Special Issue on Nondestructive Evaluation and Testing for Bridge Inspection and Evaluation

Abstract

I served as the guest editor of the July/August 2010 issue of the Journal of Bridge Engineering. During the last 2 years, partly because of the failure of the I-35 Bridge inMinnesota in 2007 and other incidents, there has been significant focus and healthy discussion among bridge infrastructure stakeholders, including several elected leaders, in using nondestructive methodologies in assisting bridge inspection, evaluation, and maintenance. At present, nondestructive evaluation and testing (NDE/NDT) methods, such as ground penetrating radar and infrared thermography, are being commonly used by most transportation agencies. Several federal and state agencies are funding significant resources in developing and researching nondestructive test methods for quantitative evaluation of bridge infrastructure to augment visual inspection data. This special issue presents some of the recent advances and applications of nondestructive test methods and structural health monitoring for bridge evaluation and management. A majority of bridge failures are attributed to scour damage that is hard to detect in real time and appropriate preventivemeasures that are hard to apply when scour damage is detected. Hence, scour monitoring is an important topic for transportation owners, especially during high-flood events and in coastal areas. The technical paper “VibrationBased Method and Sensor for Monitoring of Bridge Scour” by Zarafshan et al. introduces a new fiber-optic Bragg grating (FBG) scour sensor. The scour-depth detection is based on the inverse relationship between the fundamental frequency and the length of the sensor rod embedded in the riverbed. This paper describes development of the theoretical basis for the sensor, computational methodology for detection of the riverbed foundation properties, laboratory and small-scale field verification tests, and installation and remote monitoring of scour in a multispan scour critical bridge in Illinois. Cable-stayed bridges are increasingly popular in the United States because of their elegance and the advantages they offer for relatively long spans. When these unique bridges are built, several design assumptions are made and may have to be verified after their construction. A cable-stayed bridge was recently constructed by the Ohio Department of Transportation. Following recent trends, the stays at this bridge were built without the use of grout for the purposes of inspection and possible replacement in the future. The bridge incorporated measures put forth to mitigate stay motion. The technical paper “Cable-Stayed Bridges: Case Study for Ambient Vibration-Based Cable Tension Estimation” by Kangas et al. presents experiments that were performed to determine the viability of using traditional vibration techniques that assume an integral sheath to estimate cable tension with this new configuration. Acoustic emission (AE)-based techniques have been widely used for detecting breaks in suspension and cable-stayed bridges. The technical paper “Detection of the Presence of BrokenWires in Cables by Acoustic Emission Inspection” by Zejli et al. studies AE techniques to detect the presence and location of broken wires in anchorages. Structural health monitoring (SHM) is becoming popular in bridge monitoring. System configuration is very important to effectively monitor performance parameters of interest. The technical paper “Measurement System Configuration for Damage Identification of Continuously Monitored Structures” by Laory et al. discusses a systematic approach to determine the appropriate number and location of sensors to configure measurement systems in which static measurement data are interpreted for damage detection using model-free (nonphysics-based) methods. A railway truss bridge in Zangenberg, Germany, is used as a case study to illustrate the applicability of this proposed approach. The technical paper “Approach to Reduce the Limitations of Modal Identification in Damage Detection Using Limited Field Data for Nondestructive Structural Health Monitoring of a Cable-Stayed Concrete Bridge” by Ismail et al. proposes a technique to reduce the limitations of modal identification in damage detection using reduced field data for nondestructive SHM of a cable-stayed concrete bridge. Use ofmonitoring systems for bridgemaintenance is also gaining popularity. The technical note “Automated Ice Inference and Monitoring on the Veterans’Glass City Skyway Bridge” by Kumpf et al. presents an ice inference system installed on Veterans’ Glass City Skyway (VGCS) Bridge to assist the Ohio Department of Transportation in managing the response to icing events. Variation in modal properties because of the environment has to be studied before they can be correlated to possible structural damage. If variation in modal properties, caused by temperature variations to which the structure is subjected, is less than the variation caused by the damage of interest, thismethod cannot be reliably used for damage detection. Hence, the technical note “Effect of Temperature on Daily Modal Variability of a Steel-Concrete Composite Bridge” by Mosavi et al. investigated the effect of temperature variations onmodal characteristics of a two-span, steel-concrete composite bridge in North Carolina, and addresses the extent and reason of the daily changes observed in its dynamic properties. The deck is a major component of a bridge structure and is in direct contact with live traffic, subjected to inclement weather, and deicing salts are directly applied over it. Deck performance directly affects the durability and life-cycle costs of a bridge. The technical paper “In-Service Condition Assessment of Bridge Deck Using Long-Term Monitoring Data of Strain Response” by Ni et al. focuses on obtaining information of interest (such as peak stress distribution and dynamic internal forces) to structural engineers using data from the instrumented Tsing Ma Bridge. Inspection and evaluation considerations are very important from planning and design stages to preserve the structural health and durability while minimizing life-cycle costs. The technical paper “Damage Evaluation for Concrete Bridge Deck byMeans of StressWave Techniques” by Shiotani et al. focuses on detection of the fatigue damage of concrete bridge decks utilizing propagation of stress waves. This experimental study concludes that by using sparsely arrayed AE technology, global integrity of bridge decks could be carried out so that local NDE methods can be employed for further investigation of areas of interest. Use of ground penetrating radar, impact echo, and infrared thermography based techniques are widely used by bridge owners to augment visual inspection data from bridge decks for informed