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Code for design of steel structures
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GB 55006-2021: PDF in English GB 55006-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
UDC
P GB 55006-2021
General specification for steel structures
ISSUED ON: APRIL 09, 2021
IMPLEMENTED ON: JANUARY 01, 2022
Issued by: Ministry of Housing and Urban-Rural Development of PRC;
State Administration for Market Regulation.
Table of Contents
Foreword ... 3
1 General ... 6
2 Basic requirements ... 6
3 Materials ... 8
4 Components and connection design ... 9
4.1 Ordinary steel components ... 9
4.2 Cold-formed steel components ... 10
4.3 Stainless steel components ... 10
4.4 Steel structure connection ... 11
4.5 Fatigue ... 11
4.6 Construction requirements ... 12
5 Structural design ... 12
5.1 Steel structure of light-weight house with portal frame ... 12
5.2 Multi-floor and high-rise steel structures ... 13
5.3 Large-span steel structure... 14
5.4 Tower mast steel structure ... 15
5.5 Steel silo structure ... 16
5.6 Urban steel bridge ... 17
6 Seismic and protection design ... 17
6.1 Seismic design ... 17
6.2 Seismic isolation and damping design ... 18
6.3 Protection design... 19
7 Construction and acceptance... 19
7.1 Production and installation ... 19
7.2 Welding ... 20
7.3 Acceptance ... 21
8 Maintenance and removal ... 22
8.1 Maintenance ... 22
8.2 Structural disposal ... 22
8.3 Demolition ... 23
General specification for steel structures
1 General
1.0.1 In order to ensure the quality and safety of steel structure projects,
implement policies on resource and energy conservation and rational utilization,
protect the ecological environment, ensure the safety of people’s lives and
property and personal health, prevent and reduce steel structure engineering
accidents, improve the level of green development of steel structure projects,
this specification is hereby formulated.
1.0.2 Except for the following projects, steel structure projects must implement
this specification.
1 Highway and railway bridges;
2 Pressure vessels, chemical vessels, gas pipelines;
3 Water conservancy, hydraulic engineering, water transportation, waterway
engineering.
1.0.3 The construction of steel structures shall follow the following principles:
1 Meet the requirements of applicability, economy, durability;
2 Improve project construction quality AND operation and maintenance level;
3 Comply with national policies on energy conservation, environmental
protection, disaster prevention and mitigation, emergency management;
4 In line with the development direction of construction technology;
encourage the application of new technologies.
1.0.4 Whether the technical methods and measures, which are adopted in the
project construction, meet the requirements of this specification, shall be
determined by the relevant responsible entities. Among them, innovative
technical methods and measures shall be demonstrated AND meet the relevant
performance requirements in this specification.
2 Basic requirements
2.0.1 For the steel structure engineering, it shall determine the design service
life, based on factors such as use function, construction cost, use and
maintenance cost, environmental impact. It shall adopt different safety levels,
according to the severity of the possible consequences of structural damage;
reasonably determine the structural action and action combination, seismic
action and action combination; adopt appropriate design methods, to ensure
the safety, applicability, durability of the structure.
2.0.2 For steel structures, it shall select a reasonable structural system,
according to the functional requirements of the building (structure), the on-site
environmental conditions, etc.
2.0.3 Within the design service life, the steel structure shall meet the following
requirements:
1 It shall be able to withstand various actions, within the design load range,
that may occur during normal construction and use;
2 It shall be kept in normal use;
3 It shall have durability that can reach the design service life, under normal
use and normal maintenance conditions;
4 It shall be able to function normally, within the specified time, under fire
conditions;
5 When explosions, impacts and other accidents occur, the structure shall
remain stable; there shall be no damage, that is not commensurate with
the cause.
