$45-90-00$ What foundational theories in civil engineering serve as the bedrock for understanding and designing structures, infrastructure, and systems? These theories encompass principles of mechanics, materials science, fluid dynamics, and thermodynamics, among others. They form the cornerstone for analyzing loads, stresses, and strains in various construction materials and configurations, enabling engineers to ensure the safety, durability, and functionality of buildings, bridges, roads, and other civil works. Understanding these theories is fundamental for civil engineers in effectively addressing the complex challenges of modern infrastructure development and maintenance.