selection, protection & detailing reinforcement

8/6/2019 Selection, Protection & Detailing Reinforcement

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Selection, Protection & Detailing

Reinforcement -1


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ReinforcementCl. 5.6 IS:456 - 2000

The reinforcement shall be any of the following:

MS, Medium Tensile Steel bars IS:432 Part - I

HYSD bars Fe 415 / 500 / 550 IS:1786

Hard drawn steel wire fabric IS:1566

Structural steel Grade A IS:2062

Modulus of Elasticity 200 kN/mm2

Characteristic yield strength shall be assumed asthe minimum yield / 0.2% proof stress specified

in the relevant standard


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IS 1786 - Fourth Revision 2007

Important Modification A new strength grade Fe 600 has been introduced

A new ductile category D has been introducedfor seismic & other applications where enhanced

ductility may be required Some new parameters like uniform elongation

have been introduced, and

Nominal sizes have been rationalized to remove7,18,22,45 and 50 mm


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Reinforcement Steel

Electronic Schedule Information

Schedules can be e-mailed by means ofcommercially available software packages tosave significant time for the fabricators and to

increase the accuracy Electronic schedule information can be linked

directly to the computer control system of theproduction equipment. It reduces errors,there are fewer queries & it is easier tochange procedures


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Receipt, Storage and Use by the

Contractor

Products must be treated properly bycontractor when received on site and thro theconstruction process

When placing pile cages into position, ensurethe correct lifting points are used to avoidpoint loading on the flexible transverse linksor rings

Use appropriate temporary works methods forlifting, handling & working with pre-assembled welded fabrications


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Stainless Reinforcing Steels

BS 6744:2001

Inherently resistant to corrosion

Allow relaxation in design for durability normallyused for carbon steel reinforced structures

Significantly decrease the inspection andmaintenance cost of structures

Extend the design life of structures

Cost saving if whole-life cost of a structureconsidered

Initial costs relatively high


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Stainless Reinforcing Steels

BS 6744:2001

Stainless steels retain passivity in concrete at low

pH levels and high chloride concentrations; use is

preferred in structures at risk of corrosion

Prevents chloride attack during life of structure

Stainless steel is 'non-ageing' because of its

austenitic structure and hence there is no

requirement to perform a re-bend test High cost; used selectively in those parts of the

structure most at risk of chloride ingress


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Reinforcement Steel

Lap Splices

Splicing is to lay two bars parallel to one another,over a the lap length & tie them with binding wire

Load present in the first bar is transmitted to the

concrete by the bond between steel andconcrete, which then transmits the load to thesecond bar

The efficiency of this joint depends on many

factors including the properties of the concrete

Lap splices lead to congestion of reinforcement;prefer couplers for 20 dia and above


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Splicing of Reinforcement Bars

Alternatives

Laps for bars up to 16 mm dia

Sleeves, couplers, welding for larger diameters

In developed countries laps are not permittedfor higher diameters to decongest & facilitateconcrete pours

Choice of splicing method depends on cost,

grade of steel, possibility of transferringcompressive or tensile stresses and availablespace


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Reinforcement Steel

Mechanical Splices

A coupler is designed to join two bars

together

Most common type of couplers are based on1) a threaded bar and coupler

2) a sleeved coupler which is swaged onto the bar

3) a combination of both or

4) a sleeved coupler which is bolted onto the bar


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Reinforcement Steel

Mechanical Splices

By creating an end-to-end bar connection, a

continuous load path is created from one bar to

another that is independent of the condition and

quality of the concrete

Mechanical splice is easy to test relative to

lapping method which requires a test in concrete

IS 456 allows both overlapped and coupled

splices with specific considerations for each


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Reinforcement - Mechanical

Connectors

Swaged couplers

Swaged and threaded couplers Parallel threaded couplers

Internal serrated saddle couplers

Couplers for threaded reinforcement bar

Tapered / Parallel thread

Swaged or thread/ swage combination


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Reinforcement Advantages of

Mechanical Connectors

Improve safety no projecting bars

Reduce steel congestion eliminate drilling of shutters

Improve access

Help avoid rust staining of concrete byeliminating projecting bars

Additional plant required; more expensive


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Reinforcement Steel

Reinforcement Continuity System

Forming construction joints on site requiresite bending and re-bending of reinforcing

steel which can adversely affect the materialproperties

Reinforcement continuity systems are

designed to maintain continuity acrossconstruction joints in concrete structures in atime saving and cost effective manner


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Reinforcement Continuity

System

Made of galvanised steel sheet

casings with nubbed backs and

short casing webs for

maintaining concrete cover of

steel components

The anchorage lengths of the

standard elements are adapted

to meet the codal requirements


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Transport of Reinforcement

Avoid.

Accidental damage or notches causing a decrease in

section

Contact with other products liable to deteriorate or

weaken bond of reinforcement

Bends requiring straightening

Damage to anti-corrosive protection, if any


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Storage of reinforcement

Index & classify reinforcement bars according to

diameter, type, grades, length and batch of origin

Steel should be kept clean without stains of

grease, oil, paint, earth, non-adherent rust etc

which may prove harmful to bonding

Sufficient storage area to facilitate handling and

provide free access for unbent reinforcement. Itmust be close to bending equipment. Bars should

be stored parallel to bending & cutting tables

selection, protection & detailing reinforcement

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