【正文】 or 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。 when antiseismic joints are provided, sufficient width shall be provided according to the intensity, ground class and building type, and the superstructures on both sides of the joint shall be pletely separated. All expansion joints and settlement joints shall ply with the requirements for antiseismic joints. An antiseismic structural system shall ply with all the following requirements: I. There shall be explicit calculation sketches and reasonable transmission route for the seismic actions。 III. It shall have necessary strength, good deformation ability and energy dissipation ability。 III. The strength grade of concrete shall be no lower than C30 for frame beams, columns and nodes in case of antiseismic class I, no lower than C15 for structural columns, stems, girths and expanded foundations, and no lower than C20 for other types of members。 II. The ratio of measured yield strength value of the bars to the standard strength value of the bars shall be no greater than for design with antiseismic grade I, and shall be no greater than for design with antiseismic grade II. Technical regulations on structural steel for highrise civilian buildings JGJ 99 – 98 The strength to yield ratio of antiseismic structural steel shall be no less than , and the elongation shall be greater than 20%. Seismic Action and Antiseismic Proof Calculation for Structures Antiseismic design specification for buildings GBJ 11 – 89 The seismic action of various types of building structures shall be taken into consideration according to the following principles: I. Under normal conditions, horizontal seismic action can be taken into consideration in both main axes directions of the building structure, and antiseismic proof calculation performed, the horizontal seismic action in each direction shall be fully undertaken by the antilateral force members in that direction。 III. For structures with apparent uneven or asymmetric mass and rigidity distribution, the torsion effect of horizontal seismic action shall be taken into consideration。 in the sectional antiseismic proof calculation, the maximum value for horizontal seismic influence coefficient shall follow Table . Max. value for horizontal seismic influence coefficient in the sectional antiseismic proof calculation Table Intensity 6 7 8 9 amax Fig. Seismic influence coefficient curve a — Seismic influence coefficient。 T — Self vibration period of structure。 II. Sectional antiseismic proof calculation shall be performed for tall highrise buildings on type IV site for intensity degree 6 and for structures for intensity degree 7 or above. The basic bination of seismic action effect and other load effect in the structural members shall be calculated using the following formula: S=γGCGGE + γEhCEhEhk + γEvCEvEvk + ΨwγwCwwk () Where S — Design value of bined internal force of the structural member, including the design value of bined bending moment, axial force and shearing force。 ?Eh, ?Ev — Respectively the partial safety factor of horizontal and vertical seismic action, and shall be taken from Table 。 GE — Gravitational load characteristics value。 Evk — Vertical seismic action standard value。 ?w — Wind load bined value coefficient, not considered for ordinary structures, and