荷载及设计原则课件chapter3-1.pptxVIP

Loads and Design Philosophy;Chapter 3 Earthquake Action;Chapter 3 Earthquake Action;Earthquake Magnitude （震级） The magnitude is a measure of the amount of energy released by an earthquake. The higher the magnitude, the more energy an earthquake releases. The most widely used scale to measure magnitude internationally is Moment Magnitude Scale (MMS). (Richter Scale) -------- 12 grades. （里氏震级） Once MMS of an earthquake attains 5 or greater, buildings or civil works may suffer damage. ;Earthquake Magnitude （震级） Hypocenter (also called focus)(震源)---- it is the position of an earthquake originates. Epicenter (震中)---- it is the point on the earth surface that is directly above the hypocenter. Depth of hypocenter (震源深度)---- it is the vertical distance from hypocenter to the earth surface. Epicenter distance (震中距)---- it is the horizontal distance from epicenter to a given place on the earth.;Focus or hypocenter;Intensity （烈度） （1）Earthquake intensity （地震烈度） Intensity is the apparent effect of the earthquake as experienced at a specific location. It is the degree of influence on the ground and buildings by earthquake. Intensity is vary with location. While an earthquake is assigned a single magnitude scale, the intensity varies according to where it is felt. Factors influencing intensity at a particular site: earthquake magnitude, epicentral distance, local soil condition; ;Intensity （烈度） （2）Basic intensity （基本烈度） It is based on the statistic survey about the probability of earthquake occurrence in some specified region. It is defined as the earthquake intensity whose value is exceeded with 10% percent probability in a 50-year period under normal soil condition. It is also defined as the maximum intensity during 474- year return period. ;Inten