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Reinforcing - Technical
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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 .
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CHARACTERISTIC MECHANICAL PROPERTIES
OF REINFORCING STEELS
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| Property |
300E
(Seismic)
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500E
(Seismic)
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Type of specified value
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Rek.U |
> 300
< 380
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> 500
< 650
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CvL: p = 0.95
CvU: p = 0.05 |
Ratio
Rm/Re
|
> 1.15
< 1.50
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> 1.15
< 1.40 |
CvL: p = 0.90
CvU: p = 0.10
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Uniform elongation
Agt(%)
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> 5.0
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> 10.0 |
CvL: p = 0.90
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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
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Mild Deformed 300E
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| H |
High Tensile Deformed 500E
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| R |
Mild Round 300E
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| HR |
High Tensile Round 500E
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| 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
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Bar Diameter
(mm) |
Minimum Bend Diameter (mm) |
300E or 500E
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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
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Bar Diameter (mm)
|
Minimum Bend Diameter (mm) |
Plain Bar
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Deformed Bar
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300E or 500E
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6 |
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)
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| Deformed |
Plain
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| 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
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82.125mm2 |
665
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5.30mm
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22.071mm2
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1000/150
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6.667 |
22.071 x
6.667
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147.147mm2
|
| 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
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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
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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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