Advances in Construction Technologies Higher Grades of Concrete & Steel

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    Advances in Construction Technologie

    Higher Grades of Concrete & Steel

    S.A.Reddi

    [email protected]

    16 Feb 0Mumbai

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    The Taj Mahal, 1632-1648

    ( Masonry )

    Gateway of India, 1920

    ( Reinforced Concrete )

    Glorious History of

    Indian Construction

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    -Derna, Baida Silos Libya (1985)

    Structure Slipformed for cost-effectiveness, spee

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    Vidyasagar Setu, Kolkata (1992)

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    I-Flex Head Quarters, Bangalore 2002

    Cable Stayed Building

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    Burj Dubai

    Worlds tallest

    building

    under construction(Nov 2006)

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    Empire State Building

    Height -381 m (1931)

    Petronas Towers, Kua

    Lumpur, Ht-451 m (199

    Shift from Structural Steel to Concrete

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    Emerging Trends in Concrete Technologies

    From 1:2:4 nominal mix to design mix

    - high slump upto 200 mm- self compacting concrete

    - slip-form concrete

    - pumped concrete

    - underwater concrete

    - fiber Reinforced concrete

    - lightweight concrete

    - heavy concrete- ultra high strength Conc up

    to 200 MPa

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    Emerging Trends in Concrete Technologies

    Development of Constituent Materials

    Variety of OPC and blended cements; Eurocodehave 27 products in family of common cements

    Mineral admixtures

    - pre-blended in cement factories or

    - mixed in the batching plants at site

    Use of silica fume has generated High

    Performance / High Strength Concrete

    Developments in chemical admixtures resulted iflowing concrete, self compacting concrete

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    Emerging Trends in Concrete Technologies

    Variety of Concrete Equipment

    Phenomenal advances in construction equipmenFrom traditional mixes,10x7 mixers and manual

    placement, we have moved to

    - computer controlled batching plants

    - truck mixers, belt conveyors

    - placement by concrete pumps, tower cranes

    - high frequency vibration

    - laser controlled screed finish- sprayed curing compounds

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    High Rise Buildings - 2 Days Per Floor

    Structural System

    Floors made of RC / PSC flat slab. Ceilings beamfree & smooth; results in lower overall height.

    Concrete preferred even for high rise buildin

    after 9/11collapse of WTC in New York.

    Concrete offers structural robustness & f

    resistance. Structural steel must be protected w

    fire proofing materials, but during constructio

    and subsequently some of the fire proofimaterial is knocked off

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    High Rise Buildings - 2 Days Per Floor

    Construction Cycle

    Used in U.S since 1950. Success depends oproper planning; Pre-assembled form panels f

    shear walls, lift shaft space & stair wells.

    Formwork provided for two floors

    Column forms, rebar cages pre-fabricated

    Concreting by crane with 2 buckets. One is lift

    while the other is being filled. 40-60 m3 of conc /

    Requires organized efforts of labour, assembliforms & steel reinforcement & at placement deck

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    Two Days Per Floor Construction CycleDay 1: 0700-1200 : Concrete the floor (50 MPa).

    1030-1230 : Lay-out columns & walls; Lift columforms, timber & plywood & erect for floor above

    1400 hrs :Floors finished; concrete staircase for

    lower floors; complete formwork for next floor

    deck & columns. Work closed for the dayDay 2: 7.00 a.m : Start fixing rebar cages

    12.00 - 15.30 : Column concreting with 60 MPa; f

    floor form work & reinforcement, ready forconcreting next day morning Work closed

    T ll t B ildi i H K 430

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    Tallest Building in Hong Kong 430 m

    Foundation Excavated to Rock, -32 m below ground leve

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    Top of Basement

    conc-steel Mega col

    3028 29 31 32

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    3028 29 31 32

    TOWER CONSTRUCT

    SEQUENCE

    B5

    B4

    B3

    B3M

    B2

    B1

    LGG

    1/F

    2/F

    4/F

    6/F

    3/F

    Cycle 2

    (14-08-00)

    (06-08-00) - C2

    Cycle 2

    (29-07-00)

    Cycle 1

    (20-07-00)

    Cycle 1

    (26-06-00)

    Cycle 2

    (30-06-00)

    Cycle 3

    (09-07-00)

    (22-09-00)

    (06-07-00) - C1 (17-07-00) - C3(13-07-00) - C2

    (27-07-00) - C1

    Cycle 1

    (07-08-00)

