Wireless Strain Monitoring System on the Hernando de Soto Bridge During Critical Repairs

Abstract

The article discusses the use of a wireless structural health monitoring system supplied by Resensys, after a major fracture was discovered in the tie girder of one of the arch span bridge units on the Hernando de Soto Bridge. The bridge is significant to the US transportation system and the business community in Memphis, as it connects Memphis to Arkansas and most western states in the US. The fracture discovery resulted in an immediate shutdown of the bridge, causing significant economic impacts due to traffic rerouting and massive congestion. According to multiple reports and studies, the cost of closure of the bridge was estimated to be $2-3 million per day. Due to the high urgency of the repairs, monitoring and instrumentation had to be done quickly and before conducting repairs on the tie girder. The Resensys SenSpot™ [1] strain gauges were a perfect solution, providing reliable, precise, and real-time data (strain and temperature) on all high-risk members. The wireless strain gauges were attached to all high-risk members to monitor loads during the repair process, which involved applying tension to the fractured members. Furthermore, the strain gauges monitored strain/stress in critical members when heavier equipment such as cranes were moved on the bridge to carry special equipment and retrofit plates. The Resensys monitoring system provided data to help the bridge repair engineers gather information around real-time strain, and studying stresses and strains on critical elements caused by thermal effects and live loads has helped to ensure that the repair process was effective. Due to the size and other complexities of this project, wiring systems and their associated installation on structures were cost prohibitive. Resensys wireless monitoring system provided numerous benefits in the project which made the implementation of the monitoring program cost-effective and practical. These advantages include longevity, fast and easy installation, cloud-based monitoring, superior sensing, advantageous in construction sites, reusability, etc. Wireless SenSpot™ sensors use non-rechargeable batteries with a battery life of ten years. SeniMax™ [2] remote communication gateways are solar powered. As a result, the complete system is energy self-sufficient and does not require access to external electrical input or infrastructure for its operation.