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AS 1720.1-2010


Timber structures, Part 1: Design methods

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Provides a code of practice for the design and acceptance of timber structures and elements, and includes design methods and design data appropriate for commonly encountered structural elements and materials and requirements to be met for specification of the design, installation and maintenance of timber structures.
Published: 21/06/2010
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Table of contents
Cited references
Content history
Table of contents
About this publication
1 Scope and general
1.1 Scope and application
1.1.1 Scope
1.1.2 Application
1.2 Normative references
1.3 Timber
1.3.1 General
1.3.2 Identification
1.3.3 Change of grade
1.3.4 Special provisions
1.3.5 Treated timber
1.4 General design considerations
1.4.1 Loads General Duration of load
1.4.2 Design methods General Strength limit state Stability limit state Serviceability limit state Experimentally based design
1.4.3 Timber dimensions for engineering calculations
1.4.4 Other design considerations Buckling restraints Erection and other extraneous forces Secondary stresses Shrinkage Durability
1.5 Design and supervision
1.5.1 Design
1.5.2 Design information
1.5.3 Design details
1.5.4 Supervision
1.6 Workmanship and maintenance
1.6.1 General
1.6.2 Moisture content
1.6.3 Corrosion
1.6.4 Shop drawings
1.6.5 Fabrication and erection
1.6.6 Maintenance
1.7 Definitions
1.7.1 Administrative definitions
1.7.2 Technical definitions
1.8 Notation
1.9 Units
2 Design properties of structural timber elements
2.1 General
2.1.1 General procedure
2.1.2 Member design capacity
2.1.3 Design rigidity of members
2.1.4 Design capacity of joints
2.2 Design properties
2.2.1 Characteristic values for calculating the design capacity of members
2.2.2 Characteristic values for calculating the design capacity of joints
2.3 Capacity factor
2.4 Modification factors
2.4.1 Duration of load Effect on strength Effect on deformation
2.4.2 Moisture condition General Unseasoned timber Seasoned timber
2.4.3 Temperature
2.4.4 Length and position of bearing
2.4.5 Strength sharing between parallel members General Strength-sharing structural systems Modification factor for strength sharing
2.4.6 Stability factor
3 Design capacity of basic structural members
3.1 General
3.2 Beam design
3.2.1 Bending strength Design capacity Bending about both axes
3.2.2 Effective span
3.2.3 Slenderness coefficient for lateral buckling under bending General Beams of rectangular cross-section
3.2.4 Stability factor
3.2.5 Flexural shear strength
3.2.6 Bearing capacity Design capacity in bearing perpendicular to the grain Design capacity in bearing parallel to grain Design bearing capacity at an angle to grain
3.2.7 Strength of notched beams
3.2.8 Concentrated loads and partial area loads on grid systems
3.3 Column design
3.3.1 Compressive strength Design compressive capacity parallel to grain Buckling about both axes
3.3.2 Slenderness coefficient for lateral buckling under compression General Columns of rectangular cross-section
3.3.3 Stability factor
3.3.4 Strength of notched columns
3.3.5 Spaced columns
3.4 Tension member design
3.4.1 Design tensile capacity parallel to grain
3.4.2 Design capacity in tension perpendicular to grain
3.5 Combined bending and axial actions
3.5.1 Combined bending and compression
3.5.2 Combined bending and tension
4 Design capacity of joints in timber structures
4.1 General
4.1.1 Scope of section
4.1.2 Joint groups
4.1.3 Joint types
4.1.4 Strength-reducing characteristics at joints
4.1.5 Tendency to split
4.1.6 Eccentric joints
4.2 Design of nailed joints
4.2.1 General
4.2.2 Characteristic capacities for nails General Type 1 joints Type 2 joints
4.2.3 Design capacity for nailed joints General Type 1 joint to resist direct loads Type 1 joint to resist in-plane moment Type 2 joint
4.2.4 Spacing, edge and end distances for nails
4.2.5 Nail length and timber thickness
4.2.6 Avoidance of splitting
4.3 Design of screwed joints
4.3.1 General
4.3.2 Characteristic capacities for screws General Type 1 joints Type 2 joints Maximum tensile load capacity Interpolation
4.3.3 Design capacity of screwed joints General Type 1 joint to resist direct loads Type 1 joint to resist in-plane bending moments Type 2 joint
