March 10, 2021
Structural health monitoring and geotechnical instrumentation ensure safer structures by providing quantitative data to prevent sudden failures.
Encardio Rite offers advanced monitoring services with geotechnical instruments. Geotechnical monitoring benefits include economic advantages, design verification, construction control, and early warning capabilities. Sensors like strain gauges enable real-time data logging for remote display, safeguarding lives, and structures, and evaluating natural calamity impacts. With technological advancements in the field of civil engineering and geotechnical engineering, magnificent structures like Burj Khalifa and Gotthard Base Tunnel have been made possible.
Let’s discuss more Structural Health Monitoring, Geotechnical Instrumentation, and how it makes the world a safer place to live.
What is Structural Health Monitoring?
Structural health monitoring is vital to avoid sudden failures and accidents. Before proceeding with any construction activity, it’s necessary to carry out the monitoring of the construction site as well as the nearby assets. Geotechnical instrumentation and monitoring supply quantitative data on the structure’s performance to aid in evaluating its safety and detecting problems at an early stage.
Structures can fail due to several reasons like design error, geological instability, poor maintenance, deterioration of construction material, etc. Structural health monitoring is a process to keep an eye on all the structures and generate early warnings to avoid mishaps.
Encardio Rite is a geotechnical instrumentation and monitoring company that provides various monitoring services along with state-of-the-art geotechnical instruments.
Why is Geotechnical Monitoring important?
Geotechnical monitoring is an important matter of economic benefit as well as public safety. Sudden structural failures can threaten life and property. The main purpose of structural health monitoring is to supply quantitative performance data to the concerned authority.
Geotechnical monitoring can prove beneficial at the following stages of construction:
1. Site Investigation: Site investigation is crucial before carrying out any construction activity. It is important to check if the land is strong enough to bear the structure. Apart from this, it’s essential to check for the safety of other assets in the vicinity of the construction land. Several Structural Health Monitoring Sensors are used to characterize and determine initial site conditions. The most common parameters of interest in a site investigation are pore pressure, the permeability of the soil, slope stability, etc.
2. Design Verification: It’s quite important to verify the design of the structure. Improper design may lead to its failure. Geotechnical instruments and structural health monitoring sensors are used to verify design assumptions. Instrumentation data from the initial stage of a project may show the need or provide the opportunity to modify the design in later stages.
For example: Data obtained from reinforcement bar strain meters installed by Encardio Rite at Teesta Barrage in the left embankment led the project authorities to revise their estimates of the requirement of steel in the right embankment.
3. Construction Control: Structural monitoring is necessary to help the engineer determine how fast construction can proceed without adverse effects on the foundation soil and construction materials used. The instruments are installed to monitor the effects of construction.
For example: The temperature rise in concrete due to the heat of hydration was monitored at Sardar Sarovar Dam on the Narmada River with Encardio Rite’s temperature meters to determine the pouring temperature of mass concrete. By mixing ice flakes, the temperature of the concrete to be poured was brought down to around 15°C. This resulted in the temperature of the setting concrete not exceeding the critical 29°C, as specified and required by the Central Water and Power Research Station (CWPRS), Pune.
4. Safety: Instruments can provide early warning of impending failure. Safety monitoring requires quick retrieval, processing, and presentation of instrument data so that analyses and decisions can be made promptly. An effective action plan for implementing corrective measures can then be prepared.
| Read More: Geotechnical Instrumentation & Monitoring: Services &Types |
Advantages of Structural Health Monitoring
Structural Health Monitoring is a critical concept and entails a list of benefits in the geotechnical world. We have already discussed the importance of Geotechnical Monitoring and now let’s list out the advantages of Structural Health Monitoring.
Structural health monitoring (SHM) is critical because:
How does Structural Health Monitoring work?
Structural health monitoring requires several geotechnical instrument installations. Structural Health Monitoring Applications are wide and present in almost every field of civil engineering. Geotechnical Sensors like strain gauges, piezometers, tilt meters, temperature sensors, pressure cells, load cells, etc. are used to measure the crucial parameters affecting the structures. These structural health monitoring sensors are installed on dams, tunnels, nuclear power plants, buildings, and monuments to measure important parameters. The measured data is logged in real-time through data loggers and displayed via a PC/laptop/mobile device at any remote location. The data loggers are capable of generating early warnings such that the concerned person can take action accordingly.
