Damage Identification Of Truss Structure Based On Strain Modal

Structural health monitoring technology (SHMT) was developed last middle century. At first, SHMT was applied in the field such as the load monitoring of aviation and Spaceflight. With the development of the economic and science, modern project structures are proceeding at the direction of maximization and complication. The complicated environments do all kinds of threat to the structures. To guarantee the structures'safety, the damage researches must be done to the structures to get the correct operation conditions, so the accurate repairing work can be done to the damage timely. It is meaningful to research how to identify the damage of the structures.Describing the status of research at home and abroad, this paper discusses and studies the diagnosis of structural damage theories and methods based on modal parameter, and discusses the theory and method of damage identification using strain modal.The truss structure is regarded as the research object. A simply supported truss was studied by numerical simulation. By the method of changing displacement of nodes to strain of elements for the special character of the truss rod, damage identification was studied on the simple truss structure.(1)In the first order modal strain, the strain modal has the trend of increasing with the increase of the degree of damage. So the first modal strain can be used to determine the location of structure damage and qualitative assess the degree of damage.(2) Most of the rod damage can be detected by high order modal strain, but for a few rods, it is ineffective to detect the damage by the high order modal strain.(3) While the simply supported truss produces the same damage degree but different location, the first order modal strain is effective to detect the damage.(4) While the simply supported truss produces the different damage degree and different location, the first order modal strain can detect the damage effectively if the two damages degree is similar; If the two different damages is significant, it can only identify the greater damage but can not identify the smaller one.Through a simulation test on the simply supported truss structure, the strain modal is obtained under harmonic excitation. And the strain modal is used to identify the damages in different cases, it shows that the parameters is effective and practical.A test is done on a simply supported truss structure and the strain modal is obtained. And the strain modal is used to identify the damages in different cases, it also shows that the parameters is effective and practical.