<p>This article presents reference-base coefficients method for structural health monitoring in stiffened plates using piezoelectric patches. In this study, for detecting the presence and location of defects, an array of piezoelectric parts is used. The amount of energy received by piezoelectric sensors will be different after passing the distance between actuators and sensors in healthy and damaged paths. This difference is used to detect the presence and location of the defects. The presence of stiffener in an actuator-sensor path causes the amount of energy received by piezoelectric sensor to be different compared to the path without stiffener. Therefore, stiffeners are recognized as defects in the visualization of probability function. In this research, the amount of energy received by sensors in pristine ribbed structure is equated with ones of a hypothetical non-ribbed structure, using correction coefficients. So, the only real defects of the structure can be recognized as damages. To identification of defects, the damage probability illustration is used and the damage index is calculated based on continuous wavelet transform. The selected structure is a ribbed aluminum plate, which is widely used in the aviation industries and the defect is considered as a gap in different locations. The obtained results show that the method of using correction coefficients improves the accuracy of detecting the presence and location of defects.</p>