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According to the requirements of Document JIANBIAO [2008] No.105 issued by the Ministry of Housing and Urban-Rural Development of the People's Republic of China - Notice on printing and distributing the development and revision plan on engineering construction standards and codes in 2008, the drafting group of this standard revised GB 50017-2003 Code for design of steel structures through the extensive investigation and study, careful summarization of practical experience and reference to relevant international and foreign advanced standards and on the basis of widely soliciting for opinions..
The main contents of this standard are: 1. General provisions; 2. Terms and symbols; 3. General design requirements; 4. Materials; 5. Structural analysis and stability design; 6. Flexural members; 7. Axially loaded members; 8. Tension-flexure members and bending members; 9. Stiffened steel shear walls; 10. Plastic and moment redistribution design; 11. Connections; 12. Joints; 13. Steel tubular joints; 14. Composite steel and concrete beams; 15. Concrete-filled steel tubular column and joints; 16. Fatigue calculation and design for brittle fracture; 17. Seismic design of steel structural members; 18. Protection of steel structures, etc.
The main revisions are as follows:
1. The classification of sections is added in “General design requirements (Clause 3)”; the contents of “selection of materials” and “design strength” are moved into the new clause “Materials (Clause 4)”; the contents of structural calculation are moved into the new clause “Structural analysis and stability design (Clause 5)”, into which the contents of “large span roof structures” and “fabrication, transportation and erection” in “Detailing requirements (Clause 8 of the former code)" are incorporated;
2. The “Calculation of flexural members (Clause 4 of the former code)” is changed to “Flexural members (Clause 6)”, into which the contents of the strengthening of openings are added and the contents related to beam design in the subclause - “structural members” of “Detailing requirements (Clause 8 of the former code)” are moved;
3. The “Calculation of axially loaded members and members subjected to combined axial load and bending (Clause 5 of the former code)” is changed to “Axially loaded members (Clause 7)” and “Members under combined axial force and bending (Clause 8)”, and the contents related to column design in the “Detailing requirements (Clause 8 of the former code)” are moved into Clause 7;
4. The “Fatigue calculation (Clause 6 of the former code)” is changed to “Fatigue calculation and design for brittle fracture (Clause 16)”, into which a simple and quick method for checking calculation of the fatigue strength is added, “requirements for crane beams and crane trusses (or similar structures)” and “requirements for preventing brittle fracture in areas of low temperature” in the “Detailing requirements (Clause 8 of the former code)” are moved, and the requirements of design for brittle fracture are added;
5. The “Calculation of connections (Clause 7 of the former code)” is changed to “Connections (Clause 11)” and “Joints (Clause 12)”, and the contents related to welded and bolted connections and the contents of the column footing in the “Detailing requirements (Clause 8 of the former code)” are incorporated into Clause 11 and Clause 12 respectively;
6. The provisions in the “Detailing requirements (Clause 8 of the former code)” are incorporated into the relevant clauses according to their contents, in which the subclause “protection and heat insulation” is moved into “Protection of steel structures (Clause 18)”;
7. The “Plastic design (Clause 9 of the former code)” is changed to “Plastic and moment redistribution design (Clause 10)”, and the design is carried out with the idea of using the plasticity of steel structures for internal force redistribution;
8. The “Steel tubular structures (Clause 10 of the former code)” is changed to “Steel tubular joints (Clause 13)”, in which the connection forms of the joints calculated are enriched and the contents of joint stiffness determination are added;
9. In the “Composite steel and concrete beams (Clause 11 of the former code, i.e. Clause 14 in this revision)”, the contents of longitudinal shear design are supplemented and the contents related to bent bar connectors are deleted.
In this revision, the clauses such as “Materials (Clause 4)”, “Structural analysis and stability design (Clause 5)”, “Stiffened steel shear walls (Clause 9)”, “ Concrete-filled steel tubular column and joints (Clause 15)”, “ Seismic design of steel structural members (Clause 17)” and “Protection of steel structures (Clause 18)” are newly added, and the contents such as “common structural systems” and “fatigue checking calculation of composite steel and concrete beams” are added in annexes.
The provisions printed in bold type in this standard are compulsory and must be enforced strictly.
The Ministry of Housing and Urban-Rural Development of the People's Republic of China is in charge of the administration of this standard and the explanation of the compulsory provisions; Capital Engineering & Research Incorporation Ltd. is responsible for the explanation of specific technical contents. During the process of implementing this standard, you are kindly requested to send your opinions and advice to Capital Engineering & Research Incorporation Ltd. (Address: No.7, Jian’an Street, Beijing Economic-Technological Development Area, Beijing, 100176， China).
Contents
1 General provisions 1
2 Terms and symbols 2
2.1 Terms 2
2.2 Symbols 5
3 General design requirements 11
3.1 General requirements 11
3.2 Structural systems 14
3.3 Actions 14
3.4 Requirements of deformation and comfort degree for structures and members 16
3.5 Classification of sections 17
4 Materials 20
4.1 Steel grades and standards 20
4.2 Models and standards of connection and fastener materials 20
4.3 Selection of materials 21
4.4 Design strength and parameters 24
5 Structural analysis and stability design 34
5.1 General requirements 34
5.2 Initial imperfections 36
5.3 First-order elastic analysis and design 39
5.4 Second-order P-Δ elastic analysis and design 39
5.5 Direct analysis method of design 40
6 Flexural members 44
6.1 Shear and flexural strength of flexural members 44
6.2 Overall stability of flexural members 47
6.3 Local stability 50
6.4 Calculation of beams considering post-buckling strength of webs 58
6.5 Strengthening of openings 62
6.6 Detailing requirements of beam 64
7 Axially loaded members 66
7.1 Strength calculation of cross-sections 66
7.2 Stability calculation of axial compression members 67
7.3 Local stability and post-buckling strength of solid-web axial compression members 81
7.4 Effective length and allowable slenderness ratio of axially loaded members 85
7.5 Bracing of axial compression members 91
7.6 Single angle steel of single-side connection 93
8 Tension-flexure members and bending members 97
8.1 Strength calculation of cross-sections 97
8.2 Stability calculation of members 98
8.3 Effective length of frame columns 106
8.4 Local stability and post-buckling strength of bending members 113
8.5 Truss members subjected to second-order moments 116
9 Stiffened steel-plate shear walls 118
9.1 General requirements 118
9.2 Calculation of stiffened steel-plate shear wall 118
9.3 Detailing requirements 121
10 Plastic and moment redistribution design 123
10.1 General requirements 123
10.2 Provisions for design using moment redistribution 124
10.3 Calculation of members 124
10.4 Slenderness ratio limitations and detailings 126
11 Connections 129
11.1 General requirements 129
11.2 Calculation of welded connections 131
11.3 Detailing requirements of welded connections 136
11.4 Calculation of fastener connections 140
11.5 Detailing requirements of fastener connections 146
11.6 Pin connections 149
11.7 Detailings of flanged connections for steel tubes 152
12 Joints 153
12.1 General requirements 153
12.2 Connecting plate joints 153
12.3 Beam-column joints 158
12.4 Cast steel joints 163
12.5 Pre-stressed cable joints 164
12.6 Bearings 164
12.7 Column footing 167
13 Steel tubular joints 173
13.1 General requirements 173
13.2 Detailing requirements 174
13.3 Calculation of circular steel tubular directly-welded joints and local stiffened joints 179
13.4 Calculation of rectangular tubular directly-welded joints and local stiffened joints 199
14 Composite steel and concrete beams 212
14.1 General requirements 212
14.2 Design of composite beams 215
14.3 Calculation for shear connector 219
14.4 Calculation of deflection 222
14.5 Calculation of concrete crack width at hogging moment region 224
14.6 Calculation of longitudinal shear 225
14.7 Detailing requirements 227
15 Concrete-filled steel tubular column and joints 229
15.4 Joint of concrete-filled steel tubular column and steel beam 230
16 Fatigue calculation and design for brittle fracture 232
16.1 General requirements 232
16.2 Fatigue calculation 232
16.3 Detailing requirements 238
16.4 Design for brittle fracture 241
17 Seismic design of steel structural members 244
17.1 General requirements 244
17.2 Calculation points 248
17.3 Basic seismic measures 262
18 Protection of steel structures 272
18.1 Fire-resistance design 272
18.2 Corrosion prevention design 272
18.3 Temperature insulation 274
Annex A Common structural systems 276
Annex B Allowable deformation of structures and members 279
Annex C Overall stability coefficient of beam 285
Annex D Stability coefficient of axial compression members 291
Annex E Effective length ratios of columns 296
Annex F Elastic buckling critical stress for stiffened steel shear walls 310
Annex G Calculation of stability of truss connecting plate under the compression of diagonal web member 321
Annex H Determination of stiffness of direct welded joints of unstiffened steel tubes 323
Annex J Fatigue checking calculation of composite steel and concrete beams 326
Annex K Classification of members and connections that are subjected to fatigue calculation 328
Explanation of wording in this standard 336
List of quoted standards 337
1 General provisions
1.0.1 This standard is formulated with a view to implementing the technical and economic policies of the nation during the design of steel structures and thus achieving advanced technology, safety and applicability, economic rationality and guaranteed quality.
