In mid-May, Infrasense began phase 1 of deck testing on 52 bridge decks throughout 12 counties in Oregon. We have started with the ground penetrating radar testing, and plan to return in July to perform infrared testing under more optimal weather conditions. Phase 2 will begin in late summer or early fall, after preliminary GPR and IR results have been completed. Targeted ultrasonic testing will be performed on select decks using these preliminary results.
Infrasense recently deployed an air-launched 3D-Radar system on projects in Iowa, Florida, and Virginia. The high-resolution system contains 21 antennas spaced 3 inches apart, and is capable of penetrating up to 5 feet below the surface. Infrasense has used this system to evaluate bridge deck, pavement, and tunnel deck conditions.
This past week, the Infrasense team spent a few days in the White Mountains to share some technical knowledge, explore the snowy outdoors, and prepare for what looks to be another busy year providing clients with accurate and useful NDE testing services.
Activities ranged from an overview of our performance in 2016, a refresher on field safety practices, a deeper discussion of our proprietary software, and training with new testing equipment. But it wasn't all tech-talk; we also found time to go skiing, hike around the beautiful Echo Lake, and cook a few meals together as a team! Here are a few shots from our 2nd annual tech retreat!
How our high resolution video complements the abilities of Infrared.
Infrared data is collected using a FLIR thermographic camera, which measures surface temperature and can provide information regarding subsurface damage in bridge decks. The camera is mounted to a vehicle and data can be collected at highway speeds with clear and accurate results. After surveying each lane, the data is stitched together to create a comprehensive plan-view thermography image.
The areas that appear white in Figure 1 are hot spots resulting from debonding or delamination. When an overlay debonds or a delamination exists at the rebar-level, the resulting air void acts as a thermal barrier, producing relatively higher temperature (white blotchy areas) in the IR image. We delineate these areas to provide both subsurface defect quantities and maps to our clients. High resolution video is also collected with the infrared data, and used to filter out surface features that produce thermal anomalies but are unrelated to subsurface conditions. Similar to the infrared, the video data can be stitched together to create a plan-view image for a bridge deck. This image can be used to identify, quantify, and map areas of patching, spalling, and cracking.
Figure 2 shows an area of thermal activity in front of the vehicle that was found to match the shape and location of surface staining in the high resolution video. As a result, this area was delineated and categorized as a "thermal obstruction" instead of a delamination. Obstructions can include discoloration, oil stains, rust deposits, debris, shadows, etc.
Figure 3 shows a few areas of thermal activity, similar to what we see in Figure 2. Playback of the video in this location shows no surface obstructions, meaning that these ‘hot spots’ are due to a subsurface thermal barrier. These were delineated and categorized as delaminated areas. With the aid of a visual to go with the IR data, we are able to confidently distinguished areas of subsurface distress.
On Thursday, December 1, 2016, Ken Maser, Ph.D., PE, will give a presentation on the state of the practice and the future of GPR and other forms of NDT for both pavement and bridge deck applications. The presentation will be in webinar format, via the Transportation Learning Network.
The 1.5-hour webinar will cover the various applications of ground penetrating radar (GPR) and other nondestructive testing (NDT) applications around the United States. Also to be covered is a recent application of Traffic Speed Deflectometer (TSD) in Idaho, as well as the use of Infrared Thermography for bridge deck surveys. The presentation will also give insights into the implementation stage of SHRP2 involving 3D radar applications.
Ken founded Infrasense in 1987, and is an internationally recognized authority in the field of nondestructive evaluation and subsurface condition investigations. Ken has served as a consultant to the Strategic Highway Research Program (SHRP), and has managed numerous network-level pavement and bridge deck evaluations throughout his career.
