AS 1720.1-1997

1 - AS 1720.1-1997 TIMBER STRUCTURES - DESIGN METHODS
4 - PREFACE
5 - CONTENTS
7 - SECTION 1 SCOPE AND GENERAL
7 - 1.1 SCOPE AND APPLICATION
7 - 1.1.1 Scope
7 - 1.1.2 Application
7 - 1.2 REFERENCED DOCUMENTS
7 - 1.3 NEW MATERIALS AND METHODS
8 - 1.4 TIMBER
8 - 1.4.1 General
8 - 1.4.2 Identification
8 - 1.4.3 Change of grade
8 - 1.4.4 Special provisions
9 - 1.4.5 Treated timber
9 - 1.5 GENERAL DESIGN CONSIDERATIONS
9 - 1.5.1 Loads
9 - 1.5.2 Design methods
10 - 1.5.3 Timber dimensions for engineering calculations
10 - 1.5.4 Other design considerations
12 - 1.6 DESIGN AND SUPERVISION
12 - 1.6.1 Design
12 - 1.6.2 Design information
12 - 1.6.3 Design details
12 - 1.6.4 Supervision
12 - 1.7 WORKMANSHIP AND MAINTENANCE
12 - 1.7.1 General
13 - 1.7.2 Moisture content
13 - 1.7.3 Corrosion
13 - 1.7.4 Shop drawings
13 - 1.7.5 Fabrication and erection
13 - 1.7.6 Maintenance
13 - 1.8 DEFINITIONS
13 - 1.8.1 Administrative definitions
14 - 1.8.2 Technical definitions
17 - 1.9 NOTATION
17 - 1.10 UNITS
18 - SECTION 2 DESIGN PROPERTIES OF STRUCTURAL TIMBER ELEMENTS
18 - 2.1 GENERAL
18 - 2.1.1 General procedure
18 - 2.1.2 Member design capacity
18 - 2.1.3 Member stiffness
18 - 2.2 DESIGN PROPERTIES
18 - 2.2.1 General
19 - 2.2.2 Properties
24 - 2.3 CAPACITY FACTOR
28 - 2.4 MODIFICATION FACTORS
28 - 2.4.1 Duration of load
31 - 2.4.2 Moisture condition
31 - 2.4.3 Temperature
31 - 2.4.4 Length and position of bearing
32 - 2.4.5 Strength sharing between parallel members
34 - 2.4.6 Size factor
35 - 2.4.7 Stability factor
36 - SECTION 3 DESIGN CAPACITY OF BASIC STRUCTURAL MEMBERS
36 - 3.1 GENERAL
36 - 3.2 BEAM DESIGN
36 - 3.2.1 Bending strength
37 - 3.2.2 Effective span
37 - 3.2.3 Slenderness coefficient for lateral buckling under bending
40 - 3.2.4 Stability factor
42 - 3.2.5 Flexural shear strength
42 - 3.2.6 Bearing strength
44 - 3.2.7 Strength of notched beams
44 - 3.2.8 Concentrated loads and partial area loads on grid systems
44 - 3.3 COLUMN DESIGN
44 - 3.3.1 Compressive strength
45 - 3.3.2 Slenderness coefficient for lateral buckling under compression
47 - 3.3.3 Stability factor
48 - 3.3.4 Strength of notched columns
48 - 3.3.5 Spaced columns
48 - 3.4 TENSION MEMBER DESIGN
48 - 3.4.1 Design tensile capacity parallel to grain
48 - 3.4.2 Notched tension members
48 - 3.5 DESIGN CAPACITY IN TENSION PERPENDICULAR TO GRAIN
49 - 3.6 COMBINED BENDING AND AXIAL ACTIONS
49 - 3.6.1 Combined bending and compression
50 - 3.6.2 Combined bending and tension
51 - SECTION 4 DESIGN CAPACITY OF JOINTS IN TIMBER STRUCTURES
51 - 4.1 GENERAL
51 - 4.1.1 Scope of Section
51 - 4.1.2 Joint groups
51 - 4.1.3 Joint types
52 - 4.1.4 Timber grade
52 - 4.1.5 Tendency to split
53 - 4.1.6 Eccentric joints
53 - 4.2 DESIGN OF NAILED JOINTS
53 - 4.2.1 General
53 - 4.2.2 Characteristic capacities for nails
58 - 4.2.3 Design capacity for nailed joints
62 - 4.2.4 Spacing, edge and end distances
62 - 4.2.5 Nail length and timber thickness
62 - 4.2.6 Avoidance of splitting
62 - 4.3 DESIGN OF SCREWED JOINTS
62 - 4.3.1 General
63 - 4.3.2 Characteristic capacities for screws
65 - 4.3.3 Design capacity of screwed joints
67 - 4.3.4 Spacing, edge and end distances
67 - 4.3.5 Screw length and timber thickness
68 - 4.3.6 Preboring
68 - 4.4 DESIGN OF BOLTED JOINTS
68 - 4.4.1 General
