GB 55008-2021 English PDF

GB 55008-2021: Code for design of concrete structures
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GB 55008-2021
UDC
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
General code for concrete structures
ISSUED ON: SEPTEMBER 08, 2021
IMPLEMENTED ON: APRIL 01, 2022
Issued by: Ministry of Housing and Urban Rural Development of the People's
Republic of China;
State Administration for Market Regulation.
Table of Contents
Foreword ... 8
1 General ... 11
2 Basic regulations ... 11
3 Materials ... 13
3.1 Concrete ... 13
3.2 Steel bar ... 16
3.3 Other materials ... 17
4 Design ... 17
4.1 General provisions ... 17
4.2 Structural system ... 19
4.3 Structural analysis ... 19
4.4 Component design ... 20
5 Construction and acceptance ... 27
5.1 General provisions ... 27
5.2 Template engineering ... 27
5.3 Steel bars and prestressing works ... 28
5.4 Concrete works ... 28
5.5 Prefabricated structural engineering ... 28
6 Maintenance and demolition ... 29
6.1 General provisions ... 29
6.2 Structure maintenance ... 29
6.3 Structure disposal ... 30
6.4 Demolition ... 31
1 General
1.0.1 This Code is formulated to ensure the quality of concrete structural engineering,
the safety of people's lives and property, personal health, and promote the green and
high-quality development of concrete structural engineering.
1.0.2 This Code must be implemented for concrete structural engineering.
1.0.3 Whether the technical methods and measures adopted in engineering construction
comply with the requirements of this Code shall be determined by the relevant
responsible parties. Among them, innovative technical methods and measures shall be
demonstrated and meet the performance requirements of this Code.
2 Basic regulations
2.0.1 Concrete structural engineering shall determine its structural design working life,
structural safety level, seismic fortification category, structural action and action
combination. Structural bearing capacity limit state, normal service limit state, and
durability design shall be carried out. They shall meet the functional and structural
performance requirements of the project.
2.0.2 The selection of strength grade for structural concrete shall meet the requirements
for bearing capacity, stiffness, and durability of the engineering structure. For concrete
structures with a design service life of 50 years, the strength grade of structural concrete
shall also comply with the following regulations. For concrete structures with a design
service life greater than 50 years, the minimum strength grade of structural concrete
shall be higher than the following regulations.
1. The concrete strength grade of plain concrete structural components shall not be
lower than C20. The concrete strength grade of reinforced concrete structural
components shall not be lower than C25. The concrete strength grade of
prestressed concrete floor structure shall not be lower than C30. The concrete
strength grade of other prestressed concrete structural components shall not be
lower than C40. The concrete strength grade of steel-concrete composite
structural components shall not be lower than C30.
2. For reinforced concrete structural components subjected to repeated loads, the
concrete strength grade shall not be lower than C30.
3. For reinforced concrete structural components with seismic resistance level not
lower than grade 2, the concrete strength level shall not be lower than C30.
4. For reinforced concrete structural components using steel bars of 500 MPa and
above, the concrete strength grade shall not be lower than C30.
2.0.3 Ordinary steel bars and prestressed steel bars used in concrete structures shall
have strength and elongation that meet the requirements of engineering structures in the
ultimate bearing capacity and normal service limit states.
2.0.4 The strength standard values of ordinary steel bars, prestressed steel bars, and
structural concrete used in concrete structures shall have a guaranteed rate of not less
than 95%. The strength design value shall comply with the following regulations:
1. The design value of structural concrete strength shall be determined by dividing
its strength standard value by the material partial coefficient. The value of
material partial coefficient shall not be less than 1.4.
2. The strength design values of ordinary steel bars and prestressed steel bars shall
be determined by dividing their strength standard values by the partial coefficients
of ordinary steel bars and prestressed steel bar materials. The material partial
coefficients of ordinary steel bars and prestressed steel bars shall be determined
based on the reliability requirements of the engineering structure, considering
factors such as the mechanical properties, process performance, and surface shape
of the steel bars.
3. The partial coefficient value of ordinary steel bar material shall not be less than
1.1. The partial coefficient value of prestressed reinforcement material shall not
be less than 1.2.
2.0.5 Concrete structures shall take measures to ensure the durability of concrete
structures based on their purpose, exposed environment, and designed service life.
2.0.6 Reinforced concrete structural components and prestressed concrete structural
components shall adopt design and construction measures to ensure the synergistic
performance of steel bars, prestressed steel bars, and concrete materials under various
working conditions.
2.0.7 Mix design shall be carried out for structural concrete. Measures shall be taken to
ensure the performance of concrete mixture, concrete mechanical performance and
durability.
2.0.8 Concrete structures shall take measures to control concrete cracks from various
aspects such as design, materials, construction, and maintenance. The calculation of
stress cracks in concrete components shall comply with the following regulations:
1. For concrete components that do not allow cracks to occur, the concrete section
shall be controlled to not generate tensile stress, or the maximum tensile stress
shall not exceed the standard tensile strength value of the concrete according to
the actual cleaning condition.
2. For concrete components that allow cracks to occur, the width of stress cracks
shall be controlled based on the component category and environmental category,
with impermeability, frost resistance, corrosion resistance, wear resistance or
other special requirements, the mud content and mud block content of the sand
shall not exceed 3.0% and 1.0% respectively; and the firmness index shall not
exceed 8%. The mud content and mud block content of the sand used for high-
strength concrete shall not be greater than 2.0% and 0.5% respectively. The
machine-made sand shall control the stone powder content according to the
methylene blue value indicator of the stone powder and the flow ratio indicator
of the stone powder.
