ABSTRACT

This chapter introduces numerous special terms which only apply to dynamic behaviour and explains dynamic behaviour by using graphs. The essential quantity for dynamic behaviour is time. Any pictorial representation of this behaviour usually includes this variable, so many of the graphs plot some important quantity against time. The basic principles of dynamic behaviour are best explained by examining how a simple idealised vibrating system acts. All the dynamic systems that have been considered have been given an initial displacement and then allowed to vibrate freely, however, this is an unusual cause of vibrations in building structures. The main reason for dynamic analysis of structures is to see how they respond to dynamic loading. The main cause of dynamic loading of structures due to earthquakes is the horizontal ground movements, and this effect is modelled by considering the building to be subjected to equivalent horizontal loads that are a percentage of the seismic load Ws of the building.