Study On Life-cycle Evaluation Model Of The Base-isolated Structure

With the development of the seismic design theory and isolated control technology in our country, many base-isolated buildings are also contrusted in China , the isolation technology has become an important new engineering seismic method. After the WENCHUAN earthquake, the demand of people on the base-isolated building is increased with each passing day. The isolation technology with the most mature theory and relatively simple construction has also made enormens progress. The obvious technical advantage of base-isolated building in the seismic capability and the shock absorption effect has been widely proved, but currently many designers and owner exist doubts about the economic rationality of isolated structure, and performance level and performance objectives of base-isolated structure are not clearly studied. Mean while, evaluation standard to describe isolated structural performance parameters is not quantitatively researched, which will block the development of base-isolation economic evaluation. In view of the above reasons, all-life-cycle economic cost evaluation model for base-isolated structures was researched in this paper , main jobs are following:1) Performance levels and performance objectives of base-isolated structures. Combined with the characteristics of isolated structure, seismic performance levels and performance objectives have been put forward, After defining different function category of isolated structures by design reference period, corresponding exceeding probabilities of three kinds of buildings with different design reference periods under three seismic levels are calculated. The paper put forward horizontal vibration-reduction coefficient for the structure with different function and the corresponding suggested intensity values of horizontal ground motion as well as seismic measures to upper structure after being isolated. Thus, alternative design scheme can be given for the designers and investors.2) Initial cost of isolated structures.Through the statistics of engineering respective examples, the cost (including seismic cost,increasing cost for isolation and reduced cost of the upper structure) evaluation has been made for isolated structures, common and personality calculating formula of the base-isolated structures are put forward. So investors and designers personnelly have more comparative analysis method about design plan.3) Life-cycle cost evaluation of isolated structures. In order to manifest potential economic advantages of the base-isolated structure more fully, this paper comprehensively evaluated total life-cycle cost of the base-isolated structures, studied the maintenance cost , loss and casualties cost based on the probability analysis of base-isolated structure during life cycle period; it is concluded that the evaluation methods of the total life-cycle cost; through the numeral example, it is proved that the isolated structures has advantage with investment-benefit criterion. Then the paper puts forward the social acceptable average mortality and the two-stage decision-making method of the optimal safety fortification for isolated structure. At the same time, the mathematics fuzzy comprehensive evaluation method is introduced to evaluate the expected loss cost of base-isolated structures; Thus, a economy analysis and evaluation tool for isolated structures can be gotten, which is more simple and more feasible and promote the popularization and application of the isolation technology.