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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 Jian Biao [2006] No.77—“Notice on Printing and Distributing the Development and Revision Plan of Engineering Construction Standards and Codes in 2006 (Batch 1)” issued by the former Ministry of Construction (MOC), this code was revised from GB 50011-2001 “Code for Seismic Design of Buildings” by China Academy of Building Research (CABR) together with other design, survey, research and education institutions concerned. During the process of revision, the editorial team summarized the experiences in building seismic damages during Wenchuan Earthquake in 2008; adjusted the seismic precautionary intensities of the relevant disaster areas; added some compulsory provisions on the sites in mountainous areas, the arrangements of the infilled wall in frame structure, the requirements for staircase of masonry structure and the construction requirements of seismic structure; and raised the requirements for the details of the precast floor slab and for the reinforced elongation. Hereafter, the editorial team carried out studies on specific topics and some tests concerned, investigated and summarized the experiences and lessons from the strong earthquakes occurred in recent years home and abroad (including Wenchuan Earthquake), adopted the new research achievements of earthquake engineering, took the economic condition and construction practices in China into account, widely collected the comments from the relevant design, survey, research and education institutions as well as seismic administration authorities nationwide. Through a multi-round discussion, revision, substantiation, and with pilot designs as well, the final version has been completed and reviewed by an expert panel. This newly-revised version comprises 14 Chapters and 12 Appendixes. Besides remaining those provisions partially revised in 2008, the main revisions at this edition are: 1. supplementing the provisions on the seismic measures for areas with the seismic precaution Intensity 7 (0.15g) and Intensity 8 (0.30g), 2. adjusting the Design Earthquake Groups of Main Cities in China in accordance with GB18306-2001 “Seismic Ground Motion Parameter Zonation Map of China”, 3. improving the soil liquefaction discriminating equation; 4. adjusting the damping modification parameter of design response spectrum, 5. modifying the damping ratio and the seismic adjusting factor for load-bearing capacity of steel structure, 6. modifying the calculation methods of the horizontal seismic-reduced factor of seismically isolated structure, 7. supplementing the calculation method for horizontal and vertical earthquake action of large-span buildings; 8. raising the seismic design requirements for concrete frame structure buildings and for masonry buildings with RC frames on ground floors. 9. proposing the classification method for the seismic grades of steel structure buildings, and adjusting the provisions on seismic measures, correspondingly; 10. improving the seismic measures for multi-storey masonry buildings, concrete wall buildings and reinforced masonry buildings; 11. expending the application scope of seismically isolated and energy-dissipated buildings; 12. adding the principles on performance-based seismic design of for buildings as well as the seismic design provisions for large-span buildings, subterranean buildings, frame-bent structure factories, buildings with composite steel brace and concrete frame structures, and buildings with composite steel frame and concrete core tube structures. 13. canceling the contents related to multi-storey masonry buildings with inner frames. The provisions printed in bold type are compulsory ones 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 code and the explanation of the compulsory provisions hereof. China Academy of Building Research (CABR) is responsible for the explanation of specific technical contents. All relevant organizations are kindly requested to sum up and accumulate your experiences in actual practices during the process of implementing this code. The relevant opinions and advice, whenever necessary, can be posted or passed on to the Management Group of the National Standard “Code for Seismic Design of Buildings” of the China Academy of Building Research (Address: No. 30, Beisanhuan East Road, Beijing City, 100013, China; E-mail: GB50011-cabr@163.com). Chief Development Organization: China Academy of Building Research (CABR). Participating Development Organizations: Institute of Engineering Mechanics (IEM) of China Earthquake Administration, China Architecture Design & Research Group, China Institute of Building Standard Design & Research, Beijing Institute of Architectural Design, China Electronics Engineering Design Institute, China Southwest Architectural Design and Research Institute, China Northwest Architectural Design and Research Institute, China Northeast Architecture Design and Research Institute, East China Architectural Design and Research Institute, Central-South Architectural Design Institute, the Architectural Design and Research Institute of Guangdong Province, Shanghai Institute of Architecture Design and Research, Institute of Building Design and Research of Xinjiang Uygur Autonomous Region, Yunnan Province Design Institute, Sichuan