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Reinforcing - Technical

Quick Links :
Material Standard
Quench and Tempered (QT)
Micro Alloy (MA)
NatSteel QT
Bar Type Abbreviations
Minimum Bend Raidus Diameter
Minimum Standard Hook
Pile Splices
Calculating Reinforcing
Mesh Conversion



Material Standard

AS/NZS 4671 was introduced in 2001 and is the joint standard for Steel Reinforcement Materials in New Zealand and Australia. 

Specific to New Zealand, AS/ NZS 4671:2001(Page 12, Table 2) stipulates .
 CHARACTERISTIC MECHANICAL PROPERTIES
OF REINFORCING STEELS
 Property 300E
(Seismic)
500E
(Seismic)
Type of specified value
 Yield stress (Mpa)
Rek.L
          Rek.U
 
> 300
< 380

>
500
< 650

CvL: p = 0.95
CvU: p = 0.05
Ratio
Rm/Re

>
1.15
< 1.50
 
>
1.15
< 1.40

CvL: p = 0.90
CvU: p = 0.10
Uniform elongation
Agt(%) 

> 5.0  

>
10.0

CvL: p = 0.90

AS/ NZS 4671 allows for the manufacture of material by both the Quench and Tempered (QT) process and the Micro Alloy (MA) process.

Quench and Tempered (QT)
Quench and Tempered (QT) – The QT process (also known as Tempcore) produces a high strength rebar with a tough outer skin and ductile core, providing exceptional toughness and ductility (refer Onsteel Website).  The process was developed in the early seventies by CRM of Belgium in order to manufacture high yield strength concrete reinforcing bars from mild steel more efficiently - without the costly addition of alloys such as Vanadium.  Today it is the most common method used worldwide for producing high strength reinforcing steel and is used in many Seismic zones throughout Europe and Japan. 
The process consists in subjecting the hot rolled steel to an in-line heat treatment in 3 successive stages:
•    as soon as it leaves the final mill stand, the product is rapidly and energetically cooled through a short cooling installation, where it undergo surface hardening (martensite layer)
•    as soon as this quenching operation is stopped, the surface layer is tempered by using the residual heat left in the core of the bar (self tempering of the martensite layer)
•    the third stage takes place while the product lies on the cooling bed where the bar is subjected to normal cooling down to ambient temperature (transformation of the residual austenite in the core)

Micro Alloy (MA)
Micro Alloy (MA) – Is a much less commonly used process world wide and involves the process of adding costly alloys such as Vanadium, Silicon, Manganese and Carbon.  Many steel mills worldwide are progressively changing their manufacturing process away from Micro Alloy – notable Onesteel of Australia (Australia’s largest reinforcing steel manufacture) now only produces 12 & 16 mm in coil in MA, all other steel is produced by QT

Natsteel QT
Natsteel manufacture 500E QT specifically to AS/ NZS 4671.  Natsteel are part of Tata Steel (one of the largest five steel producers in the world) and are a leading steel manufacture in the Asia area.  Natsteel posses a vigorous quality management system and are ISO accredited. To ensure further compliance of the 500E steel, Nauhria annually commission independent audits by SGS on Natsteels Quality Management Systems.

o    Independent audit inspection to AS/NZS 4671:2001 on the manufacturer’s quality management system as per Appendix A – demonstrates compliance with the Standard for product conformity as required by Appendix A4 – Suppliers Quality Management System and Appendix B – manufacturing control; subsection appendix B3, B4 and B6. – this test is especially important as it lends credibility to the manufacturer’s mill certificates that accompany each batch that is produced.

The above testing has been conducted in consultation with the DBH and accordingly reviewed by them attach letter.

The DBH have conducted testing on the minimum safe bend diameter for Grade 500E steel.  Results in Phase 1 of this testing showed Nauhria (Natsteel) QT outperformed all other suppliers MA or QT (including locally manufactured product) in the bend test – all other suppliers experienced brittle fractures at some point, Nauhria QT was the only supplier to experience no brittle fractures.  The result in the Phase 2 testing resulted in the DBH concluding that “For all sizes of bar tested, no significant difference was found in the performance on MA and QT variants of Grade 500E in all sizes tested. 


Bar Type Abbreviation
      D     
 Mild Deformed 300E 
H  High Tensile Deformed 500E    
R  Mild Round 300E
HR  High Tensile Round 500E
RB Reid Bar
NB. Do not use X, DH, RH, Y, T or the like



Minimum Bend Radius Diameter
as per NZS 3109

Main Bars

The minimum bend diameter for main bars, measured to the inside of the bar, shall be equal to or greater then five bar diameters for 6-20mm and six bar diameters for 25-32mm.
 MPA
 Bar Diameter
(mm)
 Minimum Bend Diameter (mm)






300E or 500E






 6 30 
 10  50
 12  60
 16  80
 20  100
 25  150
 32  192

 
Stirrups and Ties


The minimum bend diameter for main bars, measured to the inside of the bar, shall be equal to or greater then 2 bar diameters for 6-20mm and 3 bar diameters for 25-32mm for plian bar, and equal to or greater then 4 bar diameters for 6-20mm and 6 bar diameters for 25-32mm for deformed bar.