2.0.4 The use and maintenance of steel structures and components, within the
design service life, shall meet the following requirements:
1 Without technical appraisal or design permission, it shall not change the
functions and conditions of use, which are specified in the design
documents;
2 For matters that may affect the safety and durability of the main structure
AND cause public safety risks to the public, it shall establish a regular
inspection and maintenance system;
3 The components, joints, supports, parts, etc., that must be replaced
according to the design requirements, shall be replaced in time;
4 The fire protection and anti-corrosion protection layer on the surface of the
components shall be maintained or replaced, in accordance with the
design requirements and maintenance requirements;
5 When the structure, components, joints, bearings, etc. have deformation
and durability defects, that exceed the design requirements, they shall be
the tensile force is small and the bending moment is relatively large, it shall
prevent the overall instability of the tension-bending member.
4.2 Cold-formed steel components
4.2.1 For the axial tension members and tension-bending members, which are
mainly under tension, shall be subject to the verification of strength and rigidity.
4.2.2 Axial compression members, bending members, compression-bending
members, tension-bending members which are mainly subjected to bending,
shall be checked for strength, stability, rigidity.
4.2.3 In the design of rigid frames, roof trusses, purlins, wall beams, it shall
verify the strength, stability, rigidity of the members. Meanwhile, it shall also
consider the adverse effects of changes in the internal forces of the members,
due to wind suction.
4.2.4 For the cold-formed steel components, that have undergone heat
treatment, such as annealing, welding, hot-dip galvanizing, shall not adopt the
strength design value, which considers the cold-bending effect.
4.3 Stainless steel components
4.3.1 Stainless steel structural materials shall be selected, according to factors
such as the safety level of the structure, design service life, working
environment, corrosion resistance requirements, surface requirements, etc.
4.3.2 The design of stainless steel components shall meet the following
requirements:
1 The tensile strength of stainless steel components shall be calculated,
based on the net section; the compressive strength shall be calculated,
based on the effective net section; the stable bearing capacity of the
member shall be calculated, based on the effective section; the stability
coefficient shall be calculated, based on the gross section.
2 The stainless steel axial tension members and tension-bending members
shall be subject to the verification of strength and stiffness.
3 The stainless steel axial compression members, bending members,
compression-bending members shall be checked for strength, stability,
rigidity.
4 For stainless steel welded flexural members, that are directly subjected to
dynamic loads OR whose buckling strengths are not considered, it shall
verify the local stability of the web.
4.3.3 When stainless steel components are connected to carbon steel and low-
alloy steel components, by fasteners, it shall use the insulating gaskets to
separate OR other effective measures, to prevent bimetallic corrosion;
meanwhile, it shall reduce the mechanical properties at the connection.
Stainless steel components shall not be welded with carbon steel and low-alloy
steel components.
4.4 Steel structure connection
4.4.1 The calculation model of the connection and the connector shall be
consistent with the actual bearing capacity of the connection; meanwhile, it shall
respectively calculate and design a single connector, according to the bearing
capacity limit state and the normal service limit state.
4.4.2 For ordinary bolted connections, rivet connections, high-strength bolted
connections, it shall calculate the combined bearing capacity of bolts (rivets)
under shear, tension, tension & shear, as well as the bearing capacity of the
connecting plate. Meanwhile, it shall consider the influence of the weakened
bolt holes and the prying force of the connecting plate, on the bearing capacity
of the connection.
4.4.3 The processing accuracy of bolt holes, the pretension which is applied by
high-strength bolts, the treatment process of the friction surface of connecting
plate for the frictional connection of high-strength bolts, shall ensure the
reliability of the bolt connection. For the high-strength bolts, to which pretension
had applied, shall not be recycled as a force-bearing bolt, after removal.
4.4.4 The welding consumables shall be matched with the base metal. The
welding seam shall adopt the groove form and structural measures, to reduce
the welding shrinkage stress, which is perpendicular to the thickness direction.
4.4.5 During the design of steel structure, the weld quality level shall be
determined, according to the importance of the steel structure, load
characteristics, weld form, working environment, stress state.
4.4.6 When the steel structure is subjected to dynamic loads AND it requires
fatigue calculations, it is strictly prohibited to use plug welding, slot welding,
electroslag welding, gas-electric vertical welding joints.
