Collapse Simulation And Reinforcement Measures Of Grid Structure Under Strong Earthquake

China has a vast territory and is not only located at the border zone between the Eurasian plate and the Pacific plate.At the same time,there are also many small plates inside.These seismic belts are mostly located in densely populated areas in China.It will always cause the great damage to the people and losses when the earthquake occurs.According to statistics,since the earthquake records of the Revolution of 1911,there have been hundreds of earthquakes that caused the loss of property and live in China.Based on the above background,it is very urgent to increase the research on earthquake prevention and disaster reduction in the field of structural engineering.The number of long-span grid structure has become one of the indicators of a country's overall national strength,and due to its superiority in quality and redundancy over other structures.,it has been common in the terminal buildings,stations,convention centers,and other places where people gather in recent years.However,due to the large number of long-span structural members,local damage can occur in the event of an accidental load,which in turn can cause overall damage similar to dominoes.Therefore,it is of great significance to identify the key parts and strengthen the parts.This article first reviewed and summarized the current research status of the collapse mechanism of long-span grid structure and related methods of anti-seismic solutions,and clarified the research significance of this topic.Then use the finite element software SAP2000 to model an actual grid structure,input seismic wave for time history to simulate the collapse of the structure,adjust the acceleration peak according to the incremental dynamic analysis(IDA)method,and obtain the key part of the failed structure under the critical peak acceleration.Next,the viscous damper was used to study the anti-seismic effect of the structure.The details are as follows:Firstly,the related theories and criteria of the dynamic stability of the structure were sorted out.According to the differences of the structural forms,the above-mentioned theories were combined to determine the critical criteria for the dynamic stability of the long-span grid structure under strong earthquakes.Secondly,using SAP2000 to model and design an actual grid structure,and then three seismic waves: EL-Centro wave,Tangshan wave,and Artificial wave were selected to input the model from unidirectional,bidirectional,and tridirectional way in the ratio of X:Y:Z=1:0.85:0.65 to perform the non-linear time history analysis.Thirdly,design different arrangements of attaching viscous dampers to key parts of the grid,inputting EL-centro wave for time-history analysis,selecting representative rods and nodes,and counting the accelerations,vertical displacements and axial forces of the nodes before and after the layout,and select the optimal layout scheme by the analyzing above.The main conclusions obtained are:1.By inputting seismic waves of unidirectional,bidirectional,and tridirectional way,obtain the maximum node displacement data and the corresponding IDA curves of the grid.It is found that the input results of the tridirectional seismic waves are more comprehensive and the key parts resulted from it are more persuasive.2.It is through the appearance of plastic hinges under the action of earthquakes with different acceleration peaks and the areas where the plastic hinges appear before the critical failure determined that the key position is located in the mid-span and the 1/4-span position of two sides.3.From the results of the data under the five scenarios,it can be concluded that the viscous damper has a significant effect in the simulation of large-span grid structures,and the scheme that is arranged along the cross-span direction works best.By the application of the solution,the statistical critical acceleration peak has been greatly improved.Therefore,it is recommended that the method of attaching the viscous damper to the key parts should be studied in the seismic measures of the large-span grid structure.