Holger Svensson Holger Svensson was born in 1945 in Germany and received his Diploma in Structural Engineering from Stuttgart University in 1969. Since then he has worked with Leonhardt, Andrae und Partner where he is now Managing Director. In the course of his professional work he has been involved in various stages of the design, construction, checking, and supervision on site of about 30 cable-stayed bridges all over the world.

Cable-stayed bridges

The development of cable-stayed bridges started in the 1950s. Prof Leonhardt was one of the pioneers from the very beginning. I had the good fortune to contribute personally to some areas to the later development as outlined below.

The action forces under permanent loads were initially calculated for a beam on rigid supports. We thus developed computer methods to determine them by superposition with cable shortenings for any border conditions. The aerodynamic stability was originally ascertained only by the classical flutter theory. Today we can investigate buffeting by computer simulation without any wind-tunnel testing.

Originally, locked coil ropes were used, which have a low tensile strength and fatigue range. We developed parallel wire cables with HiAm anchorages for which the complete cable has nearly the same characteristics as each individual wire. When some of the cables oscillated due to rain-wind excitation we went from tie-down cables to friction dampers.

Various systems for anchoring the stay cables in concrete towerheads were not satisfactory until we developed a system of overlapping post-tensioned loops.

Initially cable-stayed bridges were considered to be economic for main spans up to about 400m. We showed early on that the advantage of cable-stayed bridges over suspension briges theoretically increases with span length until stability and construction problems govern.

Like the development of cable-styaed bridges during my career there are similar challenges for today's young engineers, for example in the design of light roofs or in the use of composite plastics as structural members.