EngAnalysis is monitoring the stresses on 3 critical steel gantry structures over a rail line in Victoria.
Our client wants to manage their risk on this structure by quantifying and monitoring the bending stresses that could cause fatigue damage of the weld between the column and base plate.
The installation includes 3x full bridge strain gauges, 600mm above the critical weld, providing temperature compensated bending and torsional stress. Data is logged and transmitted through an LTE modem to the EngAnalysis data center in Newcastle where it is processed and transmitted to a real-time portal.
The hardware setup was customized by the EngAnalysis team to suit the monitoring requirements for the structure. The system logs high frequency data and our analysis package processes the data and transforms the peak readings into 20 minute segments where it is available on our near real time visualization portal.
The portal allows our client to log in and access a near real and time history analysis of the structural stresses and also provides automatic alerting if stresses exceed a defined threshold. EngAnalysis also provide a monthly report, which includes further data analysis and predictive forecasting, taking into account the number of cycles within various stress ranges.
Our analysis also incorporates local weather by correlating peak stresses with measured wind speed. This methodology has given verification to the stresses we see and allowed us to identify and omit erroneous data, such as a period when some maintenance upgrades were being performed on the structure.
Through ongoing and real time monitoring, the project has enabled our client to mitigate their “risk of the unknown” by providing key risk indicators (stress amplitude) for the monitored structures, as well as providing a contextual data set that may be used for understanding their broader risk of similar structures across the network.
Following floods in 2021 in NSW, a program of underwater bridge inspections took place. This bridge was identified as having defects and was immediately closed to traffic, isolating a community.
EngAnalysis were engaged at short notice to provide an end to end turn key monitoring solution. The bridge engineer specified a requirement for a series of tilt meters on multiple piers. The tilt meters would initially be used to refine an FEA model of the bridge by helping define longitudinal and transverse stiffness which would become an input into assumptions for material properties and boundary conditions.
The bridge then underwent a series of progressive load tests and data was used to monitor and verify the results of load tests, and to confirm that no adverse effects were experienced at critical locations. This was a fantastic collaboration between client, engineering consultant and EngAnalysis where assumptions were validated and performance verified through data driven engineering.
The load tests were successful and the bridge was opened up to traffic. To enable opening and to provide ongoing risk indicators, EngAnalysis has continued to provide monitoring as a service. Our real time data which is accessible through our portal provides up to date tilt readings on the critical elements. If the tilt readings were to exceed predefined thresholds, an alert would be generated, triggering an immediate investigation.
This methodology allows the asset operator to open the bridge to traffic whilst repair works are planned and undertaken, all the while managing the risk to the community. This monitoring program is an excellent example of the value ad for structural health monitoring and risk indicator monitoring. What is the value of being able to maintain the bridge open to traffic? What is the value in engineers and the community being able to continue with their daily tasks, knowing the risk is being managed? These are hard to define, although we suspect the value is many times the cost of the monitoring program.
EngAnalysis deployed a customized structural health monitoring system to monitor and quantify the extent of bearing and abutment movement that is occurring in this heritage listed bridge structure.
Our client wanted the following questions answered in order to understand and manage their risk on the bridge:
- If and how the abutments are moving in a cumulative manner over time?
- The extent of movement with respect to live load and thermal cycling
- Are the bearings operating as designed?
- Is the truss propping the abutments?
Sensors and Hardware
We specified and installed a custom system to meet the monitoring scope which included tilt sensors, laser displacement sensors, strain gauges, cameras, weather sensors, data aggregation and modem.
Our system was powered by a local solar installation with battery storage and the modem software was configured to collect data, package and transmit to EngAnalysis servers.
Results and Data Analysis
A key part of the success of our projects is our experience and capability in data analysis and reporting. Using the strain gauges, we were able to detect and identify high frequency train movements on the bridge , so that results from “live load events” could be separated from thermal cycles.
We found excellent correlation of the bearing and abutment displacements with temperature and were able to report to our client the extent of movement. One of the exciting results of the analysis we undertook was that we were able to compare:
- Predicted movement due to thermal expansion
- Measured bearing movement
- Equivalent length change due to strain development in truss chords
We found the calculated predicted movement very closely matched the cumulative measured bearing movement and strain development in the truss which gives great confidence in the monitoring outcomes.
We used our video installation to verify the measured movements, and were able to see the bearings moving with thermal cycles!
