Vibration control of structures under earthquake loading by three‐stage friction‐grip elements

The behaviour of a building subjected to a strong‐motion earthquake depends highly on its energy dissipation capacity. By introducing three‐stage friction‐grip elements, the energy dissipation within each storey can be ‘designed’ according to definable stages (e.g. serviceability, medium‐ and strong‐motion earthquake). Tests on simple steel‐concrete‐ and steel‐steel‐friction‐grip connections have proved their very satisfactory behaviour under high dynamic loading, showing no considerable damage when well designed. Examples of horizontal stiffening elements are given to illustrate the construction of three‐stage elements with either steel‐steel‐ or steel‐concrete‐friction‐grip joints. By computing the response of a seven storey building designed as a steel frame (‘ductile system’ philosophy), concrete core (‘stiff system’‐philosophy) and three‐stage truss and being subjected to the 1940 El Centre earthquake, the superior performance of three‐stage elements and its economic advantage over the other two systems becomes apparent. Although this is just one illustrative example, it is nevertheless an important one, because it resembles the type of building that would respond best to the application of three‐stage building brakes. Finally, the result of an online test on a three‐stage element is given. This realistic earthquake simulation proved the behaviour to be adequately close to the basic philosophy and yielded important design implications for three‐stage elements.