4.3.4 Spacing, edge and end distances for screws
4.3.5 Screw length and timber thickness
4.3.6 Preboring
4.4 Design of bolted joints
4.4.1 General
4.4.2 Characteristic capacities for bolts General Characteristic capacity parallel to the grain Characteristic capacity perpendicular to grain Characteristic capacity for a bolted joint system Maximum tensile load capacity
4.4.3 Design capacity for bolted connections General Type 1 joint Type 2 joints Bolted joints with loads at an angle to the bolt axis
4.4.4 Spacings, edge and end distances for bolts General Loads parallel to grain Loads perpendicular to grain Loads acting at an angle to the grain
4.4.5 Washers
4.4.6 Eccentric joints
4.5 Design of coach screwed joints
4.5.1 General
4.5.2 Characteristic capacities for coach screws Type 1 joints Type 2 joints Maximum tensile capacity
4.5.3 Design capacity of coach screwed joints Type 1 joints Type 2 joints
4.5.4 Spacings, edge and end distances for coach screws
4.6 Design of split-ring fastener joints
4.6.1 General
4.6.2 Characteristic capacities for split-ring fasteners
4.6.3 Design capacity for split-ring fastener joints
4.6.4 Spacings, edge and end distances for split-ring fasteners
4.7 Design of shear-plate fastener joints
4.7.1 General
4.7.2 Characteristic capacities for shear-plate fasteners
4.7.3 Design capacity for joints with shear-plates
4.7.4 Spacings, edge and end distances for shear-plate fasteners
5 Plywood
5.1 General
5.2 Design properties
5.2.1 Characteristic values for structural design
5.2.2 Capacity factor
5.3 Modification factors
5.3.1 General
5.3.2 Duration of load
5.3.3 Moisture condition
5.3.4 Temperature
5.3.5 Plywood assembly factor
5.4 Loading normal to the plane of the plywood panel
5.4.1 General
5.4.2 Bending strength
5.4.3 Shear strength (interlamina shear)
5.4.4 Bearing strength
5.4.5 Deflection in bending
5.5 Loading in the plane of the plywood panel
5.5.1 General
5.5.2 Bending strength
5.5.3 Shear strength
5.5.4 Tension strength
5.5.5 Compression strength
5.5.6 Combined loads
5.5.7 Deflection in bending
5.5.8 Shear deformation
5.6 Joints in composite plywood to timber construction
5.6.1 Nailed and screwed joints
5.6.2 Shear strength at glued interfaces
6 Round timbers
6.1 General
6.2 Characteristic values for structural design
6.3 Design
6.3.1 Bending strength
6.3.2 Shear strength
6.3.3 Compressive strength
6.3.4 Deflections
6.4 Additional modification factors
6.4.1 Factor for immaturity
6.4.2 Shaving factor
6.5 Design details
6.5.1 Effective cross-section of untreated timber
6.5.2 Moisture content of timbers in ground contact
6.5.3 Joints
7 Glued-laminated timber construction
7.1 General
7.2 Structural design
7.3 Design properties
7.3.1 Characteristic values for strength and stiffness properties
7.3.2 Capacity factor
7.3.3 Non-GL-grade properties
7.4 Modification factors
7.4.1 General
7.4.2 Duration of load
7.4.3 Strength sharing between parallel members
7.4.4 Stability factor
8 Structural laminated veneer lumber
8.1 General
8.2 Structural design
8.3 Design properties
8.3.1 Characteristic values for strength properties and elastic moduli
8.3.2 Modulus of rigidity
8.3.3 Section properties
8.3.4 Capacity factors
8.4 Modification factors
8.4.1 General
8.4.2 Duration of load
8.4.3 Moisture condition
8.4.4 Temperature
8.4.5 Length and position of bearing
8.4.6 Strength sharing between parallel members
8.4.7 Stability factor
8.5 Joint design
8.5.1 General
8.5.2 Joint group
8.5.3 Characteristic fastener capacities
Appendix A
Appendix B
B1 General
B2 Serviceability considerations
Appendix C
C1 General
C2 Fasteners for plywood
C2.1 General
C2.2 Strength of joints with plywood
C2.2.1 Joint strength grouping
C2.2.2 Design capacity for laterally loaded nails and screws in plywood
C3 Deformation of joints
C3.1 General
C3.2 Displacement of nailed and screwed joints in solid timber
C3.3 Displacement of solid timber joints fabricated with bolts, split-rings and shear-plates
C3.3.1 General
C3.3.2 For loads acting parallel to the grain
C3.3.3 For loadings acting perpendicular to the grain
C4 Equations and tables for characteristic capacities for bolts
C4.1 Load Qkl
C4.2 Load Qkp
Appendix D
D1 General
D1.1 Limitations of acceptance testing
D1.2 Circumstances requiring tests
D1.3 Information required
D2 Definitions
D3 Method of testing
D3.1 General
D3.2 Test load
D3.3 Eccentricities
D3.4 Load-deflection curve
