Examine the process and considerations involved in the design and analysis of a multi$-$span bridge structure, focusing on aspects such as load distribution, material selection, environmental impact, and long$-$term maintenance. Discuss the theoretical underpinnings of each aspect, including the principles of structural analysis used to determine the load distribution across different spans, the criteria for selecting appropriate construction materials given the bridge's intended use and environmental conditions, and the strategies for minimizing environmental impact during both construction and the operational lifespan of the bridge. Additionally, explore the importance of planning for long$-$term maintenance and the methodologies employed to ensure the structural integrity and safety of the bridge over its anticipated life cycle. In your discussion, highlight the interrelationship between these various factors and how they collectively influence the overall design and functionality of the bridge.