IoT in Construction Industry

The Internet of Things (IoT) has changed our lives for the better, since its early beginnings in 1999. As a way to promote “radio-frequency identification”, IoT has changed many things, and most importantly, data collection. Now data collection is possible by embedding chips, sensors, actuators and other data collection technology into physical things.

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Various industries have leveraged the IoT technology by recognizing patterns and trends. And recently, building and construction innovators like us, integrated IoT to their processes, and it resulted in exceptional results in productivity, accuracy, budget management, logistics and last but not least, safety.

 

Some of already developed field of IoT in the Construction industry:

1- Remote Operation

2- Supply Replenishment

3- Construction Tolls & Equipment Tracking

4- Equipment Servicing & Repair

5- Remote Usage Monitoring

6- Power & Fuel Savings

7- Augmented Reality (AR)

8- Building Information Modeling (BIM)

 What we offer in IoT:

  • Structural Health Monitoring systems
  • Pile Integrity Testing

Tilt and Water Level SenSpot Sensors on Trancas Creek Bridge in Malibu, CA

Late 2017, Resensys installed 6 SenSpot Wireless Inclinometers, SenSpot Water Level sensor and 2 SeniMax data loggers on Trancas Creek Bridge in Malibu, CA. Trancas Creek Bridge is a coastal, 100 foot bridge that spans Trancas Creek, and carries an average of 22,100 vehicles per day. The bridge was built in 1927, and renovated in 1938.

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California transportation authorities have long been aware that Trancas Creek Bridge is at risk of scouring – a process whereby fast-moving currents erode the sediment near the base of the bridge’s supports. In 1967, the bridge’s east abundments were washed out due to a scouring-related issue. Thus, California sought a way to make the Trancas Creek Bridge safer, and monitor the incline of the bridge to insure against new scouring threats against the bridge’s structural integrity.

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Resensys’ wireless tilt SenSpots were installed on both of the bridge’s piers, allowing California authorities to constantly monitor the incline of the bridge’s structural components, and detect scour holes before the bridge’s integrity is threatened. Three tilt SenSpots were added to each pier.

Resensys’ wireless water level SenSpot was also installed. The water level SenSpot gives constant, accurate readings of the water level underneath the bridge.

With Resensys’ tilt and water level SenSpots installed, California transportation authorities will have constant access to live data about the threat of scour on Trancas Creek Bridge. Resensys offers best-in-class wireless solutions for long term, cost effective, and easy to scale bridge monitoring. The main differentiating factors of Resensys’ structural health monitoring systems are being wireless, easy to scale and long-lasting, enabling energy self-sufficiency and having high reliability. Resensys’ wireless sensors (known as SenSpot) have been designed to

address the most challenging bridge monitoring needs. This includes long-term and cost-effective monitoring of bridge bearings, piers, expansion joints, as well as monitoring and detection of deformation, deflection, settling, fatigue damage, and crack formation in various structural elements of a bridge.

A Quick Guide on Concrete Piles Assessment?

Most of Structural assessment manuals emphasise on visual inspection and physical condition of structures. The visual inspection methodology in those guidelines consists of close up visual assessment of defects in the superstructure and substructure. This methodology is limited to inspection of elements that are at the arms length. For elements with difficult access (i.e. long girders mid-span or deck over river or highways), the methodology is not very practical or accurate. Also, the methodology does not provide any information on how to evaluate concrete piles or foundations.

 

How to Evaluate Concrete Piles?

A reliable condition assessment of substructures (foundations and piles) needs a basic information about type, material and as-built dimension. When foundations and piles are accessible, visual inspection, and mechanical loading of the piles is an effective option. This involves identifying the location of piles (or group of piles), and in-place static or dynamic loading tests to evaluate the reliability of piles and foundations. However, when the access to the piles is not possible, other techniques should be used. NDT methods provide a very reliable and practical alternative for testing and evaluating this group of piles.

Non-Destructive Evaluation of Piles & Foundations

Different NDT methods exist for surveying foundations and piles. To select the best methodology for condition assessment of substructure, the factors below, need to be considered:

1. Type and material of foundation (e.g. timber, reinforced concrete pile, steel pile, composite system)
2. Structural system of substructure (e.g. pile, foundation, or a combined system of foundation and pile)
3. Pile condition (exposed or covered up by pile cap)
4. Pile surrounding area
6. Pile configuration in the layout
5. Ground water level
6. Foundation geometry

The NDT methods for unknown foundation and pile survey are in two main groups as of:

A. Surface Methods; and
B. Sub-Surface Methods.

Surface Methods

Surface methods include NDT methods in which both acoustic wave source and receiver are placed at the surface. A probe signal propagates into unknown foundations, reflected off the foundation ends and boundaries. The received signal at the surface is used for post analyses.