1.0.2 This standard is applicable to the design of steel structures in industrial and civil buildings and general structures.
1.0.3 In addition to this standard, the design of steel structures shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms and symbols
2.1 Terms
2.1.1 brittle fracture
sudden fracture of a structure or member subject to tensile stress without any alarming plastic deformation
2.1.2 first-order elastic analysis
analysis of the internal force and displacement of a structure according to the elastic stage by constructing the equilibrium condition based on undeformed structure, taking no account of the effect of geometric nonlinearity on the internal force and deformation of the structure
2.1.3 second-order P-Δ elastic analysis
analysis of the internal force and displacement of a structure according to the elastic stage by constructing the equilibrium condition based on structure after displacement, only taking account of the effects of its overall initial imperfections and geometric nonlinearity of the structure on its internal force and deformation
2.1.4 direct analysis method of design
a design method of conducting second-order nonlinear analysis with the whole structural system as the object, directly taking account of the factors such as initial geometric imperfections, residual stress, material nonlinearity and joint connection stiffness that have significant effects on the stability and strength performance of the structure
2.1.5 buckling
a state of steel structure, member or plate having another larger deformation in the direction with weaker stiffness at the time of reaching the critical stress state
2.1.6 post-buckling strength of steel plate
capacity of a steel plate to bear greater load after buckling
2.1.7 normalized slenderness ratio
a parameter, which is equal to the square root of the quotient of the yield strength of steel in flexion, shear or compression and the corresponding elastic buckling stress of member or steel plate in flexion, shear or compression
2.1.8 overall stability
capacity of a member or structure to remain stable overall under load
2.1.9 effective width
reduced width obtained by equivalently processing the width of the steel plate subject to non-uniformly distributed ultimate stress with the uniformly distributed yield stress in the calculation of the post-buckling ultimate strength of steel plate
2.1.10 effective width factor
ratio of the effective width to the actual width of a steel plate
2.1.11 effective length ratio
a factor, which is related to the buckling mode and the rotational constraints at both ends of the member
2.1.12 effective length
length used in the calculation of stability, which is equal to the product of the geometric length of the member between its effective constraint points and its effective length ratio
2.1.13 slenderness ratio
ratio of the effective length to the gyration radius of section of a member
2.1.14 equivalent slenderness ratio
corresponding slenderness ratio when the latticed member is converted to solid web member or instability caused by the flexural-torsional buckling and torsional bucking are converted to that caused by flexural bucking in the overall stability calculation of axial compression member
2.1.15 nodal bracing force
lateral force applied on the lateral bracing set for reducing the free length of compression member (or compression flange of member), in the buckling direction of the braced member (or the compression flange of member)
2.1.16 unbraced frame
a structure with resistance to load by the bending resistance of joints and members
2.1.17 bracing structure
a structure with resistance to lateral load by the axial stiffness of the bracing member obliquely arranged in the plane where the beam-column member is located
2.1.18 frame-bracing structure
a structure of lateral resistant system composed of frame and bracing
2.1.19 frame braced with strong bracing system
a frame braced with the bracing structure (bracing truss, shear wall, tube, etc.) of relatively large lateral stiffness in the frame-bracing structure, adequate to be regarded as frame without lateral displacement
2.1.20 leaning column
a column designed to bear axial force only, taking no account of the lateral stiffness
2.1.21 panel zone
zone provided with stiffener or diaphragm at the rigid joint and the upper and lower sides of column web of frame beam and column within the height scope of beam
2.1.22 spherical steel bearing
hinged bearing or movable bearing with the steel spherical surface as the bearing surface, allowing the structure to rotate in any direction at the bearing
2.1.23 steel-plate shear wall
steel plate arranged between the frame beam and column to withstand the horizontal shear in the frame
2.1.24 chord member
tubular member, e.g., a chord in truss, placed continuously at the joint in steel tubular structural member
2.1.25 brace member
tubular member, e.g., web member connected to the chord member in truss, disconnected at the joint and connected to the chord member in steel tubular structure
2.1.26 gap joint
tubular joint where the toes of two brace members are distant from each other by a gap
2.1.27 overlap joint
steel tubular joint where the two brace members are overlapped each other
2.1.28 uniplanar joint
joint where brace member and chord member are connected together in the same plane
2.1.29 multiplanar joint
tubular joint formed by connecting multiple brace members in different planes to the chord member
2.1.30 welded section
a section made of steel plate (or profile steel) by welding
2.1.31 composite steel and concrete beam
a beam formed by the composite of concrete flange plate and steel beam via shear connector and capable of bearing force as a whole
2.1.32 bracing system
a lateral force resisting system consisting of bracing, beam (including foundation beam) and column transferring the internal force
2.1.33 link
a beam section between two diagonal bracing ends or between one diagonal bracing end and the column in a eccentrically braced frame structure
2.1.34 concentrically braced frame
a frame in which the diagonal bracing and the frame beam and column intersect at a point
2.1.35 eccentrically braced frame
a frame in which at least one end of the diagonal bracing is connected with the cross beam outside the beam-column joint
2.1.36 buckling-restrained brace
a bracing where buckling will not occur, consisting of the core steel bracing, external constraint element and the unbonded structural layer between both
2.1.37 moment redistribution design
a design method for moment redistribution using the plastic performance of steel structure
2.1.38 distorsional buckling
a form of buckling that causes change in the section shape as well as displacement of at least one of the intersecting lines between steel plates
2.1.39 plastic energy dissipative zone
a zone where the structural member will first enter the plastic deformation state and also consumes energy under the action of strong earthquake
2.1.40 elastic region
a region where the structural member is still in the elastic working state under the action of strong earthquake
2.2 Symbols
2.2.1 Actions and action effect design values
F——the concentrated load;
G——the gravity load;
H——the horizontal force;
M——the bending moment;
N——the axial force;
P——the pretension of high-strength bolt;
R——the bearing reaction force;
V——the shear force.
