A$-3\mathrm{.}1$ What theoretical frameworks underpin the core principles of civil engineering? Explore foundational theories in structural mechanics, materials science, fluid dynamics, and geotechnical engineering that inform design, construction, and maintenance practices. Investigate how theories such as elasticity, plasticity, and continuum mechanics shape structural analysis and design methodologies. Consider the application of theories like Darcy's law in fluid flow through porous media and Terzaghi's principles in soil mechanics. Examine the role of theoretical models in predicting the behavior of civil engineering systems under various loading conditions and environmental factors, fostering sustainable and resilient infrastructure development.