"Discuss the design considerations and structural analysis methods involved in the development of a long$-$span bridge across a major river in a seismically active region. Address the challenges posed by both the span length and the seismicity of the area, and outline the steps involved in ensuring the structural integrity and safety of the bridge under normal operating conditions as well as during seismic events. Additionally, explore the role of materials selection, construction techniques, and ongoing maintenance strategies in enhancing the resilience and longevity of the bridge structure."