2.2.2 Calculation indexes
E——the elastic modulus of steel;
Ec——the elastic modulus of concrete;
f——the design value of tensile, compressive or bending strength of steel;
fv——the design value of shear strength of steel;
fce——the design value of the end surface bearing strength of steel;
fy——the yield strength of steel;
fu——the minimum tensile strength of steel;
f_t^a——the design value of tensile strength of anchor bolt;
f_t^b, f_v^b, f_c^b——the design values of tensile, shear and bearing strength of bolt;
f_t^r, f_v^r, f_c^r——the design values of tensile, shear and bearing strength of rivet;
f_t^w, f_v^w, f_c^w——the design values of tensile, shear and compressive strength of butt weld;
f_f^w——the design value of tensile, shear or compressive strength of fillet weld;
fc——the design value of compressive strength of concrete;
G——the shear modulus of steel;
N_t^a——the design value of tensile load-carrying capacity of one anchor bolt;
N_t^b, N_v^b, N_c^b——the design values of tensile, shear and bearing load-carrying strength of one bolt;
N_t^r, N_v^r, N_c^r——the design values of tensile, shear and bearing load-carrying strength of one rivet;
N_v^c——the design value of shear load-carrying capacity of one shear connector in composite structure;
Sb——the storey lateral stiffness of bracing structure, i.e., the ratio of the horizontal force applied to the structure to the inter-storey displacement angle produced by it;
Δu——the inter-storey displacement of a floor;
[vQ]——the allowable value of the deflection produced with consideration of only the characteristic value of variable load;
[vT]——the allowable value of the deflection produced with consideration of the characteristic values of both permanent and variable loads;
σ——the normal stress;
σc——the local compression stress;
σf——the stress vertical to the length direction of fillet weld calculated according to effective section of weld;
Δσ——the stress amplitude or the equivalent stress amplitude in fatigue calculation;
Δσe——the equivalent stress amplitude of variable-amplitude fatigue;
[Δσ]——the allowable stress amplitude of fatigue;
σcr, σc,cr, τcr——respectively the critical values of bending stress, local compression stress and shear stress of steel plate;
τ——the shear stress;
τf——the shear stress of fillet weld.
2.2.3 Geometric parameters
A——the gross sectional area;
An——the net sectional area;
b——the outstanding width of flange plate;
b0——the unsupported width of box-section flange plate between the webs; the top width of concrete haunch;
bs——the outstanding width of stiffener;
be——the effective width of steel plate;
d——the diameter;
de——the effective diameter;
do——the hole diameter;
e——the eccentricity;
H——the height of the column;
H1, H2, H3—respectively the heights of the upper, middle (or lower section of single-stepped column) and lower sections of the stepped column;
h——the full height of a section;
he——the calculated thickness of a weld;
hf——the fillet weld size;
hw——the height of web;
h0——the calculated height of web;
I——the inertia moment of gross section;
It——the free torsion constant;
Iw——the sectorial inertia moment of gross section;
In——the inertia moment of net section;
i——the radius of gyration of a section;
l——the length or the span length;
l1——the lateral supporting spacing of the compression flange of a beam; the connecting length of bolt (rivet) in the force direction;
lw——the effective length of a weld;
lz——the assumed distribution length of concentrated load on the edge of the calculated height of web;
S——the area moment of gross section;
t——the plate thickness;
ts——the stiffener thickness;
tw——the web thickness;
W——the gross section modulus;
Wn——the net section modulus;
Wp——the plastic gross section modulus;
Wnp——the plastic net section modulus.
2.2.4 Coefficients of calculation and others
K1, K2——the linear stiffness ratio of members;
nf——the number of force-transferring friction surfaces of high-strength bolt;
nv——the number of shear surfaces of bolt or rivet;
αE——the ratio of elastic modulus of steel to that of concrete;
αe——the reduction factor of section modulus of beam by taking the effective width of web into account;
αf——the equivalent coefficient of underload effect in fatigue calculation;
α_i^II——the amplification coefficient for bending moment of member bars at the ith storey due to lateral displacement of a frame, taking account of the second-order effect;
βE——the adjustment coefficient of internal force for non-plastic energy dissipative zone;
βf——the amplification coefficient for the design strength value of front fillet weld;
βm——the equivalent bending moment coefficient for the stability of bending member;
γ0——the importance coefficient of structure;
γx, γy——the plastic adaption coefficient of cross-section about the principal axes x and y;
εk——the correction coefficient of steel grade, which is the square root of the ratio of 235 to the yield point value in the steel grade;
η——the adjustment coefficient;
η1, η2——the parameters for calculating the effective length of stepped column;
μ——the anti-sliding coefficient for the friction surface of high-strength bolt; the effective length ratio of column;
μ1, μ2, μ3——respectively the effective length ratio of the upper, middle (or lower section of single-stepped column) and lower sections of the stepped column;
ρi——the effective section coefficient of various steel plates;
φ——the stability coefficient of axial compression member;
φb——the overall stability coefficient of beam;
Ψ——the amplification coefficient of concentrated load;
Ψn, Ψa, Ψd——the parameters for calculating the load-carrying capacity of directly welded steel tubular joint;
Ω——the seismic performance factor.
3 General design requirements
3.1 General requirements
3.1.1 The design of steel structures shall include the following:
1 The structure scheme design, including structure selection and member arrangement;
2 Material selection and section selection;
3 Actions and action effect analysis;
4 Limit state checking calculation of structure;
5 Details of structure, member and connection;
6 Requirements for fabrication, transportation, installation, corrosion prevention and fire protection;
7 Special performance design of structure meeting special requirements.
3.1.2 In this standard, except for fatigue calculation and seismic design, the limit state design method based on probability theory shall be adopted, and calculation shall be carried out using the partial safety factor design expression.
3.1.3 In addition to that the allowable stress method shall be adopted for fatigue design, the steel structures shall be designed according to ultimate limit state and serviceability limit state:
1 Ultimate limit state shall include: strength failure and brittle fracture of member or connection, inapplicability to continuous load carrying due to excessive deformation, loss of stability of the structure or member, transformation of the structure into maneuvering system, and overturning of structure;
2 Serviceability limit state shall include: deformation affecting the normal use or appearance of structure, member and non-structural member, vibration affecting the normal use, and local damage affecting the normal use or durability.
3.1.4 The safety grade and design service life of the steel structure shall meet the requirements of the current national standards GB 50068 Unified standard for reliability design of building structures and GB 50153 Unified standard for reliability design of engineering structures. The safety grade of steel structures in general industrial and civil buildings shall be Grade II, and that of steel structures in other special buildings shall be determined separately according to the specific conditions. The safety grade of various structural members in the buildings should be the same as that of the entire structure. The safety grade of some of the structural members may be adjusted but shall not be inferior to Grade III.
