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GB 50005-2017 English PDF (GB50005-2017)

GB 50005-2017 English PDF (GB50005-2017)

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GB 50005-2017: Standard for design of timber structures

In order to implement the national technical and economic policies in the design of timber structures, to achieve advanced technology, safety and applicability, economic rationality, quality and environmental protection, this standard is hereby formulated. This standard applies to the design of swan & log timber structure, glued laminated-timber structure, light-wood frame construction for construction engineering.
GB 50005-2017
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
UDC
P GB 50005-2017
Standard for design of timber structures
ISSUED ON. NOVEMBER 20, 2017
IMPLEMENTED ON. AUGUST 01, 2018
Issued by. Ministry of Housing and Urban-Rural Development of PRC;
General Administration of Quality Supervision, Inspection and
Quarantine.
Table of Contents
Foreword ... 7
1 General provisions ... 10
2 Terms and symbols ... 11
2.1 Terms ... 11
2.2 Symbols ... 16
3 Materials ... 22
3.1 Timber ... 22
3.2 Steel and metal connector ... 26
4 Basic requirements ... 29
4.1 Basis of design ... 29
4.2 Seismic design ... 31
4.3 Design values and allowable deformation limits ... 34
5 Calculation for members ... 47
5.1 Axial tensile members and axial compression members ... 47
5.2 Bending members ... 51
5.3 Combined bending and axial loading members ... 57
6 Design for connections ... 60
6.1 Step joints ... 60
6.2 Dowel-type fasteners ... 63
6.3 Truss plates ... 73
7 Sawn and log timber structures ... 83
7.1 General requirements ... 83
7.2 Posts and beams ... 86
7.3 Walls ... 86
7.4 Floors and roofs ... 92
7.5 Trusses ... 95
7.6 Skylights ... 98
7.7 Bracings ... 100
8 Glued laminated timber structures ... 104
9 Light wood frame construction ... 107
9.1 General requirements ... 107
9.2 Floors and roofs ... 112
9.3 Walls ... 115
9.4 Light frame wood trusses ... 118
9.5 Design of hybrid light wood frame construction ... 122
9.6 Detailing requirements ... 124
10 Fire design ... 134
10.1 General requirements ... 134
10.2 Construction details of fire protection ... 137
11 Preservation of timber structures ... 142
11.1 General requirements ... 142
11.2 Waterproof and moisture dampproof ... 142
11.3 Biological protection ... 144
11.4 Wood preservation ... 146
Appendix A Material criteria for load-bearing timber structures ... 147 Appendix B Requirements for light wood frame constructions ... 161
Appendix C Requirements for inspection & maintenance of timber structures ... 168
Appendix D Design values of strength and modulus of elasticity for imported structural timber ... 170
Appendix E Characteristic values of strength and modulus of elasticity for structural timber ... 180
Appendix F Determination of characteristic values for manufactured structural timber ... 190
Appendix G Reference design values and calculation for cross laminated- timber ... 193
Appendix H Names of timber and main characteristics of common species in this standard ... 197
Appendix J Identification requirements, basic characteristics and main
processing properties of main imported timber ... 210
Appendix K Determination of number of fasteners and group action factor ... 227
Appendix L Specific gravities of commonly-used wood species ... 232
Appendix M Design values of strength for truss plates ... 234
Appendix N Design values of the shear strength for wood-based structural panel shear walls ... 237
Appendix P Design values of the shear strength for wood-based structural panel floors and roofs ... 240
Appendix Q Calculation method of vibration control for floor joists ... 246 Appendix R Combustibility and fire resistance rating of timber members .. 251 Explanation of wording in this standard ... 256
List of quoted standards ... 257
Standard for design of timber structures
1 General provisions
1.0.1 In order to implement the national technical and economic policies in the design of timber structures, to achieve advanced technology, safety and applicability, economic rationality, quality and environmental protection, this standard is hereby formulated.
1.0.2 This standard applies to the design of swan & log timber structure, glued laminated-timber structure, light-wood frame construction for construction engineering.
1.0.3 In addition to complying with this standard, the design of the timber structure shall also comply with the requirements of current relevant national standards.
