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This Code has been overall revised in accordance with Notice of Printing and Distributing of the Establishment and Amendment of Building Construction of 1997 (JIANBIAO [1997] No.108) issued by the Ministry of Construction and the Load Code for the Design of Building Structures (GBJ 9-87) jointly approved by China Architecture Scientific Research Institute and related departments.
During the process of revising, the team has carried out monographic study, summarized design experience in recent years, referred to related contents of foreign norms and international standards, widely asked for opinions from related departments all over the country and finalized after repeated amendment.
This Code can be divided into seven chapters and seven appendices. Primary contents revised are as follows:
1. In accordance with the rule of combination stated in Unified Standard for Reliability Design of Building Structures and getting rid of Wind Combination, the combination controlled by permanent load effect was added to the load fundamental combination. In the limit design of regular service, for the short-term effect combination, characteristic and frequent combinations are listed and at the same time, the frequent value coefficient was added to the variable load. For all combination values of variable loads, respective combination value coefficient is listed.
2. Partial adjustment and amendment of floor live load.
3. Adjustment has been made to roofing rectangular distribution live load that permits no person on the roof and provisions on roof gardens and helicopter pad load have been added.
4. Character of service for crane has been changed into work classes of cranes.
5. According to new observation data, statistics of wind pressure and snow pressure from national weather stations has been collected. At the same time, the basic value of wind and snow load recurrence interval has been changed from 30 years to 50 years. In the appendix, the 10-year, 50-year and 100-year wind pressure and snow pressure in main stations all over the country have been listed.
6. One Type has been added to the terrain roughness.
7. For the wind pressure altitude variation coefficient of buildings in a mountainous area, compensation factors have been given for the consideration of terrain conditions.
8. Specific provisions have been made to wind load of envelop enclosure members.
9. The interactive influences between buildings in architectural complex have been put forward.
10. For flexible structures, the test requirements for crosswind vibration have been added. This Code may be revised as required. Information and contents revised will be published on the journal of Standardization of Engineering Constructions.
The compulsory articles in this Code shall be executed strictly. In order to improve the quality of this Code, units shall sum up experience and collect background information. For feedback of related opinions and suggestions, please contact: China Architecture Scientific Research Institute (No.30 East Road, North Third Ring).
Chief Development Organization: China Architecture Technical Research Institute
Participating Development Organizations: Construction Department of Tongji University, Building Design Institute, Beijing International Design Institute of China Light Industry, Beijing: China Institute of Architecture Standard Design Press, Beijing Institute of Architectural Design and China Weather Scientific Research Institute
Chief Drafting Staffs: Chen Jifa, Hu Dexin, Jin Xinyang, Zhang Xiangting, Gu Zicong, Wei Caiang, Cai Yiyang, Guan Guixue, Xue Hang
Contents
1. General Principles 6
2. Terms and symbols 6
2.1 Terms 6
2.2 Main symbols 8
3. Classification of loads and combination of load effect 9
3.1 Classification of loads and representative values of a load 9
3.2 Load combination 10
4. Live load of floors and roofs 12
4.1 Rectangular distribution live load on floors of civilian buildings 12
4.2 Floor live load of industrial buildings 15
4.3 Roof live load 15
4.4 Roofing dust load 16
4.5 Construction and repair load as well as handrail horizontal load 18
4.6 Dynamic coefficient 19
5. Crane load 19
5.1 Vertical and horizontal load of cranes 19
5.2 The combination of several cranes 20
5.3 Dynamic coefficient of crane loads 20
5.4 The combination value, frequent value and quasi-permanent value of crane loads 20
6. Snow load 21
6.1 The characteristic value/nominal value and reference snow pressure of snow loads 21
6.2 Coefficient of snow distribution over the roof 22
7. Wind load 25
7.1 The characteristic value/nominal value and reference wind pressure of wind loads 25
7.2 Variation coefficient of wind pressure altitude 25
7.3 Wind load coefficient 27
7.4 Downwind vibration and wind vibration coefficient 42
7.5 Gustiness factor 44
7.6 Crosswind vibration 45
Appendix A Deadweight of Commonly-used Materials and Members 47
Appendix B Method for Deciding the Floor Isoeffect Rectangular Distribution Live Load 61
Appendix C Floor live load of industrial buildings 66
Appendix D Measurement Method of Fundamental Snow Pressure and Wind Pressure 72
Appendix E Empirical Formula for the Structure Which is Natural Vibration Period 114
Appendix F Approximation of the Structural Mode Factor 117
Appendix G Wording Explanation 119
1. General Principles
1.0.1 This Code is designed to meet demands in building structure design and requirements of secure application and economic feasibility.
