Use of Nondestructive Testing in Bridge Inspection and Evaluation Practice

Use of Nondestructive Testing in Bridge Inspection and Evaluation Practice Sreenivas Alampalli, Ph.D., P.E., MBA The role of infrastructure in modern societies is multifaceted, as noted in President Obama’s inaugural speech on January 20, 2009: “We will build the roads and bridges, the electrical grids and digital lines that feed our commerce and bind us together.” Bridge and highway infrastructure are not viewed as just a means to move people and goods from one place to another, but also as a backbone of commerce. Thus, mobility, reliability, economic advantage, and security, as well as safety, are all becoming important performance measures for owners in a resource-constrained environment. At the same time, new materials and innovative construction methods are also becoming popular for the advantages they offer, such as quick construction to minimize traffic interruptions. Preserving the infrastructure of the United States is dependent on the successful implementation of advanced technology, such as nondestructive testing (NDT) methods and engineering structural health concepts, into routine evaluation to implement objective decision-making processes for effective asset management. Even though visual inspection is still predominantly used, bridge inspection techniques and technologies have been ever-evolving since the National Bridge Inspection Standards (NBIS) were established by the Federal Highway Administration (FHWA) over 50 years ago. The origins of current bridge inspection practices can be traced to the collapse of the Ohio River Bridge (known as the “Silver Bridge”) between Point Pleasant, West Virginia, and Kanauga, Ohio, in 1967. Following this tragedy, which killed 46 people, the FHWA Act of 1968 led to the establishment of NBIS, which led to systematic periodic inspections by qualified personnel and is the basis for the current NBIS. The NBIS has been modified several times, including after the failure of the Mianus River Bridge in Greenwich, Connecticut, and the Schoharie Creek Bridge near Fort Hunter, New York, which led to fracture-critical and underwater bridge inspections with established intervals. As technology has advanced, so have the tools and techniques that have become available to a bridge inspector. Periodic visual inspection, with qualified and trained inspectors using prescribed manuals and methods, is the primary technique used to perform bridge inspections. Standard bridge inspection is performed using a two-tier process: routine inspection that can trigger more detailed “in-depth” or “special” inspection. In addition to these procedures, analytical ratings of bridge load capacity are

carried out as needed to reflect the bridge condition observed during the inspection, and inspection of underwater structures is performed generally by divers at least once every 60 months. Nondestructive evaluation (NDE) methods are becoming popular for augmenting visual inspections. Even though routine inspection essentially consists of common tools, for the last two decades or more, these have been supplemented by some very basic testing tools such as a chain drag and hammer for concrete members and dye penetrant and magnetic particle testing for steel members. Ultrasonic testing is used routinely as a second level of NDE when inspectors request further investigation, as well as during steel member fabrication. During the last decade, the use of ground penetrating radar (GPR) for evaluating bridge deck condition for planning further repair and rehabilitation actions has been increasing steadily. With the use of new materials such as fiber-reinforced polymers for bridge decks and concrete member wrapping, use of NDT methods, such as thermal/infrared testing, is also used for construction quality control as well as for periodic inspection (Figure 1). Each of the NDE methods has its own advantages and disadvantages for infrastructure inspection. Combining several methods may yield higher reliability of the results by taking advantage of the efficiencies of individual methods. Type, location, accessibility, and condition of a bridge as well as the type of inspection are some of the factors that determine what techniques are used. Table 1 presents a brief synopsis of typical bridge elements and some of the standard inspection and NDE tools available to address the concerns previously described. Additionally, there are several systems that can be used to monitor a bridge to provide real-time data and alert the owner of such things as failure of load-carrying members, excessive rotation or displacement of an element, overload in a member, crack growth, scour around bridge piers, or occurrence of a significant flood event. The type of information provided is typically very specific and provides data on isolated areas or members of the bridge. The most practical of these systems are being used by owners during “in-depth” or “special” inspections or implemented for long-term monitoring. The technology in this sector is advancing rapidly with more and more owners starting to experiment and incorporate these into their asset management practices. Future trends include: • More widespread use of NDE systems as part of visual inspection, such as use of augmented reality and technology fusion for data visualization (Figure 2). • Use of advanced multi-sensor robotic platforms (Figure 3), such as unmanned ground-based systems (UGS), unmanned aerial systems (UAS), and unmanned water-based systems (UWS). Automation in both multi-sensor data collection and data processing has resulted in near real-time data images. • Large-scale wired and wireless sensor networks for bridge structural health monitoring (SHM). • Use of artificial intelligence (AI) and deep learning for data analysis. • Remote sensing using satellite-based technologies for system-wide monitoring of the structural assets as a first level of monitoring.

