This research designed and analyzed an innovative structural support system for ETFE (ethylene tetrafluoroethylene) atrium roofs between buildings. A cable-spring system was conceived, which is much lighter and more flexible than arches, frames, trusses, and beams which usually support ETFE roofs. Flexibility was a desirable property because the displacements may vary significantly among the buildings supporting the ETFE atrium roof during wind and seismic loading. The springs in the cable-spring system allow large differential displacements without exerting large support reactions on the buildings. The flexibility of the cable-spring system was compared to the cable-strut system which is used to support many other roofs. The concept of the cable-spring system was demonstrated by the design of an example problem and an experimental model. The example problem consisted of 20 m roof spans between buildings and differential displacements up to 8.5 cm. Conceptual design of the system consists of an array of intersecting cable-spring trusses that provide adequate drainage, venting, and repeatability. Detailed design includes the design of the ETFE cushion, truss depth, spring stiffness, cable sizes, and the telescoping tubes that enclose the springs. The ETFE cushions were analyzed with the MPanel software which is based on a computational process known as dynamic relaxation. The cable-spring trusses were analyzed using the principles of statics and large displacement geometry. Design curves and formulas were produced for spring sizes. A small scale experimental model was built to demonstrate the flexibility of the cable-spring support system. The weight of the atrium roof was estimated to be about 2.28 psf for the example problem. The analysis revealed that for the same spans and differential support movements the cable-spring support system had a 71% reduction in support reactions when compared to a cable-strut system.



College and Department

Ira A. Fulton College of Engineering and Technology; Civil and Environmental Engineering



Date Submitted


Document Type





Ryan Paul Bessey, atrium, ETFE, cable-spring support system