Based On The Modal Curvature Change Rate Of Bridge Damage Identification

Because of the continuous improved basic theory,the rapidly developed computer technology,as well as advances in signal processing and test technology,structural damage identification based on dynamic test method has been widely applied in civil engineering.Subjected to complex loads,environment corrosion,natural disasters,increasing loading capacity and the extended service life,the civil engineering structures inevitably appeared surface and internal defects in during serving life in the field,as well as prone to appear local rigidity degradation and uneven stiffness degradation.As for this type of problem,starting from the dynamic properties of components and considering changes of modal parameters before and after injury,with Euler-Bernoulli flexural beam set as study object,a phased recognition method applied to engineering structure damage model is proposed in the paper,the main research contents are as follows:By the sensitivity analysis of damage factor of uniform degradation model for Euler-Bernoulli beam,its sensitivity range and scope of application were defined,and the situation of regional non-uniform stiffness degradation was recognized and analyzed.It turned out that this method cannot be applied for effective calculation.Modal deflection curvature index function is deduced on the basis of the theory of flexibility matrix and the damage can be located and identified with this.All kinds of damage of the simply supported beam and continuous beam are simulated and analyzed,compared with the existed two damage location index function which is based on the modal flexibility.the sensitivity of the proposed index function and existing indicators for the various damage condition of the structure was discussed and these three index functions were compared on advantages and disadvantages.On the basis of the Euler Bernoulli beam uniform degradation model,the calculation method was improved and the frequency changing rate method applied for quantitative identification of regional non-uniform stiffness degradation model was put forward.After the damage location identification,quantitative analysis for the damage of simply supported beam was calculated and the accuracy of calculation method and the application scope were analyzed.Set as a study object,RC beam was cracked by stepping loading.The proposed modal deflection curvature index function was applied to location identification for crack region,which was classified as segment then.The stiffness degradation condition of cracks region was identified by improved frequency changing index.Through comparison among the results of finite element model,the actual results of static test and dynamic test results,the damage identification method appeared to be available and effective.