68 - 4.4.2 Characteristic capacities for bolts
77 - 4.4.3 Design capacity for bolted connections
79 - 4.4.4 Bolt spacings, edge and end distances
81 - 4.4.5 Washers
81 - 4.4.6 Eccentric joints
82 - 4.5 DESIGN OF COACH SCREWED JOINTS
82 - 4.5.1 General
82 - 4.5.2 Characteristic capacities for coach screws
84 - 4.5.3 Design capacity of coach screwed joints
86 - 4.6 DESIGN OF SPLIT-RING FASTENER JOINTS
86 - 4.6.1 General
86 - 4.6.2 Characteristic capacities for split-ring fasteners
86 - 4.6.3 Design capacity for split-ring fastener joints
88 - 4.6.4 Spacings, edge and end distances for split-ring fasteners
89 - 4.7 DESIGN OF SHEAR-PLATE FASTENER JOINTS
89 - 4.7.1 General
89 - 4.7.2 Characteristic capacities for shear-plate fasteners
89 - 4.7.3 Design capacity for joints with shear plates
89 - 4.7.4 Spacings, edge and end distances for shear-plate fasteners
91 - SECTION 5 PLYWOOD
91 - 5.1 GENERAL
91 - 5.2 DESIGN PROPERTIES
91 - 5.2.1 Characteristic strengths and elastic moduli
91 - 5.2.2 Capacity factor
92 - 5.3 MODIFICATION FACTORS
92 - 5.3.1 General
92 - 5.3.2 Duration of load
92 - 5.3.3 Moisture condition
92 - 5.3.4 Temperature
92 - 5.3.5 Plywood assembly factor
93 - 5.4 LOADING NORMAL TO THE PLANE OF THE PLYWOOD PANEL
93 - 5.4.1 General
93 - 5.4.2 Bending strength
94 - 5.4.3 Shear strength (interlamina shear)
94 - 5.4.4 Bearing strength
95 - 5.4.5 Deflection in bending
95 - 5.5 LOADING IN THE PLANE OF THE PLYWOOD PANEL
95 - 5.5.1 General
95 - 5.5.2 Bending strength
96 - 5.5.3 Shear strength
97 - 5.5.4 Tension strength
97 - 5.5.5 Compression strength
98 - 5.5.6 Combined loads
98 - 5.5.7 Deflection in bending
98 - 5.5.8 Shear deformation
98 - 5.6 JOINTS IN COMPOSITE PLYWOOD TO TIMBER CONSTRUCTION
98 - 5.6.1 Nailed and screwed joints
98 - 5.6.2 Shear strength at glued interfaces
101 - SECTION 6 ROUND TIMBERS
101 - 6.1 GENERAL
101 - 6.2 CHARACTERISTIC STRENGTHS AND ELASTIC MODULI
101 - 6.3 DESIGN
101 - 6.3.1 Bending strength
102 - 6.3.2 Shear strength
102 - 6.3.3 Compressive strength
103 - 6.3.4 Deflections
103 - 6.4 ADDITIONAL MODIFICATION FACTORS
103 - 6.4.1 Factor for immaturity
103 - 6.4.2 Shaving factor
104 - 6.5 DESIGN DETAILS
104 - 6.5.1 Effective cross°section of untreated timber
104 - 6.5.2 Moisture content of timbers in ground contact
104 - 6.5.3 Joints
105 - SECTION 7 GLUED-LAMINATED TIMBER CONSTRUCTION
105 - 7.1 GENERAL
105 - 7.2 DESIGN
105 - 7.3 DESIGN PROPERTIES
105 - 7.3.1 Characteristic strengths and elastic moduli
105 - 7.3.2 Capacity factor
106 - 7.3.3 Non-GL-grade properties
106 - 7.4 MODIFICATION FACTORS
106 - 7.4.1 General
106 - 7.4.2 Duration of load
106 - 7.4.3 Strength sharing between parallel members
106 - 7.4.4 Size factor
106 - 7.4.5 Stability factor
108 - SECTION 8 STRUCTURAL LAMINATED VENEER LUMBER
108 - 8.1 GENERAL
108 - 8.2 DESIGN
108 - 8.3 PROPERTIES
108 - 8.3.1 Characteristic strengths and elastic moduli
108 - 8.3.2 Modulus of rigidity
108 - 8.3.3 Section properties
108 - 8.3.4 Capacity factors
109 - 8.4 MODIFICATION FACTORS
109 - 8.4.1 General
109 - 8.4.2 Duration of load
109 - 8.4.3 Moisture condition
109 - 8.4.4 Temperature
109 - 8.4.5 Length and position of bearing
109 - 8.4.6 Strength sharing between parallel members
109 - 8.4.7 Size factor
110 - 8.4.8 Stability factor
110 - 8.5 JOINT DESIGN
110 - 8.5.1 General