3.1.5 In the design of steel structure according to ultimate limit state, the fundamental combination of load effects shall be considered, and the accidental combination of load effects shall be also considered where necessary. In the design of steel structure according to serviceability limit state, the characteristic combination of load effects shall be considered.
3.1.6 In the calculation of the strength and stability of structure or member and the strength of connection, the design value of load shall be used; in the fatigue calculation, the characteristic value of load shall be used.
3.1.7 For the structure that directly bears dynamic load: in the calculation of strength and stability, the design value of dynamic load shall be multiplied by the dynamic coefficient; in the calculation of fatigue and deformation, the characteristic value of dynamic load shall not be multiplied by the dynamic coefficient. In the calculation of the fatigue and deflection of a crane beam or a crane truss and its brake structure, the crane load shall be determined by the crane acting in the span with the maximum load effect.
3.1.8 The design of the prestressed steel structure shall include various working conditions in the prestressed construction phase and the use phase. The design of prestressed cable membrane structure shall include three mutually restrictive processes, i.e., shape-finding analysis, load analysis and cutting analysis, and should also include the construction process analysis.
3.1.9 For structural members, connections and joints, the following ultimate limit state design expressions shall be adopted:
1 Persistent and transient design situations:
γ0S≤R (3.1.9-1)
2 Seismic design situation:
Frequent earthquake
S≤R/γRE (3.1.9-2)
Moderate earthquake
S≤Rk (3.1.9-3)
Where,
γ0——the importance coefficient of structure, which shall not be less than 1.1 for the structural member of safety grade I, 1.0 for the structural member of safety grade II and 0.9 for the structural member of safety grade III;
S——the design value of the action combination effect under ultimate limit state, which shall be calculated according to the fundamental combination of actions under persistent or transient design situation and shall be calculated according to the seismic combination of actions under seismic design situation;
R——the design value of load-carrying capacity of structural member;
Rk——the characteristic value of load-carrying capacity of structural member;
γRE——the seismic adjustment coefficient for load-carrying capacity, which shall be taken according to the requirements of the current national standard GB 50011 Code for seismic design of buildings.
3.1.10 For structures of safety grade I or that may be subject to accidental actions such as explosion and impact, progressive collapse prevention design should be conducted to ensure a vertical load redistribution path of the structure in case of failure of some beams or columns, the stability of the structure in case of failure of some beams or floor slabs, and the capability of the joint to continue to effectively transfer the load after failure of some members.
3.1.11 In the design of steel structures, the materials, structure scheme and construction measures shall be selected reasonably to meet the strength, stability and stiffness requirements of structural members during transportation, installation and use and to meet the fire protection and corrosion prevention requirements. General and standardized members should be used, and the corresponding requirements shall be proposed when considering the possibility of replacement of some structural components. The construction of steel structures shall facilitate fabrication, transportation, installation and maintenance, make the structure stress simple and clear, reduce stress concentration, and avoid the material being stressed in three directions.
1 General provisions 2 Terms and symbols 2.1 Terms 2.2 Symbols 3 General design requirements 3.1 General requirements 3.2 Structural systems 3.3 Actions 3.4 Requirements of deformation and comfort degree for structures and members 3.5 Classification of sections 4 Materials 4.1 Steel grades and standards 4.2 Models and standards of connection and fastener materials 4.3 Selection of materials 4.4 Design strength and parameters 5 Structural analysis and stability design 5.1 General requirements 5.2 Initial imperfections 5.3 First-order elastic analysis and design 5.4 Second-order P-Δ elastic analysis and design 5.5 Direct analysis method of design 6 Flexural members 6.1 Shear and flexural strength of flexural members 6.2 Overall stability of flexural members 6.3 Local stability 6.4 Calculation of beams considering post-buckling strength of webs 6.5 Strengthening of openings 6.6 Detailing requirements of beam 7 Axially loaded members 7.1 Strength calculation of cross-sections 7.2 Stability calculation of axial compression members 7.3 Local stability and post-buckling strength of solid-web axial compression members 7.4 Effective length and allowable slenderness ratio of axially loaded members 7.5 Bracing of axial compression members 7.6 Single angle steel of single-side connection 8 Tension-flexure members and bending members 8.1 Strength calculation of cross-sections 8.2 Stability calculation of members 8.3 Effective length of frame columns 8.4 Local stability and post-buckling strength of bending members 8.5 Truss members subjected to second-order moments 9 Stiffened steel-plate shear walls 9.1 General requirements 9.2 Calculation of stiffened steel-plate shear wall 9.3 Detailing requirements 10 Plastic and moment redistribution design 10.1 General requirements 10.2 Provisions for design using moment redistribution 10.3 Calculation of members 10.4 Slenderness ratio limitations and detailings 11 Connections 11.1 General requirements 11.2 Calculation of welded connections 11.3 Detailing requirements of welded connections 11.4 Calculation of fastener connections 11.5 Detailing requirements of fastener connections 11.6 Pin connections 11.7 Detailings of flanged connections for steel tubes 12 Joints 12.1 General requirements 12.2 Connecting plate joints 12.3 Beam-column joints 12.4 Cast steel joints 12.5 Pre-stressed cable joints 12.6 Bearings 12.7 Column footing 13 Steel tubular joints 13.1 General requirements 13.2 Detailing requirements 13.3 Calculation of circular steel tubular directly-welded joints and local stiffened joints 13.4 Calculation of rectangular tubular directly-welded joints and local stiffened joints 14 Composite steel and concrete beams 14.1 General requirements 14.2 Design of composite beams 14.3 Calculation for shear connector 14.4 Calculation of deflection 14.5 Calculation of concrete crack width at hogging moment region 14.6 Calculation of longitudinal shear 14.7 Detailing requirements 15 Concrete-filled steel tubular column and joints 15.1 General requirements 15.2 Rectangular concrete-filled steel tubular columns 15.3 Circular concrete-filled steel tubular columns 15.4 Joint of concrete-filled steel tubular column and steel beam 16 Fatigue calculation and design for brittle fracture 16.1 General requirements 16.2 Fatigue calculation 16.3 Detailing requirements 16.4 Design for brittle fracture 17 Seismic design of steel structural members 17.1 General requirements 17.2 Calculation points 17.3 Basic seismic measures 18 Protection of steel structures 18.1 Fire-resistance design 18.2 Corrosion prevention design 18.3 Temperature insulation Annex A Common structural systems Annex B Allowable deformation of structures and members Annex C Overall stability coefficient of beam Annex D Stability coefficient of axial compression members Annex E Effective length ratios of columns Annex F Elastic buckling critical stress for stiffened steel shear walls Annex G Calculation of stability of truss connecting plate under the compression of diagonal web member Annex H Determination of stiffness of direct welded joints of unstiffened steel tubes Annex J Fatigue checking calculation of composite steel and concrete beams Annex K Classification of members and connections that are subjected to fatigue calculation Explanation of wording in this standard List of quoted standards
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
According to the requirements of Document JIANBIAO [2008] No.105 issued by the Ministry of Housing and Urban-Rural Development of the People's Republic of China - Notice on printing and distributing the development and revision plan on engineering construction standards and codes in 2008, the drafting group of this standard revised GB 50017-2003 Code for design of steel structures through the extensive investigation and study, careful summarization of practical experience and reference to relevant international and foreign advanced standards and on the basis of widely soliciting for opinions..
