Seismic Response Analysis And Isolation Investigation Of The Ningbo International Conference And Exhibition Center Space Truss Structure Under Multi-dimensional And Multi-support Excitations

Space truss structure can be found in many large public buildings, such as gymnasium and airport. Thus how to increasing seismic resistance of such structure is the hot topic in structure design.A large-span flat space truss structure, Ningbo International Conference and Exhibition Center (the second phase), is taken as a calculating example. Its seismic response under multi-dimensional and multi-support excitations is studied by using numerical analyzing method. Difference between the various earthquake input methods is comparied. The optimization of the isolation bearing distribution is investigated as well. The main work and conclusions include as follows:1. ANSYS soft is employed to model the truss and static analyzing. Nine area sections are adopted. Their displacement and stress responses are studied respectively. Five truss heights are referred and result shows that the node displacement decreases with the truss height.2. By the modal analysis, the natural frequences increase with the modal order. Three earthquake waves are slected and the uniform excitation is applied to the structure. Analysis result shows that the structure has a maximum response under the earthquake in three directions.3. Assuming eight large-mass solids with the same mass are set at the bearings. Comparison is conducted between the different seismic effects corresponding to the ninth degree frequent and rare earthquake, respectively. If no traveling-wave effect is considered, a uniform acceleration time-history (single point excitation) is applied in the analysis with a unique inertial force is loaded at the bearings consequently. The displacement response of the space truss under the earthquake acting in different directions is studied beased on the above work. If the traveling-wave effect is considered, only the uniform acceleration time-history is replaced by a suitable one, or the multi-point excitation. Numerical result shows that the displacement with the uniform acceleration time-history is less than that corresponding to the non-uniform one, i.e. single point excitation leads a higher evaluation of the seismic resistance of structure. The first 20-order modal are employed and the response spectrum of acceleration is obtained based on the seismic influence coefficient curve referring in the Code for seismic design of buildings. Seiemic properties are analyzied for single-point and multi-points excitation respectively. A power spectral density function is obtained from the acceleration time-history with MATLAB program. Three earthquake waves are selected in this study. The (root mean square) displacement and supporting force are closed between each wave.4. Eight reinforced concrete columns are set at the bearings of the initial space truss model. Three distribution forms of the lead-rubber isolation bearings GZY300 are analyzied. It is found that the distribution of the bearings has a significant influence on the truss displacement. Node displacements are compared corresponding to the three earthquake waves with the top and bottom bearing. Comparing result shows that the displacement with the top bearings is less than that with the bottom bearing, i.e. the isolation effect is larger when the isotation bearings are set at the top of the columns. Force histories of support column are analyzed. Results show that the column is safer with the isolation bearing distributed at the column top. Displacement response for the structure with the ordinary rubber isolation bearings is investigated and compared with that of GZY300 case. The size of the support columns is changed and the consequent influence on the axial force history is concered. This also shows that column is safer with the isolation bearing distributed at the column top.