Steel pole structures are suitable alternate to transmission line towers, due to difficulty encountered in finding land for the new right of way for installation of new lattice towers. The steel poles have tapered cross section and they are generally used for communication, power transmission and lighting purposes. Determination of deflection of steel pole is important to decide its functionality requirement. The excessive deflection of pole may affect the signal attenuation and short circuiting problems in communication/transmission poles. In this paper, a simplified method is proposed to determine both primary and secondary deflection based on dummy unit load/moment method. The predicted deflection from proposed method is validated with full scale experimental investigation conducted on 8 m and 30 m high lighting mast, 132 and 400 kV transmission pole and found to be in close agreement with each other. Determination of natural frequency is an important criterion to examine its dynamic sensitivity. A simplified semi-empirical method using the static deflection from the proposed method is formulated to determine its natural frequency. The natural frequency predicted from proposed method is validated with FE analysis results. Further the predicted results are validated with experimental results available in literature.
This paper is concerned with the use of Schifflerised angle sections for triangular-based lattice communication towers. The torsional-flexural buckling properties of conventional 90 , 60 and schifflerised angles are compared. The experimental results obtained from the compression tests conducted on three different sizes of schifflerised angle sections are compared with the analytical results predicted from finite element analysis and with the capacities predicted from the procedure given in the literature. The capacity of schifflerised angles are underestimated by the methods suggested in the literature. The FE model non-linear analysis predicts the failure loads closer to the test results with a variation of À3 to 10%. The strength of schifflerised angles is 5 to 20% higher compared to conventional 90 angles. The behaviour of 60 m high three-legged triangular communication tower with schifflerised angles for leg members and conventional equal angles for all other members tested at Tower Testing and Research Station, CSIR-Structural Engineering Research Centre, Chennai is presented. NE-NASTRAN, a finite element software, is used to model the tower using beam column and plate shell elements for predicting the behaviour. The analytical and test results are compared with the codal provisions.
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