ABSTRACT The dynamic response of planar frame structures composed of damped Bernoulli-Euler beams is computed, with and without a crack present in the structure. The inertance changes due to the crack are investigated in relation to the crack location, with the aim of developing a diagnosis method. The optimum excitation location and frequency and the optimum locations for response measurement are determined for best diagnosis results. The effects of crack location and severity and of damping are investigated. Damping is accounted for by the complex Young's modulus. Frames are analyzed with the electrical analogy method. A crack is modeled as a torsional spring, which is represented with an electrical resistor in the analogy. The electrical analogy method is used only as an analysis tool in this study, with the resulting equations being solved on a digital computer.