Nondestructive evaluation of concrete bridge columns rehabilitiated with fiber reinforced polymers using digital tap hammer and infrared thermography

Nondestructive Evaluation of Concrete Bridge Columns Rehabilitated With Fiber Reinforced Polymers Using Digital Tap Hammer and Infrared Thermography Andrew Wheeler In 2017, the American Society of Civil Engineers (ASCE) gave bridges in the U.S. a C+ rating. Almost four out of every ten bridges are 50 years or older. In 2016, there were on average 188 million trips across a structural deficient bridge each day. With such a large number of bridges needing replaced or repaired, transportation officials are utilizing various bridge rehabilitation techniques to provide a cost effective solution to such a widespread problem. One rehabilitation technique involves the application of Fiber Reinforced Polymer (FRP) composite wraps to strengthen various bridge components. The initial and in-service, evaluation and acceptance of such FRP systems are crucial to their overall success and serviceability. Previously, several traditional methods such as visual inspection and coin tap testing of FRP composites were accepted as common practice for inspecting the quality of material and structural components. This type of evaluation was very subjective and dependent on the inspector\u27s level of experience. More recently, nondestructive testing (NDT) techniques can identify internal or external defects without affecting the form, or function of a structure. Digital Tap Hammer testing and Infrared Thermography (IRT) are two commonly used NDT techniques for field evaluation of civil infrastructure, because these techniques are user friendly and highly mobile. This problem report reviews the recent advances on the applications of digital tap hammer testing and infrared thermography at identifying defects in various elements of infrastructure and FRP composite wraps applied to bridge columns in southern West Virginia. Additionally, this report includes information on process of repairing dilapidated reinforced concrete columns in preparation for the installation of a FRP system. All of this will serve as a demonstration of how crucial non-destructive evaluation (NDE) is to the success of FRP bridge rehabilitation. Furthermore, the conclusions indicate a need for NDE to ensure quality control of field rehabilitation projects

Bridge Construction Monitoring using LIDAR for Quantified, Objective Quality-Control Quality-Assurance (QOQCQA)

Transportation infrastructure construction quality control and quality assurance demands construction monitoring by field inspectors. Currently, these inspectors monitor infrastructure by measuring and photographing structures. These tasks allow them to assess any correction decision during construction or to inform about the quality of the construction process for the future. In order to promote and objective decisions obtained during infrastructure construction, the proposed research project developed and implemented a methodology to measure construction progress and compared it with the designed 3D shape, quantifying the difference. This proposed project includes implementation for the development of DOT standards that could be added in near future bridge construction documents. The New Mexico Department of Transportation (NMDOT) showed a strong interest in this topic. The experience of the PIs on bridge design and construction, field inspection, and LIDAR technology was integrated in order to evaluate the results with impact both in research and in industry. Specifically, the research results outline recommendations about standards for implementation of technology in specifications for NMDOT or other DOTs

Review of Modern Nondestructive Testing Techniques for Civil Infrastructure

The repair and maintenance of aging infrastructures, in the United States alone, are estimated to have backlogs of trillions of dollars. This has posed widespread concerns about the existing and proposed infrastructures to adequately sustain the quality of life in the near future. Efficient and cost-effective approaches, such as nondestructive testing (NDT), are therefore required to better shape our future. Various NDT techniques have been developed over the past two decades with cutting-edge advances towards investigation and condition assessment of civil infrastructures. While the performance of NDT techniques has reached unparalleled heights, limitations remain. On one side, are the instrument limitations such as penetration depth, resolution, data analysis, accessibility, etc., that are being addressed by the constantly evolving field of NDT. On the other side, there are gaps in the validation and strategic standardization of the techniques for their application in the field. These gaps are further broadened by the lack of experience and understanding of the techniques by the officials with the authority of repairing and maintaining infrastructures, such as the federal and state Department of Transportation (DOT) personnel. This report aims to be a comprehensive review of state-of-the-art nondestructive testing techniques such as Impact-echo, Ultrasonic Testing, Infrared Thermography, and Digital Tap Hammer. Research and innovation integrated into contemporary features and possible future trends of such techniques for rapid and inclusive condition assessment of concrete and timber structural members are presented in the report. As the future of NDT, this report reviews the alignment of NDT techniques with novel automated technologies, including Unmanned Aerial System (UAS). Such practices have shown promising results in the effective and proactive condition assessment of structures with greater ease and at significantly lower cost, without the need for extensive knowledge about the techniques. Hence, it is recommended that the responsible bodies such as federal and state DOTs utilize nondestructive testing techniques to improve the resiliency and service life of our infrastructures effectively

Displacement Measurement Using a Laser Doppler Vibrometer Mounted on an Unmanned Aerial Vehicles

The railroad network in the united states is one of the best in the world, handling around 40 percent of all US freight movement. To maintain the serviceability and cost-effective operation of the railway infrastructure, regular monitoring is essential. Bridges are a critical part of the railway infrastructure and their timely maintenance and repair are important. Measuring transverse bridge displacement under train loading can assist to determine the bridge condition. The traditional methods available for transverse displacement measurement include Linear Variable Differential Transducers (LVDT). However, irregular terrain, remote and inaccessible locations, and the height of railroad bridges make implementation of these sensors for transverse displacement measurement either inadequate, or risky and time-consuming, and sometimes not possible altogether. Alternatively, railroads can monitor transverse bridge displacement using non-contact sensing with instruments such as robotic total station (RTS) and high-speed cameras. In recent years, the use of Laser Doppler Vibrometers (LDV) has started to draw some attention in the field of non-contact transverse bridge displacement measurement. However, in these applications, the instruments are generally placed on a fixed reference close to the bridge. It is not always possible to find this fixed reference point, especially when a bridge is spanning over a large opening, like a water body. In addition, a fixed reference point would require calibration of the measurement for every different bridge individually. Researchers use Unmanned Aerial Systems (UAS) to acquire aerial images for Structural Health Monitoring (SHM). However, this approach requires extensive image post-processing, and in general, complex algorithms development. More importantly, current systems are not capable of measuring dynamic transverse displacements. This MS Thesis presents a novel approach to measure transverse bridge dynamic displacements using non-contact vibrometers mounted on unmanned aerial system. This research proposes algorithms for compensating the measurement errors due to the angular and linear movement vibrometer to obtain accurate transverse bridge displacement measurements. These algorithms are verified in the laboratory using a shake table simulating bridge vibration, and vibrometer movement simulating the motions of a UAS. The results of these tests show that the signal difference between the measured displacements of a moving LDV system and a LVDT are less than 10%. The Root mean squared (RMS) differences are less than 5%. This research also implements and tests the UAV-LDV system in the field. The results of these experiments show that the signal difference between LVDT and the UAS-LDV system is 10%. The RMS difference between the two systems is 8%. The results of this research show that the UAS and LDV can be used together to measure the dynamic transverse bridge displacements and could become an effective tool for campaign monitoring of railroad bridges with application for railroad bridge maintenance and repair prioritization