Abstract: Foundations are one of the major factors affecting the behaviour of the transmission tower as it transmits loads to the soil. Recently with increase in size of transmission tower with extra high transmission voltages, loads acting on the foundation increases and thus, requiring heavier foundation. Hence, it is necessary to design the foundation considering safety and economy. Also, it is necessary to consider the soil type for which the foundations have to be designed. In this work, Models of self-supported suspension and tension towers are analysed for 66 kV, 220 kV and 400 kV transmission voltages in STAAD PRO v8i. Comparative study for 2-stepped and 3-stepped isolated foundations of towers has been carried out for five types of soil conditions. Analysis and design of all foundations has been done for all given conditions and estimated quantities of materials are compared. It has been observed that 2-stepped isolated foundation requires 1.1 to 1.27 times more steel than 3-stepped isolated foundation for all types of soil condition. It was also shown that the minimum cost is obtained for dense soil than any other soil type. Hence, it can be concluded that the economical design of foundation is obtained by using 