Highway and bridge designers, project programmers, materials and research staff, and consultants in the transportation field should all tune in! The deadline to register is Monday, November 28, 2016. For more information, visit www.translearning.org
Here in New England, red and orange leaves have begun to brighten our daily commutes, which have become noticeably darker we inch closer to winter. Fall is here, and so is Back-to-School season, which means our group of summer interns have left some empty desks around our office. Everyone at Infrasense would like to thank Sean, Garret, and Steve for their hard work this summer, and wish them luck (though we know they won't need it) in the new academic year. Have fun, guys, we hope to see you again soon!
Infrasense just finished some fieldwork in beautiful Idaho, where plains, mountains, dark skies provided a refreshing change of scenery from our Boston office. Here's a shot of our survey vehicle on a truss bridge (not a structure we were evaluating, just a great photo op!) with the MIlky Way stretching across the sky above us. This is the third consecutive year we have had the opportunity to work in Idaho, and it has been exciting to work closely with the DOT to provide valuable bridge and pavement data while also appreciating some of the natural beauty of the state!
After just completing data collection for a group of bridges in Ohio, which included performing underside inspections, I thought it would be a good opportunity to dedicate a little time to one of the more unheralded ways we assess a bridge deck's condition. Because most of our services are predicated on efficiency and speed, we spend a lot of time inside a vehicle during data collection. Performing underside inspections allows us to get out and stretch our legs, see some unique things, and sometimes, get a little artistic!
Here's a gallery of images taken from some of our more interesting underside inspections. Note, none of the graffiti was our work - we lack both the artistic ability and the willingness to vandalize our client's property!
By: Evan Guarino
Infrasense has returned from its first annual technical retreat. After a busy and productive year, we headed up to Bromley, VT for a few days of learning, planning, and fun! The retreat included technical presentations on bridge inspection practices, bridge management, ArcGIS, pavement design, falling weight deflectometer (FWD), advanced GPR methods, and other topics. We also received training on some of our new equipment, including GSSI’s SIR-30 GPR data acquisition system. Some of the more fruitful discussions were around completed and future projects to improve and prepare ourselves for the next year. It wasn’t all work though, we took some time to go hiking and skiing on Bromley Mountain, despite the subfreezing temperatures. At the end of each day, we would gather to eat some of Ken’s delicious cooking (as shown below). All in all, the retreat was a great way to learn, plan, and recharge for the upcoming year of scanning!
With the close of an extremely busy and productive 2015, its time to take a few months and rest in preparation for the 2016 season right? Not so fast...we have spent the better part of January training our staff and improving our equipment, with a few games of ping pong thrown in the mix for the sake of sanity.
Anticipating an even busier 2016, we went ahead and doubled our GPR data collection ability with a second set of Horn antennas and a next generation data collection unit, the SIR-30.
New equipment can only mean one thing…time to start testing and training. GSSI has come through again with a solid piece of hardware, that will allow us to collect 4 channels of high resolution GPR data simultaneously, while moving at traffic speeds. The equipment comes with a new set of challenges, and more interestingly, the ability to make improvements to our existing setup. So break out the power tools, wire cutters and soldering guns…
With all the projects that we have been working on and finishing up, I have not had a chance to really get my hands dirty and improve our setup and I am excited to say that I have spent a good part of January, planning, implementing and testing our new system and its really starting to come together. The new unit is a beast, and a very powerful GPR collection tool, taking an already great system (SIR-20) and making improvements to the data quality, the user interface and overall responsiveness.
Local testing on roads and bridges indicates that we are going to be very happy with the new system. The next big step is coming up in the next week, actually bringing this beast into the field and collecting data for a client. We will be heading down to the DC area for a day or so of data collection along interstate 395, giving us a chance to put the SIR-30 through its paces.
We are looking forward to a very busy and very productive new year full of challenges and adventures.
See you on the road!
Last February I was hired by Infrasense as a Staff Engineer. Despite it being less than a year later, I feel I’ve learned quite a bit; especially regarding fieldwork. Here are 3 lessons I learned in 2015:
1. There is no such thing as over planning. A lot of work is done before we even leave the office. In addition to making travel arrangements, it’s important to review the scope of work, identify the location of all project sections/ testing sites, and establish a quality assurance protocol. It’s much easier to plan at the office than in a mountain range in Montana or alongside a sugar beet field in North Dakota.
