HELP$\_\_\_\_\_\_\_\_\_\_\_$ A foundational theory in civil engineering pertains to structural analysis, which assesses the behavior of materials and components under various loads. This theory encompasses principles of mechanics, such as equilibrium equations and stress analysis, to ensure structures withstand expected forces. Additionally, theories related to fluid mechanics are crucial for designing hydraulic structures like dams and bridges. Geotechnical theory addresses soil behavior, essential for foundation design. Transportation engineering relies on traffic flow theory for efficient road network planning. These theories collectively underpin civil engineering practice.