Capacity Evaluation of Power Transmission Line Towers under Wind Loading: A Case Study
Abstract
Pakistan is currently facing massive energy crisis and requiring huge investment into the power transmission line infrastructure. The longest transmission lines of the country are of 220 kV lines stretching up to 7359 km. The contemporary factored design wind load effects for overhead lattice transmission line tower are evaluated based on the applicable wind load factor, gust response factor and design wind speed as recommended by WAPDA/IEC Specifications (1988), ASCE-74 (1991) and ASCE-7 (2005). The current factors and design wind speed were developed considering linear elastic responses. However, information on the non-linear inelastic responses of such towers under dynamic wind loading and on the structural capacity of towers in relation to the design capacities is lacking. The knowledge and assessment of the capacity curve and its relation to the design strength is important to evaluate the integrity and reliability of these towers. Therefore, in this study, analysis was performed on 220 KV river crossing tower of 78.25 high (the highest transmission line tower in Pakistan), using a nonlinear static pushover analysis (NSPA) and incremental dynamic analysis (IDA). Firstly, NSPA was performed on 2D and 3D structural models for aforementioned codes and also for three additional load patterns according to first mode shape, power law and microburst/downburst phenomena. Afterwards, the IDA was performed for which time histories were generated by using NATHAZ Online wind simulator followed by a series of nonlinear direct integration dynamic analysis. Finally, for each loading pattern of NSPA and each time history of IDA, base shear load versus top displacement curves were plotted which are known as capacity curves. Numerical results showed that the structural capacity curves of the tower determined from the NSPA depend on the loading pattern and are similar to those obtained from IDA. The results indicated that the towers in Pakistan are reasonably reliable yet over designed due to standardized design approach across the country.References
[1] National transmission and Despatch Company Limited (NTDCL) Final Report “National power system expansion plan 2011-2030,” 2011.
[2] Hannuksela, J., "The transmission line cost calculator," Technology and Communication, 2011.
[3] Azhar, M. S., “Capacity evaluation of transmission line towers in Pakistan under wind loading,” M.Sc Thesis, U.E.T., Lahore, 2014.
[4] Computers and Structures, Inc. 2009. SAP2000 Structural Analysis Program, Nonlinear Version 14.0.0, Berkeley, California.
[5] WAPDA /NTDC Design Standards Specification, 1988.
[6] ASCE 74, Guidelines for electrical transmission line structural loading, ASCE manuals and reports on engineering practice No. 74, 1991.
[7] ASCE 7, Seismic design provisions, 2005.
[8] Krawinkler, H. and Seneviratna, K., “Pros and cons of a pushover analysis of seismic performance evaluation.” Engineering Structures, Vol. 20, No. 4-6, 1998,
[9] Vamvatsikos, D. and Cornell, A., “Incremental dynamic analysis.” Earthquake Engng Struct. Dyn., Vol. 31, 2002,
[10] NatHaz On-line Wind Simulator (NOWS) http://windsim.ce.nd.edu/int_winsim.html
[11] FEMA (2000), Prestandard and commentary for the seismic rehabilitation of buildings, Publication no. 356, prepared by the American Society of Civil Engineers for the Federal Emergency Management Agency, Washington, D.C.
[12] Concepción, D., Pascual, M., Mariano, V. and Osvaldo, M. Q. “Review on medelling of joint behaviour in steel frames.” Journal of constructional steel research, Vol. 67, 2011
[2] Hannuksela, J., "The transmission line cost calculator," Technology and Communication, 2011.
[3] Azhar, M. S., “Capacity evaluation of transmission line towers in Pakistan under wind loading,” M.Sc Thesis, U.E.T., Lahore, 2014.
[4] Computers and Structures, Inc. 2009. SAP2000 Structural Analysis Program, Nonlinear Version 14.0.0, Berkeley, California.
[5] WAPDA /NTDC Design Standards Specification, 1988.
[6] ASCE 74, Guidelines for electrical transmission line structural loading, ASCE manuals and reports on engineering practice No. 74, 1991.
[7] ASCE 7, Seismic design provisions, 2005.
[8] Krawinkler, H. and Seneviratna, K., “Pros and cons of a pushover analysis of seismic performance evaluation.” Engineering Structures, Vol. 20, No. 4-6, 1998,
[9] Vamvatsikos, D. and Cornell, A., “Incremental dynamic analysis.” Earthquake Engng Struct. Dyn., Vol. 31, 2002,
[10] NatHaz On-line Wind Simulator (NOWS) http://windsim.ce.nd.edu/int_winsim.html
[11] FEMA (2000), Prestandard and commentary for the seismic rehabilitation of buildings, Publication no. 356, prepared by the American Society of Civil Engineers for the Federal Emergency Management Agency, Washington, D.C.
[12] Concepción, D., Pascual, M., Mariano, V. and Osvaldo, M. Q. “Review on medelling of joint behaviour in steel frames.” Journal of constructional steel research, Vol. 67, 2011
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Published
2017-02-15
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Section
Civil Engineering,Structures, Construction, Geo technology, Water, Transportation
