Reinforcement systems (historic)
In the early days of reinforced concrete (from the 1890s to 1920s), a number of proprietary reinforcement systems were used. Many of these were developed in France, Germany and USA and imported into the UK. Details can be found in The era of the proprietary reinforcing systems by Bussell (see Reference below), which also covers various patented floor systems. Some examples of the use of the systems in bridges are given in the separate entry Development of reinforced concrete bridges.
The importance of the bond between the reinforcement and the concrete was identified at an early stage. Most of the systems are recognisable as variations on modern bars, with a wide variety of surface characteristics. For example, the Hennebique System used plain round (mild steel) bars with flattened ‘fish tail’ ends for anchorage.
A very unusual product was the Kahn bar, which consisted of a square section with two projecting strips on diagonally opposite corners. These were slit along short lengths and bent up to form shear reinforcement. In the USA and UK the system was adopted by the Trussed Concrete Steel Company, which became abbreviated to Truscon.
Further information on how reinforcement has developed over the years is given in Concrete Society Technical Report 70, Historical approaches to the design of concrete buildings and structures.