damage detection in 4-story steel braced frames using residual forces based on wavelet transform

wavelet transform, which was first introduced in 1980, is operating on a modified basis functions and makes them a new function. wavelet analysis capability using a new method to analysis the signals and time-frequency signal processing offers. by replacing the wavelet network rather than rigorous analysis, accurate operation will not reduce the computational time is reduced dramatically.(roland, 2000). wavelet analysis is an efficient tool to detect structural damages like cracks and stiffness degradation (kim and melhem, 2004). in this study, residual forces and damage detection procedure by wavelet transform of residual forces were described. a four story space frame with diagonal braces with several damage states was considered. for every state of damage mass and stiffness matrices, mode shapes and natural frequencies were evaluated. finally dynamic responses of structure were conducted under wavelet analysis and for all cases, damages were successfully detected. after wavelet analysis on responses, wavelet analysis curves of residual forces showed peak points on degree of freedoms of damaged members. the damage locations, when damage occurs, are easily determined simultaneously by the ridges in the residual forces based on wavelet transform. the degrees-of-freedom that have large magnitudes in residual wavelet force (rwf) are associated with the potential damage members within the structure.