**4. Resilience and reliability**

Disaster response is another major concern in the design of engineering systems. The ability of a system to recover after being exposed to a major event, whether that is a natural hazard and/or a man-made event, is one of the major concerns that engineering systems are now required to address [4, 5]. Resilience is known to reflect such ability, while reliability is meant to reflect the ability of such system to survive such events. Recent performance-based design approach led the way to further interest in structural resilience, which is concerned with such ability, at the component and system levels.

Resilience could be considered at three main levels, namely, structure and/or system level, infrastructure network level, and finally the community/urban level [5]. It is important to ensure the ability of systems, at all three levels, to recover and function satisfactorily after a major event.

At the structure and/or system level, this relates to structural systems and their redundancy which allow them to operate and function safely and reliably, even after such an event and until regain of full capacity is achieved. This is achieved through an acceptable level of redundancy that allows continuing function even after a local damage and/or failure occurs to one or more underlying components.

At the infrastructure level, this relates to the ability of highways, power grids, and all other utility networks to function and their inherent redundancy to ensure sufficient operation of such networks, if some damage is incurred and to ensure that such local damage does not propagate through the whole network and cause full disruption of services.

At the community and/or urban level, this relates to the socioeconomic performance of communities after a major disruptive event and the ability to recover and function normally.

The performance at these three levels is expected to be evaluated and expressed in terms of reliability measures since all such events are uncertain in nature. There are several attempts to evaluate and assess resilience measures that are available in the literature [4, 5, 22].

### **5. Health monitoring and reliability**

Health monitoring relates to the continuous supervising of the performance of civil structures and systems throughout their lifetime. The advances in electronic devices, computer systems, and sensor technology paved the way for the development of integrated applications that can monitor the performance of civil systems, real time [23], and send alerts and alarming messages to the relevant authorities about potential damage and or recommended maintenance procedures.

Such a mechanism would enhance the reliability of targeted systems and ensures their continuous uninterrupted operation throughout their lifetime. However, the reliability of such systems is of major concern, since they comprise several components that are expected to operate integrally within a preset framework and work seemingly within a certain system [23].

The integration of structural health monitoring, within an engineering system, is expected to enhance its reliability. It is important to consider the reliability, of such system, in two main levels, the first is the reliability of the structural health monitoring system itself and the second is the reliability of the monitored engineering system, including the health monitoring enhancement. There is not enough research activity in reliability of structural health monitoring systems and their impact on the reliability of monitored systems. This requires a targeted research effort in this area which would support the practical implementation of such systems, especially when dealing with the conservation of historic cultural heritage.

*Introductory Chapter: Innovative Manifestations of Reliability-Based Design DOI: http://dx.doi.org/10.5772/intechopen.108658*
