Field Application of a Multi-Channel Acoustic Scanning Tool for Detecting Defects in Concrete Bridge Decks
Mehdi Rashidi, GENEX SystemsShow Abstract
Hoda Azari, Federal Highway Administration (FHWA)
The nondestructive evaluation of highway infrastructure using acoustic techniques is mostly limited to impact-echo and ultrasonic surface waves methods. However, the traditional application of these methods requires direct contact between the surface of concrete and transducers (i.e., receivers). Specifically, for massive highway infrastructure, which may require thousands of measurements, the process of attaching/detaching acoustic transducers to/from the concrete surface is time-consuming and labor-intensive. To address these challenges, a Multichannel Acoustic Scanning Tool (MAST) has recently developed at the Turner-Fairbank Highway Research Center, and its proper performance is validated. MAST applies impacts using 12 mm steel balls, and receive the signals with arrays of microelectromechanical systems (MEMS) microphones. In this paper, MAST is used to scan three concrete slabs obtained from the Haymarket Bridge Deck (structure number 000000000014178) in Virginia, USA. The slabs vary in their damage level assessed using multiple NDE techniques in 2015 (when the bridge deck was replaced.) Results obtained from scanning of slabs using MAST and a commercial handheld impact-echo instrument agree with each other. However, compared to the traditional impact-echo instrument, MAST scans the slabs at a higher speed, and higher spatial resolution.
Non-Destructive Testing of GFRP-Wrapped Reinforced-Concrete Slabs
Wael Zatar, Marshall UniversityShow Abstract
Hai Nguyen, Marshall University
Hien Nghiem, Marshall University
Cumhur Cosgun, Marshall University
Externally bonded fiber-reinforced polymer (FRP) composite systems have been increasingly used to rehabilitate concrete structures. These systems are critical to enhance the durability and capacity of the strengthened structures. There is a need to effectively evaluate the potential for debonding and deterioration of the rehabilitated system components. Non-destructive testing techniques appear to be a good solution to assess these rehabilitated structures. This paper presents an investigation on using ground-penetrating radar (GPR) and infrared tomography (IRT) methods to evaluate reinforced-concrete (RC) slabs externally bonded with glass fiber-reinforced polymer (GFRP). Four GFRP-wrapped RC slab specimens were experimentally tested. Artificial vertical cracks, voids, and debondings were made on the top surface of the RC slabs. Test parameters include the size of embedded steel rebars, depths of the vertical cracks, sizes and depths of the voids, and dimensions and thickness of the debonding. GPR image reconstruction method was established based on the modified synthetic aperture focusing technique (SAFT). An in-house developed software using this image reconstruction technique can provide sharp and high-resolution images of the FRP-strengthened RC slabs in comparison to those obtained by the device’s original software. The results reveal that the GPR technique can accurately determine locations and sizes of the embedded steel rebars and artificial voids. The pilot study of the IRT camera indicates the promising applications of the IRT technique for detecting and locating near-surface defects. This study suggests that the combinations of the GPR and IRT techniques can be an effective means for imaging internal defects of concrete structures.
Implementation of AASHTO/AWS D1.5 Phased Array Ultrasonic Weld Inspection Programs
Russell Kok, GenexShow Abstract
Hoda Azari, Federal Highway Administration (FHWA)
This paper describes highlights of phased array ultrasonic testing (PAUT) nondestructive evaluation (NDE) research activities at the Federal Highway Administration’s Advanced Sensing Technology (FAST) NDE Laboratory. This work is in support of the overarching goal to support the implementation of ultrasonic techniques in lieu of radiographic techniques for American Association of State Highway and Transportation Officials (AASHTO) / American Welding Society (AWS) D1.5 Bridge Welding Code 1 inspection of full penetration bridge fabrication welds. The paper also describes some of the advantages and disadvantages of the process to implement a PAUT inspection program. The results of this study support that goal with a good correlation of the comparative inspection results between PAUT and radiography. There is, however, a need to develop a more comprehensive set of weld flaws to ensure a fully representative flaw set is evaluated. In support of that goal, the FAST NDE lab is currently using ultrasonic simulation software to supplement the test plate data with a virtual data base of simulated flaws. A successful implementation of PAUT can result in a more efficient inspection process with detailed permanent records and images of the flaw locations mimicking the historic radiograph. As more and more bridge fabrications incorporate PAUT, there will be a broader PAUT experience base as the AWS committee, teamed with the bridge fabricators, FAST NDE Laboratory and other contributors continue to work toward replacing all required radiography in D1.5 with an option to use PAUT.
5th Generation Low-cost Efficient Wireless Intelligent Sensors (LEWIS 5) for Transportation
Joshua Murillo, University of New MexicoShow Abstract
Fernando Moreu, University of New Mexico
Marlan Ball, University of New Mexico
Low-cost Efficient Wireless Intelligent Sensors (LEWIS) are a version of standard Wireless Smart Sensors (WSS) that allow for high versatility while minimizing cost and maximizing energy efficiency. LEWIS implements energy harvesting capabilities, wireless communication, and an interchangeable sensor interface. Additionally, LEWIS contains multiple generations, which have proven beneficial in structural health monitoring. However, the 5th and newest generation, LEWIS 5, has been developed to conduct a series of different tasks. These tasks include structural health monitoring and tasks such as water quality monitoring, which can be applied to resolve some critical issues of transportation. This paper serves to showcase LEWIS 5 and its capabilities alongside its potential applications within the field of transportation. Keywords: Low-cost Efficient Wireless Intelligent Sensors (LEWIS), Wireless Smart Sensors (WSS), Transportation, Energy System, Measuring System
Crack Detection of a Reinforced Concrete Wall using Low Cost RFID-based Sensors
Rinchen Sherpa, University of ConnecticutShow Abstract
Pierre Fils, University of Connecticut
Shinae Jang, University of Connecticut
This study presents the implementations of a cost-effective method to detect cracks and cracking patterns of a reinforced concrete (RC) wall. Cracks in RC structures are generally expected due to concrete’s lower tensile capacity; however, deeper cracks in concrete can cause further damage in rebars, and detection of severe cracks are important. Typically, crack detection has been conducted with visual inspection or other nondestructive evaluation techniques in the field. During recent years, deterioration of deeper core of concrete due to pyrrhotite reaction, so called ‘crumbling foundation’ has been an issue in Eastern Connecticut. To monitor affected walls in many houses, a cost effective way is desired. A wet inlay passive Radio Frequency Identification (RFID) tag is low cost (~ 10 cents) and the state of a crack in a structure can be easily monitored. In this study, the RFID-based crack sensors have been implemented in a residential building with cracks from crumbling foundation. A hand-held RFID reader, RFID tags with a specific measurement method to control environmental effects are used to monitor the health of a RC structure. Conducting this crack monitoring is vital as it will aid critical decision making especially in the case of crumbling foundation as any decision can be extremely costly. Likewise, it can provide a cost-efficient, convenient, and non-invasive alternative for the other current testing methods. The results show that the frequent testing with the proposed method can allow for rapid monitoring of RC buildings and bridges with cracks.
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