Architectural Design Institute, Shenzhen General Institute of Architectural Design and Research, Beijing Geotechnical Institute, Shanghai Tunnel Engineering and Rail Transit Design and Research Institute, China Construction (Shenzhen) Design international, Architecture Design General Institute of China Metallurgical Group Corporation, China National Machinery Industry Corporation, China IPPR International Engineering Corporation, Tsinghua University, Tongji University, Harbin Institute of Technology, Zhejiang University, Chongqing University, Yunnan University, Guangzhou University, Dalian University of Technology and Beijing University of Technology Chief Drafters: Huang Shimin, Wang Yayong (The following is according to the Chinese phonetic alphabetically) Ding Jiemin, Fang Taisheng, Deng Hua, Ye Liaoyuan, Feng Yuan, Lu Xilin, Liu Qiongxiang, Li Liang, Li Hui, Li Lei, Li Xiaojun, Li Yaming, Li Yingmin, Li Guoqiang, Yang Linde, Su Jingyu, Xiao Wei, Wu Mingshun, Xin Hongbo, Zhang Ruilong, Chen Jiong, Chen Fusheng, Ou Jinping, Yu Yinquan, Yi Fangmin, Luo Kaihai, Zhou Zhenghua, Zhou Bingzhang, Zhou Fulin, Zhou Xiyuan, Ke Changhua, Lou Yu, Jiang Wenwei, Yuan Jinxi, Qian Jihong, Qian Jiaru, Xu Jian, Xu Yongji, Tang Caoming, Rong Baisheng, Cao Wenhong, Fu Shengcong, Zhang Yiping, Ge Xueli, Dong Jincheng, Cheng Caiyuan, Fu Xueyi, Zeng Demin, Dou Nanhua, Cai Yiyan, Xue Yantao, Xue Huili and Dai Guoying Chief Examiners: Xu Peifu, Wu Xuemin, Liu Zhigang (The following is according to the Chinese phonetic alphabetically) Liu Shutun, Li Li, Li Xuelan, Chen Guoyi, Hou Zhongliang, Mo Yong, Gu Baohe, Gao Mengtan, Huang Xiaokun and Cheng Maokun Contents 1 General 12 2 Terms and Symbols 13 2.1 Terms 13 2.2 Symbols 14 3 Basic Requirements of Seismic Design 16 3.1 Category and Criterion for Seismic Precaution of Buildings 16 3.2 Earthquake Ground Motion 16 3.3 Site and Soil 16 3.4 Regularity of Building Configuration and Structural Assembly 17 3.5 Structural System 20 3.6 Structural Analysis 21 3.7 Nonstructural Components 22 3.8 Isolation and Energy-Dissipation 23 3.9 Materials and Construction 23 3.10 Seismic Performance-Based Design of Buildings 24 3.11 Seismic Response Observation System of Buildings 26 4 Site, Soil and Foundation 27 4.1 Site 27 4.2 Natural Soil and Foundation 30 4.3 Liquefied Soil and Soft Soil 31 4.4 Pile Foundation 36 5 Earthquake Action and Seismic Checking for Structures 37 5.1 General 38 5.2 Calculation of Horizontal Earthquake Action 42 5.3 Calculation of Vertical Earthquake Action 47 5.4 Seismic Checking for the Sections of Structural Member 48 5.5 Seismic Checking for the Storey Drift 50 6 Multi-storey and Tall Reinforced Concrete Buildings 54 6.1 General 54 6.2 Essentials in Calculation 60 6.3 Details of Seismic Design for Frame Structures 65 6.4 Details of Seismic Design for Seismic Wall Structures 71 6.5 Details of Seismic Design for Frame-seismic-Wall Structures 74 6.6 Requirements for Seismic Design of Slab-column-seismic-Wall Structures 75 6.7 Requirements for Seismic Design of Tube Structures 76 7 Multi-storey Masonry Buildings and Multi-storey Masonry Buildings with RC Frames on Ground Floors 79 7.1 General 79 7.2 Essentials in Calculation 84 7.3 Details of Seismic Design of Multi-storey Brick Buildings 89 7.4 Details of Seismic Design of Multi-storey Concrete Block Buildings 94 7.5 Details of Seismic Design of Multi-storey Masonry Buildings with RC Frames and Seismic-Walls on Ground Floors 97 8 Multi-Storey and Tall Steel Buildings 101 8.1 General 101 8.2 Essentials in Calculation 103 8.3 Details for Steel Frame Structures 109 8.4 Details for Steel Frame-concentrically-braced Structures 112 8.5 Details for Steel Frame-eccentrically-braced Structures 113 9 Single-storey Factory Buildings 116 9.1 Single-storey Factory Buildings with Reinforced Concrete Columns 116 9.2 Single-storey Steel Factory Buildings 126 9.3 Single-storey Factory Buildings with Brick Columns 132 10 Large-span Buildings 136 10.1 Single-storey Spacious Buildings 136 10.2 Large-span Roof Buildings 138 11 Earth, Wood and Stone Houses 143 11.1 General 143 11.2 Unfired Earth Houses 144 11.3 Wood Houses 145 11.4 Stone Houses 147 12 Seismically Isolated and Energy-Dissipated Buildings 149 12.1 General 149 12.2 Essentials in Design of Seismically Isolated Buildings 150 12.3 Essentials in Design of Seismic-energy-dissipated Buildings 155 13 Nonstructural Components 160 13.1 General 160 13.2 Basic Requirements for Calculation 160 13.3 Basic Seismic-Measures for Architectural Members 162 14 Subterranean Buildings 167 14.1 General 167 14.2 Essentials in Calculation 167 14.3 Seismic Details and Anti-liquefaction Measures 169 Appendix A The Seismic Precautionary Intensity, Design Basic Acceleration of Ground Motion and Design Earthquake Groups of Main Cities and Towns in China 171 Appendix B Requirements for Seismic Design of High Strength Concrete Structures 206 Appendix C Requirements for Seismic Design of Prestressed Concrete Structures 208 Appendix D Section Seismic Check for the Beam-column Joint Core Zone of Frames 210 Appendix E Requirements for Seismic Design of the Transfer Storey Structures 214 Appendix F Requirements for Seismic Design of Reinforced Concrete Small-sized Hollow Block Seismic -Wall Buildings 216 Appendix G Requirements for Seismic Design of Buildings