ALI M MEMARI - Assistant Professor, Sharif Univ. of Tech., Tehran, Iran And Acting Director for Research, IIEES, Tehran, Iran
MOHAMMAD M AHMADI - Instructor, Sharif Univ. of Tech., Tehran, Iran Researcher, IIEES, Tehran, Iran
BIZHAN REZAEE - Graduate Assistant, Sharif Univ. of Tech., Tehran, Iran

The behavior of the water towers in Rasht during the ۱۹۹۰ Manjil-Roudbar earthquake is investigated. Three different models were used, a single degree of freedom system, a two degree of system and a multidegree of freedom beam model. The load requirements based on standards ۵۱۹ and ۲۸۰۰ are compared and it is concluded that the structures were designed properly according to standard ۵۱۹, but are under designed based on standard ۲۸۰۰. The spectral accelerations due to three different PGA's are obtained and an estimate of the required spectral acceleration to cause failure is made. The effects of sloshing and P-A are found to be negligible