1. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
2. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
7. Components
Roof Systems
Protect the structure from
environmental elements.
Provided skeleton for
sheeting material
Design to withstand wind,
snow, and other loads,
Detailing is crucial
10. Components
Floor Systems
Stable platform for
occupants and support live
loads.
Design considerations
Jointst, beams, subfloor
material etc.
Meet strength and
deflection criteria.
11. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
17. Joints and Connections
Bolted connection
Welded connection
Riveted connection
Pinned connection
Moment resisting connections
Dowel Joints
Mortise and Tenon Joints
18. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
19. Timber Truss
Truss is a structural framework designed to bridge
the space above a room and to provide support for
a roof.
Truss Material -- Timber – Timber Truss
20. Timber Truss
Components of Truss
1. Top Chord
2. Bottom Chord
3. Web Members
4. King Posts
5. Queen Posts
21. Timber Truss Connection
Mortise and Tenon Joints
Half Lap Joint
Scarf Joint
Dovetail Joint
Gusset Plate
Steel Connectors
Bolted Connectors
Nail Plates or Toothed Plates
Wood Screws
22. Timber Truss Connection
Mortise and Tenon Joints
Half Lap Joint
Scarf Joint
Dovetail Joint
Gusset Plate
Steel Connectors
Bolted Connectors
Nail Plates or Toothed Plates
Wood Screws
23. Timber Truss -Types
King Post
Vertical Central Post that supports the
apex of the triangle formed by the top
chord.
Joints: Mortise and tenon joints are often
used at the intersection of the king post,
top chord, and bottom chord.
Connections: Gusset plates or steel
connectors may be used to secure the
joints
24. Timber Truss -Types
Queen Post Truss
Offer increased stability and load
bearing capacity compared to king
Post truss.
Joints: Mortise and tenon joints are
used at the intersection of the queen
posts, king post, top chord, and
bottom chord.
Connections: Gusset plates or steel
connectors are commonly used to
secure the joints.
25. Timber Truss -Types
Howe Truss
Form a series of triangles. Diagonal
member slope towards The center,
providing efficient Load distribution Used
for longer span And heavier load
Joints: Mortise and tenon joints at the
intersection of vertical and diagonal
members.
Connections: Gusset plates or steel
connectors secure the joints. Steel bolts
may be used to fasten the connections.
26. Timber Truss -Types
Fink Truss
W-Shaped design Good combination
of strength And simplicity
Joints: Typically use mortise and
tenon joints at the intersections of
diagonal and vertical members.
Connections: Gusset plates or steel
connectors are employed to secure
the joints.
27. Timber Truss -Types
Scissor Truss
Bottom chord that sloped upward,
creating a scissor like appearance. Offers
vaulted ceilings and an open interior
space.
Joints: Typically use mortise and tenon
joints or steel connectors where the
sloping members intersect.
Connections: Gusset plates or steel
connectors secure the joints.
28. Timber Truss -Types
Mono Truss
Bottom chord that sloped upward,
creating a scissor like appearance. Offers
vaulted ceilings and an open interior
space.
Joints: Typically use mortise and tenon
joints or steel connectors where the
sloping members intersect.
Connections: Gusset plates or steel
connectors secure the joints.
29. Timber Truss -Types
Parallel Chord Truss
Bottom chord that sloped upward,
creating a scissor like appearance. Offers
vaulted ceilings and an open interior
space.
Joints: Typically use mortise and tenon
joints or steel connectors where the
sloping members intersect.
Connections: Gusset plates or steel
connectors secure the joints.
30. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
31. Timber Flooring
Is any product manufactured from timber
that is designed for use as flooring either
structural or aesthetic.
35. Timber Flooring -Types
Solid Hard Wood
Flooring
Consist of Solid Pieces of
wood
Can be sanded and
refinished multiple times
Offers a timeless and
authentic look.
36. Timber Flooring -Types
Engineering Wood Flooring
Is composed of two or more
layers of wood in the form of a
plank.
Most commonly used globally.
