Guyed Masts Exposed to Guy Failure

Abstract

The number of collapses of guyed masts is relatively bigger than for other types of structures. Many collapses of guyed masts are related to failure of a guy rope or the terminations of the guy ropes. Guyed masts have often not been analyzed for guy failures in the design phase. But a design requirement for guy rupture has in the recent codes for analysis and design of guyed masts been introduced for structures of high reliability, see for instance the Eurocode EC3: Part 3.1 and the American Code TIA/EIA 222-G. The most important load effect to the shaft of guyed masts is normally the wind load and the forces from the guy ropes, whereas the dead load of the structure itself has little impact. The rupture of guy ropes leads to a significant different stress scenario in the members of a guyed mast, compared to what wind and other loads initiates: the tensile forces in the leg members in the upper part of the guyed masts are normally increased significantly compared to what originates from the wind load. The forces in the guy rupture situation are determined by the initial tension of the guy rope, and a lower initial tension will lead to lower forces during guy rupture but also larger deflections during normal load conditions. This paper describes different methods for analyzing of guy rupture and the results from an analysis of influences of guy failures using a full dynamic method in the time domain and compares it with different static approaches. The simplified methods adopted in the codes are also briefly discussed.