300E or 500E 
Bar Diameter (mm)
Minimum Bend Diameter (mm) 
 Plain Bar
Deformed Bar
 


300E or 500E
 
 
 

 12  24
 10  20  40
 12  24  48
 16  32  64
 20  40  80
 25  75  150
 32 96
 192

If for any reason you believe it is not possible to achieve the minimum bend radius, please seek Engineers approval before making any adjustments.  No adjustments are to be made without engineer approval.

Minimum Standard Hook

There are three types of standard hooks

A.    Semi-Circular Hook – A semi-circular turn plus an extension of at least four bar diameters but equal or greater than 65mm at the free end of the bar;

Bar Diameter (mm)  Minimum Semi-circular Hook Lingth (mm)
 6  65
 10  65
 12  65
 16  65
 20  80
 25  100
 32 128 


B.    90˚ Hook – a 90˚ turn plus an extension of at least 12 bar diameters at the free end of the bar for a deformed bar and 16 bar diameters for plain bars;

Bar Diameter (mm)
 
Minimum 90˚ Hook Length (mm)
 Deformed        Plain    
 6  72   96
 10  120  160
 12  144  192
 16  192  256
 20  240  320
 25  300  400
 32  384  512




C.   Stirrup Hook – a 135˚ turn around a longitudinal bar plus an extension of at least six stirrup bar diameters for deformed bars and eight stirrup bar diameters for plain bars at the free end of the bar embedded in the core concrete member.

Bar Diameter 
 
  Minimum stirrup Hook Length (mm)
 Deformed        Plain    
 6  36  48
 10  60  80
 12  72  96
 16  96  128
 20  120  160
 25  150  200
 32 192  256


If for any reason you believe it is not possible to achieve the minimum bend radius and or minimum standard hook length, please seek Engineers approval before making any adjustments.  No adjustments are to be made without engineer approval.


Pile Splices

NZ 3101 and 3109 require the anchorage of all pile splices/ laps to be one of the following:

•    A 135˚ hook (as per a stirrup hook)
•    A welded lap splice
•    A mechanical connector



The above technical data is taken from the Standards 3101 and 3109, full copies are available from Standards New Zealand. Or contact us for further information.

Calculating Reinforcing Steel

 NB: All calculations are external dimensions

Calculating Weights in KG

To calculate the weight of a bar take the length of the bar and multiple it by the factor below corresponding to the bar diameter

     Bar size      
    Kg/metre     
 6mm  0.222
 10mm  0.617
 12mm  0.888
 16mm  1.578
 20mm  2.466
 25mm  3.853
 32mm  6.313
 40mm 9.865 
 
_____________________________________  
    
Stirrups – Calculating the Cut Length

Length of bar = (2 x A) + (2 x B) + C

 
C
  6mm     =     100mm
10mm     =     120mm
12mm     =    150mm
16mm     =    180mm   
_____________________________________

Links – Calculating the Cut Length

Length of bar = A + C
   

 
C
  6mm     =     150mm
10mm     =     200mm
12mm     =    250mm
16mm     =    300mm   
20mm     =    360mm       
_____________________________________

Hooks – Calculating the Cut Length

L-bar = A + C
   

 C
  6mm     =     100mm
10mm     =     120mm
12mm     =    150mm
16mm     =    180mm   
20mm     =    200mm   
_____________________________________

Legs – Calculating the Cut Length

Length of bar = A + B - C
   
 
C
  6mm     =     10mm
10mm     =     25mm
12mm     =    30mm
16mm     =    40mm   
20mm     =    50mm   
25mm     =    70mm
32mm     =    90mm    


Mesh Conversion Factors:
Smooth wire fabric / Ribbed wire fabric

   Sectional area Bars / meter Sectional area / meter
 668  4.00mm  12.571mm2 1000/150   6.667 12.571 x
6.667 
 83.811mm2
 84  5.60mm  24.640mm2  1000/300  3.333  24.640 x
3.333
 82.125mm2
 665 
 5.30mm 
 22.071mm
 1000/150
 6.667  22.071 x
6.667
 147.147mm
 147  7.50mm  44.196mm2  1000/300  3.333  44.196 x
3.333
 147.305mm2
 664  6.00mm  28.286mm2  1000/150  6.667  28.286 x
6.667
 185.582mm2
 188  7.50mm  44.196mm2  1000/235  4.255  44.196 x
4.255
 188.054mm2
 663  6.30mm  31.185mm2  1000/150  6.667  31.185 x
6.667
 207.910mm2
 212  9.00mm  63.643mm2  1000/300  3.333  63.643 x
3.333
 212.122mm2
 662  7.10mm  39.608mm2  1000/150  6.667  39.608 x
6.667
 264.067mm2
 265  9.00mm  63.643mm2  1000/240  4.167  63.643 x
4.167
 265.200mm2
 661  7.50mm  44.196mm2  1000/150  6.667  44.196 x
6.667
 294.655mm2
 295  9.00mm 63.643mm2
 1000/215 4.651   63.643  x
4.651
 296.004mm2


Please
contact us with any questions you may have








                    
 
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