Seismic response of structures with Coulomb damping

Abstract

The usefulness of Coulomb (friction) damping in earthquake-resistant design of structures is examined by studying the seismic response characteristics of structures with various arrangements of sliding interfaces. First, three basic arrangements are studied for their effectiveness in reducing lateral displacements of the supporting frame, accelerations of the floor slab and the resulting secondary floor spectra. These are: (1) slab sliding system which has the sliding interface between the floor slab and the supporting frame, (2) double sliding system which consists of sliding interfaces at both top and bottom interfaces (a combination of slab sliding and base sliding), and (3) spring-assisted slab sliding system which is a slab sliding system aided by lateral springs attached to the columns to resist excessive sliding displacement of the slab. The responses are obtained for structures with different frequencies and are presented in response spectrum form. The isolation characteristics of one slab sliding system are compared with those of the base sliding and hysteretic systems. Non-dimensional design parameters defined in terms of the corresponding elastic design spectra are introduced for design purposes and for a consistent presentation of the results. Methods for predicting the important response quantities using the non-dimensional parameters are discussed and their applicability is evaluated.

Next, the response of a simple slab sliding arrangement to simultaneous horizontal and vertical ground motion input is studied to see the effects of the vertical excitation on the isolation efficiency of that arrangement. Finally the suitability of adopting such sliding arrangements in multi-story structures is also examined. The seismic responses of multi-story structures with floor slabs sliding at different story levels are obtained and compared with the response of non-sliding structure and base sliding to examine the effectiveness of such sliding arrangement.