2. Safety, safety, safety. Traffic control is one of the more important tools that can be used while collecting highway bridge deck and pavement data. Traffic control alerts drivers and protects our crew. It’s particularly important to ensure you’re on the same page as your traffic control contractor, and have a clear and efficient means of communication.
3. Ask for help when needed. Coworkers back at the office can be an invaluable resource to help with navigating, identifying data collection settings, troubleshooting equipment issues, and providing quality assurance of field data.
I look forward to continuing to learn in 2016!
by Seth Brewster, Staff Engineer
Infrasense co-presented at the AGC New York State Construction Industry Conference yesterday. The presentation was on a "value engineering" case study where ground penetrating radar (GPR) was used to facilitate a deck rehabilitation design. The use of GPR saved the NYS Thruway over $520k on this particular project!
The Infrasense fieldwork season is finally winding down, and it sure was a busy one - between May and October, we scanned over 300 bridge decks and 3000 miles of pavement! As a Project Engineer at Infrasense, I handled a lot of the planning and execution of all that fieldwork. Now that the cold weather, and even snow, has begun to set in across much of the northern US, it seems like the opportune time to settle into the office and reflect on some of my favorite fieldwork memories of 2015. Thanks to my growing photography hobby, I was able to capture some of these moments on my camera, and now I’d like to share them with you!
Hover your cursor over the photo to see where it was taken, and get more information about that particular project.
This summer was challenging, but it was also full of great experiences and rewarding moments. Fieldwork provides some of the best opportunities to learn new things and grow both professionally and personally. I'm happy to be able to share some of these experiences; keep checking in with our Recent News page to see where else we've been, or where the next year will take us!
- IR camera's "integration time" (typically >10 ms).
- The faster the speed, the more the image is blurred (a vehicle at 60 mph moves almost 0.9 ft. in 10ms).
- Low speed method requires a rolling lane closure
- Higher speed would have some advantages
- No closures (safer)
- Lower cost
- Higher production rate
As a result, several agencies have specified high-speed IR and a number of high-speed projects have been carried out by Infrasense and others.
- Michigan DOT (11 decks, 2015)
- Wyoming DOT (32 decks, 2015)
- Nevado DOT (Las Vegas viaduct, 2015)
- Colorado DOT (15 decks, 2014)
How good are the results? When is it appropriate to do high-speed vs. low speed?
Infrasense has tested the effects of speed on the quality of the IR data
Typical Corresponding Visual and IR Data Frames at Low Speed
IR Images vs Speed - Patches under an AC Overlay
IR Images vs. Speed - Deck Delaminations
Summary of findings:
- Low speed provides more detailed delineation of delaminations
- When delaminations are clear in the IR data, high speed and low speed results match reasonably well
- When delaminations are not as clear (as occurs with overlays), high speed data is harder to interpret (based on project experience)
- High speed does not allow for confirmation sounding
Conclusions - Low-Speed vs. High-Speed
- Low-Speed is a preferred option for:
- Project level evaluations and mapping of repairs
- Low-speed, low-volume roads
- Decks with concrete overlays
- High-Speed is a viable option for:
- Network level evaluations
- High-speed, high-volume roads (no closures)
- Decks without overlays
Ken Maser, Senior Principal at Infrasense, gave a presentation today at the Falling Weight Deflectometer Users Group Meeting, held in Raleigh, North Carolina. Ken's presentation, titled "Integration of FWD and GPR for Rehabilitation Design and Substructure GeoDatabase Development in Idaho", focused on recent Infrasense projects across the state of Idaho.