Bridge Element

Steel Pins/ Hangers/ Eye Bars

Steel Girders/ Trusses / cables

Main Concern

Delamination/ Rebar Corrosion

Fatigue cracks

Standard Practice

Chain Drag / Hammer sounding

Dye Penetrant/ Magnetic Particle

Fatigue Cracks

Dye Penetrant / Magnetic Particle

Concrete Pre-Stressed Girders

Tendon Corrosion

Hammer sounding

NDE Tools

Ground Penetrating Radar (GPR)

Electric Resistivity

Impact Echo (IE)/ Ultrasonic Surface Wave (USW) Infrared Thermography (IR)

Ultrasonic (UT) and Phased array

Eddy Current (EC)

Ultrasonic (UT) and Phased array

Infrared (IR)

Radiography

Acoustic Emissions (AE)

Magnetic Flux Leakage

Strain gauges

Tendon Corrosion, Grout Holes

Hammer sounding

Magnetic Flux Leakage

Ground Penetrating Radar (GPR)

Strain gauge

Ultrasonic Echo, acoustic monitoring Ground Penetrating Radar (GPR)

Movement, Lack of Movement

Rebar Corrosion

X-ray

- Tilt Meters

Hammer sounding

Ground Penetrating Radar (GPR)

Ultrasonic Pulse Velocity (UPV)

Infrared Thermography

Tilt Meters

Underwater sonar imaging

Ground Penetrating Radar (GPR)

The American Society for Nondestructive Testing (ASNT), the world’s largest technical society for NDT professionals, has a major role to play in working with infrastructure owners and regulating agencies; in moving towards the implementation of NDE methods into routine inspection process through development of handbooks and standards; and in providing training and certification of personnel. ASNT has an infrastructure committee that comprises members representing owners, industry, and regulators. The committee organizes a biennial ASNT topical conference geared towards technology transfer and works with other professional societies including the Transportation Research Board’s standing committee AFF40 on “Testing and Evaluation of Transportation Structures” to advance the NDE technologies into practice and further develop them.

Acknowledgement

Author thanks Farrokh (Frank) Jalinoos and Jill Ross for assistance in preparation and review of the article. Part of the content of this article was taken from a paper published by Alampalli and Jalinoos in the ASNT journal Materials Evaluation in 2009. Content has been updated to incorporate recent developments.

Nigel J. Cassidy

School of Engineering,

University of Birmingham, Edgbaston,

Birmingham, B15 2TT, UK n.j.cassidy@bham.ac.uk

Sreenivas Alampalli, Ph.D., P.E., MBA

Structures Management Bureau

New York State Department

of Transportation Sreenivas.Alampalli@dot.ny.gov

Nigel Cassidy is Professor of Geotechnical Infrastructure Engineering at the University of Birmingham in the School of Engineering. He has over 30 years’ academic and industrial experience in near-surface geophysics, hydrological & geotechnical engineering and numerical modelling research. Nigel’s current work is focused on the development of sensing technologies for infrastructure and environmental monitoring applications and the development of machine learning processes for the autonomous interpretation of sensor data. He is Deputy Director of the new National Buried Infrastructure Facility (NBIF) at the University which forms part of the wider, UK capital investment to support the UK Collaboratorium for Research in Infrastructure and Cities (UKCRIC).

Dr. Sreenivas Alampalli is the Director of the Structures Management Bureau at the New York State Department of Transportation. He is a Fellow of the American Society for Nondestructive Testing (ASNT), the American Society for Civil Engineers, the Structural Engineering Institute, and the International Society for Structural Health Monitoring of Intelligent Infrastructure. Dr. Alampalli obtained his Ph.D. in Civil Engineering and his MBA in Management and Technology from Rensselaer Polytechnic Institute. He has authored or co-authored more than 250 technical publications including books on infrastructure health in civil engineering, risk management in civil infrastructure, and multihazard considerations in civil infrastructure. He also coedited two books on the inspection, evaluation, and maintenance of suspension bridges. Dr. Alampalli has been a member of ASNT since 1992 and currently serves as an associate technical editor for the ASNT journal Materials Evaluation. Dr. Alampalli has been a member of the ASNT Infrastructure Committee since 2001 and served as its chair from 2006 through 2009. He also served on ASNT’s Board of Directors from 2003 to 2006. He received the William Via Bridge NDT Lifetime Service Recognition from ASNT in 2014 for outstanding voluntary service to the bridge and highway nondestructive testing and evaluation (NDE) industry. He also received the Mentoring Award from ASNT in 2009.