with Steel Brace-Concrete Frame Structures and Steel Frame-Reinforced Concrete Core Tube Structures 224 Appendix H Requirements for Seismic Design of Multi-storey Factory Buildings 227 Appendix J Seismic Effect Adjustment for Transversal Planar-Bent of Single-Storey Factory 234 Appendix K Longitudinal Seismic Check for Single-Storey Factory 237 Appendix L Simplified Calculation for Seismically Isolated Design and Seismically Isolated Measures of Masonry Structures 243 Appendix M Reference Procedures of Performance-based Seismic Design 248 Explanation of Wording in This Code 255 List of Quoted Standards 256 1 General 1.0.1 This code is formulated with a view to implementing the relevant laws and regulations on construction engineering and protecting against and mitigating earthquake disasters, carrying out the policy of “prevention first”, as well as alleviating the seismic damage of buildings, avoiding casualties and reducing economic loss through seismic precautionary of buildings. The basic seismic precautionary objectives of buildings which designed and constructed in accordance with this code, are as follows: 1) under the frequent earthquake ground motion with an intensity being less than the local Seismic Precautionary Intensity, the buildings with major structure undamaged or requiring no repair may continue to serve; 2) under the earthquake ground motion with an intensity being equivalent to the local Seismic Precautionary Intensity, the buildings with possible damage may continue to serve with common repair; or 3) under the rare earthquake ground motion with an intensity being larger than the local Seismic Precautionary Intensity, the buildings shall not collapse or shall be free from such severe damage that may endanger human lives. If the buildings with special requirements in functions or other aspects are carried out with the seismic performance-based design, more concrete and higher seismic precautionary objectives shall be established. 1.0.2 All the buildings situated on zones of Seismic Precautionary Intensity 6 or above must be carried out with seismic design. 1.0.3 This code is applicable to the seismic design and the isolation and energy-dissipation design of the buildings suited on zones of Seismic Precautionary Intensity 6, 7, 8 and 9. And the seismic performance-based design of buildings may be implemented in accordance with the basic methods specified in this code. As for the buildings suited on zones where the Seismic Precautionary Intensity is above Intensity 9 and the industrial buildings for special purpose, their seismic design shall be carried out according to the relevant special provisions. Note: For the purposes of this code, “Seismic Precautionary Intensity 6, 7, 8 and 9” hereinafter is referred to “Intensity 6, 7, 8 and 9”. 1.0.4 The Seismic Precautionary Intensity must be determined in accordance with the documents (drawings) examined, approved and issued by the authorities appointed by the State. 1.0.5 Generally, the seismic precautionary intensity of buildings shall be adopted with the basic seismic intensity (the intensity values corresponding to the design basic acceleration of ground motion value in this code) determined according to the “Seismic Ground Motion Parameter Zonation Map of China”. 1.0.6 In addition to the requirements of this code, the seismic design of buildings also shall comply with the requirements specified in the relevant current standards of the State. 2 Terms and Symbols 2.1 Terms 2.1.1 Seismic precautionary intensity The seismic intensity approved by the authority appointed by the State, which is used as the basis for the seismic precaution of buildings in a certain region. Generally, it is taken as the seismic Intensity with a 10% probability of exceedance in 50 years. 2.1.2 Seismic precautionary criterion The rule for judging the seismic precautionary requirements, which is dependent on the Seismic Precautionary Intensity or the design parameters of ground motion and the precautionary category of buildings. 2.1.3 Seismic ground motion parameter zonation map The map in which the whole county is divided into regions with different seismic precautionary requirements according to the ground motion parameter (that is the degree of earthquake ground motion intensity indicated by acceleration). 2.1.4 Earthquake action The dynamic response of structure caused by earthquake ground motion, including horizontal and vertical earthquake action. 2.1.5 Design parameters of earthquake ground motion The parameters of earthquake ground motion used in seismic design, including the acceleration (velocity or displacement) time history of the earthquake ground motion , the acceleration response spectrum and the peak value of ground acceleration 2.1.6 Design basic acceleration of earthquake ground motion The design value of seismic acceleration with a 10% probability of exceedance in the 50-years design reference period. 2.1.7 Design characteristic period of earthquake ground motion The period value corresponding to the starting point of the descending section of the seismic influence coefficient curve used for seismic design, that is dependent on the earthquake magnitude, epicentral distance, site class and etc. For convenience, it is named as “characteristic period” for short. 