1.0.2 This Code is applicable to the building structure design.
1.0.3 This Code has been made in accordance with principles stated in Unified Standard for Reliability Design of Building Structures (GB 50068-2001).
1.0.4 Effects involved with the building structure design include direct effect (combination of loads) and indirect effect (including subbase deformation, concrete shrinkage, welding deformations, temperature fluctuation or effects caused by earthquakes). In this Code, only provisions on combination of loads are stated.
1.0.5 The design reference period adopted in this Code is 50 years.
1.0.6 Effects or combination of loads involved with the building structure design shall be in accordance with this Code as well as other current national provisions.
2. Terms and symbols
2.1 Terms
2.1.1 Permanent load
During the utilization period of structures, the value of the combination of loads shall have no change with the passage of time or the variation is negligible compared with the average, or the variation is monotonous and tends to the limitation.
2.1.2 Variable load
During the utilization period of structures, the value of combination of loads shall be changed with the passage of time and the variation is negligible compared with the average.
2.1.3 Accidental load
During the utilization period of the structure, the combination of loads does not necessarily appear, but one it appears, the value is great but the duration is short.
2.1.4 Representative values of a load
The value of combination of loads adopted during the design for the checking of limiting state, such as characteristic value/nominal value, combination value, frequent value and quasi- permanent value.
2.1.5 Design reference period
The time parameter selected for deciding the representative value of the variable load.
2.1.6 Characteristic value/nominal value
The basic representative value of loads refers to the maximum characteristic value (such as typical value, mode, median or some place value) of statistical distribution of loads in the design reference period.
2.1.7 Combination value
The value of combination of loads that makes the load effect exceed probability during the design reference period and make the solitude appearance of the combination of loads has a unified value of combination of loads or make the structure has unified value of combination of loads with reliability index stated in the provision.
2.1.8 Frequent value
For variable load, during the design reference period, the exceeded total time is the minimum ratio or the exceeded frequency is the value of the combination of loads of the assigned frequency.
2.1.9 Quasi- permanent value
For variable load, during the design reference period, the exceeded total time is about half of the value of combination of loads in the design reference period.
2.1.10 Design value of a load
The arithmetic product of the representative values of a load and the partial load factor.
2.1.11 Load effect
Reaction of structures or structural elements caused by the combination of loads, such as internal force, distortion and crack
2.1.12 Load combination
In the limit design, to guarantee the built-in reliability, provisions for all kinds of design values of a load have been made.
2.1.13 Fundamental combination
In the limit of bearing capacity state, the combination of permanent effect and variable effect
2.1.14 Accidental combination
In the limit of bearing capacity state, the combination of permanent effect, variable effect and an accidental combination
2.1.15 Characteristic/nominal combination
In the regular service limiting state, the characteristic value/nominal value or combination value adopted is the combination of representative values of a load.
2.1.16 Frequent combinations
In the regular service limiting state, the frequent value or permanent value is adopted in the variable load is the combination of representative values of a load.
2.1.17 Quasi- permanent combinations
In the regular service limiting state, the quasi- permanent value adopted by the variable load is the combination of the representative values of a load.
2.1.18 Equivalent uniform live load
During the structure design, the actual load of continuous distribution above or under the floor is always by substituted by the evenly distributed load. The equivalent uniform live load refers to the load effect received by the structure can keep in line with the evenly distributed load of the actual load effect.
2.1.19 Tributary area
The tributary area is adopted during the calculation of the beam column members. It refers to the floor space of the calculated member load. It shall be divided by the zero line of the floor slab. In the practical situation, it can be simplified.
2.1.20 Dynamic coefficient
Structures and members that receives dynamic load, when designed according to the static force, shall adopt the value that is the ratio of the maximum power effect of structures or members and relevant static force effect.
2.1.21 Reference snow pressure
The reference pressure of snow load shall be decided by the maximum value of the 50-year period calculated from the probability statistics according to the observation data from the deadweight of snow on the local open and equitable terrain.
2.1.22 Reference wind pressure
The reference pressure of wind load shall be decided by the maximum wind speed for a 50-year period calculated from the probability statistics according to the observation data of average speed in 10min at 10m on the local open and equitable terrain. Also, relevant air density shall be considered and the wind pressure shall be calculated according to the formula (D.2.2-4).
2.1.23 Terrain roughness
When the wind passes 2km range before reaching the structure, the class used to describe the distribution pattern of irregular barriers on the ground.
