Temperature And Humidity Interference Removal Algorithm Of Concrete Beam Ultrasonic Signal

Due to its rich information and sensitivity to weak changes in the medium,ultrasonic coda wave shows potential engineering application value in the stress measurement of concrete structures,and has received continuous attention in recent years.With the deepening of research,the influence of environmental factors such as temperature and humidity on the results of ultrasonic coda wave stress test has attracted attention.At present,some scholars have carried out research on this.Among them,thermal deviation control technology and optimal baseline selection algorithm are the two most typical methods to eliminate the influence of temperature and humidity,and their effectiveness under laboratory conditions has been proved.However,these two methods have strict requirements on the completeness of test conditions and the richness of data sets.These technical difficulties still need to be solved in the subsequent development of practical engineering applications.Therefore,it is necessary to further study new methods to solve the above problems.Based on the ultrasonic coda wave data itself,this thesis establishes a signal interference removal algorithm based on the difference matrix SVD(Singular Value Decomposition),in order to create conditions for the subsequent research of ultrasonic stress testing technology.The topic comes from the National Natural Science Foundation of China ’s ’ Study on non-loading and unloading measurement of stress field of concrete structure based on coda wave interference ’(approval number : 51478072).The main research work and conclusions are as follows :1 、 The research status of concrete ultrasonic coda wave testing technology is investigated,and the research progress and existing problems in this field are summarized.Therefore,the research topic of this thesis is put forward,and the technical route of the research is clarified.This thesis focuses on the relevant literature on the influence of temperature and humidity on ultrasonic coda wave test,and analyzes the characteristics of the above two typical methods to solve the problem of temperature and humidity.It is determined that this thesis uses the advantages of SVD in signal feature extraction to establish a new algorithm to remove the influence of temperature and humidity factors on concrete ultrasonic coda wave signal.2、The ultrasonic test of concrete beams under non-stress state is designed and implemented to collect ultrasonic signals affected by environmental temperature and humidity.Under the natural changing indoor environment conditions,the ultrasonic test of two concrete I-beams in the adjacent position under non-stress state was carried out at the same time.Two groups of test data were collected in two different temperature and humidity change intervals(interval Ⅰ : { 6.5℃ ～ 12.5℃,65% ～ 90% },interval Ⅱ : { 20℃～ 27.5℃,72% ～ 90% }).The ultrasonic coda signal of each group was collected for 14 days,and the changes of ambient temperature and humidity data were recorded synchronously during the test.3 、 Test whether the signals of the two test beams are affected by the same interference source,and further explore the specific sources of homologous interference factors.Through the signal fluctuation index constructed in this thesis,the correlation of the two beam test signals is analyzed to determine whether they are affected by homologous interference factors.On this basis,the specific sources of homologous interference factors are explored,and the effects of ambient temperature and humidity on signal fluctuation indexes are analyzed respectively.The above analysis results are verified and compared from the perspective of wave velocity change rate,and the convenience and effectiveness of signal fluctuation index are pointed out.The results show that the signals of the two test beams are mainly affected by homologous interference factors.The ambient temperature change is the main source of this homologous interference factor,and the humidity change is the secondary source.4、Aiming at the influence of temperature and humidity on ultrasonic signals,a signal interference removal algorithm based on residual matrix SVD is established.The signal residual matrix is composed of the deviation between the test signal and the reference signal,and SVD is performed to extract the feature information(interference vector)of the environmental temperature and humidity interference,and the consistency of the feature information is tested.Therefore,the projection relationship between the test signal and the interference vector can be used to rotate the test signal to the highdimensional direction corresponding to the reference signal,so as to remove the temperature and humidity interference of the signal.The effectiveness of the algorithm is verified on the concrete I-beam.The research results show that the established signal interference removal algorithm can effectively remove most of the environmental temperature and humidity change interference components in the ultrasonic coda wave signal.