Study On The Seismic Performance And Retrofit Of Reinforced Concrete Chimney With Different Forms Of Opening

Chimney is one of the most important high-rise structures in industrial buildings.With the increasing complexity of the technology and the process flow,the situation of multi-machine sharing a chimney is gradually increasing.Besides,the chimney with circular exhaust opening is also increasing.The multi-hole and circular exhaust opening can cause the diversity and complexity of the opening forms for chimney structure,and also bring new problems to the seismic safety of the chimney.In this paper,the numerical simulation method is employed to analyze and compare the structural response and stress concentration of tall reinforced concrete chimneys with different numbers and forms of openings under seismic action.At the same time,some suggestions for improvement of reinforcement around chimney holes in Chinese Code for Design of Chimneys are given.The main contents can be illustrated as follows:(1)The shell element model of chimneys with different opening parameters and shapes are established using ANSYS finite element software on the basis of a practical reinforced concrete chimney.The response spectrum method is adopted to analyze and compare the structural responses of the chimney models under earthquake action.The seismic response analyses include the situation of chimney with one,two and three rectangle openings and circular opening.The corresponding analysis results can provide reference for the size parameters selection of the chimney openings for practical chimney structures.(2)The stress concentration around the hole for chimneys with different opening parameters is studied under earthquake action.Referring to the definition of stress concentration factor when the rectangular plate is uniformly tensioned,the concept of stress concentration coefficient is proposed,which can be used to quantitatively analyze the stress concentration around the hole for chimneys with different opening parameters.The analysis results show that the size parameters of flue holes have a greater impact on the stress concentration degree around the chimney hole,but a smaller impact on the stress concentration range.(3)The rationality of reinforcement around chimney holes in Chinese Code for Design of Chimneys is discussed.The elastic-plastic models using solid element for chimney with different openings are built using ANSYS program and the pushover analyses are performed for this chimney models.The time history analysis is employed to verify the pushover analysis result of the chimney.According to the pushover analysis results of chimney structures with different reinforcement around chimney holes for different openings,a more reasonable reinforcement around chimney hole is suggested,which means to reduce the amount of reinforcement required by the code and increase the reinforcement area accordingly.This suggestion can reduce the amount of steel bars and prevent reinforcement crowding around the hole and facilitate construction.The results show that reasonable reduction of reinforcement amount around the chimney hole and increase of reinforcement area will not have too great impact on the overall seismic performance of the chimney structure.