引言本世纪中叶以来,随着科技、经济和社会的发展,城市已产生了引人注目的变化。人口和基础设施的增加,以及居民社会和经济条件的显著变化成为当今城市的典型特征。最近数10年地震造成的数以千计的严重伤亡事故和数以百万美元计的经 Introduction Since the middle of this century, with the development of science and technology, economy and society, cities have made remarkable changes. The increase in population and infrastructures, as well as the significant changes in the social and economic conditions of the inhabitants, have become typical features of today’s cities. Thousands of serious casualties caused by the recent 10-year earthquake and millions of dollars