110 - 8.5.2 Joint group
110 - 8.5.3 Characteristic fastener capacities
111 - APPENDIX A - REFERENCED DOCUMENTS
113 - APPENDIX B - GUIDELINES FOR SERVICEABILITY
113 - B1 GENERAL
113 - B2 SERVICEABILITY CONSIDERATIONS
118 - APPENDIX C - JOINTS IN TIMBER STRUCTURES
118 - C1 GENERAL
118 - C2 FASTENERS FOR PLYWOOD
118 - C2.1 General
118 - C2.2 Strength of joints with plywood
119 - C3 DEFORMATION OF JOINTS
119 - C3.1 General
119 - C3.2 Displacement of nailed and screwed joints in solid timber
120 - C3.3 Displacement of solid timber joints fabricated with bolts, split°rings and shear plates
122 - C4 EQUATIONS AND TABLES FOR CHARACTERISTIC CAPACITIES FOR BOLTS
122 - C4.1 Load Qkl
123 - C4.2 Load Qkp
124 - APPENDIX D - ACCEPTANCE TESTING OF TIMBER STRUCTURES AND ELEMENTS
124 - D1 GENERAL
124 - D1.1 Limitations of acceptance testing
124 - D1.2 Circumstances requiring tests
125 - D1.3 Information required
125 - D2 DEFINITIONS
125 - D2.1 Prototype testing
125 - D2.2 Proof testing
125 - D3 METHOD OF TESTING
125 - D3.1 General
125 - D3.2 Test load
125 - D3.3 Eccentricities
125 - D3.4 Load°deflection curve
126 - D4 PROOF TESTING
126 - D4.1 Equivalent test load
126 - D4.2 Loading
127 - D4.3 Acceptance for strength
127 - D4.4 Acceptance of deflection
127 - D5 PROTOTYPE TESTING
127 - D5.1 General
127 - D5.2 Materials
127 - D5.3 Manufacture
127 - D5.4 Equivalent test load
128 - D5.5 Test procedure
129 - D5.6 Acceptance of prototype
129 - D6 REPORT OF TESTS
130 - APPENDIX E - FURTHER DESIGN METHODS FOR MEMBERS
130 - E1 SCOPE
130 - E2 THE MATERIAL CONSTANT
132 - E3 SLENDERNESS COEFFICIENTS FOR COLUMNS
132 - E3.1 End supported columns
133 - E3.2 Continuously restrained columns
134 - E4 SPACED COLUMNS
134 - E4.1 Geometry of spaced columns
134 - E4.2 Special requirements for spaced columns
135 - E4.3 Shear between components
136 - E4.4 Design capacity
137 - E5 BEAM-COLUMN BENT ABOUT BOTH AXES
137 - E6 SLENDERNESS COEFFICIENTS FOR BEAMS
137 - E6.1 General
138 - E6.2 End°supported beams
140 - E6.3 Beams with no intermediate buckling restraints but with torsional restraints at the ends
140 - E6.4 Continuously restrained beams
141 - E7 BUCKLING RESTRAINTS
141 - E7.1 Effectiveness of buckling restraints
142 - E7.2 Notation
142 - E7.3 Columns
143 - E7.4 Beam with lateral restraints
143 - E7.5 Beam with torsional restraints
144 - E8 CONCENTRATED LOADS AND PARTIAL AREA LOADS ON GRID SYSTEMS
144 - E8.1 General
144 - E8.2 Concentrated load
146 - E8.3 Partial area load
146 - E9 NOTCHED BEAMS
147 - E10 NOTCHED COLUMNS
147 - E11 NOTCHED TENSION MEMBERS
147 - E12 SINGLE-TAPERED STRAIGHT BEAMS
147 - E12.1 Geometry
148 - E12.2 Design bending capacity of single-tapered beams
148 - E12.3 Critical section for bending
149 - E12.4 Grain orientation modification factor ktg
149 - E12.5 Taper angle factor ktb
150 - E13 DOUBLE-TAPERED, CURVED AND PITCHED-CAMBERED BEAMS
150 - E13.1 Geometry
151 - E13.2 Double-tapered, curved and pitched-cambered beams
155 - APPENDIX F - NOTATION AND FACTORS
166 - APPENDIX G - DESIGN PROPERTIES OF STRUCTURAL TIMBER
166 - G1 ADDITIONAL INFORMATION
166 - G2 EXAMPLES OF LOAD DURATION FACTORS FOR TYPICAL LOAD COMBINATIONS
167 - APPENDIX H - DESIGN WITH IN-GRADE TESTED MATERIAL
167 - H1 GENERAL
167 - H2 MGP GRADES
167 - H2.1 General
167 - H2.2 Material requirements