Have layers of wood glued
together
37. Timber Flooring -Types
ADVANTAGE
It looks fabulous and provided
its installed correctly
It is very appealing
DISADVANTAGES
Swells in damp condition and
shrink in dry conditions.
Expensive for entry level
products
Required skilled professional
for installation
38. Timber Flooring -Types
Laminated Wooden
Flooring
Compressed fibre
board planks covered
by a photographic
image of wood, stone
or tile with a
protective overlay.
39. Timber Flooring -Types
ADVANTAGE
Relatively Cheap
Resistance to abrasion
Moisture protection
Easy and fast to lay
Perfectly interlocked using clip
system
Eco friendly and healty friendy
DISADVANTAGES
Swallen by moisture
Joints wear over time, and
once the surface is damaged it
is hard to fix
40. Timber Flooring -Types
Bamboo Flooring
Grow very rapidly
and its physical
properties similar to
true hard wood
Used mostly in
commercial area.
41. Timber Flooring - Installation
Glue less / Floating
Have tongue and lock edges
that interlock, conjoining to
form a tight bond.
42. Timber Flooring - Installation
Glue
Glued together with the help
of adhesive.
43. Timber Flooring - Installation
Nail Down
Nailing down
hardwood floor is the
most common
installation method.
Nail are nearly visible.
44. Timber Structure
Design of timber with various components, their structural functions
Types of beams, columns and foundation, including joints and connection
Types of timber roof trusses with joints and connections
Timber Floors
Design of simple timber trusses, timber beams, and timber columns
49. Design
Modification factors for permissible stresses.
i) For change in slope of grain.
When the timber has major defects
like slope of grains, knots, and checks or shakes (but not beyond permissible
value), the permissible stresses given in Table 13.4 are multiplied by the
modification factors K
1 for different slopes of grain as given in Table 13.5 as per
IS : 883 –1994.
52. Design
Bearing stress in timber
The bearing stress or compressive stress on a surface depends
upon the inclination of surface with the direction of grain, bearing
length, and distance from the end of a structural member.
54. Design
Q. The safe working stress in compression of a standard
timber (dhaman) for inside location, parallel to the grain is 12
N/mm2 and that perpendicular to the grain is 6 N/mm2.
Determine the safe working stress for this timber, if the timber
is of selected grade and if the timber is of common
grade (i.e., grade II).
55. Design
For standard grade. The safe working stress in compression parallel to the grain is 12
N/mm2. The safe working stress in compression perpendicular to the grain is 6 N/mm2.
For selected grade. The safe working stress in compression parallel to the grain
(1.16 × 12) = 13.92 N/mm2
The safe working stress in compression perpendicular to the grain
(1.16 × 12) = 6.96 N/mm2
For common grade. The safe working stress in compression parallel to the grain
(0.84 × 12) = 10.08 N/mm2
The safe working stress in compression perpendicular to the grain
(0.84 × 6) = 5.04 N/mm2.
56. Design - Column
The columns are defined as the structural members which support load
primarily by inducing compressive stress along the grain.
i) Solid Wood Columns
These column consist of a single piece of wood. Generally have
rectangular cross section.
ii) Built up and Box Columns
Built up wooden columns consist of wooden pieces joined together
with spikes bolts, nails, screws or glue or with other mechanical
fasteners.
57. Design - Column
Slenderness Ratio (
𝑠
𝑑
): in case of solid wood, defined as the ratio of
unsupported length (effective length), s, of the column to the dimension
of least side, d.
