Construction of uniform hazard spectra and uniform risk spectra in Xi’an region

Abstract:

To ensure that the structures in different regions have the same collapse probability under earthquakes, uniform risk spectra are investigated in this paper. First, the uniform hazard spectra of Xi’an region were obtained through probabilistic seismic hazard analysis, and the uniform risk spectra were obtained through risk integral method. By comparing the uniform hazard spectra with the uniform risk spectra, it was found that seismic design based on the uniform hazard spectra resulted in different collapse probabilities of structures under earthquakes. Then, the uniform risk spectra in Xi’an region were constructed through analytical method, and the uniform risk spectra obtained by risk integral method and analytical method were compared. It was found that the difference in the uniform risk spectra was small if the seismic hazard of the site was well described by the seismic hazard function. Finally, the effects of the logarithmic standard deviation (β) of seismic fragility on the uniform risk spectra, risk coefficient (R_c), and coefficient among risk-targeted ground motions were analyzed. Results show that β had little effect on the uniform risk spectra of maximum considered earthquake, while it had significant effect on the uniform risk spectra of design basis earthquake and very rare earthquake when β was less than or equal to 0.7 and greater than 0.7, respectively. When β was less than 0.7, R_c decreased with the increase of β, while R_c increased with the increase of β when β was greater than or equal to 0.7. The effect of β on the coefficient between the risk-targeted very rare earthquake and design basis earthquake was greater than that on the coefficient between the risk-targeted maximum considered earthquake and design basis earthquake.