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GB 50005-2017: PDF in English
GB 50005-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S 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 γRE 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 tapered incision; it should not use the
right-angled incision;
Where.
[w] - The deflection limit of the flexural member (mm), which shall be used
according to the provisions of Table 4.3.15 of this standard;
w - The deflection of the member as calculated by the standard combination
of load effects (mm).
5.2.10 The bidirectional flexural members shall be verified according to the
following provisions.
1. When verified according to the bearing capacity, it shall be verified as
follows.
2. When verified according to the deflection, it shall be verified as follows.
Where.
Mx, My - The design value of the bending moment as generated relative to
the x-axis and y-axis of the member’s cross-section (N • mm);
fmx, fmy - The design value of the bending strength of the member in forward
bending or lateral bending (N/mm2);
Wnx, Wny - The resistance moment of the net cross-section of the member’s
cross-section along the x-axis and y-axis (mm3);
wx, wy - The deflection for the x-axis and y-axis direction of the cross-section
of the member as calculated on the standard combination of load effects
(mm).
5.3 Combined bending and axial loading members
5.3.1 The bearing capacity of the tension-flexural members shall be verified as
follows.
Where.
N, M - Design value of axial tensile force (N), design value of bending
4. The tooth’s depth of the step joint shall not be less than 20 mm for square
timber and shall not be less than 30 mm for logs.
5. The tooth’s depth at the seat’s node of the truss shall be not more than
h/3, the tooth’s depth of the intermediate node shall be not more than h/4,
where h is the member’s cross-section height along the depth direction of
tooth.
6. In the double-tooth connection, the depth hc of the second tooth shall be
at least 20 mm larger than the depth hc1 of the first tooth. The length of the
sheared plane of the single tooth and the first tooth of double tooth shall
not be less than 4.5 times the tooth’s depth.
7. When it can only be made by wet materials due to restrictions of conditions,
the length of the sheared plane of the step joint at the seat’s node of timber
truss shall be 50 mm longer than the calculated value.
6.1.2 Single-tooth connections shall be verified according to the following
provisions.
1. When the timber is compressed, it shall be verified as follows.
Where.
fcα - The design value of the compressive strength along the direction at an
angle to grain of timber (N/mm2), which shall be determined according to the
provisions of clause 4.3.3 of this standard;
N - The design value of axial pressure which acts on the tooth’s surface (N);
Ac - The area of the compressive plane of tooth, (mm2).
2. When the timber is sheared, it shall be verified as follows.
Where.
fv - The design value of the shear strength along the direction parallel to grain
of the timber (N/mm2);
V - The design value of shear force acting on the shear plane (N);
lv - The calculated length of the shear plane (mm), which shall not be more
than 8 times the tooth’s depth hc;
of the lower-chord.
6.1.5 The setting and verification of the shear bolts shall comply with the
following requirements.
1. The shear bolt shall be perpendicular to the axis of the upper-chord.
2. The shear bolts shall be subjected to the tensile verification of the net
cross-section according to the provisions of clause 4.1.15 of this standard,
the axial tension shall be determined by the following formula.
Where.
Nb - The axial tension of the shear bolt (N);
N - The design value of the axial pressure of upper-chord (N);
α - The angle between the upper-chord and lower-chord (°).
3. The design value of strength of the shear bolt shall be multiplied by an
adjustment factor of 1.25.
4. The double-tooth connections should use two shear bolts of the same
diameter, but the adjustment factors as specified in 7.1.12 of this standard
are not considered.
6.2 Dowel-type fasteners
6.2.1 The minimum size of the end pitch, margin, spacing and line spacing of
the dowel-type fasteners shall comply with the requirements of Table 6.2.1.
When using bolts, pins or hexagonal timber screws as fasteners, the diameter
shall not be less than 6 mm.
α - The angle between the load and the direction of grain.
4. When d < 6 mm, the compressive capacity of the dowel-groove fe shall be
determined as follows.
5. When the dowel-type fastener is inserted into the end of the main member
and parallel to the timber’s grain direction of the main member, the
compressive strength of the dowel-groove on the main member is taken
as fe,90.
6. The compressive strength of the fasteners on the steel is calculated
according to 1.1 times the design value of the compressive strength of the
dowel-groove of the bolt-connected member as specified in “Code for
design of steel structures” GB 50017.
7. The compressive strength of the fasteners on the concrete members is
calculated as 1.57 times the standard value of the compressive strength
of the concrete cube.
6.2.9 When the penetration depth of the dowel-type fastener is less than 10
times the dowel’s diameter, the length of the bearing surface shall not include
the length of the tip portion of the dowel.
6.2.10 When three members which are mutually asymmetrical are connected,
the design value Zd of the bearing capacity of shear plane shall, based on the
side member which has the minimum compressive length of the dowel-groove
of the two side members as the calculation criteria, use the calculation of
symmetrical connection to obtain the design value of the bearing capacity of
the minimum shear plane, as the design value of the bearing capacity of the
connected shear plane.
6.2.11 When four or more members are connected, each shear plane shall be
calculated as a single-shear connection. The design value of bearing capacity
of the connection shall take the result of the design value of the bearing capacity
of the minimum shear plane multiplied by the number of shear planes and the
number of dowels.
6.2.12 When the load in the single-shear connection is at an angle other than
90° from the axis of the fastener, the load component acting perpendicular to
the axis of the fastener shall not exceed the design value of the bearing capacity
of the shear plane of the fastener. For the load component which is parallel to
the axis direction of fastener, it shall take reliable measures to meet the local
pressure requirements.
Cr1 - Deign value of shear-tension composite bearing capacity of truss plate
along the l1 direction (N/mm);
Cr2 - Deign value of shear-tension composite bearing capacity of truss plate
along the l2 direction (N/mm);
l1 - The length of the considered rod as covered by the truss plate along the
l1 direction (mm);
l2 - The length of the considered rod as covered by the truss plate along the
l2 direction (mm);
Vr1 - Design value of shear strength of the truss plate along the l1 direction
(N/mm);
Vr2 - Design value of shear strength of the truss plate along the l2 direction
(N/mm);
Tr1 - Design value of tensile strength of the truss plate along the l1 direction
(N/mm);
Tr2 - Design value of tensile strength of the truss plate along the l2 direction
(N/mm);
θ - The angle between the axis of the bars (°).
6.3.10 The anti-sliding bearing capacity of the plate’s teeth shall be calculated
as follows.
Where.
Ns - The anti-sliding bearing capacity of the plate’s teeth (N);
Ns - Design value of the anti-sliding strength of the plate’s teeth (N/mm2),
which shall be valued according to the provisions of Appendix B of this
standard;
A - The net cross-section of the truss plate’s ......
......
| Standard ID | GB 50005-2017 (GB50005-2017) | | Description (Translated English) | Standard for design of timber structures | | Sector / Industry | National Standard | | Classification of Chinese Standard | P23 | | Word Count Estimation | 238,217 | | Date of Issue | 2017-11-20 | | Date of Implementation | 2018-08-01 | | Older Standard (superseded by this standard) | GB 50005-2003 | | Regulation (derived from) | The Ministry of Housing and Urban-Rural Development Announcement No. 1745 of 2017 |
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