Shivprakash Iyer

A robust approach for automatic detection and segmentation of cracks in underground pipeline images

Cracks in underground pipeline images are indicative of the condition of buried infrastructures like sewers and water mains. This paper presents a three step method to identify and extract crack-like structures from pipe images whose contrast have been enhanced. The proposed method is based on mathematical morphology and curvature evaluation that detects crack-like patterns in a noisy environment. Careful observation reveals that the cracks resemble a tree-like geometry in most cases which can be a usable feature for registration between successive images of the same region taken from various depths in the thickness of the buried pipe (3D visualization). In this study, segmentation is performed with respect to a precise geometric model to define crack-like patterns. Cracks in pipe images can be defined as clearly visible patterns (darkest in the image), locally linear and branching in a piece-wise fashion. First, the cracks are enhanced by mathematical morphology with respect to their spatial properties. In order to differentiate cracks from analogous background patterns, cross-curvature evaluation followed by linear filtering is performed. We discuss its implementation on 225 pipe images taken from various cities in North America and statistically evaluate its accuracy and robustness with respect to varying pipe background color, crack geometries and background noise.

Non-contact ultrasonic sensor and state-of-the-art camera for automated pipe inspection

The United States is critically dependent on natural gas, petroleum liquids, water and sewer transported through pipelines. The infrastructure that currently transports these resources is aging, with a significant fraction being more than 50 years old. The enormity of the problem of deteriorating pipeline infrastructure is apparent. Since rebuilding the piping system is not financially realistic, pipeline operators require the capacity to monitor the condition of buried pipes. Thus, a reliable pipeline assessment system is necessary so that pipeline operators can develop cost-effective maintenance, repair, and rehabilitation programs. A research is underway at Penn State to determine if non-contact ultrasound (NCU) can be used to quantify the state of defects in pipelines. The goal of this research is to develop a test method that can add complementary pipe information to existing surface image assessments. Superposing an ultrasonic image onto an optical image of the sample creates a visual context in which interpretation and analysis are easily achieved.

Semi-Automated Faulting Measurement for Rigid Pavements

Faulting measurements have traditionally been conducted manually by means of fault meters. However, operating any manual device such as a fault meter close to vehicular traffic is hazardous to both the operator and the traveling public. Automated methods, such as those associated with high-speed profilers, offer a safer, more efficient, and cost-effective alternative. Therefore, there is a need to develop an automated method for measuring joint faulting with longitudinal profiles from high-speed profilers. A study was initiated with the primary objective of determining an appropriate profiler sampling interval to accurately locate transverse joints. A secondary objective was to determine how well faulting estimated from profile elevation compares with faulting measured with a Georgia fault meter. An algorithm was developed: it can accurately detect on average 95% of transverse joints from profile data collected at highway speed with a 0.68-in. (17.3-mm) sampling interval. This algorithm was also adapted to estimate faulting measured with a Georgia fault meter (AASHTO R36-04). Although the algorithm results are repeatable, the algorithm overestimated the faulting at joints by 0.05 in. (1.3 mm) to 0.06 in. (1.5 mm) compared with faulting measured with the Georgia fault meter.

Non-contact ultrasonic imaging for post-tensioned bridges to investigate corrosion and void status

Corrosion of the nations transportation infrastructure is a widespread and costly problem. Recent corrosion problems in post-tensioned bridge structures have increased the need for a reliable method for determining grout voids and level of corrosion in post-tensioned tendons. Corrosion monitoring techniques such as half-cell potential and corrosion rate measurements face problems when used in this type of structure and standard NDE (nondestructive evaluation) methods such as impact-echo have also encountered problems. This study begins the evaluation of a method called C-Scan ultrasonic imaging to evaluate grouted post-tensioned tendons. While this paper focuses on post-tensioning applications, the C-Scan technique may be valuable for investigation of any type of reinforced concrete structure.

ULTRASONIC C-SCAN IMAGING: PRELIMINARY EVALUATION FOR CORROSION AND VOID DETECTION IN POSTTENSIONED TENDONS

Corrosion of the nation’s transportation infrastructure is a widespread and costly problem. The most prevalent durability issue in reinforced concrete structures is chloride-induced corrosion of the reinforcing steel. A reliable method of determining grout voids and corrosion levels in posttensioned bridge structures is needed. Traditional techniques of corrosion monitoring (e.g., half-cell potential and corrosion rate measurement) are problematic when used in this type of structure, as are standard nondestructive evaluation (NDE) methods, such as impact echo. C-scan imaging, an ultrasonic technique used primarily in the composites industry for detecting delamination, is examined as a method of evaluating grouted posttensioned tendons. This method exhibits many promising qualities: it can be used for internal or external tendons and on metal or plastic ducts; access to only one side of a specimen is required; strong imaging allows easy interpretation of results; the technique poses no risk to users or the environment; and the method has strong potential for development as a handheld field tool. The C-scan technique may be valuable for the investigation of not only posttensioning applications but other types of reinforced concrete structures as well. Results of preliminary investigations on lab specimens indicate that the C-scan technique holds promise. The ultimate goal of the research is to provide a user-friendly, robust system for the NDE of posttensioned tendons for voids, corrosion, and wire breaks. Recommendations for optimal acquisition and processing techniques as well as for the future development of the equipment as a field tool are proposed.

Ultrasonic nondestructive evaluation in thin‐walled concrete for flaw detection

Accurate inspection techniques for today’s infrastructure have become an area of great interest. Several ultrasonic techniques for testing and evaluating concrete have been established and show great promise. However, much of the work is concerned with concrete piles or thick‐walled specimen (greater than 500 mm). Vast amounts of concrete piping in sewer systems and water mains require testing techniques applicable to thinner‐walled systems (less than 100 mm). This work aims to extend ultrasonic inspection techniques to thin‐walled systems. Impact‐echo and resonant ultrasonic spectroscopy (RUS) techniques are explored. Finite‐element models have been developed to describe the propagation characteristics in different specimen. Several specimens have been tested experimentally to determine the effects of steel reinforcements, pipe curvature, and simulated defects. The influence of sensor configuration, transducer characterization, and data capture on measurement accuracy and inspection time is examined. The...