1. Preloaded anchors (WP 1.4 background document presentation) Institute of Steel Structures Aristotle Univ. of Thessaloniki

2. Preloaded anchors Configuration Configuration Partially prestressed anchors in Partially prestressed anchors in circumferencial direction Base & embedded washer plates Base & embedded washer plates No contact between the anchors & the concrete No contact between the anchors & the concrete

3. Preloaded anchors Finite Element model (Foundation section)‏  Concrete & shrink-mortar : Brick elements  Washer plates : Plate elements  Anchors : cable type elements active only in tension  Unilateral contact to the ground

4. Preloaded anchors Finite Element model (cross-section to the foundation)‏

5. Preloaded anchors Finite Element model (anchoring detail)‏  Each anchor is a single element connecting only the washer plates (active in tension)‏  Unilateral contact conditions between the base washer plate and the shrink mortar & between the embeded washer plate and the concrete

6. Preloaded anchors Non-Linear analysis Wind loading combinations  1 st iteration step: Self weight of the tower is applied  Apply anchor prestress step by step  Step by step apply loads for the specific load combination Seismic loading (spectral response analysis not compatible with nolinearities)‏  Solve the spectral response case, the tower rigidly connected to the foundation  Determine forces acting on the pedestal using SRSS comb.  Construct a new model for the foundation only incorporating all non-linearities  Execute the iterative analysis as above, applying the reactions of the tower to the foundation.

7. Preloaded anchors Design of the foundation-anchoring system  Washer & base plates (Von mises stresses)‏  Prestressed anchors (tensile forces)‏  Non-shrink mortar (compressive & shear stresses)‏  Concrete (compressive,shear & punching shear stresses)‏  Reinforcing bars  Rigid body equilibrum for the structure

8. Preloaded anchors Reinforcement check points Reinforcement check points 1,2 : Footing, bottom mesh 3,4 : Footing, top mesh 5 :Top of pedestal mesh 6 :Pedestal vertical rebars (transfer of tensile anchor forces)‏ 7 :Circumferencial reinforecement (split-up forces)‏