Seismic Control And Optimization Design Of Large-Span Space Structures With Viscous Dampers

This thesis studies the seismic control on large-span space structures, primarily on double-layer cylindrical latticed shells with viscous dampers and their optimal locations, and solves the applied problem of viscous dampers in large-span space structures according to the seismic control design of a railway station hall. The main achievements of this thesis are shown as following.1. The principle of seismic control of viscous dampers is illustrated for latticed shells, and it is demonstrated that the time-history analysis method and the energy method are applicable for the seismic control design of large-span space structures.2. Considering different setting manners, locations, numbers, and damping coefficients of viscous dampers, and multiple rise-span ratios of latticed shells and the comparison between linear dampers and nonlinear ones, the parameter analysis of seismic control of double-layer cylindrical latticed shells is carried out by inputting earthquake waves along one direction and three directions respectively. Then the important parameters and the corresponding rules are concluded which influence the effect of seismic control of viscous dampers on latticed shells. The results indicate that this seismic control method using viscous dampers is feasible and the control effect is remarkable.3. The optimal locations of viscous dampers are investigated in large-span space structures. Firstly a thread is put that the location optimization of dampers can be transformed into maximizing the sum of the percentage of modal strain energy of total replaced members, and then a simple and applicable mathematical model is built up, finally an optimization program named VDLO (Viscous Dampers' Location Optimization) is accomplished using Genetic Algorithm.4. The VDLO program is applied to 3 examples of searching optimal locations of viscous dampers in double-layer cylindrical latticed shells, and the results confirm the validity of the program. On the basis of this, the effect of the rise-span ratio of latticed shells is studied on optimal locations of dampers, and the rules of optimal locations of dampers are summarized in double-layer cylindrical latticed shells, which are available for practical engineering. The rules show that in the latticed shells with rise-span ratio of 1/4 dampers should replace the transverse top-chord members located in 1/4 span, and when the rise-span ratio of latticed shell increases to 1/3 or more, dampers should be considered replacing a part of web members located in 1/4 span besides the transverse chord members, and when the rise-span ratio of latticed shell decreases to 1/5 or less, dampers should replace the transverse bottom-chord members located in 1/4 span.5. The seismic control design of a railway station hall is finished by using viscous dampers and the above rules of location optimization. The results indicate that in comparison with the original structure without dampers, after the locations of dampers are optimized the effect of seismic control is obvious and the structural internal forces and displacements are reduced evidently so that the structure satisfies the seismic fortification criterion "no damage under moderate earthquake, repairable under rare earthquake". At the same time, it is proved that the rules of location optimization of dampers are correct.