Insight into technological aspects of the evolution of the Hennebique reinforced concrete system

The Frenchman François Hennebique (1842-1921) is well known for his involvement in promoting reinforced concrete at the end of the 19th century and the beginning of the 20th century. However, the efficiency of his famous system regarding the carrying capacity has not been evaluated yet even though it is a crucial parameter for reusing any construction. Moreover, this system has changed during the decades of practice of the Hennebique Company considering the evolution and large diffusion of reinforced concrete around the 1910s. We have the opportunity to analyse original computation details and technical constructive blueprints for several Belgian projects from the Hennebique office from 1900 up to 1930 to follow the evolution of the patented system. This paper describes two complementary structural aspects of the system based on these cases studies. Firstly, the evolution of the type and location of the rebars of the system is analysed. Secondly, the design methods are reviewed for the beam-floor element. Indeed, a careful attention is paid to the typical straight T-beam as it is the main structural element of the Hennebique monolithic construction. This study investigates the calculation methods and practical implementation of the Hennebique system in order to identify its possible structural weaknesses.According to our research, the Hennebique firm changes his system along the years but kept his calculation method, at least until the 1930s. Therefore, the identification of the system Hennebique in an early r.c. construction, i.e. dating before the 1930s, is rather straightforward in practice.