Foundation with pedestal and ribs for towers
OwnerAhmed M. Phulyinventor
Life of this patent
Estimating the term…
Abstract
A wind turbine foundation comprising a concrete support slab having a horizontal rebar grid therein, a concrete pedestal integral with the support slab and having vertical post tensioning elements therein and a plurality of concrete ribs on top of and integral with the support slab and integral with the pedestal, the ribs having rebar therein and extend outwardly from the pedestal, the pedestal, slab and ribs are connected to each other to form a monolithic foundation. The foundation design reduces the weight and volume of materials used, reduces cost, and improves heat dissipation conditions during construction by having a small ratio of concrete mass to surface area thus eliminating the risk of thermal cracking due to heat of hydration.
Claims50
A cast in situ wind turbine foundation comprising:
- a concrete slab-on-grade, having horizontal rebar therein;
- a laterally restrained and vertically prestressed concrete pedestal with a base and a predetermined height, the pedestal being integral with the support slab, and having vertical rebar and bursting reinforcing around an array of vertical post tensioning elements therein;
- an array of ribs conjointly cast and integral with the pedestal, the ribs comprising horizontal cantilevered girders of tapering height that are fixed to the pedestal at inner ends thereof such that the minimum height dimension of the ribs is proximate to the slab at outer ends of the foundation and a maximum height dimension proximate to a top of the pedestal at the junctions of the ribs with the pedestal, and each rib having diagonally extending upper flexure reinforcing elements with embedded connection elements extending from the rib into the pedestal through the vertical rebar and vertical post-tensioning elements;
- connection elements extending from the ribs into the slab at spaced intervals along a length dimension of the ribs;
- a tower base supported atop the pedestal;
- wherein the pedestal is kept under a combination of heavy post compression stress and lateral confinement to thereby provide reduced stress range amplitudes, reduced deflections, increased bearing capacity and improved fatigue resistance.
A wind turbine foundation for a wind tower comprising:
- an excavation pit at a foundation construction site;
- a continuous support slab-on-grade that is cast in situ out of concrete over a prepared subgrade at the bottom of the excavation pit below grade elevation and having generally horizontal rebar mesh therein;
- a vertically extending and laterally braced tower supporting pedestal having a top and a base, the pedestal encompassing a vertical reinforcing cage and bursting reinforcing around an array of vertical post tensioning elements therein;
- a plurality of concrete ribs on top of and integral with the support slab and integral with the pedestal, the pedestal and the ribs being conjointly cast, in situ, out of concrete, the ribs having connection elements extending therefrom into the pedestal and into the slab such that the ribs, slab and pedestal form a monolithic foundation, the ribs being tapered downwardly and outwardly from the pedestal and with inner ends of the ribs having a height corresponding to the height of the pedestal to thereby provide lateral bracing and confinement to the pedestal;
- and
- a compacted backfilling material placed over and around the foundation to substantially bury the foundation and restore grade such that the pedestal top protrudes above grade and is adapted to support a base of a wind tower pylon near grade elevation.
A cast in situ foundation comprising a continuous concrete support slab on grade placed at the bottom of an excavation pit and having horizontal rebar therein, a laterally restrained concrete pedestal integral with the support slab having a vertical rebar cage therein, a plurality of concrete ribs on top of and integral with the support slab and integral with the pedestal, the ribs being conjointly fixed at their inner ends to the pedestal and having a height that is tapering downwardly as they extend outwardly from the pedestal such that the minimum height dimension of the ribs is proximate to the slab at outer ends of the foundation and a maximum height dimension of the ribs is proximate to a top of the pedestal at the junctions of the ribs with the pedestal, and the ribs having lateral connection elements extending from the ribs into the pedestal and further connection elements extending from the ribs into the slab, the ribs thereby providing lateral bracing and confinement to the pedestal;
- and compacted backfilling material placed over and around the foundation to substantially bury the foundation and restore grade such that the pedestal protrudes above grade and is adapted to support a base of a wind tower near grade elevation.
A method of constructing a foundation for a wind turbine tower having a continuous slab, a pedestal, and a plurality of tapered ribs of cantilevered girder construction comprising the steps of:
- a) preparation of the site including the placement of a construction barrier over a flattened subgrade at the bottom of an excavation pit;
- b) placing an anchor-bolt cage and foundation reinforcement at the excavation pit;
- c) installation of formwork including a slab form, an array of cantilevered rib forms and a pedestal form in the excavation pit;
- d) placing of flowable concrete inside the said forms and allowing the concrete to harden such that the ribs become integral with the support slab and integral with the pedestal when the concrete hardens forming a monolithic foundation;
- e) removing of formwork wherein step (b) is carried out in the following sub-steps carried out in any order;
- (b1) placing the reinforcement of the slab on grade with an upper and a lower horizontal rebar meshes therein;
- (b2) placing in position the anchor-bolt cage with leveling and positioning means connected to the anchor-bolt cage to ensure its proper positioning and vertical alignment;
- (b3) placing reinforcement of the pedestal comprising a vertically extending and tightly meshed pedestal cage assembly around the said anchor-bolt cage;
- and
- (b4) placing an array of rib reinforcement cages around the said anchor-bolt cage, the said rib reinforcing cages being of tapering height and having vertical stirrups and diagonally extending upper flexure reinforcing running in the stirrups with dowels extending into the pedestal cage and the vertical stirrups extending from the ribs into the slab at spaced intervals and housing a laterally extending bottom flexure reinforcing near the bottom of the stirrups.
Dependencies are inferred from the claim text.