Energy-based Probabilistic Seismic Demand Analysis And Structural Seismic Design Research

Performance-based seismic design is one of the main research contents in the21stcentury. Although this theory has existed when it was purposed dozens years ago, andthere is great development in both theory study and practical application, but it still alittle bit far away from application in engineering and adopting in the contents ofdesign rules. The researches of performance-based seismic design can be generallydivided into two main parts: one is the seismic evaluation based on performance, andthe other one is the method of design, which are the works this dissertation involvedinto.1. A mount of records including the far-field and near-field effects have beenchosen here, which are used for the time analysis of a mass of single degree offreedom systems. According the time analysis results, the model of strength reductionfactor is purposed here, which considers the effects of displacement ductility, site typeand far-field and near-field records. The characteristic periods Tgis used fornormalizing the abscissa, so the demand of structure strength calculated from the far-field records and the near-field records, respective, can be described by the sameregression model.2. Several intensity indexes are adopted here for the correlation analysis with thedemand of structure energy imposed by the near-field records, and the best index IAispicked up, which is considered to correlate well with the demand of structure energy.Assuming the value of hysteretic deformation of structures is equal when thestructures are imposed by the back and forth horizontal load, the number of constant-valued hysteretic cycles neqis estimated, which the structures can undertake. Therelationship between neqand the other two factors (intensity index IAand strengthreduction factor R) is built, and the regression model is also given here after thestatistics calculation. Based on the above, the models of hysteretic energy and totalinput energy are deduced here, respectively. The energy reduction factor REispurposed here for considering the difference between the elastic input energy and theinelastic input energy.3. The theory background of pushover method is introduced here, and theprecision of the estimation of the target displacement is considered to be the key ofjudging whether the seismic performance of structure can be evaluated properly bythis method. Based on the energy concept, the target displacement of structure can be evaluated and the inter-story shear amplification factor is used here to describing thedistribution of the earthquake force. According the process of adaptive pushover, thepushover method based on hysteretic energy is built here.4. Starting from the principal of energy balance, the relation of the structuralexternal input energy between the structural internal input energy is built, which is thefoundation of energy-based design flow-chart. The process of design takes severaleffects into consideration, such as inelastic input energy, structural hysteretic modeland near-field effects. At last, a bridge pier (the single degree freedom system) and amulti-level frame structure (multiple degree freedom system) are designed here forilluminating the utility of this method.5. The model of structural damage index is deduced here, which is used toevaluated the damage of the structures by construction of the fragility curves. Theintensity index IAproved to be highly related with structural hysteretic energy is usedas the abscissa of the fragility curve. On the other hand, the combined fragility curveswhich are built by combining the results derived from the similar structures are given.Finally, the fragility analysis of a multi-level frame structure is operated fordemonstrating that the method introduced here is practical.