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Title

INFLUENCE OF GEOMETRICAL IMPERFECTIONS ON ANALYSES OF DOOR OPENINGS IN TUBULAR STEEL TOWERS FOR WIND TURBINES

Authors

Abstract

Initial geometrical imperfection is an important factor in analyses of steel structures. Towers for wind turbines are particularly sensitive to the geometrical imperfection pattern and the amplitude. Consideration of global and local geometric imperfections in design may be found in EN1993-1- 1[1], EN1993-1-5[2] and EN1993-1-6 (Annex D) [3]. Various equipment may be used for measurements of initial imperfections: Low Voltage Displacement Transducers (LVDTs) [4,5,6], close-range photogrammetry, optical levelling and Leitz PMM 866 coordinate measuring machine [7]. The most popular way is using LVDTs. In this technology, LVDTs were connected to a reference frame and moved along a member. However, it is difficult to achieve high accuracy using this technique.
The main purpose of this paper is to present the influence of geometric imperfections on the resistance. The work is organized in three steps combining experimental data and FE analysis by Abaqus [8]. Firstly, the geometric imperfection was measured by laser scanning technology and stored electronically. In the second step, measured data were evaluated using Matlab [9] and GOM Inspect software [10], and exported as input data for a nonlinear analysis. In the next step, the nonlinear analysis is performed using measured geometric imperfections and geometric imperfections recommended in Eurocode. Finally, results of FE analysis have been compared with experiments.

References

[1] EN-1993-1-1. Design of steel structures, Part 1-1: General rules and rules for buildings, Brussels, Belgium: European Committee for Standardization, 2007.
[2] EN-1993-1-5. Design of steel structures, Part 1-5: Plated structural elements, Brussels, Belgium: European Committee for Standardization, 2007.
[3] EN-1993-1-6. Design of steel structures, Part 1-6: Strength and Stability of Shell Structures, Brussels, Belgium: European Committee for Standardization, 2007.
[4] Josef S., Haim A., 1995. “The development of shell imperfection measurement techniques”. Thin- Walled Structures, Elsevier Science Limited, Vol. 23, pp. 379-398.
[5] Pircher M., Wheeler A., 2003. “The measurement of imperfections in cylindrical thin-walled members”. Thin-Walled Structures, Elsevier Science Limited, Vol. 41, pp. 419-433.
[6] Pircher M., Wheeler A., 2003. “Measured imperfections in six thin-walled steel tubes”. Journal of Constructional Steel Research, Elsevier Science Limited, Vol. 59, pp. 1385-1395.
[7] Bernard E.S., Coleman R., Bridge R.Q, 1999. “Measurement and assessment of geometric imperfections in thin-walled panels”. Thin-Walled Structures, Elsevier Science Limited, Vol. 33, pp. 103-126.
[8] Abaqus 6.12-1, Simulia Dassault Systmes, 2012.
[9] Matlab R2013b, MathWorks, 2013.
[10] GOM Inspect V7.5, GOM mbH, 2013.

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