Fatigue reistant foundation system

Abstract

A fatigue resistant gravity based spread footing under heavy multi-axial cyclical loading of a wind tower having a central vertical pedestal, a substantially horizontal continuous bottom support slab with a stiffened perimeter, a plurality of radial reinforcing ribs extending radially outwardly from the pedestal and a three-dimensional network 500 of post-tensioning elements that keep the structural elements under heavy multi-axial post compression with a specific eccentricity that is intended to reduces stress amplitudes and deflections and allows the foundation to have a desirable combination of high stiffness and superior fatigue resistance. 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.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a method for building fatigue resistant foundations for supporting columns, towers and structures under heavy cyclical loads such as wind turbines towers for onshore and offshore installations.[0003]The proposed foundation system will be used specifically for the Multi-Megawatt class wind turbines. Several wind turbine manufacturers have successfully developed large wind turbines with rated power ranging from 1.5 to 10 MW. Several wind turbine manufacturers are planning mass production of large multi Megawatt turbines for onshore and offshore installations. The installation of the E-126 model turbine by Enercon with a 7 MW rated power required a xx meter diameter circular foundation with 1,400 cubic meters of concrete and xx tons of rebar. The installation of the 5M turbine by RePower with a 5 MW rated power required a 23 meter diameter circular foundation with 1,300 cubic meters of concrete an...

AI Technical Summary

Benefits of technology

"The invention provides a fast, reliable, cost-effective foundation system for wind energy projects that is suitable for large wind turbines and tallest towers. It reduces the amount of cast in situ concrete work, the number of concrete trucks and rebar required, and the risk of thermal cracking. The foundation system has improved dissipation conditions, reduced temperature rise after casting, and improved structural properties. It also uses pre-marked spacing for splicing slab rebar with existing dowels extending from ribs, light weight rebar, and pre-fabricated components to maximize productivity and safety. The invention provides wind energy developers with the ability to select pre-approved complete foundation designs based on project and site variables, and it improves the quality and productivity of foundation construction due to experience gained from practicing standard construction techniques with repetitive production steps. It also allows for independent production of prefabricated components for offshore foundations that can be assembled on a barge without critical path interruptions."

Problems solved by technology

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

Thermal cracking often compromises the structural integrity of the foundations.

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