Home / News / News / Industry News / F grades and MGP grades LVL timber

F grades and MGP grades LVL timber

Views: 7     Author: Frank Ding     Publish Time: 2022-05-13      Origin: Site

F grades and MGP grades LVL timber

The F grade system has been used to grade structural timber for many years. In general, all timbers other than certain plantation pines are still F graded. The grading process can be done either visually (that is, by eye), or mechanically, using a machine stress grader. The alternative grading system used for specific plantation pines is MGP grading. This is always done with a machine.


Set out below is a brief summary of the two grading systems.


F grading


An F grade is a measure of the bending strength of a piece of timber. 'F' stands for force in megapascals (MPa), and is the amount of force a piece of timber can withstand without bending beyond an acceptable limit. A piece graded to F11, for example, will have a safe working stress in bending of 11 MPa.


Note that the range of grades available for some softwoods has been updated in recent years as the result of continuing research into their performance in structural applications. Radiata pine, for instance, used to be visually graded to as high as F14, which was then revised down to F11, and now has now been modified again to F8 as the highest available grade.


MGP grading


MGP stands for machine graded pine, and is a system used for particular pines, especially radiata, slash and Caribbean. Instead of being based on the bending strength of the piece, MGP is a measure of its modulus of elasticity (MOE), which takes into account other properties, such as stiffness, compressive strength and shear strength.


The higher the MOE of a piece, the stiffer it is. When this is measured by an MGP machine stress grader, the board is given a grade which is simply an abbreviation of the MOE category that it falls into.


That is:

MGP 10 has an MOE of 10,000 megapascals (MPa)

MGP 12 has an MOE of 12,700 Mpa

MGP 15 has an MOE of 15,200 Mpa


Using MGP in place of F graded timber


It's important to note that although MGP material may be substituted for F graded material, as shown below, F graded material must not be used where MGP material has been specified. This is because the MGP grades have design tables for a range of properties, whereas F grades are based on bending strength only. So it is possible that the architect or builder who has specified an MGP grade for a structural member is relying on design characteristics such as compressive strength or shear strength, which would not be accounted for in an F graded piece.


But for LVL tumber, things were different.


LVL is made of thin veneers bonded together with weather-resistant phenolic adhesive. This means that the dimensions of the final LVL product are not limited by the dimensions of the raw material, and even small-diameter logs can be used to produce large LVL beams and panels. When veneer logs are peeled to produce veneer, any natural defects in the wood, such as knots, are dispersed as small fragments across the veneer. This, together with the lamination effect, eliminates the impact of defects and results in exceptionally homogeneous material properties.


According to  AS/NZS 4357 LVL standard, the F grade is measured by MOE, stiffness, compressive strength and shear strength, similar as MGP grade. it is done with a machine. The actual properties associated with the F-grades can be obtained from the Timber Structures Code. For example F8 LVL timbers have the following properties (from AS 1720.1 Table H2.1):

Stress

grade

Characteristic values, MPa

Bending

( fb' )

Tension parallel to

grain

Shear

in

beam

( fs' )

Compression

parallel to

grain

( fc' )

Short duration

average modulus

of elasticity parallel

to the gain, MPa

(E)

Short duration

average

modulus of

rigidity, MPa

(G)


Hardwood

Softwood

( ft' )

F34

84

51

42

6.1

63

21500

1430

F27

67

42

34

5.1

51

18500

1230

F22

55

34

29

4.2

42

16000

1070

F17

42

25

22

3.6

34

14000

930

F14

36

22

19

3.3

27

12000

800

F11

31

18

15

2.8

22

10500

700

F8

22

13

12

2.2

18

9100

610

F7

18

11

8.9

1.9

13

7900

530

F5

14

9

7.3

1.6

11

6900

460

F4

12

7

5.8

1.3

8.6

6100

410


In certain cases, F grader LVL can be used to replace MGP grade according to the technical parameters in the table.


The characteristic strength properties for LVL products have been validated by in-grade testing and whilst they use an F-grade designation, they are different properties to F-graded sawn timber and have a high level of reliability. Australian produced plywood is linked to an audited, quality control and product certification system, when designated with an EWPAA (Engineered Wood Products Association of Australasia) Grade Mark.


Some third-part audited quality control programme like Bsi could supply credible certificate like Benchmark complied with AS/NZS 2269 standard.You can check your supplier if they have this certificate and stamp on the board.


Hongcheng company can supply high quality Structrual plywood, Bracing plywood, Formply and Sturctrual LVL to our customers. All products had passed the Bsi Benchmark certificate compliance with AS/NZS standard.




ABOUT US

The Expert Of Plywood Solution
We are a dynamic dedicated team. Based on abundant experiences in wooded market and special QC team, we could guarantee our quality. Up to Chinese, European and AS/NZS quality standards. We have won a good reputation among users from at home and abroad. 
 
Contact Us
CONTACT US

Home

Copyright © 2020 Shouguang Hongcheng Wood Co.,Ltd. All Rights Reserved.