    (13-08-00) - C1

    Cycle 1

    (20-08-00)

    (19-08-00) - C2

    (27-08-00) - C1

    Cycle 2

    (28-08-00)

    Pour 2

    (16-04-00)

    (03-06-00)

    Cycle 1

    (10-09-00)

    (05-09-00) - C2

    Pour 1

    (30-04-00)

    (21-09-00) - C1

    (11-09-00)

    Cycle 2

    (25-09-00)

    Raft Foundation

    Completed on 25-03

    All Mega Column Pl

    Completed on 14-06

    All Mass Filling

    Completed on 10-08-2

    (02-10-00) - C2

    Cycle 1

    (05-10-00)

    (16-10-00) - C1

    Cycle 2

    (18-10-00)

    (27-10-00) - C2

    Cycle 1 (02-11-00)

    Cycle 1

    (30-12-00)

    Cycle 2

    (08-01-01)

    All B5 Mega Colum

    Completed on 30-09

    2000

    (12-10-00) -C2 (04-10-00) -C1

    All B3 Mega Column

    Completed on 26-10-2

    All B4 Mega Colum

    Completed on 19-10

    All B3M Mega Column

    Completed on 30-10-20

    All B1 Mega Column

    Completed on 14-11-2000

    (28-10-00) -C1

    (24-11-00) - S2a(28-11-00) - S2b (29-11-00) - S1b(21-11-00) -S1a

    (04-11-00) -C2

    All B2 Mega Column

    Completed on 10-11-200

    Cycle 2 (10-11-00)

    (10-11-00) - C1 (18-11-00) - C2

    Fast track

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    Fast trackconstruction

    Twin Towers, Brussels

    28 floors+4 basement Total

    office area - 150000 sqm.

    (height 102 m)

    28 floors built in just 10months !

    High early concrete

    strength 15 MPa in 24 hrs

    Formwork cycle of 24 hrsdue to use of HPC

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    Pre-cast Hollow core UniUsed for floors up to 15 m

    spans, eliminates floor beamsWidely used in advanced

    countries, not popular in India

    Hollow core units prefabricate

    at the site were used for the IT

    Park building at Bangalore

    No factories in India for hollow

    core units

    Lifting Sling for hoistin

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    Precast Staircases

    Lifting Sling for hoistin

    precast staircases

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    Public Housing in Singapore

    800,000 prefab housing units since 1960Highly buildable designs for ease of constructio

    modular co-ordination, standardised elements

    One floor completed by 6 workers in one day in

    contrast to 12 workers x 5 days conventionallyPrefabricated reinforcement for all components

    Computerisation of structural detailing

    Prefabricated bathrooms, built-in accessories

    Premixed dry mortar powder pneumatically

    conveyed upto 35 storeys, mixed for plaster etc

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    Skeletal Frame for

    precast construction

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    Precast Columns

    Columns may be erected in one piece, i.e. withoumechanical splicing, up to 20 m in length

    Practical and economical limit is 12 to 13 m

    Column sizes in braced structures approximated

    by assuming c/s area (mm2) is equal to maximum

    ultimate axial load (N) divided by 28

    Design of the column makes due allowance for

    finishes in computing a net cross section

    Building construction

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    Building construction

    without Formwork

    Precast concrete panel 50 mm thk with integrate

    structural reinforcement and special lattice

    girders form permanent formwork

    Double precast concrete panel for walls

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    Reinforcement Steel

    Properties of

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    Properties of

    Reinforcing Steel

    Ductility to bend precisely to fitcomplicated shapes & without

    loss of cover; ductility prevents

    sudden failure

    Minimum strength for load bearing; weldability fsite fabrication

    Good bonding and fatigue properties

    Accurate cutting & bending for proper fit on site& to maintain lap & anchorage lengths & cover

    B B di O ti

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    Bar Bending Options

    MachineBending stacks of bars

    Manual

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    Lapped bars can create problems

    Concrete must be placed.

