Contributions of C. A. P. Turner to Development of Reinforced Concrete Flat Slabs 1905-1909

There is considerable uncertainty regarding both the timing and contributions of various individuals to the development of reinforced concrete flat slabs in the United States. The work of George M. Hill and the patent of Orlando W. Norcross are discussed first to provide context. The significant achievements of Claude A. P. Turner from 1905 to the end of 1909 are then described. Turner's conceptual design of flat slabs is discussed. Turner conceived a cage of reinforcement, which he called the "mushroom head," as shear reinforcement. Turner's simple design for moment led to very small areas of steel flexural reinforcement, which drew criticism from structural engineers. Some early flat-slab buildings and bridges and the load tests that Turner performed are discussed. A tangible symbol of Turner's contributions is his extant 1906 Hoffman (a.k.a. Marshall) building, which was designated an ASCE National Historic Civil Engineering Landmark in 2002. The dispiriting history of flat-slab development after the end of 1909 is briefly discussed.