What type of engineers design bridges?
Civil engineers and Structural engineers.
Different engineers do different things. Civil engineers may design dams, bridges, roads. Mechanical engineers design factories, production lines. Electrical engineers may design power systems, and chemical engineers design chemical manufacturing processes. Safety engineers design safe working procedures, and operating engineers operate boilers, locomotives, cranes, and large equipment. Aeronautical engineers design airplanes and spacecraft, and Marine engineers design ships. And there are others as well.