2.1.8 Site Locations of the project colonies, being with similar characteristics of response spectra. The scope of site is equivalent to plant area, residential area and natural village or the plane area no less than 1.0km2. 2.1.9 Seismic concept design of buildings The process of making the general arrangement for the buildings and structures and of determining details, based on the fundamental design principles and concepts obtained from the past experiences in earthquake disasters and projects. 2.1.10 Seismic measures The seismic design contents except earthquake action calculation and member resistance calculation, including the details of seismic design. 2.1.11 Details of seismic design All the detailed requirements that must be taken for the structural and nonstructural components according to seismic concept design principles and require no calculation generally. 2.2 Symbols 2.2.1 Actions and effects FEk, FEvk—— Standard values of total horizontal and vertical earthquake actions of structure respectively; GE, Geq—— Representative value of gravity load of structure (or component) and the total equivalent representative value of gravity load of a structure ,respectively; wK—— Standard value of wind load; SE—— Seismic effect (bending moment, axial force, shear, stress and deformation); S—— Fundamental combination values of the effects of earthquake action and other loads; Sk—— Effect of the standard value of action or load; M—— Bending moment; N—— Axial force; V—— Shear; p—— Pressure on bottom of foundation; u—— Lateral displacement; θ—— Storey drift 2.2.2 Material properties and resistance K—— Stiffness of structure (member); R—— Resistant capacity of structural component; f, fk, fE—— Design value, standard value and seismic design value of various material strength (including the bearing capacity of soil) , respectively; [θ]—— Allowable storey drift. 2.2.3 Geometric parameters A—— Cross-sectional area of member; As—— Cross-sectional area of reinforcement; B—— Total width of structure; H—— Total height of structure, or the column height; L—— Total length of structure (unit); α—— Distance; as, a's—— Minimal distance from the force point of the longitudinal tensile and compressive reinforcements to the margin of section, respectively; b—— Sectional width of member; d—— Depth or thickness of soil layer, or the diameter of reinforcement; h—— Depth of cross-section of member; l—— Length or span of member; t—— Thickness of wall or floor slab. 2.2.4 Coefficients of calculation α—— Horizontal seismic influence coefficient; αmax—— Maximum value of horizontal seismic influence coefficient; αvmax—— Maximum value of vertical seismic influence coefficient; γG, γE, γW—— Partial factor of action; γRE—— seismic adjusting factor for load-bearing capacity; ζ—— Calculation coefficient; η—— Enhancement or adjustment coefficient of earthquake action effect (internal force or deformation); λ—— Slenderness ratio of member, or the proportionality coefficient; ξy—— Yield strength coefficient of structure (member); ρ—— Reinforcement ratio or ratio; ø—— Stability coefficient of compressive member; —— Combination value coefficient or the influence coefficient. 2.2.5 Others T—— Natural vibration period of structure; N—— Penetration resistance (in blow number); IlE—— Liquefaction index of soil under earthquake; Xji—— The coordinate of modal displacement (relative displacement of the ith mass point of the jth mode in x direction); Yji—— The coordinate of modal displacement (relative displacement of the ith mass point of the jth mode in y direction); n—— Total number, such as number of storeys, masses, reinforcements and spans, etc.; υse—— Equivalent shear wave velocity of soil layer; Φji—— The coordinate of modal rotation (relative rotation of the ith mass point of the jth mode around the z axial direction). 3 Basic Requirements of Seismic Design 3.1 Category and Criterion for Seismic Precaution of Buildings 3.1.1 The seismic precautionary category and the seismic precautionary criterion of buildings shall be determined in accordance with the current national standard GB 50223 “Standard for Classification of Seismic Protection of Building Constructions”. 3.1.2 Unless otherwise specified in this code, Categories B, C and D buildings with seismic precautionary intensity 6 may not be carried out the calculation of earthquake action. 3.2 Earthquake Ground Motion 3.2.1 The earthquake ground motion of the zones in which buildings are suited shall be represented by design basic acceleration and characteristic period of earthquake ground motion corresponding to the seismic precautionary intensity. 3.2.2 The corresponding relationship between the seismic precautionary intensity and the design basic acceleration of ground motion shall be in accordance with those specified in Table 3.2.2. Unless otherwise stated in this code, the buildings in such zones where the design basic acceleration of ground motion is 0.15g and 0.30g shall be carried out with seismic design respectively according to the requirements of seismic precautionary intensity 7 and 8. Table 3.2.2 Corresponding Relationship Between Seismic Precautionary Intensity and Design Basic Acceleration of Ground Motion Seismic precautionary intensity 6 7 8 9 Design basic acceleration value of ground motion 0.05g 0.10 (0.15)g 0.20 (0.30)g 0.40g Note: g is the gravity acceleration. 