Structural and mechanical engineering are both subdisciplines of civil engineering. Structural engineers specialize in loads and forces put on structures and often work in residential and commercial settings to create load-bearing structures like walls, foundations, and bridges. Civil engineers work on infrastructure projects in both public and private settings. These include roadways, sewage systems, bridges, and tunnels.  Mechanical engineers design and maintain power production and power using systems such as generators, engines, turbines, refrigeration systems, escalators, and elevators.