4.5 Fatigue
4.5.1 For steel structural members and their connections, that directly bear the
greater than 0.2; the second-order effect coefficient of the multi-floor steel
structures shall not be greater than 0.25;
3 In the first-order analysis, for the frame structure, it shall determine the
calculated length coefficient of the frame column, according to the lateral
stiffness, based on the mode of lateral buckling or no lateral buckling;
4 It shall consider the imaginary horizontal load, in the second-order analysis;
the calculated length coefficient of the frame column shall be 1.0;
5 The direction of the imaginary horizontal load shall be consistent with the
direction of wind load or seismic action. The load sub-factor of the
imaginary horizontal load shall be 1.0. The combination factor shall be 1.0,
for the load combinations which include wind load; the combination
coefficient shall be 0.5, for the load combinations which include seismic
action.
5.2.4 The seismic design of high-rise steel structures shall meet the following
requirements:
1 It shall control the sequence of the plastic deformation of the structural
members and joints; it shall use the capacity design method, for
supplementary check calculations;
2 The slenderness ratio of steel frame columns and supporting members,
the limits of the width-to-thickness ratio of beams, columns, supporting
plates, shall be adapted to the seismic performance targets of different
members.
5.2.5 For the reinforced layer of high-rise steel structure AND the vertical
members and connecting parts of the upper and lower floors, the seismic
structural measures shall be increased by one level, according to the specified
seismic grade of the structure. As for the vertical members and connecting parts
of the reinforced layer, the seismic strengthening measures shall also be
designed, according to the calculation results.
5.2.6 Under normal conditions of use, multi-floor and high-rise steel structures
shall have sufficient rigidity.
5.3 Large-span steel structure
5.3.1 When calculating the large-span steel structure, it shall determine the
boundary conditions, according to the form of the lower supporting structure
and the support structure. For the large-span steel structure with complex
shape, it shall use the overall model, including the lower supporting structure,
for calculation.
5.3.2 In areas with large snow loads, it shall also consider the adverse effects
of uneven distribution of snow loads, when designing large-span steel
structures. When the body shape is complex AND there is no reliable basis, it
shall use wind and snow tests or special studies, to determine the design snow
load.
5.3.3 For arch structures, single-layer reticulated shells, double-layer
reticulated shells with relatively large spans, as well as other spatial grid
structures that are mainly compressed, it shall carry out the nonlinear overall
stability analysis. The stable bearing capacity of the structure shall be
determined, through the whole process analysis of elasticity or elastic-plasticity,
meanwhile it shall consider the influence of initial defects, in the analysis.
5.3.4 For the grid shell structure, which has a seismic fortification intensity of 8
degrees and above, AND the grid shell structure in the area, which has a
seismic fortification intensity of 7 degrees and above, they shall be subjected to
seismic calculation. When using the mode decomposition response spectrum
method for seismic checking, the number of modes shall be calculated, so that
the sum of the participating masses of each mode is not less than 90% of the
total mass. For large-span steel structures, which have complex shapes, time-
history analysis method shall be used in seismic check calculation; meanwhile
the vertical and horizontal seismic effects shall be considered, at the same time.
5.3.5 For the cable-membrane structure or pre-stressed steel structure, it shall
be respectively subjected to initial pre-tension state analysis and load state
analysis. It shall consider the geometric nonlinear effects, in the calculation.
Under the load combination, which is controlled by permanent load, the cables
and membranes in the structure shall not be slack. Under the load combination,
which is controlled by variable load, the structure shall neither cause structural
failure nor affect the normal use function of structure, due to the relaxation of
local cables or membranes.
5.4 Tower mast steel structure
5.4.1 For tower mast steel structures, which have complex terrain conditions or
complex geometric shapes, the wind-resistant design parameters shall be
determined, through wind tunnel tests or numerical simulations.
