Fiber-Optic Sensors For Infrastructure Health Monitoring, Volume I

Introduction and Fundamental Concepts

Zhishen Wu, Jian Zhang, Mohammad Noori

• Publisher: Momentum Press
• Year: 2018
• Print ISBN: 9781945612244
• eBook ISBN: 9781945612251
• Topic: Technik & Maschinenbau
• Subtopic: Bauingenieurwesen

The topic of this book, biotechnology, is about gene manipulation.

The authors will explain how genetic modification can enhance and repair DNA at the molecular level to cure genetic conditions, better plant growth, diagnose and fix major genetic disorders, and cancer, as well as learning about the human genome.

In addition, some ethical and legal cases are presented and a new tool, CRISPR, is explained. It will move biotechnology along on a brisk yet comprehensible pace.

CHAPTER 1

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INTRODUCTION

1.1 MOTIVATION FOR STRUCTURAL MAINTENANCE AND MANAGEMENT

1.1.1 INTRODUCTION

Civil infrastructure and lifeline systems are the bedrocks of any functional society, regardless of culture, religious belief, geographical location, technological advancement, and economic development. These infrastructure systems include bridges, buildings, tunnels, airports, transportation systems, and other life-supporting facilities such as water supply and distribution, waste and wastewater systems, power plants and grids, telecommunications, and oil and gas installations. A healthy infrastructure system supports the economic well-being of a society by facilitating the production of goods and services and their effective and efficient distribution. Hence, the sustainable economic growth, productivity, and the prosperity of any nation depend heavily on the safety, durability, health, and resilience of its civil infrastructure systems. The civil infrastructure around the world, which represents an enormous financial investment, faces a deterioration problem of unprecedented magnitude. Large-scale engineering structures in developed countries have already begun experiencing deterioration and aging. Figures 1.1 and 1.2 show the number of bridges starting to go through a serious aging process, in a recurring period of 2 to 4 years, in the United States and Japan, respectively. As these graphs show, the United States began experiencing a drastic growth in number of bridges that started to age and deteriorate in the 1980s, and this process began in Japan in the 2010s. Over the past decade, the problem of deteriorating infrastructure has become a topic of critical importance in Europe, and to an equal extent in the United States and Japan.

Figure 1.1. Deterioration of bridges in the United States

Source: MLITT (2013).

Figure 1.2. Deterioration of bridges in Japan

Source: MLITT (2013).

1.1.2 DETERIORATION OF INFRASTRUCTURE SYSTEMS

Deterioration of infrastructure systems due to aging and material degradation is a global phenomenon regardless of geographical location, the state of economy, or technological advancement. This problem has become the source of a great threat to public safety and investment, as well as the integrity of infrastructure. The sustainable economic growth, productivity, and the well-being of any nation depend heavily on safety, durability, health, and resilience of its civil infrastructure systems. In the following sections, these four important aspects of an infrastructure system, which define the integrity or the deterioration of infrastructure systems, are briefly discussed.

1.1.2.1 Structural Safety

Structural safety and reliability is the determination of the effects of materials, construction, modeling, and loadings on physical structures and their components. Over the past few decades the academic and industrial research communities have paid significant attention to these and carried out extensive studies in the area of structural safety and reliability of civil structures. However, lack of adequate attention to this important area, especially in the design codes and constriction practices, in many societies, has contributed to the deterioration, and sometimes catastrophic failure, of infrastructure systems and has posed a threat to further economic growth, safety, and prosperity, especially as the pace of urbanization is rapidly increasing worldwide. Several tragic incidents of catastrophic structural failure, attributed to the lack of attention to structural reliability and performance, especially due to man-made disasters, have been reported in various parts of the world over the past three decades. The sudden collapse of Sunshine Skyway Bridge in Florida on May 9, 1980, due to the collision of the freighter MV Summit Venture with a pier during a storm, sent over 365 m (about 1,200 ft) of the bridge plummeting into Tampa Bay, caused six automobiles and a bus to fall 45 m while 35 people lost their lives. The 1994 Northridge earthquake in southern California, originally classified as safe, resulted in the failure of several hundreds of steel frame structures. The Seongsu Bridge connecting Seongsu-dong and Apgujeong-dong of Gangnam-gu, in Seoul, collapsed on October 21, 1994, due to the sudden failure of a 48-m slab. This collapse was caused by the failure of bolted and welded connections of steel trusses that supported the bridge slab. The Hoan Bridge in Wisconsin was temporarily closed on December 13, 2000, after two of the three support beams of the lakefront span failed, causing the north-bound lanes to buckle and sag by several feet and leaving the span in a near collapsed state. Structural deterioration due to aging was responsible for the collapse of the Hintze Ribeiro Bridge in Castelo de Paiva, Portugal, on March 4, 2001. This resulted in the immediate closure of dozens of other bridges across Portugal for rehabilitation and repair. The more recent tragic collapse of the 40-year-old bridge in Minneapolis, during the rush-hour of August 1, 2007, shown in Figure 1.3, highlighted the urgent needs for improving the ongoing structural inspection and maintenance practices. This event underscored the importance of safety and reliability assessment of civil infrastructure despite the biannual comprehensive bridge inspections that certified the bridge to be safe

