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Advances in Construction Technologie
Higher Grades of Concrete & Steel
S.A.Reddi
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]