2.2 Main symbols
Gk——characteristic value/nominal value of permanent load;
Qk——characteristic value/nominal value of variable load;
GGk——characteristic value/nominal value of permanent load effect;
SQk——characteristic value/nominal value of the variable load effect;
S——load effect combination design value;
R——The design value of resisting power of structural members;
SA——Downwind load effect;
SC——Crosswind load effect;
T——Natural vibration period of structures;
H——Top height of structures;
B——Windward width of structures;
Re——Reynolds number;
St——Strouhai number;
sk——Characteristic value/nominal value of snow load;
s0——reference snow pressure;
wk——characteristic value/nominal value of wind load;
w0——reference wind pressure;
νcr——Critical wind velocity of crosswind sympathetic vibration;
α——Angle of gradient;
βz——Gust coefficient at height Z;
βgz——Gust coefficient at height Z;
γ0——Structure significance coefficient;
γG——Subentry coefficient of permanent load;
γQ——Subentry coefficient of variable load;
ψc——combination value coefficient of the variable load;
ψf——frequent value coefficient of variable load;
ψq——quasi-permanent value coefficient of variable load;
μr——Coefficient of snow distribution over the roof
μz——Variation coefficient of wind pressure altitude;
μs——Wind load coefficient;
η——Coefficient of wind load terrain and physiognomy amendment;
ξ——Aggrandizement coefficient of wind load pulsation;
ν——Impact coefficient of wind load pulsation;
φz——Structural vibration mode coefficient;
ζ——Structural damping ratio.
3. Classification of loads and combination of load effect
3.1 Classification of loads and representative values of a load
3.1.1 The structural combination of loads can be divided into three kinds:
1. Permanent load, such as dead load, earth pressure and prestress.
2. Variable load, such as floor live load, roof live load and dust load, crane load, wind load and snow load.
3. Accidental load, such as blasting power and force of percussion.
Note: Deadweight refers to the combination of loads (gravitation) caused by the weight of materials.
3.1.2 During the design of building structures, different combinations of loads shall adopt different representative values. For permanent loads, the representative value shall be the characteristic value/nominal value. While for variable loads, the representative value shall be the characteristic value/nominal value, combination value, frequent value or quasi- permanent value according to different design requirements. For accidental loads, the representative value shall be decided according to the utilization characteristics of building structures.
3.1.3 Permanent load characteristic value/nominal value: for structural deadweight, it shall be decided according to the design size of structural members and the deadweight of unit volume of materials; for commonly-used materials and members, it shall be decided according to appendix 1 of this Code; for materials and members (including field fabricated heat insulators, concrete thin-wall members) with major changes in deadweight, it shall be the upper value or the lower range value according to the advantage or disadvantage state to members.
Note: For commonly-used materials and members, refer to Appendix A.
3.1.4 The characteristic value/nominal value of variable loads shall be adopted according to provisions in this Code.
3.1.5 The design of limit of bearing capacity state or the regular service limiting state shall adopt the combination value as the representative value of the variable loads. The combination value of variable loads refers to the variable load characteristic value/nominal value multiplied by the combination value coefficient of combination of loads.
3.1.6 If the regular service limiting state is designed according to the frequent combinations, the frequent value, quasi-permanent value shall be adopted as the representative value. If it is designed according to the quasi-permanent combinations, the quasi-permanent value shall be adopted as the representative value of variable loads. The frequent value of variable loads shall adopt the variable load characteristic value/nominal value multiplied by the frequent value coefficient of combination of loads. The variable load quasi- permanent value shall adopt the characteristic value/nominal value of variable loads multiplied by the quasi-permanent value coefficient of combination of loads.
3.2 Load combination
3.2.1 The design of building structures shall be in accordance with the combination of loads arising in the construction during the utilization process, according to the limit of bearing capacity state and the regular service limiting state. The design shall take the most disadvantaged combination for the combination of loads (effect).
3.2.2 For the limit of bearing capacity state, the combination of loads (effect) shall adopt the fundamental combination or accidental combination of load effect. The following design expression shall be adopted:
γ0S ≤R (3.2.2)
Where,
γ0——Structure significance coefficient;
S——The design of load effect combination;
R——The design value of resisting power of structural members shall be decided by related design specifications of building structures.
3.2.3 For the design value (S) of the fundamental combination of loads and load effect, it shall be decided by the most disadvantaged value from the following combination values:
1) Combination controlled by the variable load effect;
(3.2.3-1)
Where,
γG——Subentry coefficient of permanent load shall be adopted according to Article 3.2.5.
γQi——The ith subentry coefficient of variable load. γQi is the subentry coefficient of variable load Q1, to be adopted according to Article 3.2.5.
SGk——The load effect value calculated according to the permanent load characteristic value/nominal value Gk;
SQik——The load effect value calculated according to variable load characteristic value/nominal value Qik. SQ1k is the controller of all variable load effects.
