Research On Determination Methods Of Design Ground Motion Considering Multi-earthquake Events

With a frequent occurrence of earthquake in recent years, people have paid more attention on how to determine the design ground motion considering multi-earthquake. The purpose of this dissertation is to take into consideration the multi ground motion problem when design the structure and to develop a method on the basis of current design method. This dissertation proposes a determining principle and a method to determine the design ground motion parameters. The main contents are as follows:1. The dissertation summarizes the state-of-the-art researches on multi-earthquake design both domestic and abroad, analyzes the existing problems, and introduces the current aseismic design method in detail. The feature of multi ground motion effects is summarized. Compared with current aseismic design method, the text concludes a fundamental idea of equivalence, “equal the effects of multi hazard to single”, which can not only fully consider the feature of multi ground motion effects, but also subtly bridge to current single ground motion effects considered aseismic method. The text proposes several different equivalent means, analyzes and compares them to each other. Then the method of structural damage based equivalence is chosen as the optimal method, and applied to the text.2. The method of structural damage based equivalence is elaborated in the text. The core of this method is to control the structural damage under multi ground motion to equal that under a single ground motion, and the PGA of new single ground motion is utilized as the design parameter. The text proves a positive correlation between structural damage and PGA of ground motion, and finds the function who fits the correlation best, upon which the flow chart and the example case of the method based-on structural damage equivalence to determine ground motion parameters are given. As the statistical results reveal, multi-earthquake design need to amplify the PGA of the single-earthquake design, and PGA of different intensity areas has an amplification of 10%~27%. The amplification is larger when the intensity goes higher. The ground motion parameters are determined in this way. After taking the modification of the structure into consideration, the text proposes the iterative idea and the ultimate method to determine design PGA.3. The method of Chapter 3 is improved. Based on the equivalence of structural damage, the text proposes a fitting method other than iteration to determine ground motion parameters, which can be easily applied in practical engineering. This text studies the feature of equivalent amplifying coefficient(the ratio of equivalent design PGA of single earthquake motion to original design PGA of single earthquake) along with ground motion duration parameters, frequency spectrum parameters and site classification based on the statistics data of 400 selected ground motion records.