Timber Structure.pdf
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Jan 13, 2024
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About This Presentation
structure 3
Slide Content
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
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
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
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
Timber Structure
Used as Structural elements to Ensure:
Stability
Strength
Safety
Used as Structural elements to Ensure:
Stability
Strength
Safety
Components
Beams
Carry load primary by
bending.
Size, Shape and material
properties
Design to resist bending
moments and shear
forces.
Beams
Carry load primary by
bending.
Size, Shape and material
properties
Design to resist bending
moments and shear
forces.
Components
Columns
Transfer vertical loads
and transfer by axial
action.
Column dimensions,
material properties,
connection.
Columns
Transfer vertical loads
and transfer by axial
action.
Column dimensions,
material properties,
connection.
Components
Trusses
Supports load along the
span of a structure.
To resist tension and
compression forces, and
connections.
Trusses
Supports load along the
span of a structure.
To resist tension and
compression forces, and
connections.
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
Roof Systems
Protect the structure from
environmental elements.
Provided skeleton for
sheeting material
Design to withstand wind,
snow, and other loads,
Detailing is crucial
Components
Foundation
Transfer load from
structure to ground.
Foundation
Transfer load from
structure to ground.
Components
Bracing
Provide lateral stability
Design to withstand
tension, compression and
integrity to the structure
and connection
Bracing
Provide lateral stability
Design to withstand
tension, compression and
integrity to the structure
and connection
Components
Floor Systems
Stable platform for
occupants and support live
loads.
Design considerations
Jointst, beams, subfloor
material etc.
Meet strength and
deflection criteria.
Floor Systems
Stable platform for
occupants and support live
loads.
Design considerations
Jointst, beams, subfloor
material etc.
Meet strength and
deflection criteria.
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
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
Beams
The structural
member which
primarily supports
load by its internal
resistance to
bending.
The structural
member which
primarily supports
load by its internal
resistance to
bending.
Beams
Simply Supported Beam
Cantilever Beam
Continuous Beam
Tie Beam
Composite Beam
Simply Supported Beam
Cantilever Beam
Continuous Beam
Tie Beam
Composite Beam
Columns
Vertical members.
Which resist load
by axial action.
Vertical members.
Which resist load
by axial action.
Columns
Axially Loaded columns
Eccentrically Loaded Columns
Short Columns
Slender Columns
Tied Columns
Axially Loaded columns
Eccentrically Loaded Columns
Short Columns
Slender Columns
Tied Columns
Foundations
Shallow Foundations
Deep Foundations
Mat Foundations
Raft Foundations
Shallow Foundations
Deep Foundations
Mat Foundations
Raft Foundations
Joints and Connections
Bolted connection
Welded connection
Riveted connection
Pinned connection
Moment resisting connections
Dowel Joints
Mortise and Tenon Joints
Bolted connection
Welded connection
Riveted connection
Pinned connection
Moment resisting connections
Dowel Joints
Mortise and Tenon Joints
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
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
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
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
Timber Truss
Components of Truss
1. Top Chord
2. Bottom Chord
3. Web Members
4. King Posts
5. Queen Posts
Components of Truss
1. Top Chord
2. Bottom Chord
3. Web Members
4. King Posts
5. Queen Posts
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
Mortise and Tenon Joints
Half Lap Joint
Scarf Joint
Dovetail Joint
Gusset Plate
Steel Connectors
Bolted Connectors
Nail Plates or Toothed Plates
Wood Screws
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
Mortise and Tenon Joints
Half Lap Joint
Scarf Joint
Dovetail Joint
Gusset Plate
Steel Connectors
Bolted Connectors
Nail Plates or Toothed Plates
Wood Screws
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
Timber Flooring
Is any product manufactured from timber
that is designed for use as flooring either
structural or aesthetic.
Is any product manufactured from timber
that is designed for use as flooring either
structural or aesthetic.
Timber Flooring
Environment profile, durability, and
restorability
Available in many styles, colours, cuts and
species
Environment profile, durability, and
restorability
Available in many styles, colours, cuts and
species
Why Timber Flooring?
➢Durable
➢Easy to clean
➢Easy to resurface
➢Soft for foots
➢Aesthetically appealing
➢Low maintenance
➢Soft for falling objects
➢Durable
➢Easy to clean
➢Easy to resurface
➢Soft for foots
➢Aesthetically appealing
➢Low maintenance
➢Soft for falling objects
Timber Flooring -Types
Solid Hard Wood Flooring
Engineering Wooden Flooring
Laminated Wooden Flooring
Solid Hard Wood Flooring
Engineering Wooden Flooring
Laminated Wooden Flooring
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.
