The Identification Of Plane Frame Crack By Modal Analysis

Engineering structures in the course of using usually meets crackle corrode, assemble loose and so on. It would cause the intensive destruction when its development to certain extent and fails to be aware in time, even the serious consequence. In order to measure the position and degree of damage in time, the domestic and international scholar has done a large amount of work, presenting a series of method of discerning structure damage, but the law based on mode parameter damage discern is still the most generally most basic method.Using mode parameter to discern structure damage, structure mode information before damaging is usually needed, which is often difficult to accomplish in actual structure. So, the recognition technology without mode parameter of the primitive structure is especially important. From article published at present, it is few only using damaged mode parameter of structure to identify the damage.In recent years, some researchers utilize modal curve to discern the damage of structure, which pointing out that mode gentle degree damages is better than natural frequency or the mode of vibration. Although modal flexibility on structure damage and discern has higher sensitivity, it still needs the structure mode parameter before damaging, which is not beneficial to practical application. So some scholars propose and utilize modal flexibility curve to identify the structure damage, which not only maintain high sensitivity but also avoided the needing of mode parameter of the original structure.Paper'21 has adopted this method in the cantilever beam and simple beam's crackle discerning. The result indicates that modal flexibility curve is easy and just needing few calculating amount.Indicated by relevant documents, up to now, the method of modal flexibility curve has not applied to crack identification of the plane frame crackle of structure .So this thesis utilize this method to discern the plane frame structure crackle firstly. Finite element analysis shows this method can confirm the position of the crackle and further experimental analysis indicates that it need not-the mode parameter before damaged and only by damaged structure mode parameter the crack of the crack of the frame can be discerned. But weak point is that can't estimate the severity of structure damage and a large amount of work still to do.