A Cost Effective Structural Health Monitoring System Using Multi-Sensing Approach

Ado and Machinesense, USA jointly presents a wireless connected multi-sensor system (IIoT), which tracks deflection, forced vibration and strain of the bridge elements using a compact single sensor. Data is stored, analyzed and alarms are sent to appropriate authority whenever action to inspect, repair or vacating the bridge is needed.

Structural Health Monitoring (SHM) using continuous sensor data started since 1990s. Indirect SHM, using vibrational data resulted from moving vehicles opened a wide range of possibilities for detecting internal faults. While deflection and strain measurement have been part of direct SHM methods, it provides very little information about internal damages and proved to be expensive as well. With the advent of modern Internet of Things (IoT) system, where transport and processing of sensor data continues to be cheaper and more affordable, SHM received wide range of attention from both academics and expert communities all over the world [1] [2].

SHM system, developed by Machinesense combines both direct (deflection, strain) and indirect (monitoring of natural frequencies) monitoring using a single sensor approach, which reduces the cost, form factor and logistic of installations. Due to reduced cost and form factor, easy magnetic installation and ready to cloud connectivity, installation of hundreds of such sensors on a bridge can be done quickly (within a few hours) and data will be available via cloud to anywhere in the world within minutes of the installation. Structural experts of Ado analyzed the 24x7 available deflection and vibrational frequency data for both long term and short term aspect of structural monitoring. The whole system can also be combined with a video camera feed to track the vehicle, which is causing the vibration. To validate the resulting vibration and deflection, it is extremely important to know the weight of the vehicle via image recognition system.

Figure 2A is showing a real installation in Haldiram Bridge, Kolkata. Figure 2B shows how camera captures can read the plate number and model of the vehicle required to estimate its approximate weight and axle load from database of various vehicle models.
This kind of compact cost effective single sensor system for monitoring deflection in all direction and thereby also rotation, natural frequencies and strain opens up wide range of possibilities like detailed inspection of each and every girder of the bridge deck system. The sensor system can also contribute in Non Destructive Evaluation of the structure during in-depth investigation for cracking, corrosion, location and condition of reinforcement corrosion and snapping of prestress cable etc. This SHM system can also be used to fine heavy loaded trucks that are not supposed to cross the bridge. Also if any bridge has been declared vulnerable because of structural deficiency, alarms/SMS can be automatically sent to police and related authority for public safety so that no human live is lost from sudden collapse.

Acknowledgement: We are deeply grateful to Mr Debasis Sen (IAS, Chairman Hidco) and Mr Suman Neogi (Chief Engineer, Hidco) for providing us with the logistical facility of Haldiram Bridge

1. PI: Jacobo Bielak , Bridge Monitoring, Final Report “ Technologies for Safe and Efficient Transportation” Carnegie Melon University , 2015
2. Zengshun Chen et al, “Deployment of Smart Structural Monitoring Health System for Long Span Arch Bridges: “Journal of Sensors (MDPI), Sept 2017