Claude Allen Porter Turner (July 4, 1869 – January 10, 1955) was an American

structural engineer Structural engineers analyze, design, plan, and research structural components and structural systems to achieve design goals and ensure the safety and comfort of users or occupants. Their work takes account mainly of safety, technical, economic ...

who designed a number of buildings and bridges, particularly in the midwestern U.S. states of

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the ...

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

, and

Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...

. Turner was born in

Lincoln, Rhode Island Lincoln is a town in Providence County, Rhode Island, United States. The population was 22,529 at the 2020 census. Lincoln is located in northeastern Rhode Island, north of Providence. Lincoln is part of the Providence metropolitan statistical are ...

, and attended

Lehigh University Lehigh University (LU) is a private research university in Bethlehem, Pennsylvania in the Lehigh Valley region of eastern Pennsylvania. The university was established in 1865 by businessman Asa Packer and was originally affiliated with the Epis ...

's school of engineering in

Bethlehem, Pennsylvania Bethlehem is a city in Northampton and Lehigh Counties in the Lehigh Valley region of eastern Pennsylvania, United States. As of the 2020 census, Bethlehem had a total population of 75,781. Of this, 55,639 were in Northampton County and 19, ...

, graduating in 1890. He worked for several companies in the eastern United States before moving to

Minneapolis, Minnesota Minneapolis () is the largest city in Minnesota, United States, and the county seat of Hennepin County. The city is abundant in water, with thirteen lakes, wetlands, the Mississippi River, creeks and waterfalls. Minneapolis has its origins ...

, in 1897. He formed his own company in 1901 and received a

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...

in 1908 for an innovative flat-slab support system, known as the Turner System or the Spiral Mushroom System, using

reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...

, although this patent was invalidated in 1915 and 1916 in favor of similar patents filed by American engineer O.W. Norcross. Turner's patent, however, was licensed to overseas designers including

Hugh Ralston Crawford Hugh Ralston Crawford (1876–1954), practiced both as an engineer and architect in Australia and the United States in the first half of the 20th century. Biography Crawford was born in the United States in 1876, and moved to Queensland, Austr ...

in Australia. Turner would eventually receive 30 patents related to reinforced concrete. He died in

Columbus, Ohio Columbus () is the state capital and the most populous city in the U.S. state of Ohio. With a 2020 census population of 905,748, it is the 14th-most populous city in the U.S., the second-most populous city in the Midwest, after Chicago, and t ...

, in 1955. Notable designs by Turner include: * the Marshall Building (a.k.a. Hoffman Building) in

Milwaukee, Wisconsin Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County, Wisconsin, Milwaukee County. With a population of 577,222 at th ...

, 1906 (a

National Historic Civil Engineering Landmark __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United State ...

) * the Lindeke-Warner Building, St. Paul, Minnesota (first American building to use the Turner System), 1909 * the 2,730 ft

Soo Line High Bridge The Soo Line High Bridge, also known as the Arcola High Bridge, is a steel deck arch bridge over the St. Croix River between Stillwater, Minnesota and Somerset, Wisconsin, United States. It was designed by structural engineer C.A.P. Turner and ...

(North of

Stillwater, Minnesota Stillwater is a city in the U.S. state of Minnesota and the county seat of Washington County. It is in the Minneapolis–Saint Paul metropolitan area, on the west bank of the St. Croix River (Wisconsin-Minnesota), St. Croix River, across from H ...

, on the St. Croix River), 1911 * the

Mendota Bridge The Mendota Bridge (full name Fort Snelling–Mendota Bridge), in the US state of Minnesota carries State Highway 55 (MN 55) and MN 62 over the Minnesota River between Fort Snelling and Mendota Heights. It is the final bridge over th ...

in the

Twin Cities Twin cities are a special case of two neighboring cities or urban centres that grow into a single conurbation – or narrowly separated urban areas – over time. There are no formal criteria, but twin cities are generally comparable in statu ...

, 1926 * re-engineering the

Aerial Lift Bridge The Aerial Lift Bridge, earlier known as the Aerial Bridge or Aerial Ferry Bridge, is a landmark in the port city of Duluth, Minnesota. The span began life in 1905 as the United States' first transporter bridge: Only one other was ever constructe ...

Duluth, Minnesota , settlement_type = City , nicknames = Twin Ports (with Superior), Zenith City , motto = , image_skyline = , image_caption = Clockwise from top: urban Duluth skyline; Minnesota ...

, from a

transporter bridge A transporter bridge, also known as a ferry bridge or aerial transfer bridge, is a type of movable bridge that carries a segment of roadway across a river. The gondola is slung from a tall span by wires or a metal frame. The design has been use ...

into a lift bridge, 1929 * the

Liberty Memorial Bridge The Liberty Memorial Bridge, across the Missouri River connecting the "twin cities" of Bismarck and Mandan, North Dakota, also known as Missouri River Bridge, was a Warren-Turner through truss structure that was built in 1920. It was listed on t ...

between Bismarck and

Mandan, North Dakota Mandan is a city on the eastern border of Morton County and the eighth-largest city in North Dakota. Founded in 1879 on the west side of the upper Missouri River, it was designated in 1881 as the county seat of Morton County. The population was ...

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* {{DEFAULTSORT:Turner, C.A.P. 1869 births 1955 deaths Concrete pioneers American structural engineers American bridge engineers Lehigh University alumni Engineers from Rhode Island People from Providence County, Rhode Island 20th-century American engineers

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