Figure 1.3. Collapse of I-35W Bridge in Minneapolis

Figure 1.4 shows the sudden collapse of 36-year-old overpass on the Boulevard de la Concorde in Laval, a suburb of Montreal, Canada, and Kisogawa Ohashi Bridge in Mie Prefecture of Japan. The collapse of the de la Concorde Bridge was attributed to design error caused mainly by underestimation of the traffic volumes. On the other hand, the failure of Kisogawa Ohashi Bridge was caused by the fracture of diagonal member of steel truss on National Road 23. Not only did these tragic accidents cause tremendous casualties and economic losses, but they also attracted significant public attention due to drastic social impact.

Figure 1.4. Collapse of de la Concorde overpass in Japan on September 30, 2006

There are other causes and factors, as part of structural reliability and safety assessment, which have contributed to the deterioration and failure of structures. As reported by the U.S. Department of Defense, in 2013 an estimated $20.8 billion annual expense were related to preventing and mitigating corrosion of assets, including facilities and infrastructure. As of 2007, over 50 percent of the world population live in cities, and the balance has tipped toward urbanization and subsequently an increased demand on infrastructure and urban safety. In the United States alone, it is expected that over the next 15 years 50 percent of the nation’s bridges, nearly 300,000, exceed their intended 50-year lives, requiring more vigilant inspections. Moreover, thousands of commercial and other aircrafts are aging. These are only a few examples and reasons that demonstrate the importance of the consideration of reliability and safety assessment of infrastructure systems and the catastrophic impacts that may result due to lack of such consideration.

1.1.2.2 Structural Durability

Structural durability and life-cycle assessment of a structure are also components of structural reliability analysis and uncertainty quantification. The long-term durability and longevity of infrastructural systems is a topic of growing concern. This problem has been intensified as a result of the rapid urban development and urbanization since early 2000, as well as due to the fact that the life-cycle assessment and uncertainty quantification were not considered in the design and construction of the vast majority of infrastructure systems that are currently in service. For instance, when the Severn Bridge between England and Wales was opened in 1960, its lightweight deck was regarded as a landmark in aerodynamic design, and it was estimated that the bridge would function with high level of safety for a few decades. However, the bridge began to fall apart under the increasing traffic load 15 years after its construction. This was due to lack of taking into account numerous uncertainties associated with the design, materials, and other aspects. The collapse of Mianus River Bridge on Interstate 95 in the state of Connecticut on June 28, 1983, was attributed to corrosion and fatigue loading of steel support members due to heavy traffic volume, as well as eventual failure of the pin and hanger assembly supporting the span. The effect of these factors which play important roles in estimating the life cycle, and thus the durability, was considered in the design of this bridge.

What raises concern is that despite the growing trend in infrastructure aging and deterioration, the existing practices, and even numerous building codes, do not consider the need for a radically new approach to address the infrastructure deterioration by taking into account the structural reliability analysis and uncertainty quantifications. For instance, the Chinese Standard of Durability Design of Concrete Structures defines structural durability as “structural component enables itself to keep applicability and safety during designed service life in terms of environmental effect, repair and usage confirmed by design.” This criteria is defined, and is based on, the Structural Reliability Design Standard that states, “[W]orsening of structural material ability will not cause unaccepted failure probability in specified working conditions and due period.” It might be true that under ideal design circumstances and normal use a structure is able to serve through the end of the specified designed service life. However, and unfortunately, due to ever-increasing demand worldwide on infrastructure systems—which has resulted due to rapid and unexpected growth in urbanization, transportation, population, as well as environmental, climate change, and natural hazards—these perceived “normal” conditions have changed drastically and are no longer present. Fortunately, over the past two decades, developed countries have begun investing greatly in scientific research in reliability assessment and reliability-based design. Findings from these research studies have resulted in enhancing the durability of construction materials and, subsequently, infrastructures. For instance, to improve the durability of concrete structures we have witnessed encouraging developments. As an example, to address the problem with salt scaling and freeze-thaw damage of roads and bridges in Ontario, Canada, smallest thickness of concrete and steel containment vessels increased gradually from 2.5 cm in the 1950s to 4 to 6 cm and then to 7 cm in the 1970s. The lowest grade of concrete strength increased from C25 in the 1950s to C40. The requirements for using concrete in bridge panels shifted from not considering additional air-entraining agent, and no requirement for a waterproof layer, to strict usage of air-entraining, and utilizing advanced waterproof films and epoxy-coated steel. In China, although an extensive and large volume of research in structural durability has been carried out over the past two decades, the relatively short life of infrastructures is still a challenging problem that needs to be overcome.