3.2.3 The characteristic period of earthquake ground motion shall be determined according to the design earthquake groups and the site class of the building site. The design earthquakes in this code are totally divided into three groups, and their characteristic periods shall be adopted according to the relevant provisions in Chapter 5 of this code. 3.2.4 The seismic precautionary intensity, design basic acceleration of ground motion and design earthquake groups of the central areas in the main cities in China may be adopted according to Appendix A of this code. Contents Chapter 1 General Chapter 2 Terms and Symbols 2.1 Terms 2.2 Symbols Chapter 3 Basic Requirements of Seismic Design 3.1 Category and Criterion for Seismic Precaution of Buildings 3.2 Earthquake Effect 3.3 Site and Base 3.4 Regularity of Building Configuration and Structural Assembly 3.5 Structural System 3.6 Structural Analysis 3.7 Nonstructural Components 3.8 Isolation and Energy-Dissipation 3.9 Materials and Construction 3.10 Performance-Based Design of Buildings 3.11 Seismic Response Observation System of Buildings Chapter 4 Site, Base and Foundation 4.1 Site 4.2 Natural Base and Foundation 4.3 Liquefied Soil and Soft Soil Bases 4.4 Pile Foundations Chapter 5 Earthquake Action and Seismic Checking for Structures 5.1 General 5.2 Calculation of Horizontal Earthquake Action 5.3 Calculation of Vertical Earthquake Action 5.4 Section Seismic Check 5.5 Seismic Deformation Check Chapter 6 Multi-storey and Tall Reinforced Concrete Buildings 6.1 General 6.2 Essentials in Calculation 6.3 Details of Seismic Design for Frame Structures 6.4 Details of Seismic Design for Seismic Wall Structures 6.5 Details of Seismic Design for Frame-seismic Wall Structures 6.6 Requirements for Seismic Design of Slab-column-seismic Wall Structures 6.7 Requirements for Seismic Design of Tube Structures Chapter 7 Multi-storey Masonry Buildings and Multi-storey Masonry Buildings with R.C. Frames on Ground Floors 7.1 General 7.2 Essentials in Calculation 7.3 Details of Seismic Design of Multi-storey Brick Buildings 7.4 Details of Seismic Design of Multi-storey Concrete Block Buildings 7.5 Details of Seismic Design of Multi-storey Masonry Buildings with R.C. Frames on Ground Floors Chapter 8 Multi-Storey and Tall Steel Buildings 8.1 General 8.2 Essentials in Calculation 8.3 Details for Steel Frame Structures 8.4 Details of Seismic Design of Steel Frame-concentrically-supported Structures 8.5 Details for Seismic Design of Steel Frame-eccentrically-supported Structures Chapter 9 Single-storey Factory Buildings 9.1 Single-storey Factory Buildings with R.C. Columns 9.2 Single-storey Steel Factory Buildings 9.3 Single-storey Factory Buildings with Brick Columns Chapter 10 Large-span Buildings 10.1 Single-storey Spacious Buildings 10.2 Large-span Roof Buildings Chapter 11 Earth, Wood and Stone Houses 11.1 General 11.2 Unfired Earth Houses 11.3 Wood Houses 11.4 Stone Houses Chapter 12 Seismically Isolated and Energy-Dissipated Buildings 12.1 General 12.2 Essentials in Design of Seismically Isolated Buildings 12.3 Essentials in Design of Energy-dissipated Buildings Chapter 13 Nonstructural Components 13.1 General 13.2 Essentials in Calculation 13.3 Essential Measures for Architectural Members 13.4 Essential Measures for Supports of Mechanical and Electrical Components Chapter 14 Subterranean Buildings 14.1 General 14.2 Essentials in Calculation 14.3 Details and Anti-Liquefaction Measures Appendix A The Seismic Precautionary Intensity, Design Basic Acceleration of Ground Motion and Design Earthquake Groups of Main Cities in China Appendix B Requirements for Seismic Design of High Strength Concrete Structures Appendix C Requirements for Seismic Design of Prestressed Concrete Structures Appendix D Section Seismic Check for the Beam-column Joint Core Zone of Frames Appendix E Requirements for Seismic Design of the Transfer Storey Structures Appendix F Requirements for Seismic Design of Small Armored Concrete Hollow Block Buildings with Seismic Wall Appendix G Requirements for Seismic Design of Buildings with Steel Support-Concrete Frame Structures and Steel Frame-Armored Concrete Core Tube Structures Appendix H Requirements for Seismic Design of Multi-storey Factory Buildings Appendix J Earthquake Action Effect Adjustment for Transverse Plane Bent Frame of Single-storey Factory Buildings Appendix K Seismic Check for Single-storey Factory Buildings in Longitudinal Direction Appendix L Simplified Calculation of Seismic Isolation Design and Seismic Isolation Measures for Masonry Structures Appendix M Reference Methods for Achieving Performance-Based Seismic Design Explanation of Wording in This Code List of Quoted Standards 1 总 则 1.0.1 为贯彻执行国家有关建筑工程、防震减灾的法律法规并实行以预防为主的方针,使建筑经抗震设防后,减轻建筑的地震破坏,避免人员伤亡,减少经济损失,制定本规范。 按本规范进行抗震设计的建筑,其基本的抗震设防目标是:当遭受低于本地区抗震设防烈度的多遇地震影响时,主体结构不受损坏或不需修理可继续使用;当遭受相当于本地区抗震设防烈度的设防地震影响时,可能发生损坏,但经一般性修理仍可继续使用;当遭受高于本地区抗震设防烈度的罕遇地震影响时,不致倒塌或发生危及生命的严重破坏。使用功能或其他方面有专门要求的建筑,当采用抗震性能化设计时,具有更具体或更高的抗震设防目标。 1.0.2 抗震设防烈度为6度及以上地区的建筑,必须进行抗震设计。 1.0.3 本规范适用于抗震设防烈度为6、7、8和9度地区建筑工程的抗震设计以及隔震、消能减震设计。建筑的抗震性能化设计,可采用本规范规定的基本方法。 抗震设防烈度大于9度地区的建筑及行业有特殊要求的工业建筑,其抗震设计应按有关专门规定执行。 注:本规范“6度、7度、8度、9度”即“抗震设防烈度为6度、7度、8度、9度”的简称。 1.0.4 抗震设防烈度必须按国家规定的权限审批、颁发的文件(图件)确定。 1.0.5 一般情况下,建筑的抗震设防烈度应采用根据中国地震动参数区划图确定的地震基本烈度(本规范设计基本地震加速度值所对应的烈度值)。 