Approach to A Reliability Framework for Membrane Structure Design and Analysis

Research into structural reliability for tensile structures is needed. The semi-probabilistic format for verification of so-called form-passive structures is well-established in the Eurocodes. Partial factors are the main features of this semi-probabilistic or design value method. Whereas for conventional structures these partial factors are calibrated to previous experience [1], appropriate partial factors have to be proposed and evaluated for tensile structures. A cable net structure built in 1958 was used as a case study to gain insight into the effect of partial factors according to Eurocode 3 (steel structures). Prestress contributes to the stiffness in the non-linear structural behaviour of membrane structures and thus increasing the prestress with factor 1.35 according to the Eurocodes might be non-conservative. The article investigates the effect of the partial factor for prestress (1.0 or 1.35) on a membrane structure. A similar geometry as the steel cable net structure is designed and analysed for comparison with the cable net structure. For the primary steel structure the partial factor for prestress 1.35 has to be applied. An in-depth study of the effect of the partial factor for prestress on the stress distribution in the membrane in warp and weft direction is performed. The stress distribution clearly depends on the boundary conditions. A sound conclusion though requires a thorough in-depth study for different shapes and membrane types. In a first step towards a reliability approach, the structural reliability of a three segments cable net structure is currently being analysed, taking into account the uncertainties associated with the pre-tensioned system.