Longitudinal cracking of the lower flange of precambered composite steel and concrete bridge girders

A thorough inspection of a 55-year-old composite steel-concrete railway bridge across the Antwerp circular motorway has revealed significant cracking in the concrete encasement of the precambered girders. Verifications based on analytical equations show that the bridge certainly meets the original and the current requirements. The longitudinal cracks are due to neglecting the effect of the spreading of precambering force on thin steel flanges, across a much larger area of the concrete cross-section. These splitting stresses further combine with shear stresses in the vertical sense. The light transverse reinforcement, customary at the time of construction, is insufficient to prevent this cracking, the location of the cracks exactly corresponding to the outward point of the steel flanges. In addition, it should be mentioned that the design load at the time of construction, was larger than the present LM 71. This example clearly shows that an aspect of the essence of structural engineering also consists of handling equations for phenomena that are often not detected with elaborate FE simulations.