Numerical studies on the seismic performance of three structural systems

Abstract

For many years, the basic intent of the building code seismic provisions has been to provide buildings with an ability to withstand intense ground shaking without collapse, but potentially with some significant structural damage.
The damage to buildings, transportation structures and lifelines wrought by the 1989 Loma Prieta earthquake, the 1994 Northridge earthquake, and the 1999 Hanshin earthquake near Kobe, has forced structural engineers, disaster response agencies and building officials to carefully consider seismic response of the building environment in terms of performance rather than life-safety.
Civil engineering structures normally rely on their ability to dissipate energy to resist dynamic forces such as strong earthquakes. In recent years, to keep the vibration of these structures within the functional and serviceability limits and to reduce structural and architectural damage caused by extreme loads, different passive protective systems have been proposed. Addition of energy dissipation devices (EDDs) is considered one of the viable strategies for enhancing the seismic performance of building structures. For many building structures, EDDs may provide considerable performance improvement or cost saving.
This paper provides a comparison of the performance indices of a three story building with three different structural systems – moment frame, viscously damped frame and a base isolated frame. Fluid viscous damping and base isolation have the same objective of significantly decreasing the response of a structure to earthquake excitation. With both fluid viscous damping and base isolation it is possible to have a structure remain within the elastic region, so there is no permanent deformation from a seismic event. Each of the models were analyzed as linear structures and subjected to time histories for 3 different earthquakes of Vrancea type. The non-dimensional performance indices considered for the models are: Peak Drift ratio, Peak Base Shear and Peak Level Acceleration.
In summary, the viscously damped frame has the best overall relative performance of the three framing schemes. The base isolated frame is better than moment frame.