This article examines the piezoelectric-based energy harvesting on civil infrastructures. Piezoelectric cantilever–based harvesters are adopted considering their wide usage. Four concrete slab-on-girder bridges that represent the majority of bridges in the United States are used as the platforms for the energy harvesting. In the simulation, the distributed-parameter model is used for the energy harvester, while four three-dimensional bridges with HS20-44 truck models are developed using ANSYS and MATLAB. Two scenarios for the bridge–vehicle systems are simulated: bridges with only one passing vehicle and bridges with a continuous vehicle flow. A parametric study is carried out to study the effect of various properties of the bridge and vehicle on energy harvesting. The simulation result shows that the energy output power increases with poorer road conditions and smaller bridge span lengths. Optimal vehicle speeds and energy harvester positions are also investigated and discussed in this article.