What are the key factors that influence the structural integrity of bridges, and how do civil engineers mitigate potential risks associated with these factors during the design and construction phases? Discuss the interplay between material selection, environmental conditions, and load$-$bearing capacities, highlighting the importance of comprehensive risk assessment methodologies in ensuring the long$-$term stability and safety of bridge structures. Additionally, analyze the role of innovative technologies and advanced simulation techniques in predicting and addressing structural vulnerabilities, emphasizing the need for continuous monitoring and maintenance strategies to prolong the lifespan of bridges in various geographical contexts and usage scenarios.