Pre and Post Rehabilitation Testing and Monitoring of a Rail Over Bridge at JNPT, Mumbai using NI CompactDAQ with various modules and LabVIEW

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"With NI CompactDAQ and LabVIEW we were successfully able to integrate a Structural Testing system which had provided a comprehensive platform for all sensors. We were economically and effectively able to analyse and present data. The whole exercise was successfully executed."

- Abhay Bambole, Sardar Patel College of Engineering

The Challenge:
Developing a structural health monitoring solution for an Bridge undergoing Major rehabilitation and strengthening. The bridge was also to be provided with 24x7 monitoring system for strains and accelerations.

The Solution:
We developed a testing and data acquisition system using NI CompactDAQ with Labview Software which offered a whole lot of functionality for data acquisition, analysis and storage. For 24x7 monitoring system NI CompactRIO platform is being used.

Author(s):
Abhay Bambole - Sardar Patel College of Engineering
Yogesh Indolia - 21SHM Consultants Pvt. Ltd
Gopal Rai - 21 SHM Consultants Pvt Ltd

The Jawaharlal Nehru Port, which is managed by JNPT, handles more than 65% of overall container traffic of India. The Rail Over Bridge at Karal Junction in JNPT is the one connecting the port and Panvel highway via road. If this bridge is not functional all trailers and other container vehicles have to travel 22 KM around to cover to reach Panvel. The ROB had developed serious distress for past several years and it was required to rehabilitate as it cannot be stopped.

Load testing for static and dynamic cases have to be carried out on the bridge before and after rehabilitation to check for the efficacy of Rehabilitation technique and also to find the present status of bridge. 21 SHM Consultants and SPCE, Mumbai were appointed to carry out the testing and monitoring of the bridge.

The following were identified as the critical measurements which were to be carried out and the sensors which were placed at critical positions throughout the spans.

  • Piezoelectric Single Axis Accelerometers placed below the girders below both the lanes. This is to measure Acceleration and Fundamental frequency of vibration induced by standard test procedure
  • Foil Type Strain Gauges Gauge length 90mm below the girders for measuring Flexural strains induced in the beams.
  • For Crack width Measurement at of cracks near the support on the beams where shear stress is maximum. Sensors used were Omega Type displacement transducers. 
  • Linear potentiometers for measuring the deflection at the center of girders.

The testing methodology included use of two fully loaded trailers each of 32 Tons placed at various positions to induce maximum stains deflections and displacements. These were in accordance with the IRC (Indian Road Congress) Codes.

For measuring the Dynamic responses of the bridge the two loaded vehicles were moved with a speed of 25 km/hr one behind the other with spacing of 3 m. This induced vibration in bridge which was then measured using the data acquisition system.

For the above tests all data were recorded analysed and stored using the CompactDAQ having NI 9237 (5 nos), NI 9234 (2 nos) and NI 9205 (1 no) modules. External power supplies were provided to the linear potentiometers and the same was also measured with the NI 9205 for reference voltage of Linear potentiometer.

All the data was recorded, analysed, stored and reported. NI Report Generation Toolkit  was used to produce data reports for all the measurements. Frequency and acceleration measurements were carried out very easily with the functions like power spectrum, FFT, Distortion etc which were inbuilt in the LabVIEW Software.

The client was impressed with the ability of the data acquisition system to acquire and produce useful data without much effort and time. The results had shown significant decrease in strains, acceleration and deflections. The results had also shown increase in fundamental frequency which is a sign of better overall stiffness of bridge.

Future Deployments

A 24x7 monitoring system for the bridge is to be made using NI CompactRIO platform which will be able to acquire data from accelerometers, VW strain gauges and tiltmeters. The data will be available over a centralized hub and a web-portal. It is being designed to give alarms on anomalies like higher strains due to overloaded vehicle which will then trigger a camera to take photo of the vehicle which caused the anomaly. The alerts are to be sent on mobile networks and will be in form of SMS to concerned authorities for further actions.

Conclusion

With NI CompactDAQ and LabVIEW we were successfully able to integrate a Structural Testing system which had provided a comprehensive platform for all sensors. We were economically and effectively able to analyse and present data. The whole exercise was successfully executed.

Author Information:
Abhay Bambole
Sardar Patel College of Engineering
Bhavan’s Campus, Munshi Nagar, Andheri (West)
Mumbai 400058
India
abhay.bambole@gmail.com

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