The main contents of this standard are: 1. General provisions; 2. Terms and symbols; 3. General design requirements; 4. Materials; 5. Structural analysis and stability design; 6. Flexural members; 7. Axially loaded members; 8. Tension-flexure members and bending members; 9. Stiffened steel shear walls; 10. Plastic and moment redistribution design; 11. Connections; 12. Joints; 13. Steel tubular joints; 14. Composite steel and concrete beams; 15. Concrete-filled steel tubular column and joints; 16. Fatigue calculation and design for brittle fracture; 17. Seismic design of steel structural members; 18. Protection of steel structures, etc.
The main revisions are as follows:
1. The classification of sections is added in “General design requirements (Clause 3)”; the contents of “selection of materials” and “design strength” are moved into the new clause “Materials (Clause 4)”; the contents of structural calculation are moved into the new clause “Structural analysis and stability design (Clause 5)”, into which the contents of “large span roof structures” and “fabrication, transportation and erection” in “Detailing requirements (Clause 8 of the former code)" are incorporated;
2. The “Calculation of flexural members (Clause 4 of the former code)” is changed to “Flexural members (Clause 6)”, into which the contents of the strengthening of openings are added and the contents related to beam design in the subclause - “structural members” of “Detailing requirements (Clause 8 of the former code)” are moved;
3. The “Calculation of axially loaded members and members subjected to combined axial load and bending (Clause 5 of the former code)” is changed to “Axially loaded members (Clause 7)” and “Members under combined axial force and bending (Clause 8)”, and the contents related to column design in the “Detailing requirements (Clause 8 of the former code)” are moved into Clause 7;
4. The “Fatigue calculation (Clause 6 of the former code)” is changed to “Fatigue calculation and design for brittle fracture (Clause 16)”, into which a simple and quick method for checking calculation of the fatigue strength is added, “requirements for crane beams and crane trusses (or similar structures)” and “requirements for preventing brittle fracture in areas of low temperature” in the “Detailing requirements (Clause 8 of the former code)” are moved, and the requirements of design for brittle fracture are added;
5. The “Calculation of connections (Clause 7 of the former code)” is changed to “Connections (Clause 11)” and “Joints (Clause 12)”, and the contents related to welded and bolted connections and the contents of the column footing in the “Detailing requirements (Clause 8 of the former code)” are incorporated into Clause 11 and Clause 12 respectively;
6. The provisions in the “Detailing requirements (Clause 8 of the former code)” are incorporated into the relevant clauses according to their contents, in which the subclause “protection and heat insulation” is moved into “Protection of steel structures (Clause 18)”;
7. The “Plastic design (Clause 9 of the former code)” is changed to “Plastic and moment redistribution design (Clause 10)”, and the design is carried out with the idea of using the plasticity of steel structures for internal force redistribution;
8. The “Steel tubular structures (Clause 10 of the former code)” is changed to “Steel tubular joints (Clause 13)”, in which the connection forms of the joints calculated are enriched and the contents of joint stiffness determination are added;
9. In the “Composite steel and concrete beams (Clause 11 of the former code, i.e. Clause 14 in this revision)”, the contents of longitudinal shear design are supplemented and the contents related to bent bar connectors are deleted.
In this revision, the clauses such as “Materials (Clause 4)”, “Structural analysis and stability design (Clause 5)”, “Stiffened steel shear walls (Clause 9)”, “ Concrete-filled steel tubular column and joints (Clause 15)”, “ Seismic design of steel structural members (Clause 17)” and “Protection of steel structures (Clause 18)” are newly added, and the contents such as “common structural systems” and “fatigue checking calculation of composite steel and concrete beams” are added in annexes.
The provisions printed in bold type in this standard are compulsory and must be enforced strictly.
The Ministry of Housing and Urban-Rural Development of the People's Republic of China is in charge of the administration of this standard and the explanation of the compulsory provisions; Capital Engineering & Research Incorporation Ltd. is responsible for the explanation of specific technical contents. During the process of implementing this standard, you are kindly requested to send your opinions and advice to Capital Engineering & Research Incorporation Ltd. (Address: No.7, Jian’an Street, Beijing Economic-Technological Development Area, Beijing, 100176， China).
Contents
1 General provisions 1
2 Terms and symbols 2
2.1 Terms 2
2.2 Symbols 5
3 General design requirements 11
3.1 General requirements 11
3.2 Structural systems 14
3.3 Actions 14
3.4 Requirements of deformation and comfort degree for structures and members 16
3.5 Classification of sections 17
4 Materials 20
4.1 Steel grades and standards 20
4.2 Models and standards of connection and fastener materials 20
4.3 Selection of materials 21
4.4 Design strength and parameters 24
5 Structural analysis and stability design 34
5.1 General requirements 34
5.2 Initial imperfections 36
5.3 First-order elastic analysis and design 39
5.4 Second-order P-Δ elastic analysis and design 39
5.5 Direct analysis method of design 40
6 Flexural members 44
6.1 Shear and flexural strength of flexural members 44
6.2 Overall stability of flexural members 47
6.3 Local stability 50
6.4 Calculation of beams considering post-buckling strength of webs 58
6.5 Strengthening of openings 62
6.6 Detailing requirements of beam 64
7 Axially loaded members 66
7.1 Strength calculation of cross-sections 66
7.2 Stability calculation of axial compression members 67
7.3 Local stability and post-buckling strength of solid-web axial compression members 81
7.4 Effective length and allowable slenderness ratio of axially loaded members 85
7.5 Bracing of axial compression members 91
7.6 Single angle steel of single-side connection 93
8 Tension-flexure members and bending members 97
8.1 Strength calculation of cross-sections 97
8.2 Stability calculation of members 98
8.3 Effective length of frame columns 106
8.4 Local stability and post-buckling strength of bending members 113
8.5 Truss members subjected to second-order moments 116
9 Stiffened steel-plate shear walls 118
9.1 General requirements 118
9.2 Calculation of stiffened steel-plate shear wall 118
9.3 Detailing requirements 121
10 Plastic and moment redistribution design 123
10.1 General requirements 123
10.2 Provisions for design using moment redistribution 124
10.3 Calculation of members 124
10.4 Slenderness ratio limitations and detailings 126
11 Connections 129
11.1 General requirements 129
11.2 Calculation of welded connections 131
11.3 Detailing requirements of welded connections 136
11.4 Calculation of fastener connections 140
11.5 Detailing requirements of fastener connections 146
11.6 Pin connections 149
11.7 Detailings of flanged connections for steel tubes 152
12 Joints 153
12.1 General requirements 153
12.2 Connecting plate joints 153
12.3 Beam-column joints 158
12.4 Cast steel joints 163
12.5 Pre-stressed cable joints 164
12.6 Bearings 164
12.7 Column footing 167
13 Steel tubular joints 173
13.1 General requirements 173
13.2 Detailing requirements 174
13.3 Calculation of circular steel tubular directly-welded joints and local stiffened joints 179
13.4 Calculation of rectangular tubular directly-welded joints and local stiffened joints 199
14 Composite steel and concrete beams 212
14.1 General requirements 212
14.2 Design of composite beams 215
14.3 Calculation for shear connector 219
14.4 Calculation of deflection 222
14.5 Calculation of concrete crack width at hogging moment region 224
14.6 Calculation of longitudinal shear 225
14.7 Detailing requirements 227
15 Concrete-filled steel tubular column and joints 229
15.1 General requirements 229
15.2 Rectangular concrete-filled steel tubular columns 229
15.3 Circular concrete-filled steel tubular columns 230
15.4 Joint of concrete-filled steel tubular column and steel beam 230
16 Fatigue calculation and design for brittle fracture 232
16.1 General requirements 232
16.2 Fatigue calculation 232
16.3 Detailing requirements 238
16.4 Design for brittle fracture 241
17 Seismic design of steel structural members 244
17.1 General requirements 244
17.2 Calculation points 248
17.3 Basic seismic measures 262
18 Protection of steel structures 272
18.1 Fire-resistance design 272
18.2 Corrosion prevention design 272
18.3 Temperature insulation 274
Annex A Common structural systems 276
Annex B Allowable deformation of structures and members 279
Annex C Overall stability coefficient of beam 285
Annex D Stability coefficient of axial compression members 291
Annex E Effective length ratios of columns 296
Annex F Elastic buckling critical stress for stiffened steel shear walls 310
Annex G Calculation of stability of truss connecting plate under the compression of diagonal web member 321
Annex H Determination of stiffness of direct welded joints of unstiffened steel tubes 323
Annex J Fatigue checking calculation of composite steel and concrete beams 326
Annex K Classification of members and connections that are subjected to fatigue calculation 328
Explanation of wording in this standard 336
List of quoted standards 337
1 General provisions
1.0.1 This standard is formulated with a view to implementing the technical and economic policies of the nation during the design of steel structures and thus achieving advanced technology, safety and applicability, economic rationality and guaranteed quality.
