  As social infrastructures rapidly age, it is crucial to create a digital SOC
(Social Overhead Capital) maintenance system for preventive maintenance. Using
IoT sensors installed on the structures, abnormal signals produced by the
structures may be rapidly identified and the best judgments can be made. In
this study, a multimetric IoT sensor was integrated into a digital SOC
monitoring system for long-term monitoring, use in a cloud computing server for
automated and powerful data analysis, and for creating databases to perform:
(1) multimetric sensing, (2) long-term operation, and (3) LTE-based direct
communication. The created sensor included five strain sensing axes and three
acceleration axes, and it also had an event-driven power management system that
only turned on the sensors when the vibration reached a certain threshold or
the timer started. Long-term operation might be made possible by the power
management system and an extra solar panel charging. Real-time data
transmission to the server from the sensors was accomplished using low-power
LTE CAT.1 connection, which does not need an additional gateway device.
Additionally, a displacement fusion technique was created on the cloud server
to get reference-free structural displacement for ambient structural assessment
after receiving multi-variable data from the sensor. A steel railroad and
concrete girder bridge were used to experimentally evaluate the suggested
digital SOC system.
