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Stress distribution around door opening

Stress distribution around door-opening Prof. Ch. Baniotopoulos I. Lavassas, G. Nikolaidis, P.Zervas Institute of Steel Structures Aristotle Univ. of Thessaloniki, Greece. Main objectives to check: Stress distribution around the door opening Shell buckling at door position

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Stress distribution around door opening

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  1. Stress distribution around door-openingProf. Ch. BaniotopoulosI. Lavassas, G. Nikolaidis, P.ZervasInstitute of Steel StructuresAristotle Univ. of Thessaloniki, Greece

  2. Main objectives to check: Stress distribution around the door opening Shell buckling at door position Linear static analysis has been performed in all cases Wind load direction x+ (producing maximum compressive stresses to the door position) Stress distribution around door opening Ideal stress distribution around door opening

  3. Buckling analysis – no ring at all Buckling analysis No stiffening at all causes 1st to 7th buckling modes to appear in door position When stiffening the door by any type (thick ring, comb type stiffeners), no one of the first 10 buckling modes stands on the door.

  4. Max σvm ~= 300 Mpa for the tower (excluding door position) In this case: Max σvm=565Mpa >> fy around the opening No stiffeners – Vm stress distribution

  5. A: Stiffening with a rigid ring (d=70 mm) around the door (existing case) Max σvm ~= 300 Mpa for the tower (excluding door position) In this case: Max σvm=335Mpa around the opening First 10 eigenmodes appear to the upper part of the shell

  6. B: Stiffening with a weak ring (d=30 mm) around the door and additional stiffeners of comb type Max σvm ~= 300 Mpa for the tower (excluding door position) In this case: Max σvm=320Mpa around the opening Max σvm =450 to the ring >> fy  needs redesign First 10 eigenmodes appear to the upper part of the shell (identical to A:)

  7. C: Stiffening with a ring (d=60 mm) around the door and additional stiffeners of comb type Even with presence of stiffeners, ring needs to be at least 60 mm thick Max σvm ~= 300 Mpa for the tower (excluding door position) In this case: Max σvm=320Mpa around the opening Max σvm =337 to the ring First 10 eigenmodes appear to the upper part of the shell (identical A: & B:) Stress state is almost identical to A:

  8. Door stiffening comparison on another 45 m high 1 MW turbine tower a) Weak ring + comb type stiffeners + vertical stiffeners : Max σvm ~= 311 Mpa b) Weak ring + comb type stiffeners : Max σvm ~= 345 Mpa c) Only one rigid ring: Max σvm=335Mpa around the opening

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