1.0.2 This standard is applicable to the design of steel structures in industrial and civil buildings and general structures.
1.0.3 In addition to this standard, the design of steel structures shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms and symbols
2.1 Terms
2.1.1 brittle fracture
sudden fracture of a structure or member subject to tensile stress without any alarming plastic deformation
2.1.2 first-order elastic analysis
analysis of the internal force and displacement of a structure according to the elastic stage by constructing the equilibrium condition based on undeformed structure, taking no account of the effect of geometric nonlinearity on the internal force and deformation of the structure
2.1.3 second-order P-Δ elastic analysis
analysis of the internal force and displacement of a structure according to the elastic stage by constructing the equilibrium condition based on structure after displacement, only taking account of the effects of its overall initial imperfections and geometric nonlinearity of the structure on its internal force and deformation
2.1.4 direct analysis method of design
a design method of conducting second-order nonlinear analysis with the whole structural system as the object, directly taking account of the factors such as initial geometric imperfections, residual stress, material nonlinearity and joint connection stiffness that have significant effects on the stability and strength performance of the structure
2.1.5 buckling
a state of steel structure, member or plate having another larger deformation in the direction with weaker stiffness at the time of reaching the critical stress state
2.1.6 post-buckling strength of steel plate
capacity of a steel plate to bear greater load after buckling
2.1.7 normalized slenderness ratio
a parameter, which is equal to the square root of the quotient of the yield strength of steel in flexion, shear or compression and the corresponding elastic buckling stress of member or steel plate in flexion, shear or compression
2.1.8 overall stability
capacity of a member or structure to remain stable overall under load
2.1.9 effective width
reduced width obtained by equivalently processing the width of the steel plate subject to non-uniformly distributed ultimate stress with the uniformly distributed yield stress in the calculation of the post-buckling ultimate strength of steel plate
2.1.10 effective width factor
ratio of the effective width to the actual width of a steel plate
2.1.11 effective length ratio
a factor, which is related to the buckling mode and the rotational constraints at both ends of the member
2.1.12 effective length
length used in the calculation of stability, which is equal to the product of the geometric length of the member between its effective constraint points and its effective length ratio
2.1.13 slenderness ratio
ratio of the effective length to the gyration radius of section of a member
2.1.14 equivalent slenderness ratio
corresponding slenderness ratio when the latticed member is converted to solid web member or instability caused by the flexural-torsional buckling and torsional bucking are converted to that caused by flexural bucking in the overall stability calculation of axial compression member
2.1.15 nodal bracing force
lateral force applied on the lateral bracing set for reducing the free length of compression member (or compression flange of member), in the buckling direction of the braced member (or the compression flange of member)
2.1.16 unbraced frame
a structure with resistance to load by the bending resistance of joints and members
2.1.17 bracing structure
a structure with resistance to lateral load by the axial stiffness of the bracing member obliquely arranged in the plane where the beam-column member is located
2.1.18 frame-bracing structure
a structure of lateral resistant system composed of frame and bracing
2.1.19 frame braced with strong bracing system
a frame braced with the bracing structure (bracing truss, shear wall, tube, etc.) of relatively large lateral stiffness in the frame-bracing structure, adequate to be regarded as frame without lateral displacement
2.1.20 leaning column
a column designed to bear axial force only, taking no account of the lateral stiffness
2.1.21 panel zone
zone provided with stiffener or diaphragm at the rigid joint and the upper and lower sides of column web of frame beam and column within the height scope of beam
2.1.22 spherical steel bearing
hinged bearing or movable bearing with the steel spherical surface as the bearing surface, allowing the structure to rotate in any direction at the bearing
2.1.23 steel-plate shear wall
steel plate arranged between the frame beam and column to withstand the horizontal shear in the frame
2.1.24 chord member
tubular member, e.g., a chord in truss, placed continuously at the joint in steel tubular structural member
2.1.25 brace member
tubular member, e.g., web member connected to the chord member in truss, disconnected at the joint and connected to the chord member in steel tubular structure
2.1.26 gap joint
tubular joint where the toes of two brace members are distant from each other by a gap
2.1.27 overlap joint
steel tubular joint where the two brace members are overlapped each other
2.1.28 uniplanar joint
joint where brace member and chord member are connected together in the same plane
2.1.29 multiplanar joint
tubular joint formed by connecting multiple brace members in different planes to the chord member
2.1.30 welded section
a section made of steel plate (or profile steel) by welding
2.1.31 composite steel and concrete beam
a beam formed by the composite of concrete flange plate and steel beam via shear connector and capable of bearing force as a whole
2.1.32 bracing system
a lateral force resisting system consisting of bracing, beam (including foundation beam) and column transferring the internal force
2.1.33 link
a beam section between two diagonal bracing ends or between one diagonal bracing end and the column in a eccentrically braced frame structure
2.1.34 concentrically braced frame
a frame in which the diagonal bracing and the frame beam and column intersect at a point
2.1.35 eccentrically braced frame
a frame in which at least one end of the diagonal bracing is connected with the cross beam outside the beam-column joint
2.1.36 buckling-restrained brace
a bracing where buckling will not occur, consisting of the core steel bracing, external constraint element and the unbonded structural layer between both
2.1.37 moment redistribution design
a design method for moment redistribution using the plastic performance of steel structure
2.1.38 distorsional buckling
a form of buckling that causes change in the section shape as well as displacement of at least one of the intersecting lines between steel plates
2.1.39 plastic energy dissipative zone
a zone where the structural member will first enter the plastic deformation state and also consumes energy under the action of strong earthquake
2.1.40 elastic region
a region where the structural member is still in the elastic working state under the action of strong earthquake
2.2 Symbols
2.2.1 Actions and action effect design values
F——the concentrated load;
G——the gravity load;
H——the horizontal force;
M——the bending moment;
N——the axial force;
P——the pretension of high-strength bolt;
R——the bearing reaction force;
V——the shear force.
