Review of Infrastructure Health in Civil Engineering, Volume I: Theory and Components, and Volume II: Applications and Management by Mohammed M. Ettouney and Sreenivas Alampalli

The first volume, Theory and Components, is divided into eight chapters covering overview and theories, components such as sensors, structural identification, damage identification, and decision making.

The background is provided in Chapter 1. Infrastructure health is defined as the “current ability to provide intended level of service in safe, secure, cost-effective manner against hazards it is designed for or expected during its life.” Common visual inspection can only provide 5% of the solution; the techniques outlined in these books can provide the other 95%.

Chapter 2 covers “Elements of Structural Health in Civil Engineering.” The process of health monitoring starts with problem definition and then requires measurements (balancing number of sensors and cost), structural identification, damage detection, and finally decision making. Capacity/demand design is considered to be time dependent, with gradual or abrupt changes starting from construction. Over time, capacity can decrease, and new demands may be put on a structure. Structural health monitoring can update both capacity and demand. The chapter also discusses nondestructive testing (NDT) as a supplement to and in comparison with structural health monitoring (SHM). The NDT techniques described are ultrasound/sonar, acoustic emission, thermography, penetrating radiation, and vibration monitoring, as well as other methods. For example, ultrasound/sonar methods can be used to detect bridge scour.

Case studies, or perhaps more properly short vignettes, are offered in several of the chapters, particularly in Chapter 3. They either refer to landmark bridge collapses or examples of field instrumentation. Examples of bridge failures presented include the Tay Rail Bridge, U.K., Quebec Bridge, Tacoma Narrows Bridge, Silver Bridge (Point Pleasant), Mianus River Bridge, Schoharie Creek Bridge, and Minneapolis I-35W Bridge. Changes in bridge inspections were spurred by the 1967 collapse of the Silver Bridge.

Chapter 4 focuses on theoretical background, with a focus on comparing costs to benefits. The costs consist of fixed costs and variable costs, such as different numbers of sensors. The intent of the approach is to reduce uncertainty to an acceptable level. The approach may be used to show that two different techniques, such as strain measurements or natural frequency (vibration) measurements, may be used together to achieve a much higher probability of detection of damage then either alone.

Different types of sensors can provide different information about a structure, and different sensors and sensor technologies are discussed in Chapter 5. Types of sensors include voltage-generating or piezoelectric sensors, resistive strain sensors, sensors based on change of capacitance, LVDTs, and optics-based sensors, as well as some NDT-specific sensors. Inclinometers measure changes in angles or tilts. Recently, corrosion sensors have been developed. Other sensors are available to measure pressures and temperatures. The emerging technologies of fiber optic sensors are discussed in detail. Wireless sensors are particularly useful for bridge monitoring. Cost, ease of use, and sensitivity can vary widely between sensor types. Remote sensing methods, including infrared thermography and ground penetrating radar, also show considerable promise.

Chapters 6 and 7 address “Structural Identification” and “Damage Identification,” respectively. Structural identification is a technique for improving the accuracy of estimation of structural engineering properties. It is applicable to condition assessment, construction safety, monitoring time-dependent changes, updating analytical models for new and existing structures, damage identification, and accurate life cycle analysis. Damage identification techniques need to be adequate from technical, utility, and cost-benefit standpoints. For each type of damage, such as fatigue or corrosion, there are important damage parameters that should be measured, such as cause, location, and extent. NDT techniques are particularly useful for damage identification. Finally, Chapter 8 addresses the health monitoring decision-making process.

The second volume, Applications and Management, has 11 chapters that provide detailed specific information on a variety of topics. Chapter 1 addresses scour. Scour is one of the most important causes of bridge failure. Damaging mechanisms include local scour at piers and abutments, scour from pressure flow, contraction scour, aggradation and degradation, and stream shifting. Scour monitoring requires specialized sensors and instrumentation, particularly to detect and map scour holes under bridge foundations.

Health monitoring of bridges for seismic events, reviewed in Chapter 2, can be divided into before event, during event, and after event phases. The seismic response may be complicated by the condition of joints and bearings, e.g., corrosion. Piers and abutments may also be damaged. Although a bridge is affected globally by an earthquake, damage may be localized. Some specific examples of bridges instrumented for earthquakes are presented.

Other specific applications discussed in this volume include “Corrosion of Reinforced Concrete Structures” (Chapter 3), “Prestressed Concrete Bridges” (Chapter 4), “Fatigue” (Chapter 5), “Fiber-Reinforced Polymer Bridge Decks” (Chapter 6), and “Fiber-Reinforced Polymers Wrapping” (Chapter 7). These are subject to different failure mechanisms and often require specialized techniques.

The last section of the second book covers asset management, encompassing “Load Testing” (Chapter 8), “Bridge Management and Infrastructure Health” (Chapter 9), “Life Cycle Analysis and Infrastructure Health” (Chapter 10), and the “Role of Structural Health Monitoring in Enhancing Bridge Security” (Chapter 11).

The books have some typographical errors and awkward syntax, and overall would have benefited from tighter copyediting. Many acronyms are used, and at times it is difficult to keep track of them. A master list of acronyms would have been useful, although the index can be used to identify most of them.

Some figures are repeated. For example, Fig. 4.17 is the same as Fig. 7.2 in volume I. In at least one case, a figure is repeated in the same chapter: Figs. 7.2 and 7.70 in volume II are identical.

On the whole, however, these two volumes represent a very useful contribution to this important field. They are likely to be of value to researchers and practitioners in the structural health monitoring field.