This bridge had identified issues with approach embankment settlement. Soft embankments and hard transitions in stiffness between approach and bridge structure can pose a risk to trains and the bridge due to sudden geometry changes in the rail.
EngAnalysis were engaged to develop a monitoring solution that could measure and quantify the amount of rail displacement under dynamic, fast-moving trains. Some challenges in doing this include:
- System must operate remotely in harsh rail environment
- System must operate and relatively high speed to capture dynamic effects
- System must be accurate to less than 1mm
- System must be installed in short shutdown window
The speed and accuracy requirements ruled out several traditional displacement monitoring methods and EngAnalysis proposed to develop and trial a unique system.
We installed remote PTZ cameras outside of the rail exclusion zone. The cameras are wired to a cabinet where data is transmitted via an LTE modem to the EngAnalysis data center. The cameras, computer and modem are powered by a solar system including panel and battery. Video recording is triggered by a train detection sensor which enables high speed video recording and transmission during train passes. The cameras can also be logged onto remotely at any time for static, manual monitoring.
There are 30 IR targets installed on the rail, sleepers and bridge. Core to the monitoring success has been the software and digital image analysis techniques developed by our team. Our custom-built software measures changes in pixel intensity on the targets and incorporates a weighted centroid to achieve sub-pixel resolution. We are then able to monitor changes in displacement at the frame rate of the camera and can achieve 1mm accuracy.
This is a cutting-edge monitoring application and the results delivered have provided valuable insights to our customer. We observed a gradual loss of stiffness of the approach with increasing dynamic displacement behind the bridge abutment. We were able to then develop a trend for the loss of stiffness and make predictions for when thresholds would be reached. Further, our system detected the results of a re-tamping operation, showing that the re-tamp was highly effective in restoring stiffness behind the abutment.
With this system, our client is able to remotely monitor the situation, plan maintenance work and verify the effectiveness of that work, resulting in significant risk reduction, increase in safety and allowing our client to focus their resources on other problems.
EngAnalysis was recently approached, asking if it would be possible to automate the monitoring of a 110yo bridge abutment that was experiencing major ground consolidation during the build of a replacement duplication bridge. The project requirements were to supply the half hourly displacements of the abutment over a 24hr period on a daily basis.
The current monitoring methods proved expensive, inconsistent and lacked easily digested reporting and trending. We took an agnostic approach to the technology used, by augmenting traditional monitoring methods. Enganalysis proposed permanently installing an S9 Trimble Total Station, recording target locations on a half hour basis with automated reporting and alarming using a combination custom data portal backed by MATLAB scripts and twice daily automated emailing of 24 hour displacements and project lifetime trending.
The onsite system was installed within days from purchase order/ first contact, with semi-automated reporting arriving in our client’s inbox within 7 days. Full automation was progressively implemented with displacement reports, long term trend plots and alarm reporting emailed twice daily, as an end result.
We are proud of this project because a number of long-term benefits expanded client’s radar of technology options. Previous manual 24-hour reporting did not allow for metered reactions, and made decisions and workflow volatile. Customer feedback was extremely positive, with statements such as “The data was very easy to follow and gave me confidence to not complete repairs that previous conservative models would have demanded”, and “This project has opened my eyes to many other possibilities and ways to improve our structural asset management using models based on real data”.
EngAnalysis were engaged with the challenge of designing a structural monitoring system that was to be installed during the construction of a 5 story steel framed building at a University campus.
Working with the University Engineering Faculty and closely with the construction company, EngAnalysis were able to install sensors on all floors from the ground floor up to the top floor. The intensive construction schedule with completion due before the start of 2020 Lectures required our team to grow and shrink with construction progression as the locations for sensor mounting become accessible.
Fire proofing materials present on all steel members presented us with a unique installation requirement of removal and reinstate of the materials after sensors were in-place and tested to confirm operation.
Sensors were positioned throughout the building to measure/detect movement of the structure and also the behaviour of the structure to climatic changes and internal loadings. The system contained the following sensor types:
- Accelerometers
- Full Bridge strain
- Quarter bridge strain
- Embedded concrete strain and temperature
- Vibrating wire strain
57 pairs of accelerometers were installed on all 5 floors to detect lateral movements of the building structure
3 zones of major structural frame were instrumented with Full bridge strain gauges
For the 3 zones a total of 86 Full bridge strain gauges were installed on all the structural members to measure and record for the long term…
A Concrete slab area was selected and installed with sensors that were embedded in the pour, including the upper and lower surfaces of the concrete for measuring the Rebar, Bondek and concrete behaviours. A steel member central span was gauged and the Bondek, Rebar and concrete directly above also instrumented.
