AN INVESTIGATION OF DAMPING RATIO EFFECT ON EARTHQUAKE ENERGY INPUT

Recentearthquakes show that the strength and displacement-based methods in manyseismic design codes are not as reliable as the energy-based methods in seismicdesign and evaluation of structures. The determination of earthquake energyinput to structures is the main concern for the energy-based structural designmethods. The seismic energy input to structures mainly depends on the strongground acceleration and the velocity time history of the structures. Currentstudies about the seismic energy input show that the bases of researches areestablished almost entirely for the single-degree-of-freedom (SDOF) systems.This study investigates the variation of earthquake input energy of SDOFsystems which have different period and damping ratio values. Five real earthquakerecords are selected to perform nonlinear time history analyses. SDOF systemsare assumed to be located on the same type of soil profile according to theshear wave velocity values of the first thirty meters of the soil. Bilinearhysteretic model is used and constant ductility is considered. Three differentdamping ratios as three, five and ten per cent are taken. Energy time-historiesof bilinear SDOF systems are obtained graphically for selected earthquakes andfor different damping ratios. The main objective of the research is to see towhat extent the energy input has changed for different damping ratio values.