scholarly journals Strengthening Mechanism of Studs for Embedded-Ring Foundation of Wind Turbine Tower

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 710
Author(s):  
Junling Chen ◽  
Jinwei Li ◽  
Qize Li ◽  
Youquan Feng
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Development Stage ◽  
Numerical Results ◽  
Structural Defects ◽  
Lateral Side ◽  
Design Codes ◽  
Principal Stresses ◽  
Concentration Phenomena ◽  
Strengthening Method

The embedded-ring wind turbine foundations were widely applied in the early development stage of wind power industries because of its properties such as easy installation and adjustment. However, different damages occurred on some embedded-ring wind turbine foundations in recent years. Based on the common damage phenomena of embedded-ring wind turbine foundations, the structural defects and damage mechanisms of embedded-ring wind turbine foundations are analyzed in a gradual way. Cheese head studs are proposed to be welded on the lateral wall of the steel ring to strengthen the connection between the steel ring and the foundation concrete. The foundation pier is elevated 1 m to increase the embedded depth of the steel ring. The circumferential confining pressure is applied on the lateral side of the foundation pier to lead it into a state of pressure. One simplified method is proposed to calculate the contribution of welding studs in this strengthening method. Taking an embedded-ring wind turbine foundation as an example, the numerical analyses for the original foundation and the reinforced one are carried out to compare the stress and strain distribution changes. Based on the numerical results corresponding to the peak and valley value loads, the fatigue life of the concrete and studs are evaluated according to the relevant design codes. The numerical results show that this strengthening method can coordinate the deformation of the embedded steel ring and the foundation concrete by circumferential prestressing and welding studs. The maximum principal stresses of the foundation pier and the fatigue stress range of the concrete around the bottom of the steel ring have been greatly reduced after strengthening. The gaps between the embedded steel ring and the foundation pier are also obviously decreased because of these strengthening measures. The stress concentration phenomena of the concrete around the T-shaped flange have been remarkably improved. The fatigue life can meet the requirements of relevant design codes after strengthening. Therefore, it can be concluded that the safety performance and service life of the embedded-ring foundation can be guaranteed.

scholarly journals Numerical Investigation of the Strengthening Method by Circumferential Prestressing to Improve the Fatigue Life of Embedded-Ring Concrete Foundation for Onshore Wind Turbine Tower

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 533 ◽  
Author(s):  
Junling Chen ◽  
Yiqing Xu ◽  
Jinwei Li
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Damage Zone ◽  
Horizontal Displacement ◽  
Windward Side ◽  
Model Code ◽  
Concrete Foundation ◽  
Wind Turbine System ◽  
Before And After ◽  
Strengthening Method

An embedded-ring foundation connected to the steel tower above it by inserting the steel ring into the concrete foundation is a traditional and widely used form for wind turbine towers. An insufficiently embedded depth of the steel ring leads to stress concentration on the corner of the concrete above the windward-side T-shaped plate. A damage zone of concrete develops, leading to gaps between the steel ring and the foundation concrete and a decline in the restrain stiffness of the foundation pier, which induces a larger horizontal displacement of the steel tower and a decrease in the natural frequency for the wind turbine system. To improve the fatigue life of the concrete around the steel ring under the precondition of not destroying the original foundation, a strengthening method using a circumferential prestressing technique is proposed in this paper. A series of numerical analyses were carried out to analyze the stress state change in the foundation concrete before and after strengthening. The fatigue life of the concrete above the T-shaped plate was evaluated according to CEB-FIP model code (fib Model Code for Concrete Structures 2010). The results show that the strengthening method can effectively decrease the fatigue stress amplitude and improve the fatigue life of the concrete above the T-shaped plate.

scholarly journals Comparison of planetary bearing load-sharing characteristics in wind turbine gearboxes

2018 ◽  
Vol 3 (2) ◽  
pp. 947-960 ◽  
Author(s):  
Jonathan Keller ◽  
Yi Guo ◽  
Zhiwei Zhang ◽  
Doug Lucas
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Load Sharing ◽  
Position Error ◽  
Bearing Clearance ◽  
Roller Bearings ◽  
Bearing Load ◽  
Tapered Roller ◽  
Tapered Roller Bearings ◽  
Cylindrical Roller

Abstract. In this paper, the planetary load-sharing behavior and fatigue life of different wind turbine gearboxes when subjected to rotor moments are examined. Two planetary bearing designs are compared – one design using cylindrical roller bearings with clearance and the other design using preloaded tapered roller bearings to support both the carrier and planet gears. Each design was developed and integrated into a 750 kW dynamometer tests, the loads on each planet bearing row were measured and compared to finite-element models. Bearing loads were not equally shared between the set of cylindrical roller bearings supporting the planets even in pure torque conditions, with one bearing supporting up to 46 % more load than expected. A significant improvement in planetary bearing load sharing was demonstrated in the gearbox with preloaded tapered roller bearings with maximum loads 20 % lower than the gearbox with cylindrical roller bearings. Bearing life was calculated with a representative duty cycle measured from field tests. The predicted fatigue life of the eight combined planet and carrier bearings for the gearbox with preloaded tapered roller bearings is 3.5 times greater than for the gearbox with cylindrical roller bearings. The influence of other factors, such as carrier and planet bearing clearance, gravity, and tangential pin position error, is also investigated. The combined effect of gravity and carrier bearing clearance was primarily responsible for unequal load sharing. Reducing carrier bearing clearance significantly improved load sharing, while reducing planet clearance did not. Normal tangential pin position error did not impact load sharing due to the floating sun design of this three-planet gearbox.

Fatigue Life of Wind Turbine Tower Bases throughout Colorado

2015 ◽  
Vol 29 (4) ◽  
pp. 04014109 ◽  
Author(s):  
Trung Q. Do ◽  
Hussam Mahmoud ◽  
John W. van de Lindt
Keyword(s):  
Fatigue Life ◽  
Wind Turbine ◽  
Wind Turbine Tower

Rational Reinforcing of the Honeycomb Facets Variable Thickness for Wind Turbine

2004 ◽  
Vol 261-263 ◽  
pp. 777-782 ◽  
Author(s):  
Yun Hae Kim ◽  
J.D. Kim ◽  
V.A. Shuripa ◽  
Cheolmun Yim ◽  
Tae Gyu Park
Keyword(s):  
Wind Turbine ◽  
Glass Fiber ◽  
Variable Thickness ◽  
Resin Composite ◽  
Thickness Distribution ◽  
Surface Model ◽  
State Variables ◽  
Principal Stresses ◽  
Element Analysis ◽  
Honeycomb Sandwich

Decreasing of wind turbine blade weight by using honeycomb sandwich collides with strength lack of the honeycomb facets at the high loaded places of the blade under heavy wind load. For providing tensile and compressive strength profiling of the variable thickness facets was made. By using response surface model based on design space the facets rational thickness distribution was performed by using optimization. The condition of evenly distributed stresses at narrow range of values for reinforced facets was used like state variables for optimum designing. By combining finite element analysis and sequential programming the response of the thickness within the process integration framework on criteria the rationalization of the facets thickness was performed. The facets thickness variations are assigned by polynomial of fifth degree to provide small difference of stresses in the facets for blade. The angles of the glass fiber stacking relatively of the blade axis for mass minimization were selected on the similar stress reinforcement condition for outside and inside facets of the honeycomb sandwich. The structure of the reinforcing was built to coincide the principal stresses and strains of the facets to longitudinal and transversal direction of the blade. Calculation results were obtained for glass fiber -epoxy resin composite material having and shown that decreasing total mass of the blade 19% compare to shape optimization.

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