Claude Allen Porter Turner (July 4, 1869 – January 10, 1955) was an American structural engineer who designed a number of buildings and bridges, particularly in the U.S. states of Iowa, Minnesota, and Wisconsin.
Turner was born in Lime Rock (a small town near Lincoln), Rhode Island, and attended Lehigh University's school of engineering in Bethlehem, Pennsylvania, graduating in 1890. While at Lehigh he was the librarian of the Engineering Society, involved in the Electrical Engineering Society, a member of the fraternity Alpha Omega, Alpha chapter, vice president of St. Andrew's Guild, and a member of the Fencing and Broadsword clubs.
After college, Turner worked for several companies in the eastern United States including the New York & New England Railroad, Edgemore Bridge Co. in Philadelphia, Columbus Bridge Co. in Ohio, Pittsburgh Bridge Co. and the Pennsylvanian Pottsville Iron & Steel Co. before moving to Minneapolis, Minnesota in 1897. Before he formed his own company, the C.A.P. Turner Co., in 1901, Turner worked for the Gillette Herzog Co. and the American Bridge Company. He received a patent in 1908 for a flat-slab support system (also known as "mushroom cap" columns) using reinforced concrete and would later receive 30 additional patents for his work in reinforced concrete. Turner died in Columbus, Ohio in 1955.
Notable designs by Turner include the Aerial Ferry Bridge in Duluth, Minnesota, the 2,730 ft Arcola High Bridge (North of Stillwater, MN, on the St. Croix River), the Mendota Bridge (once the longest continuous concrete-arch bridge in the world) between Fort Snelling and Mendota, the Johnson-Bovey Building and Wisconsin Central Freight Station, both in Minneapolis, the Lindeke-Warner Building, Hamm Brewing Co. stockhouse, and West Publishing Co. in St. Paul, the Liberty Memorial Bridge between Bismarck and Mandan, North Dakota, the Soo Line railroad bridge in New Richmond, Wisconsin, and the Hoffman Building in Milwaukee.