2 Terms and symbols
2.1 Terms
2.1.1
Timber structure
A load-bearing structure made of wood-based members.
2.1.2
Log
Short-cut wood which is made through branch-removal of the felled trunk and bucking process.
2.1.3
Sawn timber
Finished or semi-finished materials which are made through bucking
process of logs, divided into plank and square timber.
2.1.4
Square timber
Sawn timber which has a right-angle sawing and a width-to-thickness ratio of less than 3, also known as square-edged timber.
2.1.5
Plank
Sawn timber which has a right-angle sawing and a width-to-thickness ratio more than or equal to 3.
2.1.6
Dimension lumber
The normalized timber which is made by processing the timber according to the specified sizes of cross-sectional width and height.
2.1.7
Structural composite lumber
also known as laminated timber or structural glulam.
2.1.14
Cross laminated timber
A timber product obtained by laminating, assembling, gluing the orthogonal laminates which have a thickness of 15 mm ~ 45 mm, also known as
orthogonal laminated timber.
2.1.15
Laminated log
A timber product obtained by gluing a sawn timber which has a thickness of more than 30 mm and number of layers of not more than 4 in the direction parallel to grain. It is commonly used in log cabins or beam-post timber structure.
2.1.16
Wood I-joist
A bending member which has an I-shaped cross-section, formed by using
the dimension lumber or structural composite lumber as flange, the wood- based structural planks as web, the structural adhesive for gluing.
2.1.17
Stud
Vertical load-bearing frame members in light wood frame structure which are arranged at regular intervals.
2.1.18
Visually stressed-graded lumber
The timber the grade of which is determined by visual inspection.
2.1.19
Machine stress-rated lumber
The timber the strength grade of which is determined based on the timber?€?s bending strength and elastic modulus which are obtained by using a
mechanical stress measuring device to carry out non-destructive test against the timber.
An architectural structure consisting of timber-frame walls, floor panels, roof systems which are made of dimension lumber, wood-based structural panels, or gypsum board.
2.1.27
Glued laminated timber structures
An architectural structure whose load-bearing members are mainly made of glued-timber, also known as glued laminated timber structure.
2.1.28
Log cabins; log house
The timber structure whose main load-bearing system is made from the well- shaped timber wall which uses the logs, square timbers, laminated log
whose cross-section is appropriately processed as the basic members,
superimpose the members in layers upwards, uses the inter-layer cross-bite connection at the intersection ends of the members.
2.1.29
CHUANDOU-style timber structure
According to the spacing of the roof purlin, erect a row of timber columns along the depth direction of a house, the purlin is directly braced by column, there is no beam between columns, which are laterally-tied by the square- column which penetrates through the column, to form a truss of timber
structure. Use DOUFANG and pike to connect every two trusses of timber
structures to form a load-bearing spatial timber-frame.
2.1.30
TAILIANG-style timber structure
In the direction of the depth of the house, brace the timber beam above the timber column; above the timber beam, use short column to brace the above layer of shortened timber beams; follow this method to superimpose several layers of gradually-shortening beams to form a truss of timber structure. The roof purline is placed at the ends of beams of each layer.
2.1.31
Post and beam with shear wall construction
In the square timber log structure, the timber structure system which mainly uses the ground-beam, beam, transverse beam and column to form a
Rf - The design value of the bearing capacity of the residual timber members after combustion at fire endurance;
Sd - The design value of the effect of action-combinations;
Sk - The design value which is used to verify the effect of the accidental combination of loads of the damaged timber members after a fire;
Tr - The design value of the tensile capacity of truss plate;
V - The design value of shear force;
Vd - The design value of the shear capacity of shear wall, floor and roof; Vr - The design value of the shear capacity of truss plate;
Wd - The design value of uplifting capacity of hex-head timber screws;
Zd - The design value of the shear capacity of each shear-plane of the dowel- type fastener;
Z - The reference design value of shear capacity;
w - The deflection of a member as calculated according to the standard
combination of load effects;
wx, Wy - The deflection as calculated according to the standard combination of load effects along the x-axis and y-axis directions of the cross-section of the member.
