Risk-targeted Ground Motion And Its Application

The performance-based approach to determining design ground shaking parameters for major projects has gradually become a mainstream direction,while(collapse)risk-based ground shaking parameter zoning for general buildings will also be an inevitable trend in future seismic zoning.By determining the design ground shaking parameters through a performance-based or risk-based approach,it is possible to ensure that the designed structure will have the expected risk or performance for a certain number of years to come.However,there is a lack of research and application of risk-based or performance-based methods for determining ground vibration parameters in China.This paper addresses this problem by conducting research in the following areas.Firstly,the current single probability level seismic hazard expression of China's seismic zoning map seriously hinders the application of risk-based ground shaking determination methods.In order to express the full-probability seismic hazard in a simple way,a seismic hazard function based on the characteristic coefficient k is proposed.For the first time,a"full-probability seismic hazard map"is proposed and a hazard characteristic coefficient k zoning map is prepared for different response spectral periods(PGA,0.2s and 1s)in China's mainland.In addition,it is suggested that the sites with lower k values are located at the locations with relatively strong seismicity in the surrounding environment,while the sites with higher k values are located at the locations with relatively weak seismicity in the surrounding environment.At present,the current seismic zoning maps in China are still based on consistent risk ground shaking as an indicator,and insufficient consideration is given to the consistency of general building collapse risk in different regions with large volumes.The concept of seismic risk integral in ATC 3-06 and the principle of the design factor method recommended by ASCE 43-05 are introduced,and the values of three key parameters(standard deviation of susceptibility function,target collapse risk and collapse probability corresponding to design ground shaking)affecting the consistent risk ground shaking are discussed,and the design ground shaking based on consistent collapse risk for China's mainland is obtained using the design factor method.The effects of different parameter values on the risk-based ground shaking results are analysed.The DF-AR empirical function method for determining the consistent ground shaking parameters for collapse risk to match the seismic protection requirements of the Chinese ground shaking parameter zoning map was proposed.In addition,the application of the performance-based design method to major projects is investigated using the Tianwan Nuclear Power Plant as an example,and the applicability of the performance-based ground vibration determination method to major projects is discussed.The performance-based ground shaking determination method given in RG1.208 is used to obtain a site-specific SL-2 ground shaking response spectrum(GMRS)for the Tianwan plant in conjunction with the seismic hazard information from the Fifth-Generation Map.Most of the current risk-based methods for determining ground shaking are based on the Poisson process.A time-dependent seismic risk assessment method is developed by combining the results of time-dependent seismic hazard analysis with the susceptibility curves of structures.Based on the BPT recurrence interval model of characteristic earthquakes and the ground shaking attenuation relationship considering the fault rupture scale,a time-dependent seismic risk calculation formula is given.Using the time-dependent seismic risk evaluation method for the Xianshui River Fault Zone,the time-dependent seismic risk distribution(also known as risk prevention and control map)for the next 50 years for the area near this fault zone under several different scenarios is given,and some conclusions are obtained through comparative analysis.The reasonable calculation of the very low exceedance probability is of great importance to the seismic risk assessment of major projects such as nuclear power plants.The current problems in the calculation of the very low exceedance probability are investigated in depth and a method for calculating the very low exceedance probability is established.The results show that the GPD can better describe the distribution of ground shaking residuals in the tails than the log-normal model.The results of the PSHA show that the results of the low exceedance probability calculations are mainly controlled by the tails of the ground shaking residuals.The results of the PSHA show that the results of the low exceedance probability calculations are mainly controlled by the tail of the model,and that the seismic hazard curves obtained from the four ground shaking prediction models(non-truncated lognormal model,3 times standard deviation truncated lognormal model,overall GPD composite model and grouped GPD composite model)are significantly different below 10^-5.