Study Of Damage Detection For Frame Buildings Using Change In Slope Of First Order Mode Shape

Health monitoring and damage detection for structures can effectively prevent catastrophic failure,and the earlier the damages are found,the lower expense will be needed for the maintenance. This dissertation will discuss slopes of the first order mode shape. When the change in slope of the first order mode shape is bigger than 0, this floor would be the damage unit---this conclusion can be used to detect and demarcate damages; establish the damage in the structure, and use this damage index to detect this damage; change structure's rigidity and story height, and observe the change of the damage index. In this dissertation, following several aspects are studied, and some results are achieved:1)The methods based on modal parameters and change in slopes of first order mode shape have been studied ,and the theoretical analysis about identifying damage location have been made.The results of these analysis can be considered as the basis of identifying damage locations and sizes.2)Using the ETABS software to establish finite element analysis model—frame building which has 9 levels, simulate the damage through the change of damage spot's rigidity, carry on the modal analysis to confirm the validity of the recognition parameter—change in slopes of first order mode shape. In the sole damage mode, The changes in slopes of first order mode shape can accurately recognize the position of damage,while in the multi-damage mode it can't.It needs utilizing aiding methods to carry on the damage detection.3)Change model's own characters such as rigidity of beam and story height, and observe the change of damage index along with the model physical property's change. The accuracy of change in slopes of first order mode shape in these situations is insufficient. In the sole damage mode, it can unite the change in displacement of first order mode shape and change in slopes of first order mode shape to detect damages. In the multi-damage mode,using recognition parameters—DLAC and MDLAC to eliminate the misinterprets of damage.