Now that you understand what is structural health monitoring, let’s take a look at how it works in different fields of application.
1. Structural Health Monitoring of Bridges
There are numerous rail and road bridges built across the globe. They are an essential component of transportation networks and, hence, structural health monitoring of bridges is crucial. Any damage or collapse of bridges due to their deteriorating performance disrupts transportation systems and may result in the loss of life as well as property. The railway bridges are well-documented and have a laid-down system for checking and maintenance. The Ministry of Road Transport & Highways in India has established an Indian Bridge Management System (IBMS) to carry out condition surveys and instrumentation of all bridges on National Highways in India. To date, an inventory of more than 170,000 bridges and culverts has been compiled.
Bridges must function safely at all times. A large number of bridges are quite old and not designed for the heavier and faster-moving vehicular loads that they are currently subjected to.
Online Cloud-Based Web Data Monitoring Service
Encardio Rite offers public cloud-based online web data monitoring services for the safety of existing rail and road bridges. The service forms an important part of the Bridge Management System. The heart of the online structural monitoring instrumentation system is a web data monitoring service (WDMS) offered by Encardio Rite. It is a web-based data-management and presentation tool for retrieving data from the sensors through Encardio Rite's range of automatic data loggers.
WDMS consists of Drishti, data management software that acts as a data collection agent, a database server, and a web server hosted on a high-reliability server computer. The host computer periodically collects data from the remote data logger over cell phone networks. Users interact with the software using their web browser when connected to the Internet. The only requirement is that the data logger site is covered by a cell phone service provider who can provide reliable GSM/GPRS-enabled cellular data connection locally. Multiple authorized users at different locations assigned with an individual password are allowed to view any data or report from the structure simultaneously.
Graphs & reports can be viewed using popular web browsers like Microsoft Internet Explorer or Mozilla Firefox amongst others. Details like sensor identification tag, last recorded sensor reading, and values of programmed alert levels can be viewed on the first page of the site that shows the location of installation. If any of the alarm levels exceeds, the sensor location turns to a red dot. Clicking the pop-up table brings up an associated data window where the sensor data can be seen either as a table or as a graph. Site administrators can set alarm limits which are generally considered as “alert level” and “evacuate level”.
WDMS can also be programmed to send SMS alert messages or e-mails to selected users as soon as any sensor data crosses its predefined alarm levels, either while going above or below the alarm level.
Bridge Monitoring Instrumentation Scheme
Taking the application of Structural Health Monitoring forward. there are two types of instrumentation schemes to monitor the health of the bridges.
Structural health monitoring examples: The picture on the left is a typical installation of a robotic total station to automatically gather data from prism targets installed on the structure of a bridge. The structural health monitoring sensor shown in the middle is a mini prism target. The figure on the right shows points at which prism targets may be installed on a typical bridge. More than one robotic total station may be required for proper monitoring of a structure.
| Read More: A Guide on Geotechnical Instruments: Types, & Application |
Screenshots of some sample long-term monitoring data
The figure above shows structural crack monitoring over one year using the Encardio Rite Model EDJ-40V crack meter. The structural health monitoring example shows the crack opening in blue and the variation in temperature in red. The initial opening of the crack gauge was set at 5.12 mm.
The above image shows the structural tilt monitoring of the bridge from September 12, 2015, to December 8, 2016, using the Encardio Rite Model EAN-92M biaxial tilt meter. Tilt variation in the two directions is shown by the blue and black lines. The maximum change in tilt recording during this period is 0.04 deg.
The two horizontal red lines at the top and bottom are the alarm limits set at ± 0.1 deg. The red line gives the temperature variation during this period.
The above structural health monitoring example shows monitoring of groundwater level along with daily rainfall for two years. Piezometric pressure is in blue and daily rainfall is in purple. The maximum rainfall recorded on any day during this period is 73 mm. Ground water table variation during this period has been between 50 and 52 m of water column.
Structural Health Monitoring Sensors used are Encardio Rite piezometer Model EPP-30V and Rain Gauge Model ERG-200 tipping bucket type.