Solid Hard Wood
Flooring
Consist of Solid Pieces of
wood
Can be sanded and
refinished multiple times
Offers a timeless and
authentic look.
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
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
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
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
Timber Flooring -Types
Laminated Wooden
Flooring
Compressed fibre
board planks covered
by a photographic
image of wood, stone
or tile with a
protective overlay.
Laminated Wooden
Flooring
Compressed fibre
board planks covered
by a photographic
image of wood, stone
or tile with a
protective overlay.
Timber Flooring -Types
ADVANTAGE
Relatively Cheap
Resistance to abrasion
Moisture protection
Easy and fast to lay
Perfectly interlocked using clip
system
Eco friendly and healtyfriendy
DISADVANTAGES
Swallenby moisture
Joints wear over time, and
once the surface is damaged it
is hard to fix
ADVANTAGE
Relatively Cheap
Resistance to abrasion
Moisture protection
Easy and fast to lay
Perfectly interlocked using clip
system
Eco friendly and healtyfriendy
DISADVANTAGES
Swallenby moisture
Joints wear over time, and
once the surface is damaged it
is hard to fix
Timber Flooring -Types
Bamboo Flooring
Grow very rapidly
and its physical
properties similar to
true hard wood
Used mostly in
commercial area.
Bamboo Flooring
Grow very rapidly
and its physical
properties similar to
true hard wood
Used mostly in
commercial area.
Timber Flooring -Installation
Glue less / Floating
Have tongue and lock edges
that interlock, conjoining to
form a tight bond.
Glue less / Floating
Have tongue and lock edges
that interlock, conjoining to
form a tight bond.
Timber Flooring -Installation
Glue
Glued together with the help
of adhesive.
Glue
Glued together with the help
of adhesive.
Timber Flooring -Installation
Nail Down
Nailing down
hardwood floor is the
most common
installation method.
Nail are nearly visible.
Nail Down
Nailing down
hardwood floor is the
most common
installation method.
Nail are nearly visible.
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
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
Design
Factor of Safety:
Depends upon strength of timber, effect of moisture,
the presence and location of structure.
Factor of Safety:
Depends upon strength of timber, effect of moisture,
the presence and location of structure.
Design
Working stress:
Working stress:
Design
Permissible Stress:
Permissible stress refers tothe maximum stress that a material can
withstand without undergoing excessivedeformation or failure.
Permissible Stress:
Permissible stress refers tothe maximum stress that a material can
withstand without undergoing excessivedeformation or failure.
Design
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.
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.
Design
Modification factors for permissible stresses.
i)For change in slope of grain.
Modification factors for permissible stresses.
i)For change in slope of grain.
Design
Modification factors for permissible stresses.
i)For change in the duration of load
Modification factors for permissible stresses.
i)For change in the duration of load
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.
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.
Design
Bearing stress in timber
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Bearing stress in timber
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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).
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).
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.
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.
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.
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.
Design -Column
Slenderness Ratio (
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�
): 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
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≤11
ii)Intermediate columns
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Slenderness Ratio (
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): 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
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≤11
ii)Intermediate columns
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Design -Column
i)Long Column
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Permissible stress for long column is determine as follows:
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=(
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)
In solid wood columns, the slenderness ratio
s/d should not exceed 50.
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i)Long Column
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Permissible stress for long column is determine as follows:
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�=
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=(
0.329�
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2
)
In solid wood columns, the slenderness ratio
s/d should not exceed 50.
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Design -Column
In Built up columns,
Columns are classified into three categories
i)Short columns
�
�
1
2
+�
2
21/2
≤8
ii)Intermediate columns
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1
2
+�
2
21/2
≤�
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2 = least overall dimension of core in box column in mm.
In Built up columns,
Columns are classified into three categories
i)Short columns
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2
21/2
≤8
ii)Intermediate columns
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�=������� �� �����??????�??????��
�
�??????=����??????��??????��� ������ �������� �� ���??????�
�ℎ���,
�
1=����� ������� �??????��ℎ �� ��� ������ ??????� ��,
�
2 = least overall dimension of core in box column in mm.
Design -Column
In Built up columns,
i)Long Column
�
�
1
2
+�
2
21/2
>�
9
??????
9=�������� ������ �����,�,� ��� �
�??????
??????
9=
??????
2
�.�
5.�.�
�??????