5.4.2 When designing similar structures such as TV towers, radio tower masts,
power transmission towers, in ice-covered areas, it shall consider the effects of
the increased load and wind-shielding area, which is caused by the icing of
surface of structural members, overhead lines, ropes, as well as the
unfavorable effects of uneven ice removal. For the structure of the transmission
tower, it shall also consider the action of breaking tension, which is caused by
icing.
1 It shall have a clear calculation diagram AND a reasonable transmission
path of seismic action;
2 It shall be ensured that the connecting joints are not destroyed before the
components;
3 It shall be avoided that the entire structure loses its anti-seismic capacity
OR its bearing capacity for gravity loads, due to the destruction of part of
the structure or components;
4 It shall have good deformability and plastic energy dissipation capacity;
5 Measures shall be taken to improve the seismic resistance of the weak
parts, that may appear.
6.1.2 In addition to meeting the provisions of clause 3.0.2 of this specification,
for the steel materials of the components or parts, that undergo plastic
deformation, under the action of rare earthquakes, the super-strength
coefficient shall not be greater than 1.35.
6.1.3 When calculating the seismic bearing capacity of steel structural members,
the value of the seismic adjustment coefficient of bearing capacity shall comply
with the requirements of current relevant national standards.
6.1.4 For the connection of the plastic energy dissipation zone of the seismic
members of the steel structure, the ultimate bearing capacity shall be greater
than the bearing capacity of the connected members, when they are fully
plastically deformed.
6.2 Seismic isolation and damping design
6.2.1 In the design of seismic isolation and energy dissipation, the seismic
isolation device and damping components shall meet the following
requirements:
1 The performance parameters of the seismic isolation device and energy
dissipation components shall be determined by tests;
2 It shall take measures, to facilitate inspection and replacement, for the
installation positions of seismic isolation devices and energy dissipation
and damping components;
3 The design documents shall indicate the performance requirements for the
seismic isolation device and energy dissipation and damping components;
it shall carry out sampling inspection, before installation.
7.2.3 All welds shall be visually inspected. The first-level and second-level
welds, that require full penetration, shall be subject to non-destructive testing of
internal defects. The flaw-detection ratio of first-level weld shall be 100%; the
flaw-detection ratio of second-level weld shall not be less than 20%.
7.2.4 The judgement of results of the welding quality sampling inspection shall
meet the following requirements:
1 Except for crack defects, when the unqualified rate of the number of welds,
in the sampling inspection, is less than 2%, the batch is accepted. When
the unqualified rate of the number of welds, in the sampling inspection, is
greater than 5%, the batch is unqualified. When the unqualified rate, of
the number of welds, in the sampling inspection, is 2% ~ 5%, other
uninspected welds shall be randomly inspected, at a flaw-detection ratio
of not less than 2%; meanwhile, it shall respectively add one place, along
the extension line of the welds, on both sides of the original unqualified
part; if the unqualified rate of all welds, under sampling inspection, is not
more than 3%, this batch is accepted; if it is more than 3%, this batch is
rejected.
2 When there is 1 cracking defect in the inspection, it shall double the number
for inspection. If no cracking defect is found in the double sampling
inspection of the weld, the batch shall be accepted. If the inspection finds
multiple cracking defects or the double sampling inspection also finds a
cracking defect, the batch shall be rejected, AND all the remaining welds
of the batch shall be inspected.
3 When the batch acceptance is unqualified, all the remaining welds of the
batch shall be inspected.
7.3 Acceptance
7.3.1 Steel structure's anticorrosive coatings, number of coating passes,
coating thickness shall all meet the requirements of the design and coating
product specification. When the design does not require the thickness of the
coating, the total thickness of the dry paint film of the coating shall be 150 µm
outdoor, 125 µm indoor, AND have an allowable deviation of -25 µm. The
inspection quantity and inspection method shall meet the following
requirements:
1 Randomly check 10% of the number of components; there shall be not less
than 3 similar components;
2 Inspect 5 locations for each component; the value of each location is the
average value of the dry paint film thickness of the coating, at 3 measuring
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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