Acoustic Emission Monitoring of Prefabricated and Prestressed Reinforced Concrete Bridge Elements and Structures

Prefabricated and pre-stressed reinforced concrete beams and girders are integral components of many highway structures, including those build by rapid construction techniques. Concerns exist regarding the development of cracks during curing, form removal, detensioning, transport, installation, and operation. Non-destructive, Acoustic Emission (AE) sensing techniques have the potential for detecting and locating cracking in prefabricated, prestressed concrete girders used as Prefabricated Bridge Elements and Systems (PBES) in rapid construction practices as part of a Quality Assurance/Quality Control (QA/QC) program. AE sensing records transient elastic waves produced by the release of stored elastic energy resulting in plastic deformations (i.e., crack nucleation and growth) with an array of point sensors. The AE instrument system is relatively portable which can allow for it to be an option for both off-site fabrication QA/QC as well as on-site field QA/QC. This report presents a multi-stage research initiative on acoustic emission measurements of prefabricated and pre-stressed concrete beams used in highway bridge construction during detensioning, craned removal from formwork and transport to bridge sites, along with supporting laboratory tests and numerical analysis. The project objectives are: 1. Identify suitable instruments to monitor pre-stressed and/or post-tensioned concrete girders for cracking activity; 2. Design and develop a reusable instrumentation package; 3. Measure performance and condition of concrete girders during fabrication and transport; 4. Identify test protocols and possible accept/fix/reject criteria for structural elements based on information from monitoring system; and 5. Develop plans for reusing monitoring instruments on multiple bridge projects. Presented are results from laboratory, full-scale girder fabrication, and transport monitoring, along with recommendations for future testing procedures and quality assurance protocol development

Cost-Effective and Rapid Concrete Repair Techniques

Concrete is a principal component of many transportation structures. While highly durable, a variety of processes degrade and damage concrete. Replacement is expensive. Many cases warrant repair instead of replacement. Since many damage processes are progressive, early and properly timed repairs can reduce costs. Overall lifetime cost of ownership approach to selection and design of repairs has merit, but requires good information about costs and outcomes. There is a possibility that effective timing and application of repairs can be of great benefit to maintenance activities – including lifetime costs and rapid techniques that allow for expedited designs of repairs and minimizing repair times. The specific objectives of this research were to: (1) Assess present practices of concrete repair – This will establish what is being done in Vermont and elsewhere. (2) Develop flow chart of decision-making and options for repair practice and evaluation – This will create a guide with recommendations for maintenance personnel and engineers. (3) Develop procedures for integrating repair options and decisions into asset management – This will aid in reducing lifetime costs of ownership and assist in statewide maintenance planning. (4) Recommend areas for further study and tech transfer to make cost effective repairs

Self-healing cable for extreme environments

Self-healing cable apparatus and methods disclosed. The self-healing cable has a central core surrounded by an adaptive cover that can extend over the entire length of the self-healing cable or just one or more portions of the self-healing cable. The adaptive cover includes an axially and/or radially compressible-expandable (C/E) foam layer that maintains its properties over a wide range of environmental conditions. A tape layer surrounds the C/E layer and is applied so that it surrounds and axially and/or radially compresses the C/E layer. When the self-healing cable is subjected to a damaging force that causes a breach in the outer jacket and the tape layer, the corresponding localized axially and/or radially compressed portion of the C/E foam layer expands into the breach to form a corresponding localized self-healed region. The self-healing cable is manufacturable with present-day commercial self-healing cable manufacturing tools

Scour Damage to Vermont Bridges

Scour is by far the primary cause of bridge failures in the United States. Regionally, the vulnerability of bridges to flood damage became evident from the damage seen to Vermont bridges in the 2011 Tropical Storm Irene. Successfully mitigating scour-related problems associated with bridges depends on our ability to reliably estimate scour potential, design effective scour prevention and countermeasures, design safe and economical foundation elements accounting for scour potential, and design reliable and economically feasible monitoring systems. This report presents research on two particular aspects related to bridge scour – 1) System-level analysis of damage observed at Vermont bridges from Tropical Storm Irene. Example case studies are presented including description of the bridge damage, as well as the pre-storm condition of the bridges. Statistical comparison to non-damaged bridges is included to identify significant factors that determine bridge vulnerability to storm damage; and 2)Development of a low-cost scour sensor suitable for monitoring scour and redeposition continuously and communicating the readings wirelessly in real time to stake holders