A networked array of 8 National Instruments DAQ units were installed around the building to gather the data from the sensors for analysis and long term data logging.
To operate a vehicle on the RailCorp network vehicles must comply with the interface requirements set by the Asset Standards Authority. To demonstrate compliance to many of these requirements, a measurement program is needed. EngAnalysis have expertise in undertaking on-track measurement campaigns in the rail industry.
The wagon is instrumented with an array of displacement transducers to measure the wagon body roll, vertical bounce, and lateral movement during on-track operation. The project scope included:
- Instrumentation of the wagon and bogie, and set up of data acquisition equipment
- Remote monitoring of tests and real-time visualisation of test parameters, including GPS position and speed.
- Review of test results against operating standards
- In addition to this, detailed analysis of results can be undertaken to understand correlations between measured variables, for example the geographic dependence of peak events.
As part of Transport for NSW’s project to reduce rail squeal generated through the wheel-rail interface, EngAnalysis was involved in the measurement and analysis of rail bogie warp stiffness. This included static testing of the warp stiffness of bogies, trials to modify the warp stiffness through component changes, and on-track testing to verify changes.
EngAnalysis developed analysis and reporting software to provide the test results and statistics from the data gathered on the bogie warp testing rig and undertook a statistical review of static testing and dynamic on track test results linking angle of attack, bogie warp, warp stiffness and noise.
A rail operator was experiencing chipping of wheel flanges in their vehicle fleet operating on a single network. Damage to the wheel flange increases both maintenance costs and derailment risk, and this issue required immediate attention. EngAnalysis were engaged to undertake an urgent measurement and analysis campaign on a wagon in operation to identify track locations that may have been causing the wheel chipping.
EngAnalysis instrumented a bogie with high speed data acquisition equipment, accelerometers, displacement transducers, and a GPS module, and ran the remotely operated measurement campaign for 1 week.
Axle box acceleration and suspension travel measurements were used to detect high impact events and potential track geometry defects. Events were ranked by severity and presented for the operator and track maintainer to prioritise inspections and maintenance.
A number of track locations were identified to cause high impact events, with the potential to cause significant damage to the wheel flanges and vehicle.
EngAnalysis was engaged to design, deploy, and operate a retro-fitted load monitoring system for several struts over an excavation site used to manage the risk of wall collapse. The timeframe from the beginning of concept design to deployment was less than 4 weeks.
The deployed system monitors the axial load in the 9 struts by using an array of strain gauges, with an instrumentation cabinet for logging hardware and communication. The raw data is securely uploaded to EngAnalysis data servers for processing, before being sent directly to integrate into the site’s data management system.
The system has provided significant insight into changes in loading to the struts due to the excavation as well as the effects of seasonal and daily ambient temperature and radiant heat fluctuations. To take the system further, a predictive tool which accounts for seasonal temperature variance and time dependant excavation rates was developed to forecast peak loads during summer, allowing site management to plan and make informed decisions.
Working in collaboration with the team at CSIRO, EngAnalysis instrumented a number of structural members below the road deck and rail line on the Sydney Harbour Bridge. The instrumentation array included accelerometers and strain gauges, and the data was used to define the operational loads.
The project involved designing a weatherproof instrumentation cabinet housing equipment for power management, communications for secure data transfer, strain amplifiers and logging equipment.
In-service rail test program utilising dynamic strain gauging, displacement and temperature measurements and video surveillance in the draft pocket of a coal wagon to investigate a recurring failure of draft gear components.
A testing campaign was operated for 6 weeks to gather data to compare the operational behavior which leads to failures of different draft gear. Measurements included dynamic strain gauging in the draft pocket, use of non-contact IR thermometers, drawbar axial and torsional loading, IP67 string pot displacement sensors for measuring drawbar yaw, pitch and roll angles, and follower plate movement and rotation, and the use of high speed, global shutter cameras to observe the behaviour in the draft pocket.
Post analysis used machine vision algorithms to track draft gear components, identifying times of large displacements and what this correlates to. Results were reported by integrating video footage with strain and displacement data channels to create video reports, visualising stresses and displacements on graphs and as vector animations, with the corresponding video stream.
The significance of results and differences between were presented from a statistical perspective, leading to insightful explanations of the operational behaviour leading to failure.