    Where bars are lappedcheck their thickness and spacing

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    Mechanical Splicing Avoids Laps

    IS 1786 Specification for HSD bars

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    IS 1786 Specification for HSD barsImportant Modification in 4th Revision (2007

    A new ductile category D introduced for seism& other applications requiring enhanced ductility

    Diameter rationalized; 7,18,22,45 & 50 mm delete

    Strength grades : Fe 415, Fe 415D

    Fe 500, Fe 500D

    Fe 550, Fe 550D

    Fe 600 ( New strength grade )

    IS 1786 Reinforcement Steel

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    IS 1786 Reinforcement Steel

    Indian Practice

    Code allows 4 grades : Fe 415, Fe 500, Fe 550,Fe 600Consultants specify only Fe 415 leading to congestion

    reinforcement in many structures

    Fe 415 already obsolete in developed world. Min grade

    per Euro Code is Fe 500

    Designers specify odd sizes creating difficulties during

    execution due to non-availability

    20 and 22 mm dia or 18 and 20 mm dia are not visuallydistinguishable, leading to mistakes

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    Recommended Reinforcement Bar Dia

    European practicerecommends-

    8,10,12,16,20,25,

    32,40,50 mm diameter

    Bars distinguishablewith naked eyes

    Each bar dia approx.

    sum of two precedingbar dia, facilitating

    combinations

    2

    3

    10

    16

    25

    40

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    Reinforcement Information and Supply

    New computer software called Steel-pac allows

    fabricators to receive schedules directly from

    designers, improving the planning process,

    optimizing material use and reducing waste

    These system need to be fully exploited

    Centralised Bar Bending

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    Centralised Bar Bending

    Standard Practice in Dubai,UK

    Cut and bent bars provided as per design by barmanufacturers or third parties in developed worl

    Wastage of steel reduced. Better quality.

    Application of IT simplifies production. Structura

    designer/detailer electronically transmit BBS to

    bending machines of manufacturer for furtherprocessing reinforcement.

    Need for High Strength

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    Need for High Strength

    Reinforcement Bars

    Reduce congestion ofreinforcement

    Avoid large diameter

    reinforcement

    Utilize permissible

    higher stress

    Align with

    International practice

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    Structural Steel

    Structural Steel India Europe

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    Structural Steel India EuropeMax. depth of RSJ 600 1100 mm

    Max. flange thickness 23.60 125

    Max. width of flange 250 454Parallel flange section No Yes

    Less welding & constn time with deep sections

    40 m span at JNPT, with 1100 mm sections

    Composite construction

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    Reinforcement

    surrounding steel column

    Composite construction

    World tallest Building

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    g

    Taipei Financial Centre Corporation

    Column sizes: 3 m x 2.4 m, 8 cm thk steel used

    Design loads: 38000 t

    Heavy steel reinforcement, 85 MPa concrete

    surrounding structural steel columns

    106000 t structural steel.

    Grade 60 reinforcement, 25% stronger than std,

    made using thermo-mechanical control process

    for lower carbon, higher weldability.

    Column erection started-Jun00, completed Jul0

    Composite Joists

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    Composite JoistsThickness of composite deck 50mm

    Conc. poured 115mm

    Less const. time

    Less expensive

    Hollow Box Section

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    Hollow Box Section

    Suitable for versatile construction; for fabricatio

    of formwork and other enabling structures

    In the absence of larger sections, convention

    rolled steel products used, increasing the tonna

    and cost of construction

    Euro Code 3 Classification

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    Euro Code 3 - Classification

    Circular hollow sections :

    outside diameter : between 21.3 & 508 mm

    thickness : between 3.2 & 50 mm

    mass per meter : 1.43 kg to 565 kg

    Square hollow sections :

    size : 20 x 20 mm to 400 x 400 mm

    thickness : 2 mm to 20 mm

    Rectangular hollow sections :

    size : 50 x 25 mm to 500 x 300 mm

    Hollow Steel Sections

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    European / Indian availabilityCORUS U.K. can supply

    Circular sizes up to 508 OD x 16 thk

    Larger circular sizes up to 2134 mm dia

    Square sizes up to 400 x 400 x 16

    Rectangular sizes up to 500 x 300 x 20

    Oval sizes : up to 500x250x60 mm

    Indian supplies are limited to 132 x 132 (square)

    and 172 x 92 (rectangular); smaller sections limitthe scope for application

    Concrete & Steel Practices

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    A ComparisonConcrete construction moved from nominal site

    mixes to design mixes supplied by RMC plants

    Reinf & structural steel practices should follow

    Minimum Fe 500 grade bars should be cut & ben

    in factories; contractors should order ready to ucages (common in rest of the world)

    Structural steel of higher grades & deeper rolled

    sections should be introduced

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    Any comments, queries, suggestionsare welcome

    Please contact [email protected]