Columns are classified into three categories
i) Short columns
𝑠
𝑑
≤ 11
ii) Intermediate columns
11 <
𝑠
𝑑
≤ 𝑘8
𝐾8 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑑𝑒𝑝𝑒𝑛𝑑 𝑢𝑝𝑜𝑛 𝐸 𝑎𝑛𝑑 𝑓𝑐𝑝
𝐾8 =
𝐸
𝑓𝑐𝑝
1
2
𝐸 = 𝑀𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝐸𝑙𝑎𝑠𝑡𝑖𝑐𝑖𝑡𝑦
𝑓𝑐𝑝 = 𝑝𝑒𝑟𝑚𝑖𝑠𝑠𝑖𝑏𝑙𝑒 𝑠𝑡𝑟𝑒𝑠𝑠 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙 𝑡𝑜 𝑔𝑟𝑎𝑖𝑛
58. Design - Column
i) Long Column
𝑠
𝑑
> 𝑘8
Permissible stress for long column is determine as follows:
𝑓𝑐 =
𝑃
𝐴
= (
0.329𝐸
𝑠
𝑑
2 )
In solid wood columns, the slenderness ratio
s/d should not exceed 50.
𝐾8 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑑𝑒𝑝𝑒𝑛𝑑 𝑢𝑝𝑜𝑛 𝐸 𝑎𝑛𝑑 𝑓𝑐𝑝
𝐾8 =
𝐸
𝑓𝑐𝑝
1
2
𝐸 = 𝑀𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝐸𝑙𝑎𝑠𝑡𝑖𝑐𝑖𝑡𝑦
𝑓𝑐𝑝 = 𝑝𝑒𝑟𝑚𝑖𝑠𝑠𝑖𝑏𝑙𝑒 𝑠𝑡𝑟𝑒𝑠𝑠 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙 𝑡𝑜 𝑔𝑟𝑎𝑖𝑛
59. Design - Column
In Built up columns,
Columns are classified into three categories
i) Short columns
𝑠
𝑑1
2
+ 𝑑2
2 1/2
≤ 8
ii) Intermediate columns
11 <
𝑠
𝑑1
2
+ 𝑑2
2 1/2
≤ 𝑘9
𝐾9 = 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡 𝑑𝑒𝑝𝑒𝑛𝑑 𝑢𝑝𝑜𝑛𝑈, 𝐸, 𝑞 𝑎𝑛𝑑 𝑓𝑐𝑝
𝐾9 =
𝜋
2
𝑈. 𝐸
5. 𝑞. 𝑓𝑐𝑝
1
2
𝐸 = 𝑀𝑜𝑑𝑢𝑙𝑢𝑠 𝑜𝑓 𝐸𝑙𝑎𝑠𝑡𝑖𝑐𝑖𝑡𝑦
𝑓𝑐𝑝 = 𝑝𝑒𝑟𝑚𝑖𝑠𝑠𝑖𝑏𝑙𝑒 𝑠𝑡𝑟𝑒𝑠𝑠 𝑝𝑎𝑟𝑎𝑙𝑙𝑒𝑙 𝑡𝑜 𝑔𝑟𝑎𝑖𝑛
𝑊ℎ𝑒𝑟𝑒,
𝑑1 = 𝑙𝑒𝑎𝑠𝑡 𝑜𝑣𝑒𝑟𝑎𝑙𝑙 𝑤𝑖𝑑𝑡ℎ 𝑜𝑓 𝑏𝑜𝑥 𝑐𝑜𝑙𝑢𝑚𝑛 𝑖𝑛 𝑚𝑚,
𝑑2 = least overall dimension of core in box column in mm.
61. Design - Column
In built up columns, permissible stresses are calculated as follows:
For short columns,
𝑓𝑠 = 𝑞. 𝑓𝑐𝑝
For intermediate columns,
𝑓𝑠 = 𝑞. 𝑓𝑐𝑝[1 −
1
3
𝑠
𝐾9 𝑑1
2
+ 𝑑2
2 1/2
4
]
For long columns
𝑓𝑐 =
0.329 𝑈. 𝐸
𝑠
𝑑1
2
+ 𝑑2
2 1/2
2
62. Design - Column
Spaced Columns:
The spaced columns consist of two or more
wooden members with their longitudinal axes
parallel joined at their ends and at intermediate
points by block pieces.
65. Design - Column
Column Subjected to combined stress --- Both axial compression and
bending
𝑓𝑎𝑐
𝑓𝑐𝑝
+
𝑓𝑎𝑏
𝑓𝑏
< 1
66. Design Column - Steps
Step 1: Check for slenderness ratio and column type ( Short,
Intermediate, and long column)
Step 2: Determine safe working stress by appling possible modification
factor
Step 3: Determine size of safe axial load
Step 4: Suggest size or determine safe axial load.
