Occasionally, failures of engineering systems catch public attention and raise concern over the safety and performance of the systems. The cause of the malfunction and failure could be natural phenomena, human error, or deficiency in design and manufacture. Reliability engineering is a field developed in recent decades to deal with such safety and performance issues.
Based on their setup, engineering systems can be classified loosely into two types, namely, manufactured systems and infrastructural systems. Manufactured systems are those equipment and assemblies, such as pumping stations, cars, computers, airplanes, bulldozers, and tractors, that are designed, fabricated, operated, and moved around totally by humans. Infrastructural systems are the structures or facilities, such as bridges, buildings, dams, roads, levees, sewers, pipelines, power plants, and coastal and offshore structures, that are built on, attached to, or associated with the ground or earth. Most civil, environmental, and agricultural engineering systems belong to infrastructural systems, whereas the great majority of electronic, mechanical, industrial, and aeronautical/aerospace engineering systems are manufactured systems.
The major causes of failure for these two types of systems are different. Failure of infrastructures usually is caused by natural processes, such as geophysical extremes of earthquakes, tornadoes, hurricanes or typhoons, heavy rain or snow, and floods, that are beyond human control. Failure of such infrastructural systems seldom happens, but if a failure occurs, the consequences often are disastrous. Replacement after failure, if feasible, usually involves so many changes and improvements that it is essentially a different, new system.
On the other hand, the major causes of failure for manufactured systems are wear and tear, deterioration, and improper operation, which could be dealt with by human abilities but may not be economically desirable. Their failures usually do not result in extended major calamity. If failed, they can be repaired or replaced without affecting their service environment. Their reliability analyses are usually for production, quality control, or for maintenance service and warranty planning. Thus failures of manufactured systems often are classified into repairable and nonrepairable types. Conversely, failures of infrastructural systems can be classified as structural failures and functional failures, as will be explained in Sec. 1.5.
The approaches and purposes of reliability analysis for these two types of systems are related but different. As described in Sec. 1.3, reliability analysis for manufactured systems has a history of more than 70 years and is relatively more developed than reliability analysis for civil engineering infrastructural systems. Many books and papers have been published on reliability engineering for manufactured systems. One can refer to Ireson and Coombs (1988), Kececioglu (1991), Ushakov (1994), Pecht (1995), Birolini (1999), and Modarres et al. (1999) for extensive lists of the literature. Conversely, this book deals mainly with reliability issues for hydrosystem engineering infrastructures. Nonetheless, it should be noted that many of the basic theories and methods are applicable to both systems.
