Study On Wooden Beam Damage Identification Technology Based On Curvature Mode

Because of the artificial and natural factors,the existing ancient wooden buildings have been on the verge of destruction.It is urgent to strengthen the protection of ancient wooden buildings.Considering the ancient building health monitoring and damage detection is an effective way to protect the ancient wooden building,it is necessary to develop a set of accurate wood testing and analysis equipment and improve the theory of damage detection.In this paper,the method of curvature mode is used for damage detection,and the research status of structural damage identification at home and abroad is summarized and analyzed.By using the finite element analysis software-ABAQUS,the finite element models were established and they were analyzed by modal method,obtained without damage,including single damage but the damage degree is different,at the same time with two lesions,with a degree of damage in different position of the vibration mode and curvature mode.Through analysis,it is concluded that: the vibration mode is not sensitive to damage which can’t be used to determine the damage alone;the curvature mode is more sensitive to damage,and the damage location and the extent of damage can be determined by the curvature mode shapes of mutation and the degree of mutation respectively.The damage detection using curvature mode is feasible and effective.By defining curvature mutation coefficient combining the modal test and the finite element modal analysis,a method that can be used to determine the degree of damage is proposed,which is based on the curvature mode and operated by fitting different damage degree and the corresponding curvature mutation coefficient.This methodusability is strong,but the method has some limitation that can not be applicable to large number.According to the knowledge of free vibration of beams in structural dynamics and the definition of curvature mutation coefficient,the theoretical formula of damage degree determination under different support conditions is proposed.Due to a large number of assumptions and the existing difference with the real condition of the damaged beam detection,the versatile formula needs a further research.Finally,the data of the frequency and mode shape is obtained from small modal test,which is analyzed by the central difference method.The results show that the finite element simulation results is correct,and the numerical fitting method are feasible.