Approximately 35% of Korean railroad bridges are classified as steel plate girder bridges. Their connections in the vicinity of stiffeners and other secondary members toward the main girder can be progressively deteriorated owing to stress concentrations, residual stress, welding defects, and harsh environmental conditions. Most bridges of this type were built in the early 1900s, hence, they suffer from aging and progressive degradation of connection zones, and they require extensive maintenance. In accordance with these efforts, the objective of this study is to address the detailed analysis of thin steel plates with bolt connections in order to simulate a method for detecting damage due to loosening in mechanically fastened zones of steel plate girders. For simplicity, we confine this study to previous laboratory-scale experiments for bolt connection problems using PZT (Lead-Zirconate-Titanate) sensors, and we carry out a comparative study with the aid of stress wave transmission using the finite element method, signal processing using wavelets, and piezoelectricity. We carried out fundamental modal analysis and transient dynamic analysis with 3D piezoelectric elements as a sensor/actuator in an open circuit. The material deviation effect of the piezoelectric patch manufacturing process, poling directional properties, geometrical modeling of bolts (bolt pressure), waveform sensitivity, and phase/group velocity characteristics of generated Lamb waves are discussed in conjunction with time-frequency-scale domain analysis.