Maseod Mirtaheri - Assistant Professor, K.N.T University,Tehran,Iran
Mojtaba Nosrati - graduate Student,

The results of vibration tests carried out on medium-rise concrete structure are used in conjunction with a standard structural analysis computer program to identify the stiffness characteristics of the buildings. The effect of incorrect analytical modeling at the design stage is then studied by considering the forces carried by individual members when the buildings are subjected to loads. It is shown that the actions of partitions and shear walls can significantly change the loads carried by individual members. The implications of this to earthquake resistant design are discussed.