A System for In-Service Strain Monitoring of Ordinary Bridges
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An In-Service Bridge Monitoring System (ISBMS) has been developed to provide near real-time web-based monitoring of live load strains in a bridge. The monitoring system is small, battery-operated, can be rapidly deployed, and is programmed and interrogated via a user-friendly web interface. The ISBMS has been designed to be portable and used on an “as-needed” as a diagnostic tool or for health monitoring of ordinary bridges. The system is based on a small single-board-computer with analog inputs; it also includes a cellular digital packet data modem for communication via the existing cellular network. Strains are measured using either a full bridge strain transducer or a quarter bridge foil strain gage. The system has three modes of operation; the peaks program records peak live load strains that exceed a specified threshold, the time history program captures dynamic waveforms that exceed a specified threshold, and the rainflow program counts varying amplitude strain cycles. The selection and setup of the program, and retrieval of data is handled through a custom designed web interface. The system has been tested in the laboratory and in the field on a heavily traveled steel girder bridge. The data obtained from the ISBMS can be used for load rating, fatigue assessment, monitoring of stresses due to overload vehicles, and long-term health monitoring of bridges.