1.0.6 建筑的抗震设计,除应符合本规范要求外,尚应符合国家现行有关标准的规定。 2 术语和符号 2.1 术 语 2.1.1 抗震设防烈度 seismic precautionary intensity 按国家规定的权限批准作为一个地区抗震设防依据的地震烈度。一般情况,取50年内超越概率10%的地震烈度。 2.1.2 抗震设防标准 seismic precautionary criterion 衡量抗震设防要求高低的尺度,由抗震设防烈度或设计地震动参数及建筑抗震设防类别确定。 2.1.3 地震动参数区划图 seismic ground motion parameter zonation map 以地震动参数(以加速度表示地震作用强弱程度)为指标,将全国划分为不同抗震设防要求区域的图件。 2.1.4 地震作用 earthquake action 由地震动引起的结构动态作用,包括水平地震作用和竖向地震作用。 2.1.5 设计地震动参数 design parameters of ground motion 抗震设计用的地震加速度(速度、位移)时程曲线、加速度反应谱和峰值加速度。 2.1.6 设计基本地震加速度 design basic acceleration of ground motion 50年设计基准期超越概率10%的地震加速度的设计取值。 2.1.7 设计特征周期 design characteristic period of ground motion 抗震设计用的地震影响系数曲线中,反映地震震级、震中距和场地类别等因素的下降段起始点对应的周期值,简称特征周期。 2.1.8 场地 site 工程群体所在地,具有相似的反应谱特征。其范围相当于厂区、居民小区和自然村或不小于1.0km2的平面面积。 2.1.9 建筑抗震概念设计 seismic concept design of buildings 根据地震灾害和工程经验等所形成的基本设计原则和设计思想,进行建筑和结构总体布置并确定细部构造的过程。 2.1.10 抗震措施 seismic measures 除地震作用计算和抗力计算以外的抗震设计内容,包括抗震构造措施。 2.1.11 抗震构造措施 details of seismic design 根据抗震概念设计原则,一般不需计算而对结构和非结构各部分必须采取的各种细部要求。 2.2 主要符号 2.2.1 作用和作用效应 FEK、FEvK——结构总水平、竖向地震作用标准值; GE、Geq——地震时结构(构件)的重力荷载代表值、等效总重力荷载代表值; WK——风荷载标准值; SE——地震作用效应(弯矩、轴向力、剪力、应力和变形); S——地震作用效应与其他荷载效应的基本组合; SK——作用、荷载标准值的效应; M——弯矩; N——轴向压力; V——剪力; p——基础底面压力; u——侧移; θ——楼层位移角。 2.2.2 材料性能和抗力 K——结构(构件)的刚度; R——结构构件承载力; f、fK、fE——各种材料强度(含地基承载力)设计值、标准值和抗震设计值; [θ]——楼层位移角限值。 2.2.3 几何参数 A——构件截面面积; As——钢筋截面面积; B——结构总宽度; H——结构总高度、柱高度; L——结构(单元)总长度; α——距离; αs、α′s——纵向受拉、受压钢筋合力点至截面边缘的最小距离; b——构件截面宽度; d——土层深度或厚度,钢筋直径; h——构件截面高度; l——构件长度或跨度; t——抗震墙厚度、楼板厚度。 2.2.4 计算系数 α——水平地震影响系数; αmax——水平地震影响系数最大值; αvmax——竖向地震影响系数最大值; γG、γE、γw ——作用分项系数; γRE——承载力抗震调整系数; ζ——计算系数; η——地震作用效应(内力和变形)的增大或调整系数; λ——构件长细比,比例系数; ξy——结构(构件)屈服强度系数; ρ——配筋率,比率; φ——构件受压稳定系数; ——组合值系数,影响系数。 2.2.5 其他 T——结构自振周期; N——贯人锤击数; IlE——地震时地基的液化指数; Xji——位移振型坐标(j振型i质点的x方向相对位移); Yji——位移振型坐标(j振型i质点的y方向相对位移); n——总数,如楼层数、质点数、钢筋根数、跨数等; vse——土层等效剪切波速; Φji——转角振型坐标(j振型i质点的转角方向相对位移)。 3 基本规定 3.1 建筑抗震设防分类和设防标准 3.1.1 抗震设防的所有建筑应按现行国家标准《建筑工程抗震设防分类标准》GB 50223 确定其抗震设防类别及其抗震设防标准。 3.1.2 抗震设防烈度为6度时,除本规范有具体规定外,对乙、丙、丁类的建筑可不进行地震作用计算。 3.2 地震影响 3.2.1 建筑所在地区遭受的地震影响,应采用相应于抗震设防烈度的设计基本地震加速度和特征周期表征。 3.2.2 抗震设防烈度和设计基本地震加速度取值的对应关系,应符合表3.2.2的规定。设计基本地震加速度为0.15g和0.30g地区内的建筑,除本规范另有规定外,应分别按抗震设防烈度7度和8度的要求进行抗震设计。 表3.2.2抗震设防烈度和设计基本地震加速度值的对应关系 抗震设防烈度 6 7 8 9 设计基本地震加速度值 0.05g 0.10(0.15)g 0.20(0.30)g 0.40g 注:g为重力加速度。 3.2.3 地震影响的特征周期应根据建筑所在地的设计地震分组和场地类别确定。本规范的设计地震共分为三组,其特征周期应按本规范第5章的有关规定采用。 3.2.4 我国主要城镇(县级及县级以上城镇)中心地区的抗震设防烈度、设计基本地震加速度值和所属的设计地震分组,可按本规范附录A采用。 3.3 场地和地基 3.3.1 选择建筑场地时,应根据工程需要和地震活动情况、工程地质和地震地质的有关资料,对抗震有利、一般、不利和危险地段做出综合评价。对不利地段,应提出避开要求;当无法避开时应采取有效的措施。对危险地段,严禁建造甲、乙类的建筑。不应建造丙类的建筑。 3.3.2 建筑场地为I类时,对甲、乙类的建筑应允许仍按本地区抗震设防烈度的要求采取抗震构造措施;对丙类的建筑应允许按本地区抗震设防烈度降低一度的要求采取抗震构造措施,但抗震设防烈度为6度时仍应按本地区抗震设防烈度的要求采取抗震构造措施。 3.3.3 建筑场地为Ⅲ、Ⅳ类时,对设计基本地震加速度为0.15g和0.30g的地区,除本规范另有规定外,宜分别按抗震设防烈度8度(0.20g)和9度(0.40g)时各抗震设防类别建筑的要求采取抗震构造措施。 3.3.4 地基和基础设计应符合下列要求: 1 同一结构单元的基础不宜设置在性质截然不同的地基上。 2 同一结构单元不宜部分采用天然地基部分采用桩基;当采用不同基础类型或基础埋深显著不同时,应根据地震时两部分地基基础的沉降差异,在基础、上部结构的相关部位采取相应措施。 3 地基为软弱黏性土、液化土、新近填土或严重不均匀土时,应根据地震时地基不均匀沉降和其他不利影响,采取相应的措施。 3.3.5 山区建筑的场地和地基基础应符合下列要求: 1 山区建筑场地勘察应有边坡稳定性评价和防治方案建议;应根据地质、地形条件和使用要求,因地制宜设置符合抗震设防要求的边坡工程。 2 边坡设计应符合现行国家标准《建筑边坡工程技术规范》GB 50330 的要求;其稳定性验算时,有关的摩擦角应按设防烈度的高低相应修正。 3 边坡附近的建筑基础应进行抗震稳定性设计。建筑基础与土质、强风化岩质边坡的边缘应留有足够的距离,其值应根据设防烈度的高低确定,并采取措施避免地震时地基基础破坏。 3.4 建筑形体及其构件布置的规则性 3.4.1 建筑设计应根据抗震概念设计的要求明确建筑形体的规则性。不规则的建筑应按规定采取加强措施;特别不规则的建筑应进行专门研究和论证。采取特别的加强措施;严重不规则的建筑不应采用。 注:形体指建筑平面形状和立面、竖向剖面的变化。 3.4.2 建筑设计应重视其平面、立面和竖向剖面的规则性对抗震性能及经济合理性的影响,宜择优选用规则的形体,其抗侧力构件的平面布置宜规则对称、侧向刚度沿竖向宜均匀变化、竖向抗侧力构件的截面尺寸和材料强度宜自下而上逐渐减小、避免侧向刚度和承载力突变。 不规则建筑的抗震设计应符合本规范第3.4.4条的有关规定。 3.4.3 建筑形体及其构件布置的平面、竖向不规则性,应按下列要求划分: 1 混凝土房屋、钢结构房屋和钢-混凝土混合结构房屋存在表3.4.3-1所列举的某项平面不规则类型或表3.4.3-2所列举的某项竖向不规则类型以及类似的不规则类型,应属于不规则的建筑。 表3.4.3-1 平面不规则的主要类型 不规则类型 定义和参考指标 扭转不规则 在规定的水平力作用下,楼层的最大弹性水平位移或(层间位移),大于该楼层两端弹性水平位移(或层间位移)平均值的1.2倍 续表 3.4.3-1 不规则类型 定义和参考指标 凹凸不规则 平面凹进的尺寸,大于相应投影方向总尺寸的30% 楼板局部不连续 楼板的尺寸和平面刚度急剧变化,例如,有效楼板宽度小于该层楼板典型宽度的50%,或开洞面积大于该层楼面面积的30%,或较大的楼层错层 表3.4.3-2 竖向不规则的主要类型 不规则类型 定义和参考指标 侧向刚度不规则 该层的侧向刚度小于相邻上一层的70%,或小于其上相邻三个楼层侧向刚度平均值的80%;除顶层或出屋面小建筑外,局部收进的水平向尺寸大于相邻下一层的25% 竖向抗侧力构件不连续 竖向抗侧力构件(柱、抗震墙、抗震支撑)的内力由水平转换构件(梁、桁架等)向下传递 楼层承载力突变 抗侧力结构的层间受剪承载力小于相邻上一楼层 的80% 2 砌体房屋、单层工业厂房、单层空旷房屋、大跨屋盖建筑和地下建筑的平面和竖向不规则性的划分,应符合本规范有关章节的规定。 3 当存在多项不规则或某项不规则超过规定的参考指标较多时,应属于特别不规则的建筑。 3.4.4 建筑形体及其构件布置不规则时,应按下列要求进行地震作用计算和内力调整,并应对薄弱部位采取有效的抗震构造措施: 1 平面不规则而竖向规则的建筑,应采用空间结构计算模型;并应符合下列要求: 1)扭转不规则时,应计入扭转影响,且楼层竖向构件最大的弹性水平位移和层间位移分别不宜大于楼层两端弹性水平位移和层间位移平均值的1.5倍,当最大层间位移远小于规范限值时,可适当放宽; 2)凹凸不规则或楼板局部不连续时,应采用符合楼板平面内实际刚度变化的计算模型;高烈度或不规则程度较大时,宜计入楼板局部变形的影响; 3)平面不对称且凹凸不规则或局部不连续,可根据实际情况分块计算扭转位移比,对扭转较大的部位应采用局部的内力增大系数。 2 平面规则而竖向不规则的建筑,应采用空间结构计算模型,刚度小的楼层的地震剪力应乘以不小于1.15的增大系数,其薄弱层应按本规范有关规定进行弹塑性变形分析,并应符合下列要求: 1) 竖向抗侧力构件不连续时,该构件传递给水平转换构件的地震内力应根据烈度高低和水平转换构件的类型、受力情况、几何尺寸等,乘以1.25~2.0的增大系数; 2) 侧向刚度不规则时,相邻层的侧向刚度比应依据其结构类型符合本规范相关章节的规定; 3) 楼层承载力突变时,薄弱层抗侧力结构的受剪承载力不应小于相邻上一楼层的65%。 3 平面不规则且竖向不规则的建筑,应根据不规则类型的数量和程度,有针对性地采取不低于本条1、2款要求的各项抗震措施。特别不规则的建筑,应经专门研究,采取更有效的加强措施或对薄弱部位采用相应的抗震性能化设计方法。 3.4.5 体型复杂、平立面不规则的建筑,应根据不规则程度、地基基础条件和技术经济等因素的比较分析,确定是否设置防震缝,并分别符合下列要求: 1 当不设置防震缝时,应采用符合实际的计算模型,分析判明其应力集中、变形集中或地震扭转效应等导致的易损部位,采取相应的加强措施。 2 当在适当部位设置防震缝时,宜形成多个较规则的抗侧力结构单元。防震缝应根据抗震设防烈度、结构材料种类、结构 类型、结构单元的高度和高差以及可能的地震扭转效应的情况, 留有足够的宽度,其两侧的上部结构应完全分开。 3 当设置伸缩缝和沉降缝时,其宽度应符合防震缝的要求。 3.5 结构体系 3.5.1 结构体系应根据建筑的抗震设防类别、抗震设防烈度、建筑高度、场地条件、地基、结构材料和施工等因素,经技术、经济和使用条件综合比较确定。 3.5.2 结构体系应符合下列各项要求: 1 应具有明确的计算简图和合理的地震作用传递途径。 2 应避免因部分结构或构件破坏而导致整个结构丧失抗震能力或对重力荷载的承载能力。 3 应具备必要的抗震承载力,良好的变形能力和消耗地震能量的能力。 4 对可能出现的薄弱部位,应采取措施提高其抗震能力。 3.5.3 结构体系尚宜符合下列各项要求: 1 宜有多道抗震防线。 