Damage Identification Based On Dynamic Response Mode Difference Ratio

The collapse accidents of old buildings at domestic and abroad frequently occur during their designed life,which do great harm to the basic public safety and social and economic development.Material aging and damage accumulation,improper investigation,design,construction,use and maintenance in the process of structure use,increase the structure load and reduce the structure bearing capacity.In particular,the neglect of buildings when they were already visibly damaged was a major factor in a series of catastrophic accidents.If all the old buildings are demolished and rebuilt,it will cause huge social and economic problems.Therefore,it is necessary to adopt appropriate means to make scientific evaluation on the current situation of their use,and adopt adaptive schemes for reinforcement and transformation.Damage identification is the first condition of reinforcement.Dynamic response identification is a commonly used method for overall damage identification.In this method,damage identification is carried out based on the change of modal parameters immediately after the occurrence of damage.However,the sensitivity of damage indicators to damage is not the same in the current research at home and abroad.The damage identification at the structural level is mostly confined to the numerical simulation level without experimental support and basis.The research of component hierarchy mainly focuses on the damage caused by simulated stiffness reduction,so as to identify whether the damage occurs or not and to locate the damage,while there is no special research on the influence parameters of stiffness.Therefore,this study mainly focuses on establishing the damage identification method,verifying the damage identification method and determining the stiffness influencing factors.For the purpose of the research,the target is divided into three parts: damage identification based on the design model,damage identification based on the scale model and stiffness influence parameter analysis.Design model to reduce damage simulation column column section size,extraction frequency,vibration mode before and after damage,interlayerdisplacement Angle as indicators of damage after comparison and analysis,parameters,such as the ratio of the differential mode is constructed as a damage identification index,and combined with artificial neural network,implements the design model as the object of identifying damage occurs or not,the damage location and identifying damage size.By testing the scale model,measuring the modal parameters,constructing the mode difference ratio as the identification index,and substituting it into the artificial neural network established by the design model,the applicability of the damage identification method is verified.Finally,the stiffness of 11 simply supported beams with different parameters is determined to be related to concrete strength,longitudinal reinforcement ratio,concrete damage,FRP reinforcement and load.In the future,all the determined stiffness parameters can be substituted into the modified design model to improve the damage identification accuracy.