【正文】 — 1 — Section VI Antiseismic Design for Buildings 1. Basis and Classification of Antiseismic Protection Antiseismic design specification for buildings GBJ 11 – 89 The antiseismic protection intensity shall be determined with review and approval according to the power of authority specified by the state and documents (drawings) issued by the state. Antiseismic protection classification standard for buildings GB 50223 – 95 The antiseismic protection classifications for buildings shall be in four classes of A, B, C and D according to the importance of their application functions, and their classification shall ply with the following requirements: Class A buildings shall be those which will have serious impact to the society and huge loss to national economy if damaged in an earthquake, or which have special requirements. Class B buildings shall be those the application functions of which must not be interrupted or should be restored as soon as possible, and which will have major impact to the society and great loss to national economy if damaged in an earthquake. Class C buildings shall be those with average influence if damaged in an earthquake, and other buildings not included in Classes A, B and D. Class D buildings shall be those which will not affect buildings of Classes A, B and C and which will have little social impact or economic loss if damaged or collapsed in an earthquake. Generally they include singlestoreyed warehouses or similar buildings with storage of lowvalued goods and little human activity. The antiseismic protection standard for different classes of buildings shall ply with the following requirements: For buildings of Class A, design shall be made for one degree higher than the protection intensity (including seismic action and antiseismic provisions). For buildings of Class B, the seismic action shall be calculated on the basis of the antiseismic protection intensity of the region. The antiseismic provisions shall be designed as one degree higher for protection intensity of degree 6~8, and shall be enhanced for degree 9. For Class B buildings with relatively small sizes, the antiseismic provisions can be designed as for the antiseismic protection intensity of the region if economically reasonable structural systems with good antiseismic performance are used. The class of antiseismic provisions shall not be increased for ground foundations of Class B — 2 — buildings. For buildings of Class C, both the seismic action and antiseismic provisions shall be designed on the basis of the protection intensity of the region. For buildings of Class D, normally no reduction shall be made for the seismic action, and for protection intensity degree 7~9, the antiseismic provisions shall be designed at one degree lower than the protection intensity of the region, and will not be lowered for intensity degree 6. 2. Basic Provisions Seismic Impact, Site and Ground Foundation Antiseismic design specification for buildings GBJ 11 – 89 A building site shall be selected on the basis of the need of the project and the mastery of relevant data on seismic activities and engineering geology, and a prehensive assessment shall be made. When it is not possible to avoid an unfavorable ground section, appropriate antiseismic provisions shall be made。 Buildings of Classes A, B and C shall not be build on dangerous ground sections. For building site of Class I, except for buildings of Class D, the antiseismic structural provisions can be taken at one degree lower than the original intensity, and the seismic action shall still be calculated according to the original intensity, provided that no reduction shall be made in structural provisions for degree 6. The building sites shall be classified into four categories according to ground soil types and thickness of site coverage layer. In the site geological survey, the site shall be divided into favorable, unfavorable and dangerous sections to the building according to the actual needs, and the site class for the building and rock and soil seismic stability (. landslide, collapse) assessment shall be provided。 for buildings requiring supplementary calculation using timehistory analysis method, the relevant dynamic parameters of the soil and the site covering layer thickness shall also be provided according to the design requirements. In the antiseismic proof calculation for natural ground foundation, the antiseismic bearing capacity of foundation soil shall be calculated by multiplying the foundation soil static bearing capacity with foundation soil antiseismic bearing capacity adjustment coefficient. The antiliquefaction provision for the ground foundation shall be determined in a prehensive manner on the basis of the importance of the building and the liquefaction grade of the ground foundation and in conjunction with the actual conditions, Table shall be followed when the liquefied soil layer is relatively flat and homogenous. Except for buildings of Class D, untreated liquefied soil layer shall not be used as the load bearing layer for the natural ground — 3 — foundation. Antiliquefaction provisions Table Building Class Liquefaction grade of ground foundation Slight Medium Serious B Liquefaction settlement shall be partially eliminated, or make treatment to the foundation and superstructure Liquefaction settlement shall be totally eliminated, or liquefaction settlement is partially eliminated plus treatment to the foundation and superstructure Liquefaction settlement shall be totally eliminated. C Treatment to the foundation and superstructure, and it is also possible not to take any provision Treatment to the foundation and superstructure, or provision with higher requ