1
2
�=������� �� �����??????�??????��
�
�??????=����??????��??????��� ������ �������� �� ���??????�
In Built up columns,
i)Long Column
�
�
1
2
+�
2
21/2
>�
9
??????
9=�������� ������ �����,�,� ��� �
�??????
??????
9=
??????
2
�.�
5.�.�
�??????
1
2
�=������� �� �����??????�??????��
�
�??????=����??????��??????��� ������ �������� �� ���??????�
Design -Column
In built up columns, permissible stresses are calculated as follows:
For short columns,
�
??????=�.�
�??????
For intermediate columns,
�
??????=�.�
�??????[1−
1
3
�
??????
9�
1
2
+�
2
21/2
4
]
For long columns
�
�=
0.329 �.�
�
�
1
2
+�
2
21/2
2
In built up columns, permissible stresses are calculated as follows:
For short columns,
�
??????=�.�
�??????
For intermediate columns,
�
??????=�.�
�??????[1−
1
3
�
??????
9�
1
2
+�
2
21/2
4
]
For long columns
�
�=
0.329 �.�
�
�
1
2
+�
2
21/2
2
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.
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.
Design -Column
Design -Column
Design -Column
Column Subjected to combined stress --- Both axial compression and
bending
�
��
�
�??????
+
�
��
�
�
<1
Column Subjected to combined stress --- Both axial compression and
bending
�
��
�
�??????
+
�
��
�
�
<1
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.
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.
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.
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.
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.
Sol
n
:
Step 1: Slenderness ratio
Unsupported length of column, s = 1.50 m
Least dimension of column, d= 150 mm
Maximum slenderness ratio
??????
�
=
1.5 � 1000
150
=10<11 (�ℎ��� ������)
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.
Sol
n
:
Step 1: Slenderness ratio
Unsupported length of column, s = 1.50 m
Least dimension of column, d= 150 mm
Maximum slenderness ratio
??????
�
=
1.5 � 1000
150
=10<11 (�ℎ��� ������)
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.
Sol
n
:
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
�
�??????=11.2 �/��
2
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.
Sol
n
:
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
�
�??????=11.2 �/��
2
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.
Sol
n
:
Step 3: Safe axial load in column
�=
11.2 � 150 � 150
1000
=252.5 ��
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.
Sol
n
:
Step 3: Safe axial load in column
�=
11.2 � 150 � 150
1000
=252.5 ��
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 1: Slenderness ratio
Effective length of column = 4 m = 4000 mm
Assume, design column is short column, so,
�
�
<11
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 1: Slenderness ratio
Effective length of column = 4 m = 4000 mm
Assume, design column is short column, so,
�
�
<11
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 1: Slenderness ratio
Least dimension of column = d
�
�
<11
4000
�
<11
�>363.63
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 1: Slenderness ratio
Least dimension of column = d
�
�
<11
4000
�
<11
�>363.63
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Assume d = 400 mm (Nearest multiple of 50mm)
Step 2: Safe bearing capacity of timber = 102 kg/cm
2
Step 3: Check for load capacity = safe bearing capacity x Area
=102 ��/��
2
�
400
10
�
400
10
��
2
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Assume d = 400 mm (Nearest multiple of 50mm)
Step 2: Safe bearing capacity of timber = 102 kg/cm
2
Step 3: Check for load capacity = safe bearing capacity x Area
=102 ��/��
2
�
400
10
�
400
10
��
2
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 3: Check for load capacity = safe bearing capacity x Area
=102 ��/��
2
�
400
10
�
400
10
��
2
=1,63,200 ��=163.20 ����<60 ���� (�??????)
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*10
5
kg/cm
2
Permissible compressive stress parallel to Grain ??????
�??????=102 ��/��
2
Sol
n
:
Step 3: Check for load capacity = safe bearing capacity x Area
=102 ��/��
2
�
400
10
�
400
10
��
2
=1,63,200 ��=163.20 ����<60 ���� (�??????)
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.
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.
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
??????
3=0.81 (
�
2
+89400
�
2
+55000
) (D>300 mm)
B) Solid Circular cross section
??????
5=1.18
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
??????
3=0.81 (
�
2
+89400
�
2
+55000
) (D>300 mm)
B) Solid Circular cross section
??????
5=1.18
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 K
6 as
1.414
Minimum width of the beam or any flexural member
≥50 �� ��
1
50
�� �ℎ� ���� �ℎ??????�ℎ ���� ??????� �������
C) Square cross sections.
