M. R MAHERI - Research Fellow/Senior Engineer, WS Atkins Engineering Sciences, Epsom, U.K.

The region devastated by the Manjil earthquake of ۲۰th June ۱۹۹۰ is a well watered agricultural, and industrial area. As a result a number of large engineered structures such as dams, ground-based and elevated liquid storage tanks, concrete and steel bridges and industrial plants and factories were affected by the earthquake. In this paper the behaviour of some of these structures during the earthquake is discussed. Although some of the more important structures were designed against the earthquake loading, most lacked such considerations. Two important seismic design criteria, absent in most of the above structures include; appropriate seismic joints and the safety of secondary elements or systems. Inadequate seismic joints between different sections of the structure resulted in many local failures due to pounding, and widespread damage to the secondary structures, installations and equipment also reflected the lack of seismic design considerations for such elements