67. Design Column -- Example
Q. A Column 150mm x 150mm is made of babul wood. The
unsupported length of column is 1.50 m. Determine safe axial load on
the column.
68. Design Column -- Example
Q. A Column 150mm x 150mm is made of babul wood. The
unsupported length of column is 1.50 m. Determine safe axial load on
the column.
Soln :
Step 1: Slenderness ratio
Unsupported length of column, s = 1.50 m
Least dimension of column, d= 150 mm
Maximum slenderness ratio
𝑠
𝑑
=
1.5 𝑥 1000
150
= 10 < 11 (𝑆ℎ𝑜𝑟𝑡 𝐶𝑜𝑙𝑢𝑚𝑛)
69. Design Column -- Example
Q. A Column 150mm x 150mm is made of babul wood. The
unsupported length of column is 1.50 m. Determine safe axial load on
the column.
Soln :
Step 2 : Safe working stress
Assuming, column is used for inside location and wood is of standard
grade. Safe working stress in compression parallel to the grain for
babul wood
𝑓𝑐𝑝 = 11.2 𝑁/𝑚𝑚2
70. Design Column -- Example
Q. A Column 150mm x 150mm is made of babul wood. The
unsupported length of column is 1.50 m. Determine safe axial load on
the column.
Soln :
Step 3: Safe axial load in column
𝑃 =
11.2 𝑥 150 𝑥 150
1000
= 252.5 𝑘𝑁
71. Design Column -- Example
Q. Design a solid timber column to carry an axial load of 60 tons if the effective length of
column is 4m. Given
Modulus of Elasticity (E) = 1.25*105 kg/cm2
Permissible compressive stress parallel to Grain 𝜎𝑐𝑝 = 102 𝑘𝑔/𝑐𝑚2
Soln:
Step 1: Slenderness ratio
Effective length of column = 4 m = 4000 mm
Assume, design column is short column, so,
𝑠
𝑑
< 11
72. Design Column -- Example
Q. Design a solid timber column to carry an axial load of 60 tons if the effective length of
column is 4m. Given
Modulus of Elasticity (E) = 1.25*105 kg/cm2
Permissible compressive stress parallel to Grain 𝜎𝑐𝑝 = 102 𝑘𝑔/𝑐𝑚2
Soln:
Step 1: Slenderness ratio
Least dimension of column = d
𝑠
𝑑
< 11
4000
𝑑
< 11
𝑑 > 363.63
73. Design Column -- Example
Q. Design a solid timber column to carry an axial load of 60 tons if the
effective length of column is 4m. Given
Modulus of Elasticity (E) = 1.25*105 kg/cm2
Permissible compressive stress parallel to Grain 𝜎𝑐𝑝 = 102 𝑘𝑔/𝑐𝑚2
Soln:
Assume d = 400 mm (Nearest multiple of 50mm)
Step 2: Safe bearing capacity of timber = 102 kg/cm2
Step 3: Check for load capacity = safe bearing capacity x Area
= 102 𝑘𝑔/𝑐𝑚2
𝑥
400
10
𝑥
400
10
𝑐𝑚2
74. Design Column -- Example
Q. Design a solid timber column to carry an axial load of 60 tons if the
effective length of column is 4m. Given
Modulus of Elasticity (E) = 1.25*105 kg/cm2
Permissible compressive stress parallel to Grain 𝜎𝑐𝑝 = 102 𝑘𝑔/𝑐𝑚2
Soln:
Step 3: Check for load capacity = safe bearing capacity x Area
= 102 𝑘𝑔/𝑐𝑚2 𝑥
400
10
𝑥
400
10
𝑐𝑚2
= 1,63,200 𝑘𝑔 = 163.20 𝑡𝑜𝑛𝑠 < 60 𝑡𝑜𝑛𝑠 (𝑂𝐾)
75. Design-- Beam
The beams are defined as the structural members which support the
load primarily by its internal resistance to bending.
