This book addresses the fatigue behavior of riveted connections from ancient Portuguese metallic bridges as well as the fatigue crack propagation behavior of related materials. Some examples of the fatigue assessment of long-term operated metallic bridges are presented and discussed. The phenomena of degradation is discussed in chapter 2, devoted to the material aspects of the Degradation Theory. Applications of structural integrity assessment/ corrosion aspects are discussed in chapter 3; case studies in chapter 4 and fatigue and fracture test results in chapter 5.