2.2.2 Calculation indexes
E——the elastic modulus of steel;
Ec——the elastic modulus of concrete;
f——the design value of tensile, compressive or bending strength of steel;
fv——the design value of shear strength of steel;
fce——the design value of the end surface bearing strength of steel;
fy——the yield strength of steel;
fu——the minimum tensile strength of steel;
f_t^a——the design value of tensile strength of anchor bolt;
f_t^b, f_v^b, f_c^b——the design values of tensile, shear and bearing strength of bolt;
f_t^r, f_v^r, f_c^r——the design values of tensile, shear and bearing strength of rivet;
f_t^w, f_v^w, f_c^w——the design values of tensile, shear and compressive strength of butt weld;
f_f^w——the design value of tensile, shear or compressive strength of fillet weld;
fc——the design value of compressive strength of concrete;
G——the shear modulus of steel;
N_t^a——the design value of tensile load-carrying capacity of one anchor bolt;
N_t^b, N_v^b, N_c^b——the design values of tensile, shear and bearing load-carrying strength of one bolt;
N_t^r, N_v^r, N_c^r——the design values of tensile, shear and bearing load-carrying strength of one rivet;
N_v^c——the design value of shear load-carrying capacity of one shear connector in composite structure;
Sb——the storey lateral stiffness of bracing structure, i.e., the ratio of the horizontal force applied to the structure to the inter-storey displacement angle produced by it;
Δu——the inter-storey displacement of a floor;
[vQ]——the allowable value of the deflection produced with consideration of only the characteristic value of variable load;
[vT]——the allowable value of the deflection produced with consideration of the characteristic values of both permanent and variable loads;
σ——the normal stress;
σc——the local compression stress;
σf——the stress vertical to the length direction of fillet weld calculated according to effective section of weld;
Δσ——the stress amplitude or the equivalent stress amplitude in fatigue calculation;
Δσe——the equivalent stress amplitude of variable-amplitude fatigue;
[Δσ]——the allowable stress amplitude of fatigue;
σcr, σc,cr, τcr——respectively the critical values of bending stress, local compression stress and shear stress of steel plate;
τ——the shear stress;
τf——the shear stress of fillet weld.
2.2.3 Geometric parameters
A——the gross sectional area;
An——the net sectional area;
b——the outstanding width of flange plate;
b0——the unsupported width of box-section flange plate between the webs; the top width of concrete haunch;
bs——the outstanding width of stiffener;
be——the effective width of steel plate;
d——the diameter;
de——the effective diameter;
do——the hole diameter;
e——the eccentricity;
H——the height of the column;
H1, H2, H3—respectively the heights of the upper, middle (or lower section of single-stepped column) and lower sections of the stepped column;
h——the full height of a section;
he——the calculated thickness of a weld;
hf——the fillet weld size;
hw——the height of web;
h0——the calculated height of web;
I——the inertia moment of gross section;
It——the free torsion constant;
Iw——the sectorial inertia moment of gross section;
In——the inertia moment of net section;
i——the radius of gyration of a section;
l——the length or the span length;
l1——the lateral supporting spacing of the compression flange of a beam; the connecting length of bolt (rivet) in the force direction;
lw——the effective length of a weld;
lz——the assumed distribution length of concentrated load on the edge of the calculated height of web;
S——the area moment of gross section;
t——the plate thickness;
ts——the stiffener thickness;
tw——the web thickness;
W——the gross section modulus;
Wn——the net section modulus;
Wp——the plastic gross section modulus;
Wnp——the plastic net section modulus.
2.2.4 Coefficients of calculation and others
K1, K2——the linear stiffness ratio of members;
nf——the number of force-transferring friction surfaces of high-strength bolt;
nv——the number of shear surfaces of bolt or rivet;
αE——the ratio of elastic modulus of steel to that of concrete;
αe——the reduction factor of section modulus of beam by taking the effective width of web into account;
αf——the equivalent coefficient of underload effect in fatigue calculation;
α_i^II——the amplification coefficient for bending moment of member bars at the ith storey due to lateral displacement of a frame, taking account of the second-order effect;
βE——the adjustment coefficient of internal force for non-plastic energy dissipative zone;
βf——the amplification coefficient for the design strength value of front fillet weld;
βm——the equivalent bending moment coefficient for the stability of bending member;
γ0——the importance coefficient of structure;
γx, γy——the plastic adaption coefficient of cross-section about the principal axes x and y;
εk——the correction coefficient of steel grade, which is the square root of the ratio of 235 to the yield point value in the steel grade;
η——the adjustment coefficient;
η1, η2——the parameters for calculating the effective length of stepped column;
ηov——the overlap ratio of brace members at joint;
λ——the slenderness ratio;
λn,b, λn,s, λn,c, λn——the normalized slenderness ratio;
μ——the anti-sliding coefficient for the friction surface of high-strength bolt; the effective length ratio of column;
μ1, μ2, μ3——respectively the effective length ratio of the upper, middle (or lower section of single-stepped column) and lower sections of the stepped column;
ρi——the effective section coefficient of various steel plates;
φ——the stability coefficient of axial compression member;
φb——the overall stability coefficient of beam;
Ψ——the amplification coefficient of concentrated load;
Ψn, Ψa, Ψd——the parameters for calculating the load-carrying capacity of directly welded steel tubular joint;
Ω——the seismic performance factor.
3 General design requirements
3.1 General requirements
3.1.1 The design of steel structures shall include the following:
1 The structure scheme design, including structure selection and member arrangement;
2 Material selection and section selection;
3 Actions and action effect analysis;
4 Limit state checking calculation of structure;
5 Details of structure, member and connection;
6 Requirements for fabrication, transportation, installation, corrosion prevention and fire protection;
7 Special performance design of structure meeting special requirements.
3.1.2 In this standard, except for fatigue calculation and seismic design, the limit state design method based on probability theory shall be adopted, and calculation shall be carried out using the partial safety factor design expression.
3.1.3 In addition to that the allowable stress method shall be adopted for fatigue design, the steel structures shall be designed according to ultimate limit state and serviceability limit state:
1 Ultimate limit state shall include: strength failure and brittle fracture of member or connection, inapplicability to continuous load carrying due to excessive deformation, loss of stability of the structure or member, transformation of the structure into maneuvering system, and overturning of structure;
2 Serviceability limit state shall include: deformation affecting the normal use or appearance of structure, member and non-structural member, vibration affecting the normal use, and local damage affecting the normal use or durability.
