Research On Reasonable Setting Strategies And Methods Of Structural Safety Level

As the economical level of our country is going higher, more investment is made in the infrastructure. Therefore, the safety level of structures affects not only human's life but also the development of the country. The higher the safety level of structures is, the more investment would be needed. But, the safety level of structures must be suit the economical level because the resource of our country is limited. The present thesis will answer a question 'How Safe is Safe enough?',which is based on the theory of risk analysis and decision-making and the theory of structural reliability. The main contributions are shown as fellows: Firstly, the background of setting of safety level of structures and how to treat it in practice is introduced. The theory of risk analysis and structural reliability used in this thesis is also presented. Secondly, the history of structural design codes is reviewed. Comparison of the structural safety level of different periods of China and that of different countries are made. It can be concluded that today's safety level of structures in China is not only lower than that of 50 years ago but also lower than that of the developed countries. Thirdly, based on the theory of risk analysis and decision-making, the decision criterion of the safety level of structures is studied and the decision-making model of the safety level of structures is set up. Thus, the system failure probability is chosen as the decision variable, so that the theory of structural reliability and the branching-bounding method is introduced. Fourthly, using failure probability as decision variable, the decision of the range of safety level of typical structure is made by the new decision-making model. Finally, an optimal safety level of structures is given under a constant psychologic risk assumption during the economy development. Some suggestions are also given on the issue of design code development.