A vibration test for a 9-story building shows that fractures at steel beam-to-column connections change the vertical vibration characteristics at the center of the beams. By use of the result, this study proposes a fracture detecting method, in which beam vibration modes are compared by MAC (modal assurance criterion) value each other, then, fractures are detected to locate at beams related with peculiar MAC values.
Finite element method analysis is executed for the 9-story building to examine the proposed method. MCS (Monte Carlo Simulation) is also executed in order to consider the effect of variation in beam vibration, which is found in practical buildings. The MCS shows that even with 15% of the maximum displacement of beam as variation, which is around half of that measured in a test for a 3-story building, the proposed method can be informative for fracture detection. Future works are to develop the criteria to judge whether to be fractured as well as to accumulate the data on practical buildings.