2 宜具有合理的刚度和承载力分布,避免因局部削弱或突变形成薄弱部位,产生过大的应力集中或塑性变形集中。 3 结构在两个主轴方向的动力特性宜相近。 3.5.4 结构构件应符合下列要求: 1 砌体结构应按规定设置钢筋混凝土圈梁和构造柱、芯柱,或采用约束砌体、配筋砌体等。 2 混凝土结构构件应控制截面尺寸和受力钢筋、箍筋的设置,防止剪切破坏先于弯曲破坏、混凝土的压溃先于钢筋的屈服、钢筋的锚固粘结破坏先于钢筋破坏。 3 预应力混凝土的构件,应配有足够的非预应力钢筋。 4 钢结构构件的尺寸应合理控制,避免局部失稳或整个构件失稳。 5 多、高层的混凝土楼、屋盖宜优先采用现浇混凝土板。当采用预制装配式混凝土楼、屋盖时,应从楼盖体系和构造上采取措施确保各预制板之间连接的整体性。 3.5.5 结构各构件之间的连接,应符合下列要求: 1 构件节点的破坏,不应先于其连接的构件。 2 预埋件的锚固破坏,不应先于连接件。 3 装配式结构构件的连接,应能保证结构的整体性。 4 预应力混凝土构件的预应力钢筋,宜在节点核心区以外锚固。 3.5.6 装配式单层厂房的各种抗震支撑系统,应保证地震时厂房的整体性和稳定性。 3.6 结构分析 3.6.1 除本规范特别规定者外,建筑结构应进行多遇地震作用下的内力和变形分析,此时,可假定结构与构件处于弹性工作状态,内力和变形分析可采用线性静力方法或线性动力方法。 3.6.2 不规则且具有明显薄弱部位可能导致重大地震破坏的建筑结构,应按本规范有关规定进行罕遇地震作用下的弹塑性变形分析。此时,可根据结构特点采用静力弹塑性分析或弹塑性时程分析方法。 当本规范有具体规定时,尚可采用简化方法计算结构的弹塑性变形。 3.6.3 当结构在地震作用下的重力附加弯矩大于初始弯矩的10%时,应计人重力二阶效应的影响。 注:重力附加弯矩指任一楼层以上全部重力荷载与该楼层地震平均层间位移的乘积;初始弯矩指该楼层地震剪力与楼层层高的乘积。 3.6.4 结构抗震分析时,应按照楼、屋盖的平面形状和平面内变形情况确定为刚性、分块刚性、半刚性、局部弹性和柔性等的横隔板,再按抗侧力系统的布置确定抗侧力构件间的共同工作并进行各构件间的地震内力分析。 3.6.5 质量和侧向刚度分布接近对称且楼、屋盖可视为刚性横隔板的结构,以及本规范有关章节有具体规定的结构,可采用平面结构模型进行抗震分析。其他情况,应采用空间结构模型进行抗震分析。 3.6.6 利用计算机进行结构抗震分析,应符合下列要求: 1 计算模型的建立、必要的简化计算与处理,应符合结构的实际工作状况,计算中应考虑楼梯构件的影响。 2 计算软件的技术条件应符合本规范及有关标准的规定,并应阐明其特殊处理的内容和依据。 3 复杂结构在多遇地震作用下的内力和变形分析时,应采用不少于两个合适的不同力学模型,并对其计算结果进行分析比较。 4 所有计算机计算结果,应经分析判断确认其合理、有效后方可用于工程设计。 3.7 非结构构件 3.7.1 非结构构件。包括建筑非结构构件和建筑附属机电设备,自身及其与结构主体的连接,应进行抗震设计。 3.7.2 非结构构件的抗震设计,应由相关专业人员分别负责进行。 3.7.3 附着于楼、屋面结构上的非结构构件,以及楼梯间的非承重墙体,应与主体结构有可靠的连接或锚固,避免地震时倒塌伤人或砸坏重要设备。 3.7.4 框架结构的围护墙和隔墙。应估计其设置对结构抗震的不利影响,避免不合理设置而导致主体结构的破坏。 3.7.5 幕墙、装饰贴面与主体结构应有可靠连接,避免地震时脱落伤人。 3.7.6 安装在建筑上的附属机械、电气设备系统的支座和连接,应符合地震时使用功能的要求,且不应导致相关部件的损坏。 3.8 隔震与消能减震设计 3.8.1 隔震与消能减震设计,可用于对抗震安全性和使用功能有较高要求或专门要求的建筑。 3.8.2 采用隔震或消能减震设计的建筑,当遭遇到本地区的多遇地震影响、设防地震影响和罕遇地震影响时,可按高于本规范 第1.0.1条的基本设防目标进行设计。 3.9 结构材料与施工 3.9.1 抗震结构对材料和施工质量的特别要求,应在设计文件上注明。 3.9.2 结构材料性能指标,应符合下列最低要求: 1 砌体结构材料应符合下列规定: 1) 普通砖和多孔砖的强度等级不应低于MU10,其砌筑砂浆强度等级不应低于M5; 2) 混凝土小型空心砌块的强度等级不应低于MU7.5,其砌筑砂浆强度等级不应低于Mb7.5。 2 混凝土结构材料应符合下列规定: 1) 混凝土的强度等级,框支梁、框支柱及抗震等级为一级的框架梁、柱、节点核芯区,不应低于C30;构造柱、芯柱、圈梁及其他各类构件不应低于C20; 2) 抗震等级为一、二、三级的框架和斜撑构件(含梯段),其纵向受力钢筋采用普通钢筋时。钢筋的抗拉强度实测值与屈服强度实测值的比值不应小于1.25;钢筋的屈服强度实测值与屈服强度标准值的比值不应大于1.3,且钢筋在最大拉力下的总伸长率实测值不应小于9%。 3 钢结构的钢材应符合下列规定: 1) 钢材的屈服强度实测值与抗拉强度实测值的比值不应大于0.85: 2) 钢材应有明显的屈服台阶。且伸长率不应小于20%; 3) 钢材应有良好的焊接性和合格的冲击韧性。 3.9.3 结构材料性能指标,尚宜符合下列要求: 1 普通钢筋宜优先采用延性、韧性和焊接性较好的钢筋;普通钢筋的强度等级,纵向受力钢筋宜选用符合抗震性能指标的不低于HRB400级的热轧钢筋,也可采用符合抗震性能指标的HRB335级热轧钢筋;箍筋宜选用符合抗震性能指标的不低于HRB335级的热轧钢筋,也可选用HPB300级热轧钢筋。 注:钢筋的检验方法应符合现行国家标准《混凝土结构工程施工质量验收规范》GB 50204的规定。 2 混凝土结构的混凝土强度等级,抗震墙不宜超过C60,其他构件,9度时不宜超过C60,8度时不宜超过C70。 3 钢结构的钢材宜采用Q235等级B、C、D的碳素结构钢及Q345等级B、C、D、E的低合金高强度结构钢;当有可靠依据时,尚可采用其他钢种和钢号。 3.9.4 在施工中,当需要以强度等级较高的钢筋替代原设计中的纵向受力钢筋时。应按照钢筋受拉承载力设计值相等的原则换算,并应满足最小配筋率要求。 3.9.5 采用焊接连接的钢结构,当接头的焊接拘束度较大、钢板厚度不小于40mm且承受沿板厚方向的拉力时,钢板厚度方向截面收缩率不应小于国家标准《厚度方向性能钢板》GB/T 5313关于Z15级规定的容许值。 3.9.6 钢筋混凝土构造柱和底部框架-抗震墙房屋中的砌体抗震墙。其施工应先砌墙后浇构造柱和框架梁柱。 3.9.7 混凝土墙体、框架柱的水平施工缝,应采取措施加强混凝土的结合性能。对于抗震等级一级的墙体和转换层楼板与落地混凝土墙体的交接处,宜验算水平施工缝截面的受剪承载力。 3.10 建筑抗震性能化设计 3.10.1 当建筑结构采用抗震性能化设计时,应根据其抗震设防类别、设防烈度、场地条件、结构类型和不规则性,建筑使用功能和附属设施功能的要求、投资大小、震后损失和修复难易程度等,对选定的抗震性能目标提出技术和经济可行性综合分析和论证。 3.10.2 建筑结构的抗震性能化设计,应根据实际需要和可能,具有针对性:可分别选定针对整个结构、结构的局部部位或关键部位、结构的关键部件、重要构件、次要构件以及建筑构件和机电设备支座的性能目标。 3.10.3 建筑结构的抗震性能化设计应符合下列要求: 1 选定地震动水准。对设计使用年限50年的结构,可选用本规范的多遇地震、设防地震和罕遇地震的地震作用,其中,设防地震的加速度应按本规范表3.2.2的设计基本地震加速度采用,设防地震的地震影响系数最大值,6度、7度(0.10g)、7度(0.15g)、8度(0.20g)、8度(0.30g)、9度可分别采用0.12、0.23、0.34、0.45、0.68和0.90。对设计使用年限超过50年的结构,宜考虑实际需要和可能,经专门研究后对地震作用作适当调整。对处于发震断裂两侧10km以内的结构,地震动参数应计入近场影响,5km以内宜乘以增大系数1.5,5km以外宜乘以不小于1.25的增大系数。 2 选定性能目标,即对应于不同地震动水准的预期损坏状态或使用功能,应不低于本规范第1.0.1条对基本设防目标的规定。 3 选定性能设计指标。设计应选定分别提高结构或其关键部位的抗震承载力、变形能力或同时提高抗震承载力和变形能力的具体指标,尚应计及不同水准地震作用取值的不确定性而留有余地。设计宜确定在不同地震动水准下结构不同部位的水平和竖向构件承载力的要求(含不发生脆性剪切破坏、形成塑性铰、达到屈服值或保持弹性等);宜选择在不同地震动水准下结构不同部位的预期弹性或弹塑性变形状态,以及相应的构件延性构造的高、中或低要求。当构件的承载力明显提高时,相应的延性构造可适当降低。 3.10.4 建筑结构的抗震性能化设计的计算应符合下列要求: 1 分析模型应正确、合理地反映地震作用的传递途径和楼盖在不同地震动水准下是否整体或分块处于弹性工作状态。 2 弹性分析可采用线性方法,弹塑性分析可根据性能目标所预期的结构弹塑性状态,分别采用增加阻尼的等效线性化方法以及静力或动力非线性分析方法。 3 结构非线性分析模型相对于弹性分析模型可有所简化,但二者在多遇地震下的线性分析结果应基本一致;应计入重力二阶效应、合理确定弹塑性参数,应依据构件的实际截面、配筋等计算承载力,可通过与理想弹性假定计算结果的对比分析,着重发现构件可能破坏的部位及其弹塑性变形程度。 3.10.5 结构及其构件抗震性能化设计的参考目标和计算方法,可按本规范附录M第M.1节的规定采用。 3.11 建筑物地震反应观测系统 3.11.1 抗震设防烈度为7、8、9度时,高度分别超过160m、120m、80m的大型公共建筑,应按规定设置建筑结构的地震反应观测系统,建筑设计应留有观测仪器和线路的位置。 4 场地、地基和基础 4.1 场 地 4.1.1 选择建筑场地时,应按表4.1.1划分对建筑抗震有利、一般、不利和危险的地段。 表4.1.1有利、一般、不利和危险地段的划分 地段类别 地质、地形、地貌 有利地段 稳定基岩,坚硬土.开阔、平坦、密实、均匀的中硬土等 一般地段 不属于有利、不利和危险的地段 不利地段 软弱土,液化土,条状突出的山嘴,高耸孤立的山丘,陡坡,陡坎,河岸和边坡的边缘,平面分布上成因、岩性、状态明显不均匀的土层(含故河道、疏松的断层破碎带、暗埋的塘浜沟谷和半填半挖地基),高含水量的可塑黄土,地表存在结构性裂缝等 危险地段 地震时可能发生滑坡、崩塌、地陷、地裂、泥石流等及发震断裂带 上可能发生地表位错的部位 4.1.2 建筑场地的类别划分,应以土层等效剪切波速和场地覆盖层厚度为准。 4.1.3 土层剪切波速的测量,应符合下列要求: 1 在场地初步勘察阶段,对大面积的同一地质单元,测试土层剪切波速的钻孔数量不宜少于3个。 2 在场地详细勘察阶段,对单幢建筑,测试土层剪切波速的钻孔数量不宜少于2个,测试数据变化较大时,可适量增加;对小区中处于同一地质单元内的密集建筑群,测试土层剪切波速的钻孔数量可适量减少,但每幢高层建筑和大跨空间结构的钻孔数量均不得少于1个。 3 对丁类建筑及丙类建筑中层数不超过10层、高度不超过24m的多层建筑,当无实测剪切波速时,可根据岩土名称和性状,按表4.1.3划分土的类型,再利用当地经验在表4.1.3的剪切波速范围内估算各土层的剪切波速。 表4.1.3土的类型划分和剪切波速范围 土的类型 岩土名称和性状 土层剪切波 速范围(m/s) 岩石 坚硬、较硬且完整的岩石 vs>800 坚硬土或 软质岩石 破碎和较破碎的岩石或软和较软的岩石,密实的 碎石土 800≥vs>500 中硬土 中密、稍密的碎石土,密实、中密的砾、粗、中 砂,,fak>150的黏性土和粉土,坚硬黄土 500≥vs>250 中软土 稍密的砾、粗、中砂,除松散外的细、粉砂.fak ≤150的黏性土和粉土,fak>130的填土,可塑新黄土 250≥vs>150 软弱土 淤泥和淤泥质土,松散的砂,新近沉积的黏性土 和粉土,fak≤130的填土,流塑黄土 vs≤150 注:fak为由载荷试验等方法得到的地基承载力特征值(kPa);vs为岩土剪切波速。 4.1.4 建筑场地覆盖层厚度的确定,应符合下列要求: 1 一般情况下,应按地面至剪切波速大于500m/s且其下卧各层岩土的剪切波速均不小于500m/s的土层顶面的距离确定。 2 当地面5m以下存在剪切波速大于其上部各土层剪切波速2.5倍的土层,且该层及其下卧各层岩土的剪切波速均不小于400m/s时,可按地面至该土层顶面的距离确定。 3 剪切波速大于500m/s的孤石、透镜体,应视同周围土层。 4 土层中的火山岩硬夹层,应视为刚体,其厚度应从覆盖土层中扣除。 