Study On The Structural Damage Alarming In Considering The Effects Of Temperature And Operational Variations

In vibration-based damage identification, structural damage will cause thechanges of the damage characteristic parameters, the variations of the environmentaltemperature and the operating variables can also make these characteristic parameterschanges, and these changes will often cover up changes of the damage characteristicparameters induced by the structural damage so that it is impossible to distinguish thechanges of the structural damage characteristic parameters are caused by damage or thevariation of the environmental temperature and the operating variables. Therefore, it isnecessary to study on the damage identification in considering the variations of theenvironmental temperature and the operating variables. The coefficients of AR modelin the time series are used as the damage characteristic parameters, the factor analysistechnology and principal component analysis technology in multivariate statisticalanalysis are employed to remove effects of the variations of environmental temperatureand operating variables (mass loading) on the damage characteristic parametersseperately, then the standard deviation control charts is used to alarm structure damage,the main contents are as follows:(1) Review of the methods which are used to remove the effects of variations ofthe environmental temperature and the operating variables on the structural damageidentification, and the scope of their application and the existing problems are alsopointed out.(2) The basic theories of the AR model, factor analysis thenology and principalcomponent analysis thenology are briefly introduced.(3) The factor analysis technology and principal component analysis technologyin multivariate statistical analysis are employed to remove effects of the variations ofenvironmental temperature and operating variables (mass loading) on the damagecharacteristic parameters (AR model coefficient) seperately, then the standarddeviation control charts is used to alarm structure damage.(4) Two cases about the variation of the environmental temperature are considered in this study: the uniform temperature changes and nonuniform temperature changes,and the damage working conditions for the two cases are different, the numericalsimulation results show that the influence of nonuniform temperature changes on thestructural damage alarming is higher than the influence of the uniform temperaturechanges, and temperature effects on the structural damage alarming can be effectivelyremoved by factor analysis and principal component analysis seperately, and thedamage can be accurately alarmed with standard deviation control chart after theeffects of temperature on damage characteristic parameters are removed.(5) The influence of the structure quality change is achieved by changing thediagonal point accumulation quality of top deck of the offshore platform, and thedamage is introduced simultaniously, the simulation results show that the influence ofthe operation variable (mass loading) on damage alarming can be effectively removedby factor analysis and principal component analysis, and the damage can be accuratelyalarmed with standard deviation control chart after the effects of operation variable(mass loading) on damage characteristic parameters are removed.