The effective span of beams and other flexural
Members shall be taken as the distance from
Face of the supports plus one half of the required
Length of bearing at each end except that for
Continuous beams and joists, the span may be
Measured from center of bearing at those
Supports over which the beam is continuous.
76. Design-- Beam
Due to large load or unavailability of solid wood
Beam is formed with the combination of solid wood
Block such beam is known as built up column.
Bending stress
Form factor for bending stress
A) Rectangular section
𝐾3 = 0.81 (
𝐷2+89400
𝐷2+55000
) (D>300 mm)
B) Solid Circular cross section
𝐾5 = 1.18
77. Design-- Beam
C) Square cross sections.
For the beams of square cross-section where the load
Is in the direction of diagonal, the form factor K6 as
1.414
Minimum width of the beam or any flexural member
≥ 50 𝑚𝑚 𝑜𝑟
1
50
𝑜𝑓 𝑡ℎ𝑒 𝑠𝑝𝑎𝑛 𝑤ℎ𝑖𝑐ℎ 𝑒𝑣𝑒𝑟 𝑖𝑠 𝑔𝑟𝑒𝑎𝑡𝑒𝑟
78. Design-- Beam
All flexural member exceeding 𝑑 ≥ 3𝑤, shall be laterally
Restrained from twisting or buckling. And distance
Between such lateral restraints shall not exceed 50 times
Its width.
Check of Shear
The maximum horizontal shear stress occurs at the
Neutral axis can be obtained by
𝑓𝑠ℎ =
𝑉.𝑄
𝐼.𝑏
79. Design-- Beam
Check of Shear
The maximum horizontal shear stress occurs at the
Neutral axis can be obtained by
𝑓𝑠ℎ =
𝑉.𝑄
𝐼.𝑏
Where,
V = Vertical Shear at the Section
b = width of beam
I = moment of inertia of section
Q = Statical moment of area above the level under considerations
about neutral axis
81. Design-- Beam
For Rectangular Beam
The value of shall be calculated as
For concentrated loads,
𝑉 = (
10𝐶 𝑙−𝑥
𝑥
𝑑
2
9𝑙 2+
𝑥
𝑑
2 )
C= concentrated load
L = span of beam
X = distance from reaction to load
82. Design-- Beam
For Rectangular Beam
The value of shall be calculated as
For uniformly distributed loads,
𝑉 =
𝑊
2
(𝑙 − 2𝑑)
83. Design-- Beam
End Bearing in Beams
Bearing stress < Safe working stress in compression across the grain.
Bearing width should not be less than 75 mm when supported over masonry.
84. Design-- Beam
End Bearing in Beams
Bearing stress < Safe working stress in compression across the grain.
Bearing width should not be less than 75 mm when supported over masonry.
85. Design-- Beam
Checked for Deflection
Member supporting brittle material like gypsum ceiling
slates, tiles and asbestos sheets should not be greater than
1
360
𝑜𝑓 𝑡ℎ𝑒 𝑠𝑝𝑎𝑛.
The deflection in case of other flexural member should not
be greater than
1
240
𝑜𝑓 𝑠𝑝𝑎𝑛
For the cantilever beams, the deflection should not be
greater than
1
180
of span
86. Design-- Beam
Notched Beam
When a groove is cut either at the
ends or at the middle of span or
anywhere in between support in
the timber beams, then beams are
known as notched beams.
87. Design-- Beam
Flitched Beams
The flitched beams consist of
wooden beams and steel beams
joined together by means of bolts
or screws.
88. Design-- Beam
Design Steps:
1. Effective Span
2. Maximum bending moment
3. Section modulus required
4. Check for shear
5. Check for deflection
6. Check for bearing
89. Design– Beam -- Example
Q. A deodar timber beam carries a uniformly distributed load 16
kN/m inclusive of self weight of the beam. The beam is simply
supported at both ends. The clear span of beam is 5 m. Design the
timber beam.