Sub-Surface Methods

The subsurface methods mostly include a probe borehole near to unknown foundation. A borehole or a group of borehole are drilled within surrounding areas. In these methods, the probe signal emitted into unknown foundation, receiving by an adapted transducer placed within borehole.

Other NDT methods

Acoustic surface methods can obtain simultaneously the following information:

1. Pile dimension (pile length)
2. Pile stiffness variations: this parameter can be correlated to cross section variation of pile in cast in-place concrete piles
3. Crack and defect location

At Dez Pacific, we offer a cutting edge non-destructive device, called i.Pile.

 

Practical Considerations in Pile Testing

Pile Integrity Testing is a non-destructive testing method for evaluating the unknown length and integrity of piles and deep foundations. The basic concept behind the technique is determining the velocity (required) and force (optional) response of pile induced by an impact device (normally, a handheld hammer). Pile Integrity Testing works best for long structural component such as driven concrete piles, cast-in place concrete piles, concrete filled steel pipe piles, timber piles, or slender structural columns.

WATCH:    How to Perform Pile Integrity Test?

 

The procedure for low strain impact integrity has been well established, and standardised in ASTM D5882. The test has some inherent limitations, and requires an experienced technician to conduct a successful test and interpretation of results. In this article, we will briefly describe some practical considerations regarding pile integrity testing, and obtaining reliable measurements.

Considerations in Pile Integrity Testing

1- Selecting Proper Hammer

Low strain impact integrity testing is performed using a hand held hammer. The hammer can be as light as couple of hundred grams, to relatively heavier options. Hammer can be a basic one, or instrumented (optional). The impacts induced by smaller hammer have higher frequency content, and shorter rise time. Larger hammers on the other hand, induce higher energy. Sharp and narrow input pulses are reported to be better than wider ones. However, when the size is reduced, the frequencies contained in the impact increases; these waves attenuate faster, and are tend to decrease the ability of investigating longer piles. The hammer tip should be made of material that does not damage concrete during the impact, as this will impact the test results. The use of instrumented hammer when measuring the impact force is of interest to the engineer. For example, detecting deficiencies in near top sections of the pile is better to be done by instrumented hammer.

2- Surface Preparation

A firm connection between the sensor’s tip and concrete surface (pile tip) is needed for successful application of the test method. The test surface should be prepared before performing any measurements. The pile surface should be accessible, and above water. All loose concrete, soil or other foreign materials resulting from construction should be removed from pile surface. If there is any type of contamination on the surface, it should be removed (using a grinder) to reach to solid and sound concrete surface.

3- Placement of Acceleration/Velocity Sensor

The acceleration sensor should be placed at or near the pile head using a suitable, or temporary, thin layer of bonding material (that is, wax, vaseline, putty etc.) so that it is assured that it correctly measures the axial pile motion (transducer axis of sensitivity aligned with the pile axis). For circular and rectangular cross sections, place the sensor near the center of the pile. If the diameter of the pile is larger than 500 mm, additional locations should be considered to obtain useful integrity information. The low strain impact should be applied to the pile head within a distance of 300 mm from the sensor. Make sure that the impact is applied axially.

4- Number of Impacts

ASTM D 5882 requires a minimum on 10 impacts for integrity test on each pile. The reflectograms from each impact should be displayed and/or saved. It is recommended to use the average of the 10 impacts for evaluation purpose.

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Services

Dez Pacific offers a wide range of specialised testing and consulting services such as pile integrity testing, field corrosion detection, durability design of concrete materials, forensic examination, and non-destructive testing of concrete structures.

 

Our proprietary specialised services include obtaining various parameters onsite, performing field tests and then analysing them in order to examine accurately the ‘condition of concrete’.

 

 

The strength of Dez pacific lies in its team who have a robust understanding of the industry and experience in concrete ingredients and retrofit market.

We provide the client with the true state of the structure and rate of the progress of damages in order to make an informed decision confidently about the most cost-effective and long-term repair solutions and mitigation strategies.

