| In the early 1960's, the Swiss engineer Dr. Werner Heierli began the development of overfilled concrete arch systems. The objective was to build concrete arches with a minimum thickness, sufficient to carry the applied loads, but also stender enough for the passive resistance of the backfill to be mobilised by means of elastic deformations of the arch. With this concept, the fill could contribute to the load carrying capacity of the arch and become part of the structure rather than just representing a loading. This phenomenon, known as the "soil-structure-interaction", is widely used in the BEBO design approach. In 1965 the first BEBO arch was manufactured from 160 mm (6.3 inch) thick precast concrete elements. This arch was a proof of concept, full-scale experimental structure, constructed when the BEBO System was being considered for a whole series of underpasses for the Swiss highway system under construction at that time. The experimental structure more than verified the promising results of the theoretical analyses. |