Study On Urban Optimal Seismic Fortification Criterion

China is a country with high seismic, and the earthquake is a kind of devastating natural disasters. It is important for industry and structure to fortify against earthquake. Cities, gathered a large number of population and wealth, became exposure of natural disasters. At present, widely recognized as the most effective reduction of earthquake disaster measures are fortification against earthquake construction engineering. The seismic fortification criterion is very important, it's not only related to the project and the city's security, but also national and public investment. Now, there is no good way to establish the engineering seismic fortification criterion.This article take into account the characteristics of our cities, take the Seismic behavior of the city (include city building seismic hazard, earthquake economic losses, seismic investment etc.) as optimal target for determining the seismic design criterion, take the fortification levels as optimal variable. Considering security and economic factors, we establish the optimal design of seismic fortification criterion decision model in order to solve the balance problem on inputs and outputs of the earthquake-proof.The main work of this study includes five parts as follow:1,An optimal design of seismic fortification criterion decision model is studied in this paper, the design goal is minimizing the sum of the extra cost of structure with earthquake protection and economic losses. The decision-making method of the model is based on the initial cost analysis and the earthquake loss analysis of structures. We establish the objective function, which optimal variable is the Ground motion parameters, including seismic intensity and peak ground acceleration.2,By studying the initial cost about the main types of buildings in Qingdao, we get relationships among initial cost rate and seismic intensity. And obtain regression equation between the original cost rate and peak acceleration by curve fitting.3,The structural vulnerability analysis is carried out. Based on the dynamic analysis on single structure in building level under seismic effect, we obtain analytical vulnerability curve of single. And then, probability tools are utilized to estimate group building's vulnerability curve. Combine with earthquake statistics, a standard of structural damage is given. At last, we obtain the group structure's vulnerability matrix.4,In the course of studying earthquake economical losses estimation method, direct economical losses and indirect economical losses are considered. Expenses providing disaster relief is belong to indirect monetary losses. For simplicity, we defined the factorΨ as the ratio of direct economical losses.5,Based on the completion of the initial cost analysis and the earthquake loss analysis of structures, the analytical expressions of the optimal seismic fortification criterion is deduced by using the decision-making method, the seismic intensity corresponding to the least expected total loss can be regarded as the optimal seismic fortification criterion and requirements of construction can also be suggested.Take the data of Qingdao as example, we obtain optimal seismic fortification criterion is seven. But now, the current standard is six. On the circumstances, the necessity and possibility analysis of increase optimal seismic fortification criterion is carried out, which will be used in the earthquake relief work of Qingdao.