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i.Pile™

iPile Logo is a DIY device to test the integrity testing of deep foundations and piles, by pulse-echo method.

 

i.Pile™ provides an industrial-standard quality built device for integrity testing of deep foundations and piles, by pulse-echo method. i.Pile™ is a smart wireless acceleration sensor for fast, accurate and efficient testing of pile integrity.  i.Pile™ benefits from a powerful and user friendly mobile application for receiving and analyzing signals. i.Pile™ is compatible with the requirements of the ASTM D5882.

i.Pile™ is manufactured by FPrimeC Solutions in Ottawa, Canada.

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Benefits

– Efficiently Reveals Potential Defects (i.e. major cracks, necking, soil inclusions or voids)
– Predicts Pile Length
– Ruggedized and Waterproof Sensor
– Ruggedized Data Recording Unit (tablet)
– Comprehensive Data Recording Application
– Lightweight Portable Device
– 24/7 Customer Support

 

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Features:

  • Software: Collect and Analyze
    Generate Engineering Report
    Always up-to-date
  • Hardware: BLE 4.0 Wireless Connectivity
    +10 hours of battery life
    ASTM D5882 Compatible
    Low Voltage Sensor

Wireless Sensors for SHM

Dez Pacific proudly offer Resensys wireless sensors for structural health monitoring.

SHM Solutions

To protect the infrastructure systems against ageing, deterioration, and structural malfunction, Resensys has a cost effective and scalable solution for the real‐time monitoring of important structural state quantities such as strain, cracks, vibration, tilt, inclination, moisture, humidity, etc. Resensys’s solution is based on patent pending Active RF Test (ART) technology, which incorporates novel sensing, ultra energy efficient processing, and wireless communication technologies into a small, wireless, and easy to attach adhesive mount sensor. The system consists of three main components:

    • SenSpot™: attached to structure (average 10‐50 per bridge)
    • SeniMax™: collects data on site of SenSpot™ and sends to remote server (1 per structure)
    • SenScope™: software that analyses data & generates alerts (customisable, can be replaced by a client’s software)

 

Bridge Monitoring

To help assess the stability of so many structurally deficient bridges and other highway bridges so that structural issues are pinpointed and necessary maintenance and repairs can be planned to ensure bridge safety and longevity, Resensys has developed its wireless structural health monitoring solution for existing bridges and bridges under construction that features small, low-cost, easy-to-install wireless sensors that measure a variety of variables affecting the performance of a bridge.

Data collected from the sensors can provide bridge owners with diverse information on bridge structural health such as overstrain, changes in load conditions, deformation, excessive vibration, crack development and growth, and conditions that are conducive to corrosion. Resensys monitoring system is unique in that it is extremely low power. For example, an individual sensor needs only 4 μW to operate.

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Resensys’ SenSpot™ sensors are also capable to monitor specific variables that indicate favourable conditions for corrosion of reinforcing steel in concrete, moisture, electrochemical activity, and chloride concentration. These sensors possess a small probe that is inserted into the concrete at a depth that enables close proximity to the reinforcing steel. The type of probe used on the sensor corresponds with the conditions being monitored in the concrete (i.e., the amount of moisture, the concentration of chloride ions, or the presence of an electrochemical current between the steel and the concrete).

 

Structural Health Monitoring

We offer a cost-effective, easy-to-install, wireless sensor system for structural health monitoring. Our solution can be used for maintenance-free long-term monitoring (several years, decades) or short-term monitoring with our small wireless devices known as SenSepot sensors. The flexibility of our wireless solutions allows us to extend the range of our applications and even customise the sensors to the clients’ need.

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Our structural health monitoring solution consists of a variety of SenSpot sensors from strain, tilt, vibration, fatigue, corrosion, displacement, humidity and temperature sensors all provided in our wireless SenSepot sensor. We provide a real-time data at the comfort of the office or any location desired. There are several unique features which distinguish our sensors from other products. For example, our precision tilt sensor provides a highly accurate measurement such that it detects tilting as small as 0.001 degrees (3 arc sec), which can be used to monitor settling, or tiny movements, etc. Analysing and remote access of collected data from our SenSpot sensors allows our customers to get alerts if certain thresholds are exceeded. As another example, our humidity and temperature sensors provide information-rich localised data-set which helps predict building zones or locations prone to growing mould. The flexible design of the sensor with a variable length sensing probe in such sensors provides the flexibility of measuring humidity and temperature in hard to access places of a building (e.g., behind drywalls, conduits, attics, etc.)

