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Preloaded anchors (WP 1.4 background document presentation) Institute of Steel Structures Aristotle Univ. of Thessaloniki. Configuration Partially prestressed anchors in circumferencial direction Base & embedded washer plates No contact between the anchors & the concrete.
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Preloaded anchors (WP 1.4 background document presentation)Institute of Steel StructuresAristotle Univ. of Thessaloniki
Configuration Partially prestressed anchors in circumferencial direction Base & embedded washer plates No contact between the anchors & the concrete 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 Preloaded anchors
Finite Element model (cross-section to the foundation) 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 Preloaded anchors
Non-Linear analysis Wind loading combinations • 1st 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. 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 Preloaded anchors
Preloaded anchors 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)