Research On Seismic Behavior And Ddesign Method Of RC-CFST Composite Frame In Traditional Style Building

Chinese ancient architectures,with high historical value and scientific value,are the crystallization of the long historical culture of Chinese nation.In order to inherit the precious cultural heritage,the thought of Chinese traditional style building constructed with modern construction materials and structure form are put forward.The steel and concrete composite structure has good seismic performance and good application prospect in Chinese traditional style building.Reinforced concrete-concrete filled steel tube(RC-CFST)composite frame in traditional style building is a new type of structure.It not only enhances the ability and durability of the structure against disasters,but also inherits the characteristics of the ancient architecture such as graceful appearance and magnificent style.However,there is no design specification for RC-CFST composite frame in traditional style building,and only the existing modern building codes and practical engineering experience can be used for seismic design.It is significant to study seismic behavior and design method in traditional style building in following aspects.Main contents and achievements of the dissertation are as follows:(1)A 1/2-scale RC-CFST composite frame structure model in traditional style building was tested under low cyclic reversed loading.The failure process and failure characteristics were investigated.The mechanical behaviors such as load-displacement hysteretic loops,skeleton curves,strain characteristics,ductility,energy dissipation,stiffness degradation and load bearing capacity degeneration of the frame were obtained.Test results show that the rufu beam of traditional style building act as the first seismic line under the action of horizontal seismic action.The pinching phenomenon of hysteretic loops appears,indicating shear-slip property.The equivalent viscous damping coefficient is 0.146,which is smaller than that of the conventional modern concrete frame structure.The displacement ductility coefficient of the frame is greater than 3.0 and the ultimate elasto-plastic drift ratio is 1/27,indicating better deformation ability and collapse resistance capacity.(2)Based on the experimental study,static elasto-plastic analysis was presented by means of ABAQUS program.The results of elasto-plastic analysis agree well with the experiments.Parametric analysis of the structure was carried out based on the theoretical analysis.The influential rules of yield strength of steel,longitudinal reinforcement ratio of RC cloumns,axial compression ratio of RC-CFST columns,linear stiffness ratio of CFST columns and RC columns,concrete strength on the mechanical properties were obtained.The results show that with the increment of the yield strength of steel and concrete strength,the horizontal load-baring capacity and ductility are slightly improved.With the increment of the axial compression ratio of RC-CFST columns and linear stiffness ratio of CFST columns and RC columns,the horizontal load-baring capacity of frame are improved,but the ductility of the structure are decreased.With the increment of longitudinal reinforcement ratio of RC cloumns,the horizontal load-baring capacity and ductility are slightly improved.(3)A one-fourth scaled RC-CFST composite frame in traditional style building was tested on the 3D and 6-degree shaking table with four different seismic wave inputs.Dynamic characteristics such as natural frequency,damping ratio were assessed through white-noise scanning.Loading process,failure characteristics,acceleration,displacement response,inter-story shear force and strain response were investigated.The test analysis indicates that the rufu beam of traditional style building act as the first seismic line and lan'e beam act as the second seismic line under the action of horizontal seismic action.The natural frequency descends,the damping ratio ascends and the acceleration amplifying factor decreases gradually with the increase of input peak ground acceleration.The maximum inter-story drifts are found to be 1/46 and 1/51 in direction X and Y under the seismic intensities of rare 7 degree,which shows that the lateral stiffness of the structure is low.The seismic shear force does not decrease significantly along the height direction.The seismic properties of the connection area between the top of columns and the bottom of column frame are weak.(4)Based on the previous experimental study,the elastic-plastic seismic response analysis of the test frame is carried out by using the finite element analysis software SAP2000.Acceleration response,displacement response and the order of plastic hinges in the model were obtained.The elasto-plastic seismic analysis results agree well with the experiments.Parametric analysis of the structure was carried out based on the theoretical analysis.The results show that: with the increment of the stiffness ratio of rufu beam to composite column and stiffness ratio of lan'e beam to composite column,the natural frequencies of frame is increased.Under smaller earthquake action,displacement response of frame decreases gradually with with increment of the stiffness ratio of rufu beam to composite column and stiffness ratio of lan'e beam to composite column.Under larger earthquake action,displacement response of frame decreases firstly and then increases.With the increment of the axial compression ratio and,the natural frequencies of frame is decreased,but displacement response of frame is improved.The seismic performance of the structure is obviously deteriorated.Under smaller earthquake action,with increment of the stiffness ratio of CFST column to RC column,the acceleration response of the frame increases slightly and the displacement response decreases slightly.Under larger earthquake action,the bottom of the RC column is more severely damaged with frame of relatively small stiffness ratio of CFST column to RC column.Based on the above analysis results,the rationalized structure design model is put forward.(5)Referring the current codes,five performance levels are put forward for RC-CFST composite frame in traditional style building.The five performance levels and three seismic levels are combined to form the seismic performance target,respectively as the highest goal,important objective and basic goal.Based on the results of seismic performance tests on RC-CFST composite frame in traditional style building,the maximum inter-story drift angle corresponding to different performance levels were presented for the RC-CFST composite frame in traditional style building.Base on the elasto-plastic seismic analysis,the lateral displacement mode of RC-CFST composite frame in traditional style building is determined.Performance-based seismic design theory was applied to the RC-CFST composite frame in traditional style building.Combined with the structural characteristic,the design procedure was given.