The above image shows the monitoring of subsurface lateral movement for 300 days. Encardio Rite EAN-52MV vertical in-place inclinometer system has been used for monitoring lateral movement. A total of 11 sensors have been installed in the borehole from a depth of 12 m to 32 m. The maximum displacement recorded during this period has been a little more than 2 mm.
The two vertical lines are alarm values set at ± 20 mm. Readings are retrieved once an hour and transmitted four times a day for online web-based monitoring.
Automatic monitoring of Northing, Easting, and Elevation using a robotic total station and a prism target on a bridge pier for around two months. This is the end of Shm of bridges. Let’s now take a look at tunnels.
2. Structural Health Monitoring of Tunnels
Another application of Structural Health Monitoring is focused on underground tunnels. Encardio Rite offers a comprehensive web-based monitoring solution for the long-term safety monitoring of tunnels. It manufactures a wide range of sensors that have a proven track record for reliability and long-term performance under harsh conditions. It also offers advanced monitoring technologies such as automatic 3D deformation monitoring using ATS, laser scanning, and aerial surveys using drones for keeping a tab on the structural health of tunnels and appurtenant structures.
Structural Monitoring Solution for Tunnels
WDMS – Web-based Data Monitoring Solution
Web-based data monitoring solution for any type of tunnel construction such as NATM, TBM tunneling, cut & cover, micro-TBM/pipe jacking, etc. essentially comprises the following structural health monitoring sensors:
Encardio Rite offers TunnelCAD PC and TunnelCE field software. Together these provide a complete solution for graphical and numerical comparison of design vs/measured cross sections of tunnels.
The following results could be obtained using a variety of inputs such as project data, import from DWG/DXF, direct communication from tunnel CE, etc.
Laser scanning is an advanced method of surveying and conducting geometric documentation of buildings, architectural and archaeological monuments, engineering projects, or other construction works and objects that require a high degree of analysis, are difficult to reach or gain access to, or are not to be touched. Recent developments, especially in the software, have made it a very convenient and cost-effective tool to accurately monitor structural deformations in 3D. Accuracy of up to 2-3 mm is possible using the method. Due to the lighter nature of the new software, it takes significantly less time to process the results and make the same available online, almost in real time.
It is based on exceptionally dense mapping of 3D coordinates of the points on the surface that are to be surveyed, taken at speeds ranging from a few thousand up to a million points per second. Depending on the object (size, shape, desired accuracy), laser scanning may be airborne or terrestrial, static or mobile, autonomous, or in combination with other standard topographic methods. Completion of the fieldwork results in a geo-referenced point cloud which, due to its great density and its ability to bear information on the reflectivity and/or the color of each point, comes close to the term, “virtual reality”.
Depending on the case and the user’s needs, horizontal, vertical, or diagonal sections, aspects, images, videos, ortho-photographs, surface expansions, interval curves, 3D models, determination of distortion as well as several other analyses derived from the scanner’s operations in the non-visible spectrum, can be produced.
To summarize, the results of laser scanning give us:
Aerial Mapping using Unmanned Aerial Vehicles (UAV/Drone)
Inspection of huge and complex structures like tunnel construction sites requires a high degree of analysis but at times is difficult to reach or gain access to. The use of Unmanned Aerial Vehicles (UAV)/Drones is best suited for such applications. UAVs/Drones are unmanned and remotely piloted aircraft that follow a pre-programmed path for takeoff, flight, and landing. These aircraft are equipped with HD/IR/Thermal cameras that compute aerial images and videos over a defined area at a specified height.
Using UAVs/drones to video, model, and scan for cracks, erosion, corrosion, and defects in areas that would otherwise require the inspector to use a rope/harness or erect access scaffolding, is a safer, faster, and smarter choice. Large sites with complex structures necessitate aerial photogrammetry avoiding expensive ground-based surveys. This technology is useful during the construction process also- as the development occurs, managers have difficulty maintaining a true picture of the site.
With UAV-based mapping at regular intervals, this information gap can be closed.
