Gravity load is resisted by vertical panels.

Panel connection are the key structural components.

Seismic shear forces are resisted by horizontal and

vertical joints.

Horizontal panels can be hollow or solid.

Vertical panels can be load bearing and non load bearing

Vertical panels can be solid or sandwich panels.


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--FRAMEDFRAMED SYSTEMSYSTEM

CONCEPT:

All elements including facade are precast.

Precast column, precast beam and precast slab.

Nonstructural Infill walls were also cast along with Precast column and

beam.

Foundation Cast in situ, Few non typical elements can be cast insitu.

Floor system consists of Precast plank with cast in situ topping.


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Columns, beams and slabs are factory made precast elements.

SCHEMATIC DIAGRAM OF FRAMED SYSTEMS.SCHEMATIC DIAGRAM OF FRAMED SYSTEMS.




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3 PRECAST TECHNOLOGY3 PRECAST TECHNOLOGY


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BACK


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Full advantage of precast concrete construction is

achieved when the building has been designed for high

construction speed and maximum repetition.

In every precast concrete projects the following aspects

are important for the design team:

Architecture

MEP services

Structure

Manufacturing

Erection

5. DESIGN ASPECTS OF PRECAST CONCRETE

CONSTRUCTION

5. DESIGN ASPECTS OF PRECAST CONCRETE

CONSTRUCTION


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The architect should be considering the following

points:

Simple and symmetrical layout and elevations.

Achieve standardization and repetition.

Modular grids.

Modular design has big impact on costing.

Design with larger floor spans.

Minimize joints.

Keep precast elements as large as possible, but

maximum around 5 to 6 Tons.

ELEVATION

HOLLOW CORE SLAB FINISHES

5. DESIGN ASPECTS OF PRECAST CONCRETE CONSTRUCTION5. DESIGN ASPECTS OF PRECAST CONCRETE CONSTRUCTION

ARCHITECTURAL ASPECTSARCHITECTURAL ASPECTS


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ARCHITECTURAL ASPECTSARCHITECTURAL ASPECTS


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Integrate architecture services and structure .

Avoid last minute changes.

Modular Design modular principles can be

strictly followed.

A balance should be found between modular

design and customized prefabrication.

Flexibility Flexibility in precast concrete building

projects can be achieved by creating larger floor

spans with larger open spaces.




ARCHITECTURAL ASPECTS

Precast Architectural Designs
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In precast concrete building projects, it is important that the MEP service

consultants and the MEP vendors are part of the design team. Services like airconditioning, electrical and plumbing have to be an integrated part of the precast

design.

MEP SERVICES IN HOLLOW CORE SLABS


MEP SERVICES


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Wall panels can be provided with electricity conduits , electricity boxes and

openings for ducts. Hollow core slabs (HCS) can be provided with electricity boxesand block outs.

Precast planks with RCC toppings can be provided with electricity boxes and

conduits.

PLUMBING WORK IN HCS WITHOUT SUNK


MEP SERVICES

MEP SERVICE IN HOLLOW CORE SLABS.


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India being an earthquake prone country the seismic resistant requirements

are the most important criteria of the structural design.Looking at the requirements, the following design rules should be followed:

Simple and symmetrical layout.

Uniform distribution of mass and structural stiffness over the height.

Avoid torsion.

Ductile behaviour of the structure.

Transfer of vertical loads between wall panels can be achieved by direct

structural connection.

The precast floor units should be properly joined together to act as a floor

diaphragm that transfers the lateral load to the shear walls.

The shear walls will transfer the lateral loads to the foundation by acting as

cantilevered walls.


STRUCTURAL ASPECTS


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Customization according to the requirements of the project

Capabilities of manufacturing unit to be considered in

design stage

Standardization of embedded parts, lifting anchor,

reinforcement etc.

Reduction of damage by chamfering the edges of the wall.

Tapering of block outs.


MANUFACTURING ASPECTS


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MANUFACTURING ASPECTS

Mould Design.

Suitable material including steel, timber/

plywood is selected on the basis of

No of repetitions.

Required surface finish.

Complexity of Precast Element.

Cost competitiveness is enhanced by

using adjustable moulds.

Adequate no of braces, ties and struts

should be provided for proper casting

of elements.

3 D Pod Mould

Adjustable Mould

5 DESIGN ASPECTS OF PRECAST CONCRETE CONSTRUCTION5 DESIGN ASPECTS OF PRECAST CONCRETE CONSTRUCTION


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Crane position and lifting capabilities.

Lifting speed and speed of erection.

Space for mobile cranes / Crawler cranes.

Easy access to connections.

Tolerances (Ref:IS 15916:2010, PCI 117,Appen I).

Erection Sequence.

Easy and fast erection.

Filling of joints with grout / mortar.

Position of Props and supporting structures.


ERECTION ASPECTS



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DESIGN ASPECTS

Design of Precast elements. Involves understanding the method

of fabrication.

Involves aspects that facilitate the

erection and assembly of elements

on site.

Integration of different elements,

such as beam-wall system, multi-

tier columns and three dimensional

units.

Parapet Beam

3 - D Pod elements



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Structural integrity - Diaphragm action

lateral forces (seismic & wind)

Ref : Seismic design of floor

diaphragms - Farzad Naeim & R.Rao

Boppana

Designed against progressive

collapse/Robustness/ accidental

actions.


CONNECTION DESIGN ASPECTS



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The wall panels connections can be classified into horizontal joints and

vertical joints.

The horizontal joints have to transfer vertical loads as well as lateral

loads.

The vertical joint can either be structural joints which have to transfer

shear forces or non structural joints which dont have to transfer any

forces.