Permissible stress in bending for deodar wood = 10.2 N/mm2
Permissible stress in shear for deodar wood = 0.7 N/mm2
Permissible bearing stress for deodar wood = 2.6 N/mm2
91. Design– Beam -- Example
Step 1: Effective span
Clear span of beam = 5m
Assume width of bearing at each end = 300 mm
Effective span of beam = 𝟓 +
𝟏
𝟐
𝒙𝟎. 𝟑𝟎 +
𝟏
𝟐
𝒙 𝟎. 𝟑𝟎 = 𝟓. 𝟑𝟎 𝒎
Step 2: Maximum bending moment
𝑀 =
𝑤𝑙2
8
= 16 ∗
5.302
8
= 56.18 𝑘𝑁𝑚
92. Design– Beam -- Example
Step 1: Effective span
Clear span of beam = 5m
Assume width of bearing at each end = 300 mm
Effective span of beam = 𝟓 +
𝟏
𝟐
𝒙𝟎. 𝟑𝟎 +
𝟏
𝟐
𝒙 𝟎. 𝟑𝟎 = 𝟓. 𝟑𝟎 𝒎
Step 2: Maximum bending moment
𝑀 =
𝑤𝑙2
8
= 16 ∗
5.302
8
= 56.18 𝑘𝑁𝑚
93. Design– Beam -- Example
Maximum allowable bending stress along the grain for inside
location for deodar wood of standard grade = 10.2 𝑁/𝑚𝑚2
From factor for rectangular section: K3
Assume depth of beam as 400 mm,
𝐾3 = 0.81
𝐷2
+ 89400
𝐷2 + 55000
= 0.81
4002
+ 89400
4002 + 55000
= 0.9396
Maximum allowable bending stress, (Since D>300 mm)
= 0.9396 𝑥 10.2 = 9.584 𝑁/𝑚𝑚2
96. Design– Beam -- Example
Checked for lateral support required if width is :
< 1/50 x span = 1/50 * 5.30m =106 mm
< d/3 = 400/3 = 133.33 mm
So no lateral support is required.
So, width of beam = 250 mm
Depth of beam = 400 mm
97. Design– Beam -- Example
Check for shear
Maximu shear force at the edge of the support
𝑉 =
𝑊
2
𝑙 − 2𝐷 =
16
2
5.30 − 2 ∗ 0.40 = 36 𝑘𝑁
Maximum shear stress in the beam
𝑓𝑠ℎ =
𝑉𝑄
𝐼 𝑏
100. Design– Beam -- Example
Allowable deflection
1
240
𝑥5.30 𝑥 1000 = 22.1 𝑚𝑚 > 𝑦𝑚𝑎𝑥 𝐻𝑒𝑛𝑐𝑒 𝑠𝑎𝑡𝑖𝑠𝑓𝑎𝑐𝑡𝑜𝑟𝑦.
Check for bearing
Reaction at the support
16𝑥5.30
2
= 42.40 𝑘𝑁
101. Design– Beam -- Example
Bearing stress at the support
42.40 𝑥1000
300 ∗ 250
= 0.565 𝑁/𝑚𝑚2
Safe working stress in compression perpendicular to the grain
= 2.6 𝑁/𝑚𝑚2
> 𝐵𝑒𝑎𝑟𝑖𝑛𝑔 𝑠𝑡𝑟𝑒𝑠𝑠. 𝐻𝑒𝑛𝑐𝑒 𝑠𝑎𝑡𝑖𝑠𝑓𝑎𝑐𝑡𝑜𝑟𝑦.
Provide a rectangular beam 250mm x 400 mm
102. Design– Beam -- Example
Q. A deodar beam is simply supported on a clear span of 6 m. It
carries the dead load of 8 kN/m and live load of 7kN/m. The bearing
at each end is 10 cm. Design the beam and carryout necessary
checks.
Permissible stress in bending for deodar wood = 10 N/mm2
Permissible stress in shear for deodar wood = 0.7 N/mm2
Permissible bearing stress for deodar wood = 7.5 N/mm2
