At the moment, Moshanir loading code which has been provided by Tavanir Company in 1998 is used for loading transmission line towers. Also ASCE52 are applied for designing these structures.
In the above Moshanir loading code, loading parameters such as, maximum yearly ice thickness, maximum monthly ice thickness, maximum yearly wind speed and maximum monthly wind speed have been considered as certain values and partial safety factors are determined without attention to uncertainty in these random variables.
In the present paper, load and resistance parameters that are involved in designing transmission towers, have been considered randomly, and based of this assumption reliability indices have been calculated for 230 KV towers’ members in two limit states function (Compression (Buckling) and Tension) for four selected city (Bandare Abbas, Yazd, Tehran and Shahre Kord) of Iran.
At the next step, by using attained results, Target Reliability Indices, have been calculated in the above limit states, and after that load and resistance factors have been calibrated so that reliability indices for new designed members be as near as possible to selected target reliability index, therefore this way would cause uniform safety for all members.
Finally, the results show that by using new load and resistance factors designers can make uniform safety for members. Also by this theory the weight of towers would be considerably decreased and therefore, towers can be designed economically and more realistic.
)