Chapter 2 Definitions and notations 2.1 Definitions 2.1.1 Seismic Fortification Intensity The seismic intensity approved by State authority,which is used as the basis for the seismic fortification of buildings in a certain region. 2.1.2 Seismic Fortification Criterion The rule for judging the seismic fortification requirements,which depends on the seis- micfneity and imranof the builings using functions. 2.1.3 Earthquake Action The structural dynamic action due to earthquake,including horizontal seismic action and vertical seismic action. 2.1.4 Design Parameters of Ground Motion The seismic acceleration time-history curve,the response spectrum of acceleration,and the peak value acceleration used in seismic design 2.1.5 Design Basic Acceleration of Ground Motion The design value of seismic acceleration,that exceeding probability is10%during the 50-years reference period. 2.1.6 Design Characteristic Period of Ground Motion The period value corresponding to the starting point of reduced section of seismic influ ence coefficient curve,which describes the earthquake magnitude,the distance of epicenter and the site-classes etc. 2.1.7 Site An area of a building group,usually it has similar characteristic in response spectrum. Its scope approximately equivalent to a factory area,a living quarter,a village or a plain area no less than 1.0km2 2.1.8 Seismic Concept Design of Buildings The process of making the general arrangement for the architectures and structures and of determining details,that based on the design fundamental principles and the ideas ob- tained from past experiences in earthquake disaster prevention and the constructional pro- ject. 2.1.9 Seismic Fortification Measures The seismic design contents except seismic action calculation and member resistance calculation,and details of seismic design included. 2.1.10 Details of Seismic Design 2