Structural Behavior of Symmetric Spindle-Shaped Tensairity Girders: Fid-Bau Portal

Structural Behavior of Symmetric Spindle-Shaped Tensairity Girders

Luchsinger, Rolf H. / Galliot, Cédric

Abstract

The load-bearing behavior of a symmetric spindle-shaped Tensairity girder with 5-m span and thin chords is studied experimentally, numerically, and analytically. The influence of the air pressure on the load-deflection behavior is investigated for homogeneous distributed load, asymmetric distributed load, and central local load. An m-shaped deflection with two maxima at about one- and three-quarter of the span was obtained for homogeneous distributed loads whose distribution is not linearly dependent on the applied load. The slope of the load-deflection curve as well as the maximal load increases with increasing air pressure, demonstrating the stabilizing role of the inflated hull. An analytical model based on two beams coupled by an elastic foundation with air pressure-dependent properties is presented for the homogeneous distributed load case, and simple predictions for the average displacement and the maximal load are given. The model reveals the subtle interplay between the chords and the inflated hull leading to the peculiar displacement distribution of the system. Finite-element analysis shows the limiting influence of the low fabric shear modulus on the stiffness and load-bearing capacity of the Tensairity girder for local and asymmetric distributed load. The investigated spindle-shaped Tensairity girder is optimal for homogeneous distributed loads, where a live load to dead load ratio of more than 50 has been achieved.