Rebound Effects And Oscillation Motion Of Restrained Rocking Façades

Structural or non-structural masonry or r.c. elements, such as building façades or pre-cast panels subjected to out-of-plane modes, can be considered like rocking blocks restrained by horizontal springs. Restrained rocking blocks respond to earthquakes in different way from free-standing rigid elements. Horizontal restraints considered in this paper are transverse walls connected to rocking elements. Their effect could improve the dynamic response of blocks in terms of reduction of rotation amplitude, if the stiffness is properly high. Nevertheless, these restraints can affect the response in negative way, causing overturning when low values of stiffness or one-sided motion are assumed. Oscillatory motion or rebound effects are obtained depending on the linearity or non-linearity assumptions and on the value of spring horizontal stiffness. It is then preferable to have similar stiffness in clockwise and counterclockwise rotations to achieve a reduction of amplitude ratio by increasing this stiffness and make the response safer.