Numerical analysis of cable net structure with application of different pretensioning methods

Tension roofs based on cable systems are suitable for covering long span buildings. Such structures are considered to be economic, modern and aesthetic solutions in various multi-functional arenas. Development of materials and construction technologies resulted in an increased number of applications of cable systems in recent years. However, the origin of such structures dates back to 1953, when the cable net supported roof over Raleigh Arena in North Carolina was completed. Designed as self-balanced, the system was eventually pretensioned in order to provide greater stiffness. This implementation became an indispensable part of cable nets construction. A unique method of pretension was applied in one of the first and most recognizable Polish examples of tensile structure, which is the cable net roof over the open-air theater in Koszalin. The system was pretensioned through the outward rotation of simply supported edge arches, which induced tensile forces in roof cables. This simple and effective concept became an inspiration for the introduced study, which focused on the numerical application of such a solution. In this paper, the results of comparative finite element analysis of introduced cable net structure with different methods of pretensioning are presented. The investigation was preceded by the analysis of net shape, concentrated on the value of cable sags in the saddle point of parabolic hyperboloid surface. Effectiveness of the presented solutions was assessed through comparison of internal forces distribution and model deformation. Numerical verification of consecutive concepts led to a gradual reduction of directly prestressed members from 16 suspension cables to 6 cable stays in the analysed roof.