The use of multi-type joints, such as rivet joints, adhesive joints, lap joints, L-shape joints, etc., has been driven by the need for stronger and lighter structures, particularly in bridges, aerospace structures, pipeline systems, automobiles industry. Among the multi-type joints, lap joints and L-shape joints possess a considerably important position. Moreover, in many real-field situations, it is not accessible to such joints, and thus it gives additional difficulties to detect damages. Fortunately, the electro-impedance method based on the use of smart sensors provides special opportunities for damage detection of such joints, which are not easy or impossible to be accessible. The piezoelectric-ceramic sensors which simultaneously act as an actuator and sensor are widely used for structural health monitoring. In the high frequency range, the electro-impedance-based technique using a piezoelectric-ceramic patch is very sensitive for the evaluation of the incipient and small damages. A large amount of experiments were executed and several conditions were imposed to simulate real-time damage, such as the bolt loosening and bolt absence. The different indices are discussed and executed to efficiently quantify the damage conditions. The theory behind this technique and the experimental investigations are presented in this paper. The analytical results strongly show the detectability and reliability of this method.