2.2.2 Design indicators for material properties or structure
Cr1, Cr2 - The design value of the shear-tensile composite strength of truss plate along the l1 and l2 directions;
E - The average modulus of elasticity of the timber material;
Ek - The standard modulus of elasticity of the timber material;
fck, fc - The standard value and design value of compressive strength and bearing strength of timber materials along the direction parallel to grain; fca - The design value of the bearing strength of timber materials along the direction at an angle to grain;
fc,90 - The design value of the bearing strength of timber materials along the direction perpendicular to grain;
fmk, fm - The standard value and design value of bending strength of timber Bc - The effective width of the floor, roof parallel to the loading direction; b - The cross-sectional width of the member;
bn - The effective side length of the cross-section of the variable-section compressive member;
bt - The calculated width of the cross-section of the truss plate perpendicular to the direction of the tensile force;
bv - The width of the shear plane, or the width of the shear cross-section of the truss plate parallel to the shear direction
d - The diameter of the log or dowel-type fastener;
def - The thickness of the effective carbonized layer;
e0 - The initial eccentricity of the member;
h - The height of the cross-section of the member;
hd - The effective length of the threaded portion of the hex-head screw as driven into the primary member;
hn - The height of the net cross-section of the flexural member at the incision; hw - The height of the shear wall;
I - The full-section moment of inertia of the member;
i - The radius of gyration of the cross-section of the member;
l - The length of the member;
l0 - The calculated length of the compressive member;
le - The calculated length of the flexural member;
lv - The calculated length of sheared plane;
S - The area moment of the cross-sectional area above the shear plane versus the neutral axis;
tm - The thickness of the thicker or middle members in case of single-shear connection or double-shear connection;
ts - The thickness of the thinner or edge members in case of single-shear connection or double-shear connection;
W - The full-section resistance moment of the member;
1. Welded members or connectors that directly withstand dynamic or
vibration loads;
2. Members or connectors which have an operating temperature equal to or lower than -30 ??C.
3.2.4 The steel used in the load-bearing timber structure shall have the qualification guarantee of tensile strength, elongation, yield strength, sulfur and phosphorus content. The welding member or connector shall also have the qualification guarantee of carbon content. The steel used for the tie-bar of the steel-timber truss which has a lower-chord diameter d more than 20 mm, as well as the steel for the welded load-bearing structure or important non-welded load-bearing structure shall also have the qualification guarantee for the cold- bending test.
3.2.5 The ordinary bolts selected shall comply with the provisions of the current national standard ?€?Hexagon head bolts?€? GB/T 5782 and ?€?Hexagon head bolts - Product grade C?€? GB/T 5780.
3.2.6 High-strength bolts shall comply with the provisions of the current national standard ?€?High strength bolts with large hexagon head for steel structures?€? GB/T 1228, ?€?High strength large hexagon nuts for steel structures?€? GB/T 1229, ?€?High strength plain washers for steel structures?€? GB/T 1230, ?€?Specifications of high strength bolts with large hexagon head, large hexagon nuts, plain washers for steel structures?€? GB/T 1231, ?€?Sets of torshear type high strength bolt hexagon nut and plain washer for steel structures?€? GB/T 3632.
3.2.7 Anchor bolts can be made of Q235 steel as specified in the current national standard ?€?Carbon structural steels?€? GB/T 700 or Q345 steel as
specified in ?€?High strength low alloy structural steels?€? GB/T 1591.
3.2.8 The nails shall comply with the provisions of the current national standard ?€?Steel nails?€? GB 27704.
3.2.9 Welding electrodes for steel members shall comply with the provisions of the current national standards ?€?Covered electrodes for manual metal arc welding of non-alloy and fine grain steels?€? GB/T 5117 and ?€?Hot-strength steel welding electrode?€? GB/T 5118. The model of electrode shall be compatible with the mechanical properties of the main metal.
3.2.10 Metal connectors and screws shall be subjected to anti-corrosion treatment or use stainless-steel products. Metal connectors and screws that are in direct contact with the preservative timber shall be protected from corrosion caused by preservatives.
3.2.11 For load-bearing steel members that are exposed to the outdoor
environment and have special anti-corrosion requirements or under the action interlayer displacement of timber structures shall not exceed 1/250 of the structure?€?s layer height.