167 - H2.3 Design procedures
167 - H2.4 Design properties
169 - H2.5 Capacity factors
169 - H2.6 Modification factors
169 - H2.7 Structural design
170 - H3 A17 STRESS GRADE
170 - H3.1 General
170 - H3.2 Material requirements
170 - H3.3 Design procedures
170 - H3.4 Design properties
171 - H3.5 Capacity factors
172 - H3.6 Modification factors
172 - H3.7 Structural design
173 - APPENDIX I - ASSIGNMENT OF CAPACITY FACTOR (¿) TO DESIGN PROPERTIES
173 - I1 GENERAL
173 - I2 BASIS FOR ASSIGNMENT OF CAPACITY FACTOR
173 - I2.1 General
173 - ¿I2.2 Capacity factor (¿)
173 - I3 STRUCTURAL TIMBER BASED PRODUCTS
173 - I3.1 Australian Standards
173 - I3.2 Manufacturers’ specifications
175 - APPENDIX J - BUCKLING STRENGTH OF PLYWOOD DIAPHRAGMS
175 - J1 SCOPE
175 - J2 BUCKLING STRENGTH FOR DIAPHRAGMS LOADED IN°PLANE
175 - J2.1 Application
175 - J2.2 Diaphragms with lateral edges supported and subjected to uniformly loaded edge forces
178 - J2.3 Diaphragms with lateral edges free and subjected to uniformly loaded edge forces
178 - J2.4 Diaphragms subjected to concentrated edge forces
180 - J2.5 Stiffeners for beam webs
181 - J3 METHOD OF CALCULATION OF SECTION PROPERTIES
181 - J3.1 General
181 - J3.2 Definitions for use in calculation of section properties
181 - J3.3 Calculation method
183 - J4 SECTION PROPERTIES FOR STANDARD CONSTRUCTIONS

Sets out the limit state design methods to be used in the design or appraisal of structural elements comprised of timber or wood products and of structures comprised substantially of timber. Design data is provided for sawn timber, glued laminated timber, round timber, plywood, laminated veneer lumber, monitored in-grade tested material and various types of fastenings. Test methods are included for components or assemblies of unconventional design which are not readily amenable to detailed analysis. Guidelines on serviceability considerations and information on the assignment of capacity factors to timber products are also provided.

This Standard sets out limit state design methods for the structural use of timber which are based on the principles of structural mechanics and on data established by research. The Standard is intended for use in the design or appraisal of structural elements or systems comprised of timber or wood products and of structures comprised substantially of timber. To this end, the Standard provides design data for sawn timber, laminated timber, timber in pole form, plywood, laminated veneer lumber and various types of fastenings. In addition, it provides methods of test for components or assemblies of unconventional design which may not be readily amenable to detailed analysis.For ease of use, the simpler design situations are covered in the main body of the text. Related appendices, which form an integral part of the Standard, give acceptable procedures for detailed design situations.ApplicationThis Standard will be referenced in the Building Code of Australia by way of BCA Amendment 3 to be published by 1 July 1998, thereby superseding the previous edition, AS 1720.1-1988, which will be withdrawn 12 months from the date of publication of this edition.

First published as part of AS CA65-1972.
Revised and redesignated AS 1720-1975.
Revised and redesignated in part as AS 1720.1-1988.
Second edition 1997.