2. Sea sand for concrete structures must be purified.
3. The chloride ion content of sand for reinforced concrete shall not exceed 0.03%.
The chloride ion content of the sand used for prestressed concrete shall not exceed
0.01%.
3.1.3 The firmness indicator of coarse aggregate for structural concrete shall not be
greater than 12%. For concrete with impermeability, frost resistance, corrosion
resistance, wear resistance or other special requirements, the mud content and mud
block content in the coarse aggregate shall not exceed 1.0% and 0.5% respectively. The
firmness indicator shall not be greater than 8%. The mud content and mud block content
of coarse aggregate for high-strength concrete shall not be greater than 0.5% and 0.2%
respectively.
3.1.4 Admixtures for structural concrete shall meet the following requirements:
1. Concrete admixtures containing hexavalent chromium, nitrite and thiocyanate
shall not be used in concrete that is in direct contact with drinking water after
construction in drinking water projects.
2. Early-strength ordinary water reducers, early-strength agents, antifreeze agents
and waterproofing agents containing strong electrolyte inorganic salts are strictly
prohibited for the following concrete structures:
1) Concrete structures in contact with galvanized steel or aluminum;
2) Concrete structures with exposed steel bars and embedded parts without
protective measures;
3) Concrete structures using DC power;
4) Concrete structures within 100 m from the high voltage DC power supply.
3. Early-strength ordinary water-reducing agents, early-strength agents,
waterproofing agents and chloride-salt antifreezes containing chloride salts shall
not be used in prestressed concrete, reinforced concrete and steel fiber concrete
structures.
4. Early-strength ordinary water reducers and early-strength agents containing
ignored, the temperature effect and effect shall be calculated.
3. When the impact of shrinkage and creep on structural performance cannot be
ignored, the impact of concrete shrinkage and creep on structural performance
shall be calculated.
4. When the construction project requires to consider the accidental effect, the
accidental effect and its effect shall be calculated according to the requirements.
5. For structures or structural components directly subjected to dynamic and impact
loads, structural dynamic effects shall be considered.
6. The corresponding structural dynamic effects shall be considered during the
fabrication, transportation, hoisting and installation of precast concrete
components.
4.1.2 The seismic fortification objectives and anti-seismic measures of concrete
structures shall be determined according to the seismic fortification intensity of the
project location, site category, design earthquake grouping, project's seismic
fortification category, and seismic performance requirements.
4.1.3 When the stress expression is used to calculate the limit state of the bearing
capacity of concrete structural components, the following requirements shall be met:
1. The strength values of concrete and steel bars shall be determined according to
the design conditions and component performance design objectives.
2. The design stress of the steel bar shall not be greater than the strength value of the
steel bar.
3. The design stress of concrete shall not be greater than the strength value of
concrete.
4.1.4 The prefabricated concrete structure shall determine the connection structure
method and carry out connection and node design according to the structural
performance and the convenience requirements of component production and
installation construction.
4.1.5 The connection between concrete structural components and between non-
structural components and structural components shall comply with the following
requirements:
1. The stress and deformation performance requirements between the connected
components shall be met.
2. The connection between non-structural components and structural components
shall adapt to the deformation requirements of the main structure.
3. The connection shall not be broken prior to the connected component.
4.2 Structural system
4.2.1 The concrete structural system shall meet the load-bearing capacity, stiffness and
ductility performance requirements of the project.
4.2.2 The design of the concrete structure system shall meet the following requirements:
1. The mixed load-bearing structural system of concrete structural components and
masonry structural components shall not be used.
2. The building structure shall adopt a two-way lateral force resistant structure
system.
3. For high-rise buildings with a seismic fortification intensity of 9 degrees,
structures with transfer floors, structures with reinforced floors, split-level
structures and conjoined structures shall not be used.
4.2.3 The concrete floor of the house building shall meet the requirements of vertical
vibration comfort of the floor. Concrete structure high-rise buildings shall meet the
vibration comfort requirements of the 10-year return period horizontal wind load.
4.3 Structural analysis
4.3.1 The structural analysis model that conforms to the engineering reality shall be
used for the analysis of the effect of the concrete structure during the normal use stage
and the construction stage.
4.3.2 The structural analysis model shall meet the following requirements:
1. The structural and component geometric dimensions, structural material
performance indicators, calculation parameters, boundary conditions and
calculation diagrams used in the structural analysis model shall be determined.
2. The possible structural effects and their combination, initial state, etc. shall be
determined.
3. When using approximate assumptions and simplified models, there shall be theory,
test basis and engineering practice experience.
4.3.3 Structural calculation and analysis shall meet the following requirements:
1. Satisfy the mechanical balance condition.
2. Satisfy the main deformation coordination conditions.
4. The ultimate tensile strain of longitudinal tensile steel bars is taken as 0.01.
5. The stress of the longitudinal reinforcement is taken as the product of the strain of
the reinforcement and its modulus of elasticity. The stress of the steel bar shall
not exceed the design value of the compressive and tensile strength of the steel
bar. For axial compression components, the design value of the compressive
strength of the steel bar shall not exceed 400 N/mm.
6. The stress of the longitudinal prestressed tendon is taken as the product of the
strain of the prestressed tendon and its elastic modulus. The stress of prestressed
tendon shall not be greater than its design value of tensile strength.
4.4.3 When performing stress analysis and design on concrete structural components
with large volume or complex cross-sectional shape, the following regulations shall be
met:
1. The strength values and checking calculations of concrete and steel bars shall
comply with the provisions of Article 4.1.3 of this Code.
2. The amount of reinforcement shall be determined according to the projection of
the resu...