A$-3\mathrm{.}1?$ What theoretical frameworks underpin the foundational principles of civil engineering? Explore key theories concerning structural analysis, materials science, and fluid mechanics. How do these theories inform the design, construction, and maintenance of infrastructure projects? Investigate the application of principles such as Euler$-$Bernoulli beam theory, Mohr's circle, and the Navier$-$Stokes equations in civil engineering practice. Additionally, discuss the role of theoretical models in predicting and mitigating environmental impacts, ensuring safety, and optimizing resource utilization. How do advancements in theoretical understanding shape the evolution of civil engineering practices, from traditional to emerging fields like smart infrastructure and sustainable design?