Results from UAV/drone are in the following forms:
Automatic 3D deformation monitoring system
The real-time 3D deformation structural monitoring system is a systematic tracking of any alteration that may take place in the shape or dimension of the tunnel as a result of stress, load, aging, etc., or of any structure located within the zone of influence of the tunnel construction. The above deformation monitoring system consists of high-accuracy automated total stations (ATS) that can auto-target recognition (without any human interference). Each ATS has a dedicated control box that includes a computer running special software.
This control box manages the total station and schedules the frequency of the measurements, the addition or subtraction of monitor benchmarks, the filters of acceptance or repetition of each measurement, the atmospheric corrections in distance measurements, the calculation and repositioning of the total station, etc.
The whole system can be controlled/re-configured remotely after installation at the site. The on-site system transmits the collected raw data to a remote server/computer via GSM/GPRS. Raw data is processed into meaningful results and presented in the WDMS. The system has the facility of alert notifications through SMS and (or) e-mail to the authorized team for any result exceeding present alarm and critical levels.
The system provides accurate, continuous, real-time data, eliminating any human error/delay in manual data. The raw data is processed and analyzed and the result is majorly used for predictive maintenance, alarming for safety.
Tunnel Monitoring Instrumentation Scheme
3. Structural Health Monitoring of Dams
The Applications of Structural Health Monitoring are crucially and widely used to monitor dams. Dam monitoring instrumentation plays a key role in safety monitoring for dams and people, providing necessary information on the performance of the dam and detecting problems at an early and preventable stage. The extent and nature of instrumentation depend not only on the complexity of the dam and the size of the reservoir but also on the potential for loss of life and property downstream. This information is critical for the dam’s owner who is directly responsible for any consequences of its failure.
Instrumentation includes different types of sensors used for measuring pore pressure, water flow, lateral movement, deformation, stress, strain, and temperature, installed in the dam and its auxiliary structures. It also includes geodetic targets measured using surveying techniques.
Monitoring Solutions for Dam
Encardio Rite offers a simple-to-use, comprehensive, and cost-effective solution to the user for online monitoring of different types of dams and their auxiliary structures. This includes supply, installation, calibration, maintenance, data collection, and a web-based data monitoring service that provides information in the most suitable forms for easy interpretation of the monitoring data. Dams age and deteriorate with time posing a potential threat to life, health, property, and environment.
The safe functioning of dams is important. Changes in behavioral characteristics may be indicative of an impending failure of a dam. Continuous monitoring of dams is essential to detect such changes at early stages and to enhance response time to prevent disasters. This calls for online monitoring systems that are commissioned for near real-time structural health monitoring of the installed instrumentation.
The instrumentation plan will depend on the type and health status of the dam and the existing working instruments installed in the dam. Replacement of existing faulty instruments to the extent necessary and practicable and adding state-of-the-art new instrumentation systems depending on the feasibility and health of the dam should be taken up to ensure an effective monitoring system.
The following solutions are available with Encardio Rite for online monitoring:
Dam Monitoring Instrumentation Scheme
Each dam is a unique situation and requires an individual solution for its instrumentation requirements. There are no simple rules for determining the appropriate level of instrumentation and monitoring because it depends on the size and hazard potential classification of the dam, the complexity of the dam and foundation, known problems and concerns, and the degree of conservatism in the design criteria. Based on our vast experience in instrumenting over 200 dams, a few typical instrumentation schemes for online monitoring of different types of dams are given below:
The table below gives an insight into the purpose of the different instruments, along with their locations.
Typically three or more different blocks are instrumented in a concrete dam. The structural health monitoring instrumentation scheme of the blocks may differ from each other, depending upon design considerations and other factors.
Earth and rockfill dam and concrete-faced rockfill dam (CFRD)
Note: Some of the structural health monitoring methods mentioned in the previous table for concrete dams e.g. 3D deformation monitoring using robotic total stations and UAV surveys can also be used for monitoring earth & rockfill and CFRD dams.
4. Structural Health Monitoring of Buildings
If we are talking about Structural Health Monitoring Applications, it is essential to mention the buildings. Encardio Rite offers online web-based monitoring services for the following:
Structural monitoring solutions for buildings/monuments
Monitoring the health of infrastructure is an extremely crucial and critical procedure. For buildings, structures, bridges, etc., it is recommended that Structural Health be continuously monitored to ensure proper maintenance and safety of man and material.
