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IASS-SLTE Symposium 2014: Shells, Membranes and Spatial Structures: Footprints

IASS Symposium 2014

SESSION: Tension and Membrane Structures

Revised finite element modelling for creep analysis

< Table of Contents for Tension and Membrane Structures
  • Proceedings Name: IASS-SLTE Symposium 2014: Shells, Membranes and Spatial Structures: Footprints
  • ISSN: (Electronic Version) 2518-6582
  • Session: Tension and Membrane Structures
  • Title: Revised finite element modelling for creep analysis
  • Author(s): Minger WU, Yintang LI
  • Keywords: finite element formulation, viscoelastic-plastic modelling, creep analysis, membrane structures, numerical simulation
Membranes, such as PVC, PTFE and ETFE, are widely used in spatial structures, and some of them exhibit viscoelastic-plastic property in long-term tension condition. Meanwhile, finite element method (FEM) has been a significant tool for structural analysis. This paper focuses on finite element formulation for viscoelastic-plastic modelling and its application for membrane creep analysis. On the basis of Schapery’s nonlinear viscoelastic modelling, Kennedy presented finite element formulation for creep analysis. This paper developed Kennedy’s work to consider viscoplastic component, which would not recover in given time. Revised finite element formulation for the viscoelastic-plastic modelling was presented, which requiring merely quantities at current time step and previous time step, rather than quantities at whole time scale. This formulation considered both viscoelastic creep deformation and viscoplastic creep deformation, and had been programmed in FORTRAN. Two examples were used to verify this formulation. One example was a rectangle specimen under uniaxial tension. In 10 hours creep time, total creep displacement was 1.79 mm in theoretical and 1.82 in numerical simulation. Simulation creep curve also embraced good agreement comparing with theoretical result during creep process. The other example was a triangle ETFE cushion. This cushion was tested in 12 hours for creep analysis. Inner pressure was 825 Pa. Creep properties at four stresses were offered and at other stresses were determined by linear interpolation. Creep displacements at the center points of the upper and lower foils were both measured by laser sensors. The maximum creep displacement was about 3.0 mm in 12 hours creep time. Numerical simulation was done and its result was compared with test data, which showing good agreement. Therefore, the revised finite element formulation is valid in membrane structures for creep analysis.

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