This paper presents the design, implementation, and experimental validation of an Internet-of-Things (IoT)-based Structural Health Monitoring (SHM) system for suspension bridges using synchronized vibration measurements. The proposed framework integrates distributed MEMS-based sensing nodes, GPS-assisted time synchronization, low-power wireless communication, and cloud-based modal analysis to support continuous monitoring of structural conditions. The main contribution of this work is the end-to-end integration of synchronized low-power IoT sensing, multi-tier wireless communication, and cloud-based vibration analysis within a unified SHM framework, together with experimental validation on a laboratory-scale suspension bridge. In the proposed system, each leaf node incorporates a high-accuracy digital accelerometer, ESP-NOW communication, and a duty-cycled sleep mode to reduce power …