4.1.5 土层的等效剪切波速,应按下列公式计算: vse=d0/t (4.1.5-1) t= (4.1.5-1) 式中:vse——土层等效剪切波速(m/s); d0——计算深度(m),取覆盖层厚度和20m两者的较小值; t——剪切波在地面至计算深度之间的传播时间; di——计算深度范围内第i土层的厚度(m); vsi——计算深度范围内第i土层的剪切波速(m/s); n——计算深度范围内土层的分层数。 4.1.6 建筑的场地类别,应根据土层等效剪切波速和场地覆盖层厚度按表4.1.6划分为四类,其中I类分为Ⅰ。、Ⅰ1两个亚类。当有可靠的剪切波速和覆盖层厚度且其值处于表4.1.6所列场地类别的分界线附近时,应允许按插值方法确定地震作用计算所用的特征周期。 表4.1.6 各类建筑场地的覆盖层厚度(m) 岩石的剪切波速或 土的等效剪切波速(m/s) 场地类别 Ⅰ0 Ⅰ1 Ⅱ Ⅲ Ⅳ vs>800 0 800≥vs>500 0 500≥vse>250 <5 ≥5 250≥vse>150 <3 3~50 >50 vse≤150 <3 3~15 15~80 >80 注:表中vs系岩石的剪切波速。 4.1.7 场地内存在发震断裂时,应对断裂的工程影响进行评价,并应符合下列要求: 1 对符合下列规定之一的情况,可忽略发震断裂错动对地面建筑的影响: 1) 抗震设防烈度小于8度 2) 非全新世活动断裂; 3) 抗震设防烈度为8度和9度时,隐伏断裂的土层覆盖厚度分别大于60m和90m。 2 对不符合本条1款规定的情况,应避开主断裂带。其避让距离不宜小于表4.1.7对发震断裂最小避让距离的规定。在避让距离的范围内确有需要建造分散的、低于三层的丙、丁类建筑时,应按提高一度采取抗震措施,并提高基础和上部结构的整体性,且不得跨越断层线。 表4.1.7 发震断裂的最小避让距离(m) 烈度 建筑抗震设防类别 甲 乙 丙 丁 8 专门研究 200m 100m — 9 专门研究 400m 200m — 4.1.8 当需要在条状突出的山嘴、高耸孤立的山丘、非岩石和强风化岩石的陡坡、河岸和边坡边缘等不利地段建造丙类及丙类以上建筑时,除保证其在地震作用下的稳定性外。尚应估计不利地段对设计地震动参数可能产生的放大作用,其水平地震影响系数最大值应乘以增大系数。其值应根据不利地段的具体情况确定。在1.1~1.6范围内采用。 4.1.9 场地岩土工程勘察。应根据实际需要划分的对建筑有利、一般、不利和危险的地段。提供建筑的场地类别和岩土地震稳定性(含滑坡、崩塌、液化和震陷特性)评价。对需要采用时程分析法补充计算的建筑。尚应根据设计要求提供土层剖面、场地覆盖层厚度和有关的动力参数。 4.2 天然地基和基础 4.2.1 下列建筑可不进行天然地基及基础的抗震承载力验算: 1 本规范规定可不进行上部结构抗震验算的建筑。 2 地基主要受力层范围内不存在软弱黏性土层的下列建筑: 1) 一般的单层厂房和单层空旷房屋; 2) 砌体房屋; 3) 不超过8层且高度在24m以下的一般民用框架和框架抗震墙房屋; 4) 基础荷载与3)项相当的多层框架厂房和多层混凝土抗震墙房屋。 注:软弱黏性土层指7度、8度和9度时,地基承载力特征值分别小于80、100和120kPa的土层。 4.2.2 天然地基基础抗震验算时。应采用地震作用效应标准组合。且地基抗震承载力应取地基承载力特征值乘以地基抗震承载力调整系数计算。 4.2.3 地基抗震承载力应按下式计算: (4.2.3) 式中: ——调整后的地基抗震承载力; ——地基抗震承载力调整系数,应按表4.2.3采用; ——深宽修正后的地基承载力特征值,应按现行国家标准《建筑地基基础设计规范》GB 50007采用。 表4.2.3 地基抗震承载力调整系数 岩土名称和性状 岩石,密实的碎石土。密实的砾、粗、中砂,fak≥300的黏性土和 粉土 1.5 中密、稍密的碎石土,中密和稍密的砾、粗、中砂,密实和中密的 细、粉砂,150kPa≤fak<300kPa的黏性土和粉土,坚硬黄土 1.3 稍密的细、粉砂,100kPa≤fak<150kPa的黏性土和粉土,可塑黄土 1.1 淤泥.淤泥质土,松散的砂,杂填土,新近堆积黄土及流塑黄土 1.0 4.2.4 验算天然地基地震作用下的竖向承载力时,按地震作用效应标准组合的基础底面平均压力和边缘最大压力应符合下列各式要求: P≤faE (4.2.4-1) pmax≤1.2faE (4.2.4-2) 式中:p——地震作用效应标准组合的基础底面平均压力; pmax——地震作用效应标准组合的基础边缘的最大压力。高宽比大于4的高层建筑,在地震作用下基础底面不宜出现脱离区(零应力区);其他建筑,基础底面与地基土之间脱离 区(零应力区)面积不应超过基础底面面积的15%。 4.3 液化土和软土地基 4.3.1 饱和砂土和饱和粉土(不含黄土)的液化判别和地基处理,6度时,一般情况下可不进行判别和处理,但对液化沉陷敏感的乙类建筑可按7度的要求进行判别和处理,7~9度时,乙类建筑可按本地区抗震设防烈度的要求进行判别和处理。 4.3.2 地面下存在饱和砂土和饱和粉土时,除6度外,应进行液化判别;存在液化土层的地基,应根据建筑的抗震设防类别、地基的液化等级,结合具体情况采取相应的措施。 注:本条饱和土液化判别要求不含黄土、粉质黏土。 4.3.3 饱和的砂土或粉土(不含黄土),当符合下列条件之一时,可初步判别为不液化或可不考虑液化影响: 1 地质年代为第四纪晚更新世(Q3)及其以前时,7、8度时可判为不液化。 2 粉土的黏粒(粒径小于0.005mm的颗粒)含量百分率,7度、8度和9度分别不小于10、13和16时,可判为不液化土。 注:用于液化判别的黏粒含量系采用六偏磷酸钠作分散剂测定,采用其他方法时应按有关规定换算。 3 浅埋天然地基的建筑,当上覆非液化土层厚度和地下水位深度符合下列条件之一时,可不考虑液化影响: du>d0+db-2 (4.3.3-1) dw>d0+db-3 (4.3.3-2) d0+dw>1.5d0+2db-4.5 (4.3.3-3) 式中:dw——地下水位深度(m),宜按设计基准期内年平均最 高水位采用,也可按近期内年最高水位采用; du——上覆盖非液化土层厚度(m),计算时宜将淤泥和淤泥质土层扣除; db——基础埋置深度(m),不超过2m时应采用2m; d0——液化土特征深度(m),可按表4.3.3采用。 表4.3.3 液化土特征深度(m) 饱和土类别 7度 8度 9度 粉土 6 7 8 砂土 7 8 9 注:当区域的地下水位处于变动状态时,应按不利的情况考虑。 4.3.4 当饱和砂土、粉土的初步判别认为需进一步进行液化判别时,应采用标准贯入试验判别法判别地面下20m范围内土的液化;但对本规范第4.2.1条规定可不进行天然地基及基础的抗震承载力验算的各类建筑,可只判别地面下15m范围内土的液化。当饱和土标准贯入锤击数(未经杆长修正)小于或等于液化判别标准贯人锤击数临界值时,应判为液化土。当有成熟经验时,尚可采用其他判别方法。 在地面下20m深度范围内,液化判别标准贯入锤击数临界值可按下式计算: Ncr=N0β[ln(0.6ds+1.5)-0.1dw] (4.3.4) 式中:Ncr——液化判别标准贯入锤击数临界值; N0——液化判别标准贯入锤击数基准值,可按表4.3.4采用; ds——饱和土标准贯入点深度(m); dw——地下水位(m); ρc——黏粒含量百分率,当小于3或为砂土时,应采用3; β——调整系数,设计地震第一组取0.80,第二组取0.95,第三组取1.05。 表4.3.4 液化判别标准贯入锤击数基准值N0 设计基本地震加速度(g) 0.10 0.15 0.20 0.30 0.40 液化判别标准贯入锤击数基准值 7 10 12 16 19 4.3.5 对存在液化砂土层、粉土层的地基,应探明各液化土层的深度和厚度,按下式计算每个钻孔的液化指数,并按表4.3.5综合划分地基的液化等级: (4.3.5) 式中:IlE——液化指数; n——在判别深度范围内每一个钻孔标准贯入试验点的总数; Ni、Ncri——分别为i点标准贯入锤击数的实测值和临界值,当实测值大于临界值时应取临界值;当只需要判别15m范围以内的液化时,15m以下的实测值可按临界值采用; di——i点所代表的土层厚度(m),可采用与该标准贯入试验点相邻的上、下两标准贯人试验点深度差的一半,但上界不高于地下水位深度,下界不深于液化深度; Wi——i土层单位土层厚度的层位影响权函数值(单位为m-1)。当该层中点深度不大于5m时应采用10,等于20m时应采用零值,5~20m时应按线性内插法取值。 表4.3.5液化等级与液化指数的对应关系 液化等级 轻微 中等 严重 液化指数IlE 0<IlE≤6 6<IlE≤18 IlE>18 4.3.6 当液化砂土层、粉土层较平坦且均匀时,宜按表4.3.6选用地基抗液化措施;尚可计入上部结构重力荷载对液化危害的影响,根据液化震陷量的估计适当调整抗液化措施。不宜将未经处理的液化土层作为天然地基持力层。 表4.3.6 抗液化措施 建筑抗震 地基的液化等级 设防类别 轻微 中等 严重 乙类 部分消除液化沉陷,或对基础和上部结构处理 全部消除液化沉陷。或部分消除液化沉陷且对基础和上部结构处理 全部消除液化沉陷 丙类 基础和上部结构处理.亦可不采取 措施 基础和上部结构处理,或更高要求的措施 全部消除液化沉陷,或部分消除液化沉陷且对基础和上部结构处理 丁类 可不采取措施 可不采取措施 基础和上部结构处理,或其他经济的措施 注:甲类建筑的地基抗液化措施应进行专门研究,但不宜低于乙类的相应要求。 4.3.7 全部消除地基液化沉陷的措施,应符合下列要求: 1 采用桩基时,桩端伸入液化深度以下稳定土层中的长度(不包括桩尖部分),应按计算确定,且对碎石土,砾、粗、中砂,坚硬黏性土和密实粉土尚不应小于0.8m,对其他非岩石土尚不宜小于1.5m。 2 采用深基础时,基础底面应埋入液化深度以下的稳定土层中,其深度不应小于0.5m。 3 采用加密法(如振冲、振动加密、挤密碎石桩、强夯等)加固时,应处理至液化深度下界;振冲或挤密碎石桩加固后,桩间土的标准贯入锤击数不宜小于本规范第4.3.4条规定的液化判别标准贯入锤击数临界值。 4 用非液化土替换全部液化土层,或增加上覆非液化土层的厚度。 5 采用加密法或换土法处理时,在基础边缘以外的处理宽度,应超过基础底面下处理深度的1/2且不小于基础宽度的1/5。 4.3.8 部分消除地基液化沉陷的措施,应符合下列要求: 1 处理深度应使处理后的地基液化指数减少,其值不宜大于5;大面积筏基、箱基的中心区域,处理后的液化指数可比上述规定降低1;对独立基础和条形基础,尚不应小于基础底面下液化土特征深度和基础宽度的较大值。 注:中心区域指位于基础外边界以内沿长宽方向距外边界大于相应方向1/4长度的区域。 2 采用振冲或挤密碎石桩加固后,桩间土的标准贯人锤击数不宜小于按本规范第4.3.4条规定的液化判别标准贯入锤击数临界值。 3 基础边缘以外的处理宽度,应符合本规范第4.3.7条5款的要求。 4 采取减小液化震陷的其他方法,如增厚上覆非液化土层的厚度和改善周边的排水条件等。 4.3.9 减轻液化影响的基础和上部结构处理,可综合采用下列各项措施: 1 选择合适的基础埋置深度。 2 调整基础底面积,减少基础偏心。 3 加强基础的整体性和刚度,如采用箱基、筏基或钢筋混凝土交叉条形基础,加设基础圈梁等。 4 减轻荷载,增强上部结构的整体刚度和均匀对称性,合理设置沉降缝,避免采用对不均匀沉降敏感的结构形式等。 5 管道穿过建筑处应预留足够尺寸或采用柔性接头等。 4.3.10 在故河道以及临近河岸、海岸和边坡等有液化侧向扩展或流滑可能的地段内不宜修建永久性建筑,否则应进行抗滑动验算、采取防土体滑动措施或结构抗裂措施。 4.3.11 地基中软弱黏性土层的震陷判别,可采用下列方法。饱和粉质黏土震陷的危害性和抗震陷措施应根据沉降和横向变形大小等因素综合研究确定,8度(0.30g)和9度时,当塑性指数小于15且符合下式规定的饱和粉质黏土可判为震陷性软土。 Ws≥0.9WL (4.3.11-1) IL≥0.75 (4.3.11-2) 式中:Ws——天然含水量; WL——液限含水量,采用液、塑限联合测定法测定; IL——液性指数。 4.3.12 地基主要受力层范围内存在软弱黏性土层和高含水量的可塑性黄土时,应结合具体情况综合考虑,采用桩基、地基加固处理或本规范第4.3.9条的各项措施,也可根据软土震陷量的估计,采取相应措施。 |
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