Magnel

Magnel refers to a type of prefabricated concrete beam developed in France during the mid-20th century. These beams were designed by engineer André Magnel and became widely used in bridge construction. The key innovation of Magnel beams was their use of prestressed concrete, a technique where internal stresses are induced in the concrete before it is subjected to external loads. This prestressing significantly increases the concrete's tensile strength and load-bearing capacity, allowing for longer spans and more slender structures compared to conventional reinforced concrete.

The design of Magnel beams typically involved channels cast into the concrete through which steel tendons or cables were threaded. These tendons were then stressed, usually by hydraulic jacks, and anchored at the ends of the beam. This process put the concrete into compression, counteracting the tensile stresses that would occur under load. The simplicity and efficiency of the Magnel system made it particularly attractive for rapid construction and for projects with limited budgets. Many railway bridges and road overpasses across Europe were built using this method, and some of these structures remain in service today. The widespread adoption of Magnel beams contributed to the advancement of prestressed concrete technology and its application in civil engineering.