Study On The Natural Vibration And Dynamic Response Of Composite Tube Truss Floor

With the rapid development of economy in our country recently, the demands for large-span structures, especially the economical spatial structure are increased. As a new spatial structure type, composite floor tube truss structures are highly appreciated by many structure engineers because of its advantages of fewer nodes, high load capacity and light weight. However many scholars, at home or abroad still don’t pay enough attention to the study of this kind of structure performance. Most of the studies focus on the static behavior while the analysis on the dynamic performance are still lack of attention. The related theoretical calculation and design methods of that are not complete, which poses a barrier to anti-earthquake design. Based on the previous research results, this study analyzes the vibration characteristic and dynamic response of composite tube truss floor by using the finite element software SAP2000. This study also proposes some parameters that can be used in structure design. The results of the studies are listed as follows:1.According to the the research of pipe truss structure and composite floor tube truss structure at home and abroad, this study puts forward the necessity of studying the structural dynamic performance of tube truss composite floor.2. This study explains the modal analysis theory, modal decomposition response spectrum theory and Push-down theory that are referred in the study, which are also combined with the analysis of composite tube truss floor.3. Push-down method is used to analyze the advantages and disadvantages of truss structure that was formed by three different kind of cross-sections. This study selects the inverted triangular cross-section as the cross-section used in composite truss floor, which also verifies the accuracy of the model used in the study.4. Different modes of structure are gotten by doing the modal analysis of composite tube truss floor. This study analyzes 4 factors that have influences to the fundamental frequency of composite truss floor, which are width- height ratio, height-span ratio, space between trussesand thickness of reinforced concrete slab. The results show that the height-span ratio and space between trusses are the main factors to influence the fundamental frequency while the other two are not.5. Response spectrum analysis of composite tube truss floor is performed and the dynamic responses is also studied in this study. By studying the4 factors of width- height ratio, height-span ratio, space between trusses and thickness of reinforced concrete slab that have influences to the composite tube truss floor’s Dynamic response, this study proposes two parameters that are the optimal high-span ratio value of 1/15 and the optimal span-space ratio value of 9. Finally, this study calculate the coefficient of vertical earthquake action based on the internal force envelope method, which can be used to simplify the calculation. It has certain value of engineering application.