Cable post-tensioning optimization: Athens olympic stadium roofing system

The finite element Model
A global finite element model was created to assess the performance of the roofing system during all construction phases. During temporary phases modeFRONTIER was employed to determine the exact amount of pre-stress in cables such to achieve the final post-tensions determined through on-site measurements. The interaction between Straus7 and modeFRONTIER was possible through the Straus7 API module.

The Optimization
Elasticity and deformation of solids are responsible for elastic losses in a system of pre-stresses cables eventually used to increase the global stiffness. A consequence the achievement of a taeget set of post-tensions within a cable-stayed structure is a difficult, iterative and time consuming task. The large number of cables employed (116 cables) suggests that a manual iteration procedure is not feasible in practice.
With the aid of modeFRONTIER it was possible to use a structural finite element code (Straus7) as the design avaluator thus finding the optimal solution for a given tolerance. In particular any single pretension was assigned to a variable and governed using the Simplex algorithm with an initial population determined according to a gaussian distribution (Montecarlo method).