Analysis On Elastic-plastic Seismic Response Of The Long-span Truss String Structure

The long-span truss string structure is one of the new long-span pre-stressed steel structure in recent years, which has been widely used in many national and foreign engineering practices and has revealed good prospects. Aseismatic capability of these public buildings under earthquake relates to safety of lives and property, and based on development trend about disasters studies of long-span structure, this paper takes single truss string structure as a study object and analyses focusing on its elastic-plastic dynamic response trends under earthquake.On the basis of some related research, dynamic response of the single truss string structure were studied with finite element program ANSYS. Under different earthquake, the deformation of the structure,mechanics properties and some plastic development index were analyzed in this paper, and some different parameters of structural changes affecting the dynamic response under the severe earthquakes were also analyzed, the main contents of the thesis are following:1.Considering the effect of geometric large deformation, mechanics properties of the structure were analyzed under more or rare earthquakes. The node displacement,structure members internal forces and cable segment stress and so on response index all were analyzed, while by design strength for the control of index demands, the structure is at elstic operating condition under more earthquakes; some structure members and whole structure are at elastic-plastic operating condition under rare earthquakes;2. Considering both the geometric and material nonlinear effects, dynamic response capability of the structure were studied under severe earthquakes, focusing on the plastic response index. The results showed that the phenomena of local structure members enter into the plastic operating condition occurred faster with great degree development, and structural relative deformation capacity and aseismatic capability all had large consumption, result in the use of functional of the whole structure did not accord seismic requirements, and then identified the range of control load of severe earthquake, so that one conclusion were that aseismatic capacity of strut members and lower-chord steel cables higher than that of the truss members.3. Respectively considering the geometric and double nonlinear effects, the earthquake response analysis showed that reaction of internal forces of structure support have the larger changes, especially the reaction of anti-level direction with the lagest changes, which have high requirements to lower bearings and supporting structure.4. Under one strong earthquake, some parameters analysis on the dynamic response showed that the seismic responses to development trends under different input in the direction of seismic waves,different seismic waves,bearing binding changes,prestress value changes of cable or other parameters changes. All of these can be further understand the the dynamic response under severe earthquake about the specific single truss string structure in this paper.The numerical simulation analysis on elastic-plastic dynamic response of the specific structure in this paper indicates the development trend of various indexes and the effect trend of different parameters to dynamic response, the conclusions are achieved correspondingly, and the problems should studied are prospected by the paper.