Infrasense recently completed high-speed infrared thermography scanning of 11 bridge decks for the Michigan DOT. The infrared data was collected with corresponding high resolution video at driving speed using a vehicle-based system. With this, no lane closures were required, and most importantly, traffic was unaffected. The infrared and video data collected for each of the 11 decks was analyzed to quantify and map overlay debonding, rebar-level delamination, patching, and spalling. Michigan DOT plans to use the deck condition information for prioritizing and planning rehabilitation projects.
Infrared scanning is being used by an increasing number of transportation agencies to efficiently obtain quantitative and comprehensive deck condition information. The ability to evaluate the condition of a large number of decks in a single inspection season is a valuable bridge management tool. Quantities and maps resulting from infrared scanning surveys allow for robust, data-driven decisions, and help to optimize the use of shrinking budgets.
Over the past 5 years Infrasense has completed infrared surveys of over 700 bridge decks in States such as Wisconsin, Minnesota, Idaho, Illinois, Wyoming, and Nevada. A majority of these decks carry major interstates, and range in size from a single span to a 1.5 mile-long viaduct.
Infrasense carries out infrared surveys according to ASTM D 4788 – 03 using a vehicle-based system that covers one lane per driving pass. For a typical deck with 2 lanes and left and right shoulders, the survey is carried out in four passes – one in each lane and one in each shoulder. Each pass covers a deck width of 12 to 15 feet. The survey produces a series of infrared and visual images across the length of the deck. During the analysis, infrared data is reviewed simultaneously with the video data to differentiate delaminated areas from surface features (discoloration, oil stains, sand and rust deposits, etc.) that appear in the infrared, but are unrelated to subsurface conditions. Distinct areas with relatively higher temperatures that are unrelated to surface conditions are quantified and mapped. These are "hot spots" where the surface temperatures are higher due to the thermal barrier produced by the delaminations. The resulting delamination maps, which also include patching and spalling, are provided in CADD compatible format.
Infrasense, Inc., a national leader in infrastructure nondestructive evaluations, recently carried out detailed High-Resolution Video (HRV) Image survey along a three-mile stretch of road to document the pre-construction “baseline conditions” near Wichita, Kansas. The HRV image survey was performed using a vehicle mounted video camera that scans the road in front of the vehicle at high speeds without requiring lane closures and with no disruption to traffic flow. The results of the HRV image survey provided a detailed plan-view baseline conditions map of the three miles of road that outlined and quantified existing areas of distress prior to the roadways being used for access during a construction project.
A construction project near Wichita, Kansas involving the transportation of construction equipment and personnel between the state highway and a work site 3 miles down a two lane county road required a “baseline conditions” record to be produced. Infrasense, Inc. was called in to collect high resolution video to both record, and quantify the current road conditions, using the USDOT Distress Identification Manual as a guide.
The high resolution video imagery was captured using a vehicle mounted, 1080p resolution digital video camera, collecting at 30 fps with synchronous GPS coordinates. The HRV data was collected along a single continuous pass of each of the travel lanes. The Kansas project was comprised of two, adjacent two lane roads that connected the project site to a highway, requiring four traffic speed data collection passes with the camera. The combination of site specific calibration files and marks, and GPS data, allows for quick data collection without the need for lane closures, or disruptions to traffic flow.
The results of the survey consists of a digital video recording and a plan view map. The plan view map was created from the digital video using field calibration files and Infrasense’ proprietary HRV video processing software. The extracted image files are corrected for distortion, and pixel mapped prior to being digitally assembled, creating a single continuous image of the road. Infrasense engineers then analyzed and mapped out areas of distress along the road, quantifying the condition of the road in its current state.
The resulting digital video recording and plan view map were exactly what our client was looking for and will be used post-construction to identify new damage to the road following construction activities, including transportation of construction equipment and personnel.
