Structural Weaknesses of the Hennebique Early Reinforced Concrete System and Possible Retrofitting

One of the most popular reinforced concrete patterns used in many countries until the First World War was the system of Francois Hennebique (1842-1921). The best known characteristics of the Hennebique design, which was used in buildings as well as in bridges, are the monolithic structure with continuous T-beams reinforced with bent-up bars overlapping the supports and the use of flat open U-shaped stirrups as transversal reinforcements. The reasons for the success of his company have been extensively studied. However, so far, the assessment of the carrying capacity of the system remains incomplete. The first part of this paper deals with the results of experimental bending tests up to failure performed on three full-scale T-beam segments removed from a narrow gage railway viaduct built in Braine-l'Alleud (Belgium) in 1904. They aim at identifying the mechanisms of failure. The second part of the paper presents retrofitting actions to counteract the observed principal structural weakness-the too short overlapping length of the tensile rebars over the supports.