Prediction and mitigation of scour and scour damage to Vermont bridges

Over 300 Vermont bridges were damaged in the 2011 Tropical Storm Irene and many experienced significant scour. Successfully mitigating bridge scour in future flooding events depends on our ability to reliably estimate scour potential, design safe and economical foundation elements accounting for scour potential, design effective scour prevention and countermeasures, and design reliable and economically feasible monitoring systems, which served as the motivation for this study. This project sought to leverage data on existing Vermont bridges and case studies of bridge scour damage, and integrate available information from stream geomorphology to aid in prediction of bridge scour vulnerability. Tropical Storm Irene’s impact on Vermont bridges was used as a case study, providing damage information on a wide range of bridges throughout the State. Multiple data sources were combined in an effort to include data, which represents the complex, interconnected processes of stream stability and bridge scour, then identify and incorporate feature that would be useful in a probabilistic model to predict bridge susceptibility to scour damage. The research also sought to identify features that could be included in inspections and into a scour rating system that are capable of assessing network-level scour vulnerability of bridges more holistically. This research also sought to review existing scour countermeasures and scour monitoring technologies available in the literature and examine efficacy of new, indirect scour countermeasures and passive scour monitoring techniques. The specific objectives of this research were to: (1) review the literature and identify methods/technologies that are adaptable to Vermont; (2) analyze Tropical Storm Irene bridge damage information and observations by collecting and geo-referencing all available bridge records and stream geomorphic assessment data into a comprehensive database for identifying features that best represent bridge scour damage; (3) conduct watershed analysis on all bridges, including creation of stream power data to assess if watershed stream power improves the prediction of bridge scour damage; and (4) investigate new scour countermeasures and monitoring technologies, and provide recommendations on implementations

Catastrophic failure of nacre under pure shear stresses of torsion

Nacre, a composite made from biogenic aragonite and proteins, exhibits excellent strength and toughness. Here, we show that nacreous sections can exhibit complete brittle fracture along the tablet interfaces at the proportional limit under pure shear stresses of torsion. We quantitatively separate the initial tablet sliding primarily resisted by nanoscale aragonite pillars from the following sliding resisted by various microscale toughening mechanisms. We postulate that the ductility of nacre can be limited by eliminating tablet interactions during crack propagations. Our findings should help pursuing further insights of layered materials by using torsion

Mechano-Magnetic Telemetry for Underground Water Infrastructure Monitoring

This study reports on the theory of operation, design principles, and results from laboratory and field tests of a magnetic telemetry system for communication with underground infrastructure sensors using rotating permanent magnets as the sources and compact magnetometers as the receivers. Many cities seek ways to monitor underground water pipes with centrally managed Internet of Things (IoT) systems. This requires the development of numerous reliable low-cost wireless sensors, such as moisture sensors and flow meters, which can transmit information from subterranean pipes to surface-mounted receivers. Traditional megahertz radio communication systems are often unable to penetrate through multiple feet of earthen and manmade materials and have impractically large energy requirements which preclude the use of long-life batteries, require complex (and expensive) built-in energy harvesting systems, or long leads that run antennas near to the surface. Low-power magnetic signaling systems do not suffer from this drawback: low-frequency electromagnetic waves readily penetrate through several feet of earth and water. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for underground IoT-type sensing applications. However, rotating a permanent magnet creates a completely reversing oscillating magnetic field. The recent proliferation of strong rare-earth permanent magnets and high-sensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. The system used in this study represents a novel combination of megahertz radio and magnetic signaling techniques for the purposes of underground infrastructure monitoring. In this study, two subterranean infrastructure sensors exploit this phenomenon to transmit information to an aboveground radio-networked magnetometer receiver. A flow meter uses a propeller to directly rotate a diametrically magnetized neodymium magnet. A moisture sensor rotates a magnet with a low-power electric motor. Laboratory performance and field tests establish the capabilities of magnetic telemetry for IoT-linked leak-detection sensors. Remote datalogging with encryption demonstrates the viability of integrating sensors and surface receivers into a LoRa wireless IoT network

SMASIS2010-3830 SMART SELF SEALING PRESSURE VESSELS AND STRUCTURAL PANELS

ABSTRACT Structural systems that autonomously repair damage have the potential for enhanced longevities and performance envelopes. This paper addresses the issue of autonomously sensing and controlling self-repair processes in structural systems. Such an approach has the potential to expand upon self healing materials technology to the development of engineered smart self-healing structural systems. This involves coordinating damage-sensing capabilities with control of the healing processes. Much of the conceptual underpinning of this work comes from biological systems that routinely combine sensing with healing actions that span multiple spatial and temporal scales. The specific details and modalities of the response depend on the extent and vital threat of the damage