ψci——The combination value coefficient of the variable load Qi shall be adopted according to provisions in chapters.
n——The number of variable loads forming the combination.
2) Combination controlled by the permanent load effect:
(3.2.3-2)
Note: 1 The design value of fundamental combination is applicable to the linear load effect.
2. If the SQ1k can't be decided distinctively, each variable load effect shall be taken as SQ1k and the most disadvantaged load effect combination shall be selected.
3.2.4 For common bents and frame structures, the reduction rule may be adopted in the fundamental combination and the most disadvantaged value shall be selected according to the following combination values:
1) Combination controlled by variable load effect;
(3.2.4)
2) The combination controlled by the permanent load effect shall be adopted according to formula (3.2.3-2).
3.2.5 The subentry coefficient of combination of loads in the fundamental combination shall be adopted according to the following provisions:
1. Subentry coefficient of permanent load;
1) If the effect causes disadvantages to the structure,
——for the combination controlled by the variable load effect, select 1.2;
——for the combination controlled by the permanent load effect, select 1.35.
2) If the effect causes advantages to the structure, select 1.0.
2. Subentry coefficient of variable load:
——Generally, select 1.4;
——For the characteristic value/nominal value of the live load of industrial housing floor greater than 4kN/m2, select 1.3.
3. For the overturn, slippage or floating calculation, the load subentry coefficient shall be adopted according to provisions in related design codes for structures.
3.2.6 For the design value of accidental combination and load effect combination, it shall be in accordance with the following provisions: the representative value of the accidental loads doesn't multiply subentry coefficient; if it appears together with the accidental loads and other combinations of loads, the representative value shall be adopted according to the observational data and project experience. Under different circumstances, the formula of design value of the load effect shall be decided by contrary provisions.
3.2.7 In the regular service limiting state, according to different design requirement, the characteristic/nominal combination, frequent combinations or quasi-permanent combinations may be adopted and the design shall be carried out according to the following design expression:
S≤C (3.2.7)
Where,
C——The limitation of structures or structural members when they are in regular service, such as the limitation of distortion, crack, amplitude, acceleration and stress, shall be adopted according to related design codes for building structures.
3.2.8 The design value (S) characteristic/nominal combination and load effect combinations shall be adopted according to the following formula:
(3.2.8)
Note: The design value of the combination is applicable to the linear combination of loads and load effect.
3.2.9 The design value (S) of frequent combinations and load effect combinations shall be adopted according to the following formula:
(3.2.9)
Where,
ψf1——The frequent coefficient of variable load Q1 shall be adopted according to provisions in chapters.
ψqi——The quasi value coefficient of the variable load Qi shall be adopted according to provisions in chapters.
Note: The design value of the combination is applicable to the linear combination of loads and load effect.
3.2.10 The design value (S) of quasi-permanent combinations and load effect combinations shall be adopted according to the following formula:
(3.2.10)
Note: The design value of the combination is applicable to the linear combination of loads and load effect.
Contents
1. General Principles
2. Terms and symbols
2.1 Terms
2.2 Main symbols
3. Classification of loads and combination of load effect
3.1 Classification of loads and representative values of a load
3.2 Load combination
4. Live load of floors and roofs
4.1 Rectangular distribution live load on floors of civilian buildings
4.2 Floor live load of industrial buildings
4.3 Roof live load
4.4 Roofing dust load
4.5 Construction and repair load as well as handrail horizontal load
4.6 Dynamic coefficient
5. Crane load
5.1 Vertical and horizontal load of cranes
5.2 The combination of several cranes
5.3 Dynamic coefficient of crane loads
5.4 The combination value, frequent value and quasi-permanent value of crane loads
6. Snow load
6.1 The characteristic value/nominal value and reference snow pressure of snow loads
6.2 Coefficient of snow distribution over the roof
7. Wind load
7.1 The characteristic value/nominal value and reference wind pressure of wind loads
7.2 Variation coefficient of wind pressure altitude
7.3 Wind load coefficient
7.4 Downwind vibration and wind vibration coefficient
7.5 Gustiness factor
7.6 Crosswind vibration
Appendix A Deadweight of Commonly-used Materials and Members
Appendix B Method for Deciding the Floor Isoeffect Rectangular Distribution Live Load
Appendix C Floor live load of industrial buildings
Appendix D Measurement Method of Fundamental Snow Pressure and Wind Pressure
Appendix E Empirical Formula for the Structure Which is Natural Vibration Period
Appendix F Approximation of the Structural Mode Factor
Appendix G Wording Explanation