A basic system offered by Encardio Rite that can be used for most structures essentially consists of the following Structural Health Sensors:
Some other instruments may be used depending on the structure to be monitored and its location. The structure health monitoring sensors include:
With time cracks develop in buildings, structures, and monuments. Monitoring changes in their width provides important information. To online monitor changes in crack width, a suitable sensor is the model EDJ-40V vibrating wire crack meter with SDI-12 interface. Users may use several of these at representative locations to monitor the development of cracks in buildings with time. The crack gauge also has a thermistor incorporated so that temperature can be simultaneously monitored.
Encardio Rite model EPP-30V piezometer with SDI-12 interface is recommended for online monitoring of groundwater pressure/level near the structure. An online piezometric pressure monitoring system provides very important information on safety, especially during the rainy season. Take, for example, any building or structure on a hill.
In-place inclinometers for lateral movement in the ground
In-place inclinometers (IPI) are used for continuous subsurface monitoring of the ground's lateral movement, which may affect the structure's safety. For example, take a multi-story building to be constructed in an area having a lot of construction around.
The construction of the multi-story building will require a deep foundation. In such cases, IPIs installed in the ground between the excavations and adjoining structures help in controlling the construction process to ensure safety. IPIs with Web Data Monitoring Service are also used in hilly areas and mountains where buildings and structures are constructed on slopes and need online monitoring for safety.
For online monitoring of lateral movement in boreholes, Encardio Rite offers a model EAN52MV Vertical In-place Inclinometer System with SDI-12 interface sensors.
Reference guidelines for building damage classification
5. Structural Health Monitoring of Nuclear Power Plants
Structural Health Monitoring is also applied in the field of Power Plants. Encardio Rite offers online web-based monitoring services for the long-term safety monitoring of Nuclear Power Plants. It has a wide range of geotechnical sensors that have a proven track record for reliability and long-term performance under harsh conditions. It also offers newer monitoring technologies such as automatic 3D deformation monitoring using ATS, laser scanning, and aerial surveys using drones for keeping a tab on the structural health of Nuclear Power Plants.
Surface and subsurface sensors that can be used for safety monitoring of Nuclear Power Plants are given below with a typical location plan. It is noteworthy that subsurface monitoring gives important information on the ground/soil movement which may affect the stability of the plant’s structure.
The following sensors may also be considered for structural health monitoring:
Online monitoring using the above instrumentation gives a timely warning of impending danger. The purpose is to assist and inform the stakeholders about the continued performance of structures under gradual or sudden changes to their state. The main factors affecting the performance are degradation of the structure with age, undue settlement/tilt due to soil conditions or nearby construction activity, vibrations due to heavy machinery, groundwater level, atmospheric conditions, etc. This may be reflected in abnormal changes in the monitored values
What is the future of Structural Health Monitoring?
We have discussed the application of Structural Health Monitoring in great detail. Now let’s take a look into its future. OPSIS, the unique software developed by Encardio Moniterra Group is the future of Structural Health Monitoring. The terrestrial Laser Scanner or LiDAR has been used in the fields of surveying engineering and geomatics extensively as the evolution and improvements in its technology allowed the collection of increasingly more accurate data sets.
Despite the benefits of LiDAR over other data-collecting methods, such as the remarkably higher amount of data collected for the same area in reduced periods without the need to place targets, the field of Structural Health Monitoring has remained one of the few unable to implement this technology. The reason behind this is none other than the vast amounts of data that LiDAR provides. However, this advantage becomes a weakness at the post-processing stage, where the analysis of large data sets acquired regularly presents a challenge.
Hence, OPSIS was developed to overcome the impediments previously described. The idea within its core is to perform operations over the raw data provided by LiDAR to get a significantly smaller data set.
For the results obtained from the analysis of this sub-dataset to be equivalent to those we would obtain evaluating the original, the operations involved must ensure to preserve the spatial information contained within the input data.
| Read More: OPSIS: The Smart Solution For Laser Scanning Monitoring |
Subscribe to our monthly newsletter and get access to the latest industry trends,
insights & updates.
Already Subscribed your mail.
Thank you for subscribing to our newsletter.