3.1.4 The safety grade and design service life of the steel structure shall meet the requirements of the current national standards GB 50068 Unified standard for reliability design of building structures and GB 50153 Unified standard for reliability design of engineering structures. The safety grade of steel structures in general industrial and civil buildings shall be Grade II, and that of steel structures in other special buildings shall be determined separately according to the specific conditions. The safety grade of various structural members in the buildings should be the same as that of the entire structure. The safety grade of some of the structural members may be adjusted but shall not be inferior to Grade III.
3.1.5 In the design of steel structure according to ultimate limit state, the fundamental combination of load effects shall be considered, and the accidental combination of load effects shall be also considered where necessary. In the design of steel structure according to serviceability limit state, the characteristic combination of load effects shall be considered.
3.1.6 In the calculation of the strength and stability of structure or member and the strength of connection, the design value of load shall be used; in the fatigue calculation, the characteristic value of load shall be used.
3.1.7 For the structure that directly bears dynamic load: in the calculation of strength and stability, the design value of dynamic load shall be multiplied by the dynamic coefficient; in the calculation of fatigue and deformation, the characteristic value of dynamic load shall not be multiplied by the dynamic coefficient. In the calculation of the fatigue and deflection of a crane beam or a crane truss and its brake structure, the crane load shall be determined by the crane acting in the span with the maximum load effect.
3.1.8 The design of the prestressed steel structure shall include various working conditions in the prestressed construction phase and the use phase. The design of prestressed cable membrane structure shall include three mutually restrictive processes, i.e., shape-finding analysis, load analysis and cutting analysis, and should also include the construction process analysis.
3.1.9 For structural members, connections and joints, the following ultimate limit state design expressions shall be adopted:
1 Persistent and transient design situations:
γ0S≤R (3.1.9-1)
2 Seismic design situation:
Frequent earthquake
S≤R/γRE (3.1.9-2)
Moderate earthquake
S≤Rk (3.1.9-3)
Where,
γ0——the importance coefficient of structure, which shall not be less than 1.1 for the structural member of safety grade I, 1.0 for the structural member of safety grade II and 0.9 for the structural member of safety grade III;
S——the design value of the action combination effect under ultimate limit state, which shall be calculated according to the fundamental combination of actions under persistent or transient design situation and shall be calculated according to the seismic combination of actions under seismic design situation;
R——the design value of load-carrying capacity of structural member;
Rk——the characteristic value of load-carrying capacity of structural member;
γRE——the seismic adjustment coefficient for load-carrying capacity, which shall be taken according to the requirements of the current national standard GB 50011 Code for seismic design of buildings.
3.1.10 For structures of safety grade I or that may be subject to accidental actions such as explosion and impact, progressive collapse prevention design should be conducted to ensure a vertical load redistribution path of the structure in case of failure of some beams or columns, the stability of the structure in case of failure of some beams or floor slabs, and the capability of the joint to continue to effectively transfer the load after failure of some members.
3.1.11 In the design of steel structures, the materials, structure scheme and construction measures shall be selected reasonably to meet the strength, stability and stiffness requirements of structural members during transportation, installation and use and to meet the fire protection and corrosion prevention requirements. General and standardized members should be used, and the corresponding requirements shall be proposed when considering the possibility of replacement of some structural components. The construction of steel structures shall facilitate fabrication, transportation, installation and maintenance, make the structure stress simple and clear, reduce stress concentration, and avoid the material being stressed in three directions.
Contents of GB 50017-2017
1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 General design requirements
3.1 General requirements
3.2 Structural systems
3.3 Actions
3.4 Requirements of deformation and comfort degree for structures and members
3.5 Classification of sections
4 Materials
4.1 Steel grades and standards
4.2 Models and standards of connection and fastener materials
4.3 Selection of materials
4.4 Design strength and parameters
5 Structural analysis and stability design
5.1 General requirements
5.2 Initial imperfections
5.3 First-order elastic analysis and design
5.4 Second-order P-Δ elastic analysis and design
5.5 Direct analysis method of design
6 Flexural members
6.1 Shear and flexural strength of flexural members
6.2 Overall stability of flexural members
6.3 Local stability
6.4 Calculation of beams considering post-buckling strength of webs
6.5 Strengthening of openings
6.6 Detailing requirements of beam
7 Axially loaded members
7.1 Strength calculation of cross-sections
7.2 Stability calculation of axial compression members
7.3 Local stability and post-buckling strength of solid-web axial compression members
7.4 Effective length and allowable slenderness ratio of axially loaded members
7.5 Bracing of axial compression members
7.6 Single angle steel of single-side connection
8 Tension-flexure members and bending members
8.1 Strength calculation of cross-sections
8.2 Stability calculation of members
8.3 Effective length of frame columns
8.4 Local stability and post-buckling strength of bending members
8.5 Truss members subjected to second-order moments
9 Stiffened steel-plate shear walls
9.1 General requirements
9.2 Calculation of stiffened steel-plate shear wall
9.3 Detailing requirements
10 Plastic and moment redistribution design
10.1 General requirements
10.2 Provisions for design using moment redistribution
10.3 Calculation of members
10.4 Slenderness ratio limitations and detailings
11 Connections
11.1 General requirements
11.2 Calculation of welded connections
11.3 Detailing requirements of welded connections
11.4 Calculation of fastener connections
11.5 Detailing requirements of fastener connections
11.6 Pin connections
11.7 Detailings of flanged connections for steel tubes
12 Joints
12.1 General requirements
12.2 Connecting plate joints
12.3 Beam-column joints
12.4 Cast steel joints
12.5 Pre-stressed cable joints
12.6 Bearings
12.7 Column footing
13 Steel tubular joints
13.1 General requirements
13.2 Detailing requirements
13.3 Calculation of circular steel tubular directly-welded joints and local stiffened joints
13.4 Calculation of rectangular tubular directly-welded joints and local stiffened joints
14 Composite steel and concrete beams
14.1 General requirements
14.2 Design of composite beams
14.3 Calculation for shear connector
14.4 Calculation of deflection
14.5 Calculation of concrete crack width at hogging moment region
14.6 Calculation of longitudinal shear
14.7 Detailing requirements
15 Concrete-filled steel tubular column and joints
15.1 General requirements
15.2 Rectangular concrete-filled steel tubular columns
15.3 Circular concrete-filled steel tubular columns
15.4 Joint of concrete-filled steel tubular column and steel beam
16 Fatigue calculation and design for brittle fracture
16.1 General requirements
16.2 Fatigue calculation
16.3 Detailing requirements
16.4 Design for brittle fracture
17 Seismic design of steel structural members
17.1 General requirements
17.2 Calculation points
17.3 Basic seismic measures
18 Protection of steel structures
18.1 Fire-resistance design
18.2 Corrosion prevention design
18.3 Temperature insulation
Annex A Common structural systems
Annex B Allowable deformation of structures and members
Annex C Overall stability coefficient of beam
Annex D Stability coefficient of axial compression members
Annex E Effective length ratios of columns
Annex F Elastic buckling critical stress for stiffened steel shear walls
Annex G Calculation of stability of truss connecting plate under the compression of diagonal web member
Annex H Determination of stiffness of direct welded joints of unstiffened steel tubes
Annex J Fatigue checking calculation of composite steel and concrete beams
Annex K Classification of members and connections that are subjected to fatigue calculation
Explanation of wording in this standard
List of quoted standards
