The Seismic Response And Failure Mode Analysis Of The Double—Layer Cylindrical Net Shells In The Strong Earthquake

Large span space structure has the broad development prospects because of its advantages of beautiful appearance,reasonable force and large span.The importance of this type of structure is rather higher.Once it is destructed,people's life and property will be seriously harmed.So it is great practical meaningful to research the performance of the large span space structure under rare earthquake.At present,seismic analysis methods include vibration superposition reaction spectrum method,time history analysis method,PUSH-OVER analysis method,and structural random vibration method and so on.The time history analysis method is applied more extensive because it could be used to calculate the elastic stage response under the earthquake and the elastic-plastic response under rare earthquake.The time history analysis method is a direct integral method,it is direct integration of the dynamic equation of the structure to obtain displacement,acceleration and speed at every moment.In this paper,Newmark-beta method is used for calculation.Under the action of a rare earthquake,the member of a latticed shell may be subjected to tension yielding or buckling under compression.The hysteretic model of Gen steel support is adopted to analyze the performance of the member reasonably in the elastoplastic analysis.This paper takes dry coal shed for raw materials section in the coal preparation plant of a coking project in an industrial park as an example.This research selects EL-centro wave for the elastoplastic time history analysis under the rare earthquake.Through analysis,it is found that a certain number of plastic bars are generated under the seismic force of fortification intensity,and the displacements of the structures are within the controllable range,and no structural failure occurs.In the case of increasing seismic force,the number of plastic members of reticulated shell increases sharply,forming a coherent plastic region,and eventually the structure collapses.These regions are mainly located at mid-span and 1/6 spans of both sides.These three points are the seismic weak points of latticed shell structure.The measures of "strengthening arch" and "local reinforced zone" are respectively added in the original model.Through the analysis,it is found that these two kinds of strengthening methods can effectively improve the seismic performance of the structure,the effect of "local reinforced zone” method is more prominent.On the basis of the calculation and analysis,the aseismic construction measures of the “local reinforced zone” of reticulated shell are put forward.By adding this construction measures,the structure can be guaranteed to be "No Collapsing in the Strong Earthquake".Finally,the author puts forward his own suggestions and understanding on the “Code for seismic design of buildings”.The author proposes that the large span space structure should be also classified into seismic grade,and corresponding seismic measures and anti-seismic measures should be implemented according to different seismic grades.The "local strengthening belt" as an earthquake resistant construction measure should be taken and joined into the code.