Measurement of relaxation of membrane on an actual structure

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Publication year 1998
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Title Measurement of relaxation of membrane on an actual structure
Author Haruji Tsubota,Akihiro Kusaka,Masatoshi Ishida,Kuniaki Kudo,Yutaka Seto
Summary Membrane material has a significant relaxation characteristic. Therefore,in general,permanent membrane structures are required to install special devices for reintroducing membrane tensile stress. However,enough data to estimate the relaxation characteristic are not available. As the result,it is very difficult to prescribe the specification of such devices and the time for re-tensioning. Therefore,it is very important to accumulate actual data of the relaxation characteristic for developing the rational design and maintenance method of membrane structures. From this background,this paper presents the measured relaxation data of an actual membrane structure. The measurements were carried out on one roof membrane panel of Kumamoto stadium completed at Kumamoto city in 1998. The measured membrane panel was surrounded by steel frames and has a bracing cable. Membrane stresses,strains and cable force were measured at main processes of construction,at just after,at 45 days after and one year after completion. From the measured results,the membrane stress decreased to 80% in warp direction,90% in fill direction at one year after completion. Furthermore,it is considered that the decrease of membrane stress is caused not only by relaxation of membrane material itself,but also the change of boundary conditions such as cable tension.