Researh And Experimental Verification Of Deformation Index Limits Of RC Beams,Columns And Shear Walls

The deformation and energy dissipation capacity of reinforced concrete(RC)beam,column and shear wall can directly affect the seismic performance of structure.Performing accurate calculation and quantitative performance assessment on RC beam,column and shear wall is an important step in performance-based seismic design.The key technology to realize quantitative component-based performance assessment is to establish deformation index limits for RC beam,column and shear wall component.At present,performance-based seismic design concept has been introduced in the current Chinese code.However,the method to assess seismic performance on components is mainly based on bearing capacity checking.The deformation demands of components under rare earthquake action are mainly guaranteed by related constructional measures while the deformation limits of components are not mentioned.Therefore,it is unable to conduct quantitative assessment on the performance states of structural components.Moreover,seismic performance assessment of structure in our country often refers to deformation limits in foreign codes(such as ASCE/SEI 41-13,EC8-3,etc.).Since the material and constructional measures in foreign codes are different from that in Chinese codes,thus it is necessary to find out whether deformation limits in foreign codes are applicable to structures designed according to Chinese codes.Howere,existing researches on these topics are extremely rare.Given the above,it's very essential to establish deformation limits of components compliant with Chinese codes.The main research works and results of this thesis include:(1)Deformation limits of RC components,given in ASCE/SEI 41-13,EC8-3 and introduced previously by our research group,were expounded.The similarities,differences and insufficiency of these deformation limits with respect to seismic performance level,deformation index and verifiability of deformation limits etc.were compared and analyzed.On this basis,7 seismic performance states of RC components,namely,“intact”,“slightly damaged”,“slightly-moderately damaged”,“moderately damaged”,“severe-moderately damaged”,“severe damaged”,and “invalid”,were put forward,taking account related provisions of seismic performance level on components in Chinese codes.Then,based on 3 key performance points(yielding point,strength deterioration point,and strength loss point)and force-drift angle skeleton curves of components,a method which takes drift angle of components as deformation performance index was put forward to define deformation limits of RC components of each performance state.This method can provide a uniform standard for establishing deformation limits,compliant with Chinese codes,for all types of RC components.(2)A database of 103 rectangular RC beams,469 rectangular RC columns and 236 rectangular RC shear walls was collected from published literature.Compiled tests are all cyclic lateral loading RC components,with or without axial load applied.Parameters of performance points of each specimen were extracted.The database can provide a general experimental data basic for researches on seismic performance and deformation limits of RC components.(3)The influence factors of failure modes of RC beam,column and shear wall were analyzed and summarized with collected database.New failure mode classification methods,based on flexural shear ratio and shear span ratio,were proposed respectively for RC beam,column and shear wall.(4)Through regression analysis of the collected RC component database,formulas were established respectively for the drift angle limits of RC beam,column and shear wall in three key performance states(“intact”,“severe-moderately damaged” and “severe damaged”)under different failure mode.Based on these formulas and the method proposed in the paper for determining each deformation limit of RC components under each performance level,drift angle limits of RC beam,column and shear wall,with specific targeted probability of failure,were put forward for the 6 performance states: “intact”,“slightly damaged”,“slightlymoderately damaged”,“moderately damaged”,“severe-moderately damaged” and “severe damaged”.Then assessment of the drift angle limits was carried out by fragility analysis method suggested in ATC-58,results show that,the exceedance probability of drift angle limits in “intact”,“severe-moderately damaged” and “severe damaged” performance state is not larger than 35%,35% and 15% respectively.(5)Based on the collected RC component database,fragility analysis was conducted to compare drift angle limits of RC beam,column and shear wall proposed in this paper with that given in ASCE/SEI 41-13,EC8-3 and proposed previously by our research group.The accuracy,discreteness and safety of each deformation limits was summarized and the drift angle limits proposed in this paper were verified to be optimal in these deformation limits systems.This part of research work provides a theoretical basis for seismic performance assessment of actual structure.(6)Low-cyclic load tests of 9 RC beams,12 RC columns and 20 RC shear walls were conducted and the failure behaviors of each specimens under each loading level were recorded in detail.Analysis was performed to the experimental failure behaviors of each RC beam,column and shear wall specimen with their performance states.On this basis,failure characteristics of RC beam,column and shear wall,refer to the 6 performance states,namely,“intact”,“slightly damaged”,“slightly-moderately damaged”,“moderately damaged”,“severe-moderately damaged” and “severe damaged”,were obtained.And thus establish the relationship between performance state,deformation limits and the damage level,for RC beam,column and shear wall.(7)In order to verify the drift angle limits of RC beam,column and shear wall proposed in this paper,the drift angle limits of the 9 RC beams,12 RC columns and 20 RC shear walls under 3 key performance states were obtained from experimental force-displacement skeleton curves,and then compared with the drift angle limits proposed in this paper.Results show that,the drift angle limits of RC beam,column and shear wall proposed in this paper are close to and smaller than experimental values with small discreteness.(8)Deformation limits of 3 key performance points of the 9 RC beams,12 RC columns,20 RC shear walls in this paper,calculated by deformation limits systems proposed in this paper,ASCE/SEI 41-13,EC8-3 and the one proposed previously by our research group,were compared to the experimental one,results show that the deformation limits of RC beam,column and shear wall proposed in this paper are the best among these deformation limits systems,which are close to and smaller than experimental values with small discreteness.The deformation limits of RC beam,column and shear wall proposed in this paper further quantifies the deformation capacity of components and makes up the shortage of seismic performance assessment of components based on bearing capacity in Chinese codes.It provides a theoretical basis for realizing performance-based seismic design and assessment on components level.