What is the right prestress level for the architectural tensile membrane structure

Typical prestress levels are important, but for long-term performance in tensile membrane structures, several factors come into play, especially when considering the design of a tensile membrane structure, Exploring just two area a flat profile and large span.

Typical Prestress Levels:

  • PTFE Fabric: 4-8 kN/m
  • PVC Fabric: 1-4 kN/m

Impact of Prestress on Flat Profiles and Large Spans:

  • Flat Profiles: For structures aiming for a flat or near-flat profile, a higher prestress within the typical range might be necessary. This helps counteract the natural tendency of the fabric to sag and pond, especially for large spans, and ensures the flatness is maintained over time due to creep (elongation under constant stress).
  • Large Spans: For larger spans, even with a flat profile, a higher prestress might be required. This increased prestress helps distribute tension more evenly across the fabric distance and area, reducing deflection and maintaining the desired shape under wind, snow, or other loads.

Additional Considerations for Flat Profiles and Large Spans:

  • Structural Design: The design of the supporting structure and tensioning system becomes even more crucial for flat profiles and large spans. The system needs to be robust enough to handle the higher prestress forces and maintain the desired tension distribution across the fabric.
  • Fabric Selection: For flat profiles and large spans, fabrics with high tensile strength and low creep tendency are preferred.
  • Deflection Control: While prestress helps minimize deflection, additional measures like support cables or stiffeners might be incorporated into the design, especially for very large spans, to further ensure the flat profile is maintained or to be avoided.

Balancing Prestress and Other Factors:

  • Material Costs: Finding the optimal balance between prestress level, fabric choice, and cost is essential.

Conclusion:

While typical prestress ranges offer a starting point, achieving a flat profile and spanning large distances requires careful consideration of several factors. Working with a qualified structural engineer and fabricator is essential. They can help you determine the optimal prestress level, fabric choice, cables system and structural design to ensure your tensile membrane structure maintains its desired shape, stability, and aesthetics for the long term.

Here’s a quick summary table:

FactorImpact on Prestress for Flat Profiles & Large Spans
ProfileHigher prestress might be needed to maintain flatness
SpanLarger spans might require higher prestress for even tension distribution
Fabric ChoiceFabrics with high tensile strength are preferred
Structural DesignRobust design to handle higher prestress and maintain tension
Deflection ControlAdditional measures (cables, stiffeners) and safety measure might be needed
Material CostsHigher prestress might necessitate more expensive fabrics and structural solution
MaintenanceHigher prestress could lead to more frequent maintenance and checking