Resensys wireless strain and tilt sensors on fracture critical US522 over Potomac River Bridge

Resensys’s wireless strain sensors (Strain SenSpot) and wireless tilt sensors (Tilt SenSpot) were used to monitor another fracture critical bridge in Maryland. The structural health monitoring based on Resensys SenSpot sensors system was deployed on bridge US522 over Tonoloway Creek and Potomac River. The system consists of 12 tilt and 12 strain SenSpot sensors and two SeniMax data logger and remote communication gateways. The main purpose of the installation is to monitor operation of the rocker bridge bearings as well as monitoring strain in the bridge’s steel girders. Correct tilting of bearings (resulted by temperature change) is a primarily monitored. When bearings are functional and responsive, the possibility of overstrain and fatigue crack formation is relatively small; however, non-functional bearings cause cyclic strain (caused by temperature), which in turn leads to fatigue crack formation. The strain sensors provide accurate monitoring of the bridge’s critical members. Formation of fatigue crack is accurate detected by the devices. In addition, each SenSpot is battery operated. The guaranteed battery life of SenSpot is 10 years.

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Resensys Wireless SenSpot™ provides a versatile suite of remote sensing capabilities for cost effective, reliable, and long-term bridge monitoring.  SenSpot™ sensors are capable of measuring a wide spectrum of structural parameters – including strain (stress), vibration, velocity, displacement, inclination, temperature, and humidity, – in real time. Resensys SenSpots are the world’s most energy efficient wireless monitoring sensors, and a SenSpot™ sensor provides a minimum of 10 years of monitoring using a small ½-AA battery.

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Standard SenSpot sensors for monitoring strain in steel members have a resolution of 1.0 microstrain while the full-scale strain monitoring is ±4000 microstrain. Both range and resolution are customizable if desired.

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For monitoring orientation (tilt, inclination), Resensys’ wireless precision tilt SenSpot sensors is used. Similar to strain SenSpot sensors, the orientation SenSpot sensors have a battery life of 10 years, making them ideal for long term monitoring for settling, foundation instability, deflection, deformation, etc.

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Half-cell Potential Measurement

Half-cell potential measurement is the first solution comes to mind when we examine the corrosion status of a structure. In this method, surface potential measurement is used to predict the probability of corrosion. While the test provides useful information about the chance of corrosion for the area under investigation, the results can also become misleading if the potential effect of influencing parameters are not appropriately taken into account. Another limitation of the test is that it does not provide any information about the kinetics of corrosion reactions.

Several standard associations have standardised the test procedure for half-cell potential measurement including the ASTM, UNI and RILEM.

In the half cell potential method, the potential values at the surface of concrete is measured with respect to a reference point. Concrete surface should be prepared before doing the test, that is to remove paint or other nonconductive layers from the surface. The surface should have a minimum amount of moisture. A sound electrical connection should be established between the reference electrode and reinforcement.

The value is normally presented in contour plots, showing different half-cell potential values. This helps identify the areas with higher chance of corrosion. For example, ASTM C 876 introduces three different ranges for the measurement. Half-cell potential values (measured in reference to copper sulphate electrode) less than -350 mV represent area where probability of having active corrosion is more than 90%.

When measurement is higher than -200 mV, this probability is less than 10%. Results for half-cell potential values between -200 mV to -350 mV in uncertain.

Always the effect of environmental conditions (such as moisture and humidity), as well as the properties of concrete materials (dense concrete versus porous concrete, carbonated concrete) need to be taken into account. There are some complications along the way when we are performing a half-cell measurement. High electrical resistivity of concrete cover, decrease in moisture content of concrete as well as increase in the thickness of the cover, make half-cell readings less accurate. Also, a decrease in oxygen concentration at the surface of the steel reinforcement for instance for concrete in fully saturated condition will result in a more negative corrosion potential reading.
When doing a half-cell potential test, the surface should be free of paint, and chemical epoxy coatings. Also, the test on stainless steel reinforcement and epoxy coated rebar will increase the chance of error in making the measurements.

Reference: Rebar Corrosion | Concept and Measurement Techniques, Giatec Scientific inc.