Research On Dynamic Stability Of Cylindrical Reticulated Mega-Structure

Long-span space structures are widely used in series of public buildings with theadvantages of spectacular mechanical behavior,novely structural forms and capabilityof crossing large span. Once these buildings collapse, the cocpuence could hardly beeliminated.Therefore the study on the progressive failure mechanisms of long-spanspace structure has significant value in both theory and practice. At first, this paperreviewed the current research status of the study on the progressive failuremechanisms of long-span space structure under dynamic loads, introduce severalkinds of dynamic failure criterion, and the necessity and method of considering thedynamic effect due to single bar instability are also discussed briefly.The cylindrical reticulated mega-structure is a new kind of space structures toadapt to the demand for crossing super-long span of space structures. Already-existentresearches show that this structure has excellent mechanical properties. However, themechanical properties and progressive failure mechanisms of this structure underextreme dynamic loads such as snowstorm, weight impact and violent earthquakehave not been studied deeply, which become urgent problems to solve on its way topractice use. Hence, the focus analyses on this structure by using the general finiteelement software ANSYS, are as follows:Firstly, the response characteristics and hence the failure mechanism of thisstructure under vertical step load considering only elastic-plastic are compared withthat considering the dynamic effect due to diagonal bars instability,as well as thatconsidering the dynamic effect due to chord bars instability. A series of parameteranalysis are carried out for the structural response, the change law of the structuralultimate load with the changing parameters such as span, span ratio and the height ofthree-dimensional(3D) trussed arch was obtained. Also the influence of the dynamiceffect due to diagonal bars instability to the structural ultimate load under differentstructural parameters was found. Furthermore, the influence of factors such asstep-time, load distribution and initial defect to the structural ultimate load wasanalysised.Secondly, the response characteristics and hence the failure mechanism of thisstructure under horizontal step load considering only elastic-plastic are compared with that considering the dynamic effect due to diagonal bars instability,as well asthat considering the dynamic effect due to chord bars instability. A series ofparameter analysis are carried out for the structural response, the change law of thestructural ultimate load with the changing parameters such as span, span ratio and theheight of3D trussed arch was obtained. Furthermore, the influence of factors such asstep-time, load distribution and initial defect to the structural ultimate load wasanalysised. During the above analysis, the difference of the failure mechanism of thisstructure under between vertical load and horizontal load was discussed also.Finally, the response characteristics and hence the failure mechanism of thisstructure under violent earthquake considering only elastic-plastic are compared withthat considering the dynamic effect due to diagonal bars instability,as well as thatconsidering the dynamic effect due to chord bars instability. A series of parameteranalysis are carried out for the structural response, the change law of the structuralcritical acceleration with the changing parameters such as span, span ratio, the heightof3D trussed arch and surface mass was obtained. Also, the influence of differentearthquake motions to the structural critical acceleration was studied.The research in this paper provide theoretical basis and reference for theprogressive collapse design of this new-trpe structure.