Study on the severest real ground motion for seismic design and analysis

How to select the adequate real strong earthquake ground motion for seismic analysis and design of structures is an essential problem in earthquake engineering research and practice. In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions. By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground motion records collected over the world. The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential. It is noted that for different structures with different predominant natural periods and at different sites where structures are located the severest design ground motions are usually different. Finally, two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.

Seismic design and analysis of nuclear power plant structures

The seismic design and analysis of nuclear power plant (NPP) begin with the seismic hazard assessment and design ground motion development for the site. The following steps are needed for the seismic hazard assessment and design ground motion development:a. the development of regional seismo-tectonic model with seismic source areas within 500 km radius centered to the site;b. the development of strong motion prediction equations; c. logic three development for taking into account uncertainties and seismic hazard quantification;d. the development of uniform hazard response spectra for ground motion at the site;e. simulation of acceleration time histories compatible with uniform hazard response spectra. The following phase two in seismic design of NPP structures is the analysis of structural response for the design ground motion. This second phase of the process consists of the following steps:a. development of structural models of the plant buildings;b. development of the soil model underneath the plant buildings for soilstructure interaction response analysis;c. determination of instructure response spectra for the plant buildings for the equipment response analysis. In the third phase of the seismic design and analysis the equipment is analyzed on the basis of in-structure response spectra. For this purpose the structural models of the mechanical components and piping in the plant are set up. In large 3D-structural models used today the heaviest equipment of the primary coolant circuit is included in the structural model of the reactor building. In the fourth phase the electrical equipment and automation and control equipment are seismically qualified with the aid of the in-structure spectra developed in the phase two using large three-axial shaking tables. For this purpose the smoothed envelope spectra for calculated in-structure spectra are constructed and acceleration time is fitted to these smoothed envelope spectra.

Study on the Relationship of Seismic Design Ground Motion at Different Fortification Levels in the Xinjiang Region

The seismic risk analysis results of 79 cities in Xinjiang are presented, and the bedrock peak ground accelerations under three seismic levels and their ratios are discussed. Then, the relationship between earthquake environments and the seismic risk analysis results of different exceeding probabilities are researched. The results show that minor and major earthquake motion parameters calculated from moderate earthquakes do not have a consistent probability and the ratio of bedrock peak accelerations under different exceedance probabilities are dosdy correlated with earthquake environments.

Study on Site Specific Design Earthquake Ground Motion of Nuclear Power Plants in China

The main technical backgrounds and requirements are introduced with regard to earthquake ground motion design parameters in several domestic and American standards,codes and guides involved in the seismic analysis and design activities of nuclear power plants in China.Based on the research results from site seismic safety evaluation of domestic nuclear power plant projects in the last years,characteristics and differences of site specific design spectra are analyzed in comparison with standard response spectra,and the suitability of standard response spectra for domestic nuclear power plant projects is discussed.

Comparative Analysis of Equal and Unequal Grounding Grid Configurations by Compression Ratio and Least Square Curve Fitting Techniques

The primary aim of the power system grounding is to safeguard the person and satisfying the performance of the power systemtomaintain reliable operation.With equal conductor spacing grounding grid design,the distribution of the current in the grid is not uniform.Hence,unequal grid conductor span in which grid conductors are concentrated more at the periphery is safer to practice than equal spacing.This paper presents the comparative analysis of two novel techniques that create unequal spacing among the grid conductors:the least-square curve fitting technique and the compression ratio techniquewith equal grid configuration for both square and rectangular grids.Particle Swarm Optimization(PSO)is adopted for finding out one optimal feasible solution among many feasible solutions of equal grid configuration for both square and rectangular grids.Comparative analysis is also carried out between square and rectangular grids using the least square curve fitting technique as it results in only one unequal grid configuration.Simulation results are obtained by theMATLAB software developed.Percentage of improvement in ground potential rise,step voltage,touch voltage,and grid resistancewith variation in compression ratios are plotted.

Lightning Protection for the Computer Room of Electronic Information Systems

An electronic information system is composed of multiple groups of components. With the improvement of technology, its accuracy is getting higher and higher. The voltage during normal operation is only a few volts, and the information current is only microamp, so the withstand voltage to lightning electromagnetic pulse is extremely low. In this paper, the negative impact of lightning and static electricity on the computer room of an electronic information system was analyzed firstly, and then the design for the lightning protection of the computer room was discussed.

Development of seismic force requirements for buildings in Taiwan

This paper describes static and dynamic procedures to calculate seismic demand specified by the current seismic design code for buildings in Taiwan, which was issued in 2005. For design levels with a return period of 475 years, the design spectral response acceleration can be developed for general sites, near-fault sites and Taipei Basin. In addition, in order to prevent building collapse during extremely large earthquakes and yielding of structural components and elements during frequent small earthquakes, the required seismic demands at the maximum considered earthquake level （MCE, 2%/50 years） and operational level are also included in the new seismic design code.For dynamic analysis procedures, both the response spectrum method and time history method are specified in the new seismic design code. Finally, procedures to generate spectrum compatible ground motions for time history analysis are illustrated in this paper.