AN INVESTIGATION OF DAMPING RATIO EFFECT ON EARTHQUAKE ENERGY INPUT

Abstract

Recent earthquakes show that the strength and displacement-based methods in many seismic design codes are not as reliable as the energy-based methods in seismic design and evaluation of structures. The determination of earthquake energy input to structures is the main concern for the energy-based structural design methods. The seismic energy input to structures mainly depends on the strong ground acceleration and the velocity time history of the structures. Current studies about the seismic energy input show that the bases of researches are established almost entirely for the single-degree-of-freedom (SDOF) systems. This study investigates the variation of earthquake input energy of SDOF systems which have different period and damping ratio values. Five real earthquake records are selected to perform nonlinear time history analyses. SDOF systems are assumed to be located on the same type of soil profile according to the shear wave velocity values of the first thirty meters of the soil. Bilinear hysteretic model is used and constant ductility is considered. Three different damping ratios as three, five and ten per cent are taken. Energy time-histories of bilinear SDOF systems are obtained graphically for selected earthquakes and for different damping ratios. The main objective of the research is to see to what extent the energy input has changed for different damping ratio values.

Keywords

• Earthquake energy input,strong ground acceleration,single-degree-of-freedom system,damping ratio,energy input-time history

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