For the beams of square cross-section where the load
Is in the direction of diagonal, the form factor K
6 as
1.414
Minimum width of the beam or any flexural member
≥50 �� ��
1
50
�� �ℎ� ���� �ℎ??????�ℎ ���� ??????� �������
Design--Beam
All flexural member exceeding �≥3�, 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
�
??????ℎ=
�.??????
??????.�
All flexural member exceeding �≥3�, 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
�
??????ℎ=
�.??????
??????.�
Design--Beam
Check of Shear
The maximum horizontal shear stress occurs at the
Neutral axis can be obtained by
�
??????ℎ=
�.??????
??????.�
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
Check of Shear
The maximum horizontal shear stress occurs at the
Neutral axis can be obtained by
�
??????ℎ=
�.??????
??????.�
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
Design--Beam
For Rectangular Beam,
I =
��
3
12
b =b
Q =�.
�
2
.
�
4
=
�.�
2
8
�
??????ℎ=
�.
????????????
2
8
????????????
3
12
.�
=
3
2
.
�
�.�
For Rectangular Beam,
I =
��
3
12
b =b
Q =�.
�
2
.
�
4
=
�.�
2
8
�
??????ℎ=
�.
????????????
2
8
????????????
3
12
.�
=
3
2
.
�
�.�
Design--Beam
For Rectangular Beam
The value of shall be calculated as
For concentrated loads,
�=(
10��−�
??????
??????
2
9�2+
??????
??????
2)
C= concentrated load
L = span of beam
X = distance from reaction to load
For Rectangular Beam
The value of shall be calculated as
For concentrated loads,
�=(
10��−�
??????
??????
2
9�2+
??????
??????
2)
C= concentrated load
L = span of beam
X = distance from reaction to load
Design--Beam
For Rectangular Beam
The value of shall be calculated as
For uniformly distributed loads,
�=
�
2
(�−2�)
For Rectangular Beam
The value of shall be calculated as
For uniformly distributed loads,
�=
�
2
(�−2�)
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.
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.
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.
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.
Design--Beam
Checked for Deflection
Member supporting brittle material like gypsum ceiling
slates, tiles and asbestos sheets should not be greater than
1
360
�� �ℎ� ����.
The deflection in case of other flexural member should not
be greater than
1
240
�� ����
For the cantilever beams, the deflection should not be
greater than
1
180
of span
Checked for Deflection
Member supporting brittle material like gypsum ceiling
slates, tiles and asbestos sheets should not be greater than
1
360
�� �ℎ� ����.
The deflection in case of other flexural member should not
be greater than
1
240
�� ����
For the cantilever beams, the deflection should not be
greater than
1
180
of span
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.
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.
Design--Beam
Flitched Beams
The flitched beams consist of
wooden beams and steel beams
joined together by means of bolts
or screws.
Flitched Beams
The flitched beams consist of
wooden beams and steel beams
joined together by means of bolts
or screws.
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
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
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/mm
2
Permissible stress in shear for deodar wood = 0.7 N/mm
2
Permissible bearing stress for deodar wood = 2.6 N/mm
2
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/mm
2
Permissible stress in shear for deodar wood = 0.7 N/mm
2
Permissible bearing stress for deodar wood = 2.6 N/mm
2
Design–Beam --Example
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 = ??????+
�
�
??????�.��+
�
�
?????? �.��=??????.�� ??????
Step 2: Maximum bending moment
�=
��
2
8
=16∗
5.30
2
8
=56.18 ���
Step 1: Effective span
Clear span of beam = 5m
Assume width of bearing at each end = 300 mm
Effective span of beam = ??????+
�
�
??????�.��+
�
�
?????? �.��=??????.�� ??????
Step 2: Maximum bending moment
�=
��
2
8
=16∗
5.30
2
8
=56.18 ���
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 = ??????+
�
�
??????�.��+
�
�
?????? �.��=??????.�� ??????
Step 2: Maximum bending moment
�=
��
2
8
=16∗
5.30
2
8
=56.18 ���
Step 1: Effective span
Clear span of beam = 5m
Assume width of bearing at each end = 300 mm
Effective span of beam = ??????+
�
�
??????�.��+
�
�
?????? �.��=??????.�� ??????
Step 2: Maximum bending moment
�=
��
2
8
=16∗
5.30
2
8
=56.18 ���
Design–Beam --Example
Maximum allowable bending stress along the grain for inside
location for deodar wood of standard grade =10.2 �/��
2
From factor for rectangular section: K
3
Assume depth of beam as 400 mm,
??????
