Consider a scenario where a city is planning to construct a new bridge over a river. The bridge needs to accommodate heavy traffic, including trucks and buses, and must also withstand potential seismic activity in the region. Discuss the theoretical considerations that civil engineers would need to address in the design and construction of such a bridge. How would they account for factors such as load distribution, material selection, foundation design, and seismic resilience? Additionally, how might the engineers optimize the design to ensure the bridge is both structurally sound and cost$-$effective over its lifespan?