Aristotle University of Thessaloniki (AUTH) Institute of Steel Structures

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Aristotle University of Thessaloniki
(AUTH)Institute of Steel Structures

• Prof. C.C Baniotopoulos
• Iakovos Lavasas Civil Engineer
• Padelis Zervas Dr. Civil Enginner
• George Nikolaidis Civil Engineer

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Prestressed anchors

• Finite Element modelling

• Foundation is modeled using brick elements
• Anchors are modeled as non-linear tendon elements
  between the washer plates
• Unilateral contact conditions between the washer
  plates and the pedestal

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Prestressed anchors

• Prestress force is selected in order to
  eliminate anchor tensile force variation under
  operating wind loads
• Special concrete reinforcement is needed to carry
  the splitting forces on the concrete pedestal

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Seismic hazard

• Mass distribution
• Concentrated on the top of the tower with
  eccentricity
• Distributed over the tower height
• Types of analysis
• Eigenvalue analysis
• Rensponse spectrum analysis
• Eigenvalue analysis is also significant for the
  fatigue design

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Seismic hazard

• X,Y rotation spectra must be considered together
  with relevant translation spectra (EC8-3 Annex
  A).
• Soil-structure interaction must be taken into
  account in eigenvalue analysis

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Seismic hazard

• Usually seismic loads are smaller than the
  extreme wind loads
• This is not obvious when constructing in a
  seismic hazardous area.
• A simplified linear model can also give
  satisfactory results on eigenvalue analysis but
  not on seismic tower design

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Ring stiffeners

• Ring stiffeners are placed to reduce the local
  buckling of the shell
• Local buckling is produced by
• Meridional compressive stresses ? Lower part of
  the tower
• Circumferencial compressive stresses ? All over
  the tower height
• According to EC3-1-6 buckling design, ring
  stiffeners are dividing the
• tower into sections
• Local buckling is taking place in every section

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Ring stiffeners

• Ring stiffener disturbance along the tower is
  significant for the optimization of the design
• Stiffeners should be placed in order to equate
  (as possible) the total design ratios for every
  part of the tower

Design ratio
Tower parts between stiffeners
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Door stiffeners

• Scope
• Smooth the stress concentration around the
  door opening
• Reduce local buckling

Stress concentration around the door opening