Partially prefabricated modular foundation system

Abstract

A wind turbine foundation having a central pedestal, a bottom support slab, and a plurality of prefabricated radial reinforcing ribs. The pedestal and support slab are poured in situ at the site. When the concrete cures the support slab is united to the prefabricated ribs and the ribs are also united to the pedestal. The result is a continuous monolithic foundation wherein loads are carried across the structure vertically and laterally through the continuous structure by doweled and spliced reinforcing steel bars which are integrally cast into the pedestal, ribs and support slab. The slab thus behaves structurally as a continuous slab reducing deflections, improving fatigue conditions and increasing the stiffness of the foundation as well as allowing for the benefits of an economical design.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a method for building partially prefabricated foundations for supporting wind turbines towers.[0003]2. Description of the Related Art[0004]Conventional gravity style foundations for large wind turbine usually comprise a large, thick, horizontal, heavily reinforced cast in situ concrete base; and a vertical cast in situ cylindrical pedestal that is installed over the base. There are several problems that are typically encountered during the construction of such foundations.[0005]The main problem is the monumental task of managing large continuous concrete pours, which require sophisticated planning and coordination in order to pour more than four hundred yards of concrete in one continuous pour, without having any cold joints in.[0006]Another problem is logistics coordinating with multiple local batch plants the delivery plan of the large number of concrete trucks to the job site in a timely, or...

AI Technical Summary

Benefits of technology

[0012]A wind turbine foundation having a plurality of components, namely a central vertical pedestal, a substantially horizontal bottom support slab, and a plurality of radial reinforcing ribs extending radially outwardly from the pedestal. The ribs are prefabricated and transported to job site, but the pedestal and support slab are poured in situ at the site out of concrete. The prefabricated ribs are equipped with load transfer mechanisms, for shear force and bending moment, along the conjunctions with the cast in situ support slab. The prefabricated ribs are also equipped at their inner ends with load transfer mechanisms, for shear force and bending moment, along the conjunctions with the cast in situ pedestal. The ribs are arranged in a circumferentially spaced manner around the outer diameter of the pedestal cage assembly and slab reinforcing steel is installed. Forms are then arranged for the pedestal and support slab. The support slab is cast in situ by pouring concrete into the forms and then pedestal concrete is poured over the slab into the pedestal form. When the concrete cures the support slab is united to the prefabricated ribs and the ribs are also united to the pedestal. The final result is continuous monolithic polygon or circular shape foundation wherein loads are carried across the structure vertically and laterally through the continuous structure by the doweled and spliced reinforcing steel bars which are integrally cast into the pedestal, ribs and support slab. The combination of the high stiffness of the ribs, solid pedestal and continuous slab construction across the pedestal, and through or under ribs, allows the slab to behave structurally as a continuous slab over multiple rigid supports resulting in small bending and shear stresses in the slab, reducing deflections and increasing the stiffness of the foundation, improving fatigue conditions as well as allowing for the benefits of an economical design. Support slab reinforcing steel covers the entire footprint of the foundation and extends across the slab area under the pedestal to improve the structural performance of the foundation under different loading conditions.

[0045]A further object of this invention is to improve the quality and productivity of foundation construction due to experience gained from practicing standard construction techniques.

Problems solved by technology

When concrete is cast in massive sections for wind tower foundations, temperature can reach 160 degree F. and the risk of thermal cracking becomes very high unless cooling techniques are applied.

Thermal cracking often compromises the structural integrity of the foundations.

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