For fully monolithic behaviour the protruding reinforcement

connection in combination with drop in stirrups can be used.

The connection in Hollow core slabs should transfer the internal

diaphragm forces and it should be designed as structural integrity tie.





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Joints and Connections

Joints are designed on the basis of

Transfer of loads from a precast

concrete element to the supporting structure

to form the structure.

Avoiding congestion at joints.

Avoiding penetration of forms.

Allow for erection and production tolerances.

Easy assembly and accessibility.

Column-BeamJoint.

External wall joint.



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Progressive collapse / Robustness

These effects may generally be prevented if the following precautions are

taken. (Ref : IS 15916:2010)

o Notional horizontal load

o Design of ties

Peripheral ties

Internal ties

Floor to wall ties

Vertical wall ties.

Ref : Precast concrete structures

by Kim.S.Elliot.


CONNECTION DESIGN CONCEPTS



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LOCATION OF TIES IN PRECAST SKELETAL STRUCTURES

1 Internal floor ties

2 Peripheral floor ties

3 Gable peripheral floor ties4 Floor to wall ties

5 Internal Beam ties

6 Peripheral Beam ties

7 Gable Peripheral beam ties

8 Corner Column ties

9 Edge Column ties10 Vertical Column ties

11 Vertical wall ties Location of ties in Precast Skeletal Structures



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Typical Cross section

Typical Plan view

Reinforcement

designed for chord

forces (tension)


CONNECTION DETAILS : FLOOR TO FLOOR DIAPHRAGM

BACK


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Resource Efficient

Concrete- made from water, sand, aggregates and cement(limestone)

Abundantly available materials.

Waste by products from power plants and manufacturing facilities can

be used in concrete

Energy Efficient

Thermal mass of concrete saves energy by reducing temperature

swings in buildings.

Concrete has low energy requirements for production.

Concrete has low transportation energy costs as it is produced by

materials available locally.

Light colored precast concrete roof pavers reduces Heat Island

Effect.

6.6. Sustainable GoalsSustainable Goals

i bl li bl l


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Highly Durable

Concrete gets stronger with age.

Strength gained by concrete for years and even decades.

Ecologically Preferable

compared to wood, iron ore mining, extraction for constituents of

concrete is less disruptive to land

Concrete reduces construction waste and can be recycled.

Recyclable

Concrete- crushed and used as aggregate in new concrete mixtures for

infrastructure projects.

Steel reinforcement can be recycled again.


66 S i bl G lS i bl G l


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Reduction of CO2 emissions.

Industrial wastes such as slag cement and silica fume reduces the

amount of cement which in turn reduces CO2 emissions

Reduces the amount of materials used.

Precast concrete is designed to optimize the amount of concrete

used. For ex: hollow core slabs.

0

20

4060

80 Total self

weightGravel & Steel

Cement

Water

45% savings in hollow

core slabs

66 S i bl G lS i bl G l


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Reduces the toxicity of materials.

As a manufactured product under controlled conditions in the plant,

precast concrete generates less waste and waste generated has low toxicity.

Indoor Air Quality.

Concrete contains low to negligible VOCs.

Also, concrete has resistance to moisture.

No renders and plasters required for internal applications.


BACK

7 RISK MANAGEMENT7 RISK MANAGEMENT


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Risk Management is the process of planning, leading and controlling

the resources and activities of the organization to

To fulfill its objectives cost effectively

To protect and grow corporate assets

To enhance shareholder value.

Risk Management Techniques in Construction:

Structural design principles

Codal standards against Progressive collapse

Case study Effective Progressive collapse design

7. RISK MANAGEMENT7. RISK MANAGEMENT



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7. RISK MANAGEMENT7. RISK MANAGEMENT-RONAN POINT, LONDON

22 storey block of flats built in 1966-68 (one

of nine identical blocks).

Precast concrete walls and floors with in

situ joints between units. No in situ core or

shear walls.

Collapse of south east corner over full

height of building caused by a gas explosion

in corner flat on the18th floor in May 1968.

5 people died. Emergency strengthening

works carried out.

South east corner of building rebuilt and

occupation of building continued.



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Precast floor units 7in thick and reinforced.

Wall panels 6in thick with little or no

reinforcement.

Diagram shows typical connection detail with

emergency strengthening angles.

5th Amendment to the Building Regulations

in 1970 (includes requirements for the

prevention of progressive collapse).

Evacuation of Ronan Point and 8 sister blocks

1984.

Detailed survey carried out 1984.

Building dismantled 1986.

7. RISK MANAGEMENT7. RISK MANAGEMENT-RONAN POINT, LONDON


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Detailing

The code adopted addresses progressive collapse,

ties and ductile detailing.

Protruding reinforcement from floor planks

overlap with the reinforcement in adjacent plank.

After erection overlapping bars are threaded with

11mm steel strands effectively interlocking them

and are grouted.

Wall panels were casted with protruding loops

which is threaded with steel bars and grouted

with adjacent wall panels.

Bars from one level to another were connected

with nuts inside connecting bracket.

7. RISK MANAGEMENT7. RISK MANAGEMENT- KHOBAR TOWERS, SAUDI ARABIA



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Performance

The code addresses progressive collapse, ties and

ductile detailing.

Collapse was limited to the external facade wall.

Exterior shear wall was completely destroyed

but no progressive collapse.

Interior walls and slab panels had extensive

damaged but did not collapse

The precast elements had sufficient ductility

detailing to with stand the impulse force.

The interlocked ductile connections maintained

integrity of the structure preventing progressive

collapse.

7. RISK MANAGEMENT7. RISK MANAGEMENT- KHOBAR TOWERS, SAUDI ARABIA

BACK


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