Nondestructive scanning methods such as ground penetrating radar and infrared thermography are being used by an increasing number of transportation agencies to more efficiently obtain comprehensive deck condition information. The ability to evaluate the condition of a large number of decks in a single inspection season is a valuable tool for bridge owners to make data-driven planning and design decisions. Infrasense has utilized a multi-phase approach for a number of agencies to provide the maximum amount of information for a given budget. Phases include the following:
Phase 1 – Quantities for Planning-Level Decisions
A large group of decks are scanned with high-speed NDE methods and condition quantities are provided (e.g. delamination, deterioration, patching, spalling). This level of information is used by agencies to program and prioritize decks for specific preservation, rehabilitation, or replacement efforts.
Phase 2 – Maps for Rehab Design
Decks are selected for Phase 2 based on the Phase 1 results and specific agency needs. Phase 2 includes detailed mapping of the detected concrete deterioration, rebar-level delamination, spalling, and patching. AC overlay thickness and rebar cover maps can also be provided. Conditions are mapped in plan-view and provided in a CADD compatible format. Agencies use the condition maps to plan and spec rehabilitation efforts (e.g. construction bid quantities).
Phase 3 – Confirmation Testing
Some agencies have implemented a third phase to confirm the Phase 2 findings for select decks. Phase 3 is typically reserved for cases where there are significant cost implications; such as when an agency is deciding between rehab and replacement of a relatively large deck carrying a high-volume roadway. Phase 3 consists of localized confirmation testing at locations selected using the Phase 2 maps. Confirmation testing has included coring, chloride content sampling, half-cell, impact-echo, and sounding.
Infrasense, Inc. recently completed ground penetrating radar (GPR) and infrared thermography (IR) surveys of 7 bridge decks in Maine. The data was collected at driving speed, so that there was no disruption to traffic flow. The GPR and infrared thermography surveys resulted in concrete deterioration and rebar depth quantities and maps.
Infrasense, Inc., a national leader in infrastructure nondestructive evaluations, recently completed ground penetrating radar (GPR), infrared thermography (IR), and high resolution video surveys to evaluate the condition of 7 bridge decks in on the Maine Turnpike. These bridges represent nearly 46,975 square feet along I-95, and all had an asphalt overlay that severely limits the effectiveness of traditional sounding techniques. The GPR surveys were carried out at driving speeds, so no closures were required and traffic flow was not disrupted.
The GPR and IR surveys provide a deterioration quantity and map for each reinforced concrete bridge. The GPR surveys also produced rebar depth and asphalt thickness contour maps for each bridge deck. HNTB will utilize the deck condition results to plan future rehabilitation work on the Maine Turnpike.
Ground penetrating radar (GPR) data is collected at highway speeds to estimate rebar depth, corrosion conditions and deteriorated concrete. The GPR data is collected in a series of lines spaced 3 feet transversely across the width of the deck, with each line representing a cross sectional slice of the deck at a particular offset. Decks in good condition consist of strong and uniform radar reflections from the rebar. GPR data with weak and inconsistent reflections indicate rebar-level deterioration in the bridge deck. Infrasense uses software to analyze and map this data to provide comprehensive results for its clients.
The infrared data is collected in a series of passes across each deck, with each pass covering a deck width of between 12 and 15 feet. Surveys are performed at normal driving speeds to prevent lane closures and traffic disruptions. During the survey, regular visual data is collected synchronously with the infrared data, so that surface features such as staining and patching can be differentiated and mapped in the infrared images.
Ground penetrating radar and infrared data provide surveys provide transportation agencies with accurate and comprehensive bridge deck condition information, enabling effective preservation, rehabilitation, and replacement decisions. Traditionally, highway agencies have employed sounding (chain or hammer) to identify delaminated areas for project-level rehab. Although sounding has proven reliable, the labor and closures required for a sounding survey makes it prohibitive for obtaining data of a large number of decks. Also, sounding is not effective when there is an asphalt overlay. In response to these limitations, a number of highway agencies and private consulting firms, including HNTB, have utilized alternative methods such as ground penetrating radar.