What are the key principles and methodologies behind the design and construction of suspension bridges in civil engineering? Discuss the fundamental factors such as material selection, structural analysis techniques, and environmental considerations that engineers must account for when planning and executing the construction of a suspension bridge. Additionally, explore the historical evolution of suspension bridge design and highlight notable examples that showcase innovative engineering solutions. Lastly, analyze the challenges associated with maintaining and retrofitting existing suspension bridges to meet modern safety and performance standards, considering factors such as aging infrastructure, increasing traffic demands, and advances in materials and construction techniques.