Experimental study on damage identification based on operational strain modal shape

Operational strain modal shape (OSMS) as well as direct index methods for damage location detection (named as ISMSD) and damage degree detection (named as ILSMSA), which were advanced in recent years by authors, were introduced. The results of model test and numerical simulation were applied to verify the methods. The results show that the operational strain modal shape identified in the method is similar to the strain modal shape under impact excitation. According to the results, direct index methods of damage location detection and damage degree detection were also improved. The direct index value of ISMSD at damage location is greater than the index value in other area, and so the damage location can be detected in accord with actual situation. Furthermore, when damage degree is equal, the variation of ILSMSA is slight. The value of ILSMSA is independent of damage location, order number of strain modal shape and normalization. If the space between damages is greater than the damage affected region, the methods can be applied to the multi-damage detection of structure.