| Ladder form rib-ring type of spherical reticulated shell is a new type of reticulated shell in the present practical engineering. The surface of this structure has terraced shape, which has a strong architectural aesthetic feeling. So far, the static stability of this structure has been studyed a little, but the research on aseismic behavior and dynamic stability has not been started. So the study on seismic performance of this structure is extremely necessary. The main contents and achievements are shown as follows:Firstly, the software ANSYS is used to analyze the vibration characteristics of ladder form rib-ring type of reticulated shell and the variation law of its natural frequency in different parameters is studied. It shows that the frequency distribution of Ladder form rib-ring type of reticulated shell is comparatively intensive. With the decrease of the rise-span ratio, the first-order natural frequency of two basic models have displayed a tendency to increase firstly and decrease afterwards, there is a relatively optimal rise-span ratio which is 1/6. Moreover, the larger the span is, the closer and sameller the natural frequency distribution is. The change of the boundary constraint conditions has little influence on the natural vibration characteristics.Secondly, research on the internal force response of Ladder form rib-ring type of spherical reticulated shell under three-dimensional common seismic action is done. Then the impact on the seismic internal force coefficient in different variables and different seismic waves is discussed respectively, and the variation law of seismic internal force coefficient of various types of bar following different parameters is summarized. Comparing the internal force response of the shell under unidirectional seismic action with which under three-dimensional seismic action, the variation law of seismic internal force coefficient under seismic waves in different directions can be obtained.Thirdly, taking the effects of rise-span, span, boundary constraint conditions, initial imperfection and different seismic waves into consideration, the structural dynamic stability under strong earthquake action is studied. Then the judgement on the dynamic stability critical load and dynamic failure form of the shell is made. Studies have shown that, with the decrease of rise-span ratio, the dynamic stability critical load of the structure increases gradually, and structural dynamic failure mode tends to be dynamic strength failure from dynamic stability failure. When the span increases, the shell tends to come into being dynamic strength failure. There is a significant difference in dynamic stability critical loads of this shell under different seismic waves, so a number of seismic waves should be taken into account for a comprehensive study on the structural dynamic stability performance. Dynamic stability critical load of the shell has a big difference between unidirectional seismic action and three-dimensional seismic action, therefore the dynamic stability analysis should consider the three-dimensional seismic action. Under strong earthquakes, the dynamic stability of model A is better than B.Fourthly, under the analysis of static stability, the exploration on optimization of Ladder form rib-ring type of spherical reticulated shell has been carried out. By the comparison from different aspects including the section size, form and classification based on the stress of section, the effectiveness of main bars in the shell is shown as follows from high to low in turn: vertical web member in shear key, radius member, circle member, horizontal member in shear key. Through the trial, the two structural optimization programs can achieve better optimization results. |
