Advances in Construction Technologies Higher Grades of Concrete & Steel

7/29/2019 Advances in Construction Technologies Higher Grades of Concrete & Steel

1/44

Advances in Construction Technologie

Higher Grades of Concrete & Steel

S.A.Reddi

[email protected]

16 Feb 0Mumbai


2/44

The Taj Mahal, 1632-1648

( Masonry )

Gateway of India, 1920

( Reinforced Concrete )

Glorious History of

Indian Construction


3/44

-Derna, Baida Silos Libya (1985)

Structure Slipformed for cost-effectiveness, spee


4/44

Vidyasagar Setu, Kolkata (1992)


5/44

I-Flex Head Quarters, Bangalore 2002

Cable Stayed Building


6/44

Burj Dubai

Worlds tallest

building

under construction(Nov 2006)


7/44

Empire State Building

Height -381 m (1931)

Petronas Towers, Kua

Lumpur, Ht-451 m (199

Shift from Structural Steel to Concrete


8/44

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


9/44


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


10/44


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


11/44

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


12/44

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


13/44

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


14/44

Tallest Building in Hong Kong 430 m

Foundation Excavated to Rock, -32 m below ground leve


15/44

Top of Basement

conc-steel Mega col

3028 29 31 32


16/44

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


All B4 Mega Colum

Completed on 19-10

All B3M Mega Column


All B1 Mega Column


(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


Cycle 2 (10-11-00)

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

Fast track


17/44

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


18/44

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


19/44

Precast Staircases

Lifting Sling for hoistin

precast staircases


20/44

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


21/44

Skeletal Frame for

precast construction


22/44

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


23/44

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


24/44

Reinforcement Steel

Properties of


25/44

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


26/44

Bar Bending Options

MachineBending stacks of bars

Manual


27/44

Lapped bars can create problems

Concrete must be placed.

Where bars are lappedcheck their thickness and spacing


28/44

Mechanical Splicing Avoids Laps

IS 1786 Specification for HSD bars


29/44

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


30/44

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


31/44

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


32/44

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


33/44

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


34/44

Need for High Strength

Reinforcement Bars

Reduce congestion ofreinforcement

Avoid large diameter

reinforcement

Utilize permissible

higher stress

Align with

International practice


35/44

Structural Steel

Structural Steel India Europe


36/44

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


37/44

Reinforcement

surrounding steel column

Composite construction

World tallest Building


38/44

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


39/44

Composite JoistsThickness of composite deck 50mm

Conc. poured 115mm

Less const. time

Less expensive

Hollow Box Section


40/44

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


41/44

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


42/44

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


43/44

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


44/44

Any comments, queries, suggestionsare welcome

Please contact [email protected]

Documents

Advances in Construction Technologies Higher Grades of Concrete & Steel