4.1.11 The horizontal force of the floor of the timber structure should be distributed according to the subordinate area of the anti-lateral force member or the ratio of the representative value of the gravity load on the subordinate area. At this time, the distribution of horizontal force may not consider the torsional effect. But for the longer wall, it should be multiplied by a magnification factor of 1.05 ~ 1.10.
4.1.12 Under the action of wind load, the horizontal shear force as distributed to the edge wall of the light wood frame structure should be multiplied by the adjustment factor of 1.2.
4.1.13 Timber structures shall be reliably protected against timber decay or worm-damage. It shall ensure that it reaches the designed service life. 4.1.14 The glue for load-bearing structure must meet the requirements of the strength and durability of the binding portion. It shall ensure that the gluing strength is not lower than the tensile strength of the timber along the direction parallel to grain and the tensile strength of the timber along the direction perpendicular to grain. Meanwhile it shall meet the
requirements of environmental protection.
4.1.15 The design of steel members in timber structures shall comply with the provisions of the current national standard ?€?Code for design of steel structures?€? GB 50017.
4.2 Seismic design
4.2.1 The seismic design of timber structure buildings shall comply with the relevant provisions of the current national standard ?€?Code for seismic design of buildings?€? GB 50011.
4.2.2 For the timber structure building, it shall follow the provisions of the current national standard ?€?Standard for classification of seismic protection of building constructions?€? GB 50223 to determine its seismic fortification category and corresponding seismic fortification criteria.
4.2.3 The structural system of timber structures shall comply with the following provisions.
1. The plane layout should be simple and regular, with as less eccentricity as possible. The floor plane should be continuous, it should not have large bumps or openings.
2. For timber structures with weak layers, the shear force of the weak layer shall be multiplied by an increase factor of not less than 1.15;
3. For the light wood frame structure, when verifying the connection strength and local pressure-bearing of the roof panel and the lower structure, the lateral-force as caused by the seismic action is multiplied by the increase factor of 1.2.
4.2.14 For the non-structural members such as the retaining wall, partition wall, curtain wall, decorative veneer, auxiliary electromechanical equipment system installed on the floor and roof structure, as well as the connection with the main structure, it shall carry out seismic design. When the non-structural member is subjected to seismic verification, the seismic adjustment factor ??RE of the bearing capacity of the connector may take 1.0.
4.2.15 The design of timber structure building in the area where the seismic fortification intensity is 8 degrees and 9 degrees, it may use the shock-isolation and energy-dissipation design.
4.3 Design values and allowable deformation limits
4.3.1 The design indicators for timber such as square timber, logs,
ordinary glued laminated timbers, laminated logs shall be determined
according to the following provisions.
1. The strength grade of timber shall be selected according to the tree species selected from Table 4.3.1-1 and Table 4.3.1-2;
of the flexural member as a lateral brace;
3. When 5 < h/b < 6.5, the pressed edge is directly fixed on the densely- paved deck or directly fixed on the joist which has a spacing of not more than 610 mm;
4. When 6.5 < h/b < 7.5, the pressed edge is directly fixed on the densely- paved deck or directly fixed on the joist which has a spacing of not more than 610 mm; meanwhile the lateral diaphragm is installed between
flexural members, the interval is not more than 8 times the cross-sectional height of the flexural member;
5. When 7.5 < h/b ??? 9, there is continuous members to limit the lateral displacement of the upper and lower edges of the flexural member along
the length direction.
5.2.4 The shear capacity of the flexural members shall be verified as follows. Where.
fv - The design value of the shear strength along the direction parallel to grain of the member material (N/mm2);
V - The design value of the shear force of flexural member (N), which shall comply with the provisions of clause 5.2.5 of this standard;
I - The full-section moment of inertia of the member (mm4);
b - The sectional width of the member (mm);
S - The area moment of the cross-sectional area above the shear plane
versus the neutral axis (mm3).
5.2.5 If the load acts on the top surface of the beam, when calculating the design value of shear force V of the flexural member, it may not consider the action of all loads on the beam within the distance range from the support at the beam?€?s end to the height of the beam?€?s cross-section.
5.2.6 The design of the incision on the flexural members shall comply with the following requirements.
1. It shall minimize the stress concentration as caused by the incision. It should use the gradually-changed tape...

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