Research On Dynamic Characteristics Of The Concrete Slab With Cracks

As an important material for civil engineering structure,concretes application promoted the vigorous development of civil engineering.But because of the effects of complex factors such as raw material and the construction process,concrete structures often exist initial defect.Currently,concrete structures are widely used in practical engineering, and it is the structural initial defect which develops into damage and continue to accumulate under the complex and volatile load and external environment that affects the structural performance or threatens to the Structural safety. Therefore, this paper put slab with cracks as the research object and combined with the knowledge such as structural dynamics, finite element analysis, probability statistics, structural damage identification, etc.The paper established the finite element model of slab with cracks to calculate the acceleration response of the control measurement points under various mobile load conditions of random road excitation,and divided the acceleration time domain into many infinitesimal segments to carry out spectrum analysis to obtain spectrum.Based on the analysis, the paper formed the method and system which can processe uncertain damage identification problem with probabilistic algorithm. This article studied the frequency distribution of the indication frequency by using probabilistic methods,and determined the structural damage by studying the dynamic characteristics of the plate with cracks.This paper mainly completed the following work:① Based on the theory of finite element analysis, the paper established computational model of the board with cracks, defined different analysis cases,and achieved to simulate random traffic loads by using ANSYS.② This article computed the of measuring point on the model plate under a single pulse excitation. And analyszed the acceleration response spectrum to verify the effectiveness of the finite element model.③ After calculating the acceleration response of the measurement points under various conditions, the paper obtained the spectrum of the response of time domain infinitesimal segment basing on the fast Fourier transform. Add up the stable frequency points of spectrogram appling Probability and Statistics Method to find the distribution of frequency points.④ Based on the stable frequency point weighted average of each infinitesimal segment obtained by Spectrum analysis,this paper put forward the concept which is called instruction frequency according to the discipline that the weighted average of the stable frequencies decreased.⑤ Based on the probabilistic sense that natural frequency lowers when board damage occurs and the statistical characteristics of instruction frequency of the various conditions,the arrticle built the performance function which can discern the damage of board, and calculated probability of structural damage exacerbation by using performance function.