3=0.81
�
2
+89400
�
2
+55000
=0.81
400
2
+89400
400
2
+55000
=0.9396
Maximum allowable bending stress, (Since D>300 mm)
=0.9396 � 10.2=9.584 �/��
2
Maximum allowable bending stress along the grain for inside
location for deodar wood of standard grade =10.2 �/��
2
From factor for rectangular section: K
3
Assume depth of beam as 400 mm,
??????
3=0.81
�
2
+89400
�
2
+55000
=0.81
400
2
+89400
400
2
+55000
=0.9396
Maximum allowable bending stress, (Since D>300 mm)
=0.9396 � 10.2=9.584 �/��
2
Design–Beam --Example
Section modulus required to resist Bending moments
Flexural theory:
�
�
=
�
�
=
�
�
�
�
=
�
�
�
�
=
�
�
=
56.18�1000�1000
9.584
=5861853
Section modulus required to resist Bending moments
Flexural theory:
�
�
=
�
�
=
�
�
�
�
=
�
�
�
�
=
�
�
=
56.18�1000�1000
9.584
=5861853
Design–Beam --Example
Section modulus required to resist Bending moments
Flexural theory:
�
�
=
1
12
�.�
3
1
2
.�
=
1
6
.� .�
2
=5861853
1
6
.� .400
2
=5861853
�=219.82 ��
Adopt b = 250 mm
Section modulus required to resist Bending moments
Flexural theory:
�
�
=
1
12
�.�
3
1
2
.�
=
1
6
.� .�
2
=5861853
1
6
.� .400
2
=5861853
�=219.82 ��
Adopt b = 250 mm
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
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
Design–Beam --Example
Check for shear
Maximu shear force at the edge of the support
�=
�
2
�−2�=
16
2
5.30−2∗0.40=36 ��
Maximum shear stress in the beam
�
??????ℎ=
��
� �
Check for shear
Maximu shear force at the edge of the support
�=
�
2
�−2�=
16
2
5.30−2∗0.40=36 ��
Maximum shear stress in the beam
�
??????ℎ=
��
� �
Design–Beam --Example
Check for shear
�=
1
12
��
3
=
1
12
�250�400
3
=1.33 �10
9
��
4
�=
1
8
��
2
=
1
8
�250�400
2
=5 �10
6
��
3
Maximum shear stress in the beam
�
??????ℎ=
36 � 1000 � � 5 � 10
6
��
3
1.33 � 10
9
��
4
� 250 ��
=0541 �/��
2
Check for shear
�=
1
12
��
3
=
1
12
�250�400
3
=1.33 �10
9
��
4
�=
1
8
��
2
=
1
8
�250�400
2
=5 �10
6
��
3
Maximum shear stress in the beam
�
??????ℎ=
36 � 1000 � � 5 � 10
6
��
3
1.33 � 10
9
��
4
� 250 ��
=0541 �/��
2
Design–Beam --Example
Check for Deflection:
Maximum deflection
�
���=
5
384
��
3
��
5
384
16∗5.30∗1000∗5300
3
9.5�1000 �
1
12
� 250 � 400
3
12.97 ��
Check for Deflection:
Maximum deflection
�
���=
5
384
��
3
��
5
384
16∗5.30∗1000∗5300
3
9.5�1000 �
1
12
� 250 � 400
3
12.97 ��
Design–Beam --Example
Allowable deflection
1
240
�5.30 � 1000=22.1 ��>�
��� ����� ���??????��������.
Check for bearing
Reaction at the support
16�5.30
2
=42.40 ��
Allowable deflection
1
240
�5.30 � 1000=22.1 ��>�
��� ����� ���??????��������.
Check for bearing
Reaction at the support
16�5.30
2
=42.40 ��
Design–Beam --Example
Bearing stress at the support
42.40 �1000
300∗250
=0.565 �/��
2
Safe working stress in compression perpendicular to the grain
=2.6 �/��
2
>����??????�� ������.����� ���??????��������.
Provide a rectangular beam 250mm x 400 mm
Bearing stress at the support
42.40 �1000
300∗250
=0.565 �/��
2
Safe working stress in compression perpendicular to the grain
=2.6 �/��
2
>����??????�� ������.����� ���??????��������.
Provide a rectangular beam 250mm x 400 mm
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/mm
2
Permissible stress in shear for deodar wood = 0.7 N/mm
2
Permissible bearing stress for deodar wood = 7.5 N/mm
2
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/mm
2
Permissible stress in shear for deodar wood = 0.7 N/mm
2
Permissible bearing stress for deodar wood = 7.5 N/mm
2
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