Alarm setting methodology for the monitoring of cables in a stayed bridge

The Bridge and Intelligent Structures Monitoring Center in Mexico was planned for the SHM of the most important structures in highway system to assure their structural integrity, reduce rehabilitation costs, and to increase their service index. Among those, the Río Papaloapan Bridge, which is a 402 meters long cable stayed bridge, was selected for full scale instrumentation and remote permanent monitoring based on previous structural record and its location in one of the most important highways. A critical issue for permanent remote monitoring is the alarm system configuration, so warnings can be put on display on time and to allow effective damage identification or structural evaluation. In this case, monitoring included accelerometers in some cables and deformation sensors along the bridge deck; therefore, the structural diagnosis of the cables is done indirectly from pre-processed data from different sets of sensors. To determine the alarm limits, Monte Carlo simulation was used for different loading configurations, including traffic and wind loads. A combination of statistical loads and the material's resistance was used to calculate the structural reliability of the cables and define the 3 levels alarm (green, yellow and red). This methodology proved to be an alternative for structural monitoring for parameters that are not directly measured, but can be indirectly calculated.