In order to better understand the severity of this problem in China, let us consider Japan as an example. Prior to 1970, the service life of roads and bridges in Japan ranged from 30 to 40 years. In 1971 design standard of bridge deck slab was updated. Subsequently, in 1973 the design standards of roads were updated. In 1984 the standard and measures for preventing salt corrosion were updated. In 1989 related requirements for alkaline aggregates were updated, and in 2001 standard of fatigue design was updated. In the meantime numerous other regulations and guidelines regarding durability and service-life improvement were established. These measures gradually improved the expected service life of bridges and resulted in significant improvement in the service-life expectancy of bridges from 30 to 40 years to 100 hundred years. The improvement in durability of Japanese civil structure is shown in Figure 1.5. On the contrary, according to one research investigation in the 1980s, in China construction section, it has been found that most domestic industrial constructions require a major repair after serving 25 to 30 years. Constructed facilities built in severe conditions can only be in service for 15 to 20 years. Civil and public buildings, on the other hand, have relatively longer service life of more than 50 years. However, the exterior components such as balconies, rooftops, terraces, and walkways suffer from a low service life of 30 to 40 years. For major infrastructure systems such as bridges, ports, and loading ducks, durability is comparatively worse. Many constructions may face serious problems such as steel corrosion and concrete cracking only in a few years after completion of the project owing to using a steel concrete covering layer that is too thin, as well as other contributing factors such as poor compactness. Harbor wharves may need major repairs after being in service for only about 10 years due to longitudinal cracking and peeling in concrete. A few factors that may influence structural durability of concrete and need to be investigated in Chinese construction practices are concrete carbonization, concrete Alkali aggregate reaction , concrete freeze–thaw damage, corrosion due to a corrosive environment (such as sulfate and sea water), abnormal wear and deterioration, reinforcement corrosion, and so on. Overall, development of standards and construction guidelines based on structural risk and reliability analysis is badly needed in China.

Figure 1.5. Change of service life and design standard of the road bridge in Japan (MLC)

1.1.2.3 Structural Health

Structural health of civil infrastructure systems is a necessity for the prosperity of any society and for economic development. The criteria and the requirements for structural safety, durability, and health are interrelated. Maintaining the structural health provides an assurance for the structural safety and durability. Thus, any deterioration or even small-scale local damages within a structure may threaten the structural health, adversely affect its safety/reliability, and pose potential challenge to its durability and life cycle. For instance, let us consider the following “health” problems pertaining to structural health in bridges. One common type of damage to structural health is crack. In long-span steel concrete bridges cracks may regularly develop caused by subjectively oversight factors including design, structural behavior, materials, and/or construction flaws. They may also be caused by factors sparked objectively such as overload, thermal loading, concrete shrinkage, and creep. For instance, Jinan Yellow River Bridge built in 1982 has developed 1386 roof cracks, 11 bottom cracks, 52 abdomen cracks, and 1794 clapboard cracks. Chongqing Shimen Yangtze River Bridge, constructed in 1988, presently has 233 roof cracks, 84 abdomen cracks, and 78 clapboard cracks. In 1987 the Alex Fraser Bridge in Vancouver, at the time of completion acclaimed the longest cable-stayed bridge, developed cracks only 1 year after it opened. Another source of health issue is excessive deflection in the main span of bridges. For long-span prestressed concrete girder bridges the biggest “health problem” that adversely affects their durability is the excessive deflection of main span...

Table of contents

• Cover
• Half Title Page
• Title Page
• Copyright Page
• Contents
• ACKNOLWEDGMENTS
• CHAPTER 1 INTRODUCTION
• CHAPTER 2 FIBER-OPTIC SENSING TECHNOLOGIES
• CHAPTER 3 AREA DISTRIBUTED SENSING /MONITORING UTILIZING FIBER -OPTIC SENSORS (FOS)
• CHAPTER 4 DESIGN OF THE FOS-BASED STRUCTURAL HEALTH MONITORING SYSTEM
• ABOUT THE AUTHORS
• INDEX