ABSTRACT
A two-stage optimum design method for aseismic structures is presented, in which the decision of the optimal fortification load is made in the first stage, and the minimum-cost design under the optimal fortification load is made in the second stage. A more scientific objective function of decision-making for the optimal fortification load of aseismic structures is presented by taking the fortification intensity as the typical representative of the seismic fortification load. The objective can consider both the short-term investments, that is, structural cost, and the long-term benefits, that is, the loss expectation under earthquakes. Two methods for solving the minimum-cost function are presented, which include the precise method and the simplified one. A macroscopic analysis method for calculating the fuzzy probabilities of seismic damaged structures is developed according to the provisions of the current design codes and the three-level fortification principal of aseismic structures. On the basis of these, the decision-making method and the corresponding procedure for the optimal fortification load of aseismic structures are put forward. A unified relationship between the optimal fortification load and the optimal fortification reliability is deduced, and then, the method of decision-making of the optimal fortification reliability based on the optimal fortification load is advanced.