D4 Proof testing
D4.1 Equivalent test load
D4.2 Loading
D4.3 Acceptance for strength
D4.4 Acceptance of deflection
D5 Prototype testing
D5.1 General
D5.2 Materials
D5.3 Manufacture
D5.4 Equivalent test load
D5.5 Test procedure
D5.5.1 Preloads
D5.5.2 Test loading
D5.6 Acceptance of prototype
D5.6.1 For strength
D5.6.2 For deflection
D5.6.3 Acceptance of production units
D6 Report of tests
Appendix E
E1 Scope
E2 The material constant
E3 Slenderness coefficients for columns
E3.1 End supported columns
E3.2 Continuously restrained columns
E4 Spaced columns
E4.1 Geometry of spaced columns
E4.2 Special requirements for spaced columns
E4.2.1 Size of connecting pieces
E4.2.2 Bolted connections
E4.2.3 Glued connections
E4.2.4 Spacing of intermediate packing pieces and batten plates
E4.2.5 Distance between shafts
E4.2.6 Battened columns
E4.3 Shear between components
E4.3.1 Design shear force
E4.3.2 Force effects on packing pieces
E4.3.3 Force effects on batten plates
E4.4 Design capacity
E4.4.1 Slenderness coefficients
E4.4.1.1 Slenderness coefficients of individual shafts
E4.4.1.2 Slenderness coefficient of composite cross-sections
E4.4.2 Design procedure
E5 Beam-column bent about both axes
E6 Slenderness coefficients for beams
E6.1 General
E6.2 End-supported beams
E6.2.1 General
E6.2.2 Beams with intermediate buckling restraints
E6.3 Beams with no intermediate buckling restraints but with torsional restraints at the ends
E6.4 Continuously restrained beams
E7 Buckling restraints
E7.1 Effectiveness of buckling restraints
E7.2 Notation
E7.3 Columns
E7.3.1 Load capacity
E7.3.2 Force on lateral restraints
E7.4 Beam with lateral restraints
E7.4.1 Load capacity
E7.4.2 Force on lateral restraints
E7.5 Beam with torsional restraints
E7.5.1 Load capacity
E7.5.2 Torque on torsional restraints
E8 Concentrated loads and partial area loads on grid systems
E8.1 General
E8.2 Concentrated action
E8.3 Partial area load
E9 Notched beams
E10 Notched columns
E11 Notched tension members
E12 Single-tapered straight beams
E12.1 Geometry
E12.2 Design bending capacity of single-tapered beams
E12.3 Critical section for bending
E12.4 Grain orientation modification factor (ktg)
E12.5 Taper angle factor (ktb)
E13 Double-tapered, curved and pitched-cambered beams
E13.1 Geometry
E13.2 Double-tapered, curved and pitched-cambered beams
E13.2.1 Design capacity
E13.2.2 Critical section for bending
E13.2.3 Shape factor (ksh)
E13.2.4 Radius of curvature factor (kr)
E13.2.5 Volume/size factor (kv)
E13.2.6 Radial stress factor (ktp)
Appendix F
Appendix G
G1 Additional information
G2 Examples of load duration factors for typical load combinations
Appendix H
H1 General
H2 Design properties for F-grades
H2.1 General
H2.2 Characteristic values for bending and shear of beams, tension and compression and elastic moduli parallel to the grain
H2.3 Characteristic values for bearing, shear at joint details, tension perpendicular to the grain and design density
H2.4 Strength group and joint group classifications for seasoned and unseasoned, hardwood and softwood timber
H3 Design properties for MGP10, MGP12 and MGP15 and A17 stress grades
Appendix I
I1 Scope
I2 Buckling strength for diaphragms loaded in-plane
I2.1 Application
I2.2 Diaphragms with lateral edges supported and subjected to uniformly loaded edge forces
I2.2.1 Slenderness coefficient
I2.2.2 Stability factor for edge shear forces
I2.2.3 Stability factor for edge compression and edge bending moment
I2.3 Diaphragms with lateral edges free and subjected to uniformly loaded edge forces
I2.4 Diaphragms subjected to concentrated edge forces
I2.4.1 Effective width
I2.4.2 Slenderness coefficients
I2.4.3 Stability factor
I2.5 Stiffeners for beam webs
I3 Method of calculation of section properties
I3.1 General
I3.2 Definitions for use in calculation of section properties
I3.3 Calculation method
I3.3.1 Face grain parallel to the span
I3.3.2 Face grain perpendicular to the span
I4 Section properties for standard constructions
Amendment control sheet
Cited references in this standard
Carbon steels and carbon-manganese steels — Hot rolled bars and semifinished products
Structural design actions, Part 0: General principles
Steel Structures
[Pending Revision]
Timber — Heavy structural products — Visually graded, Part 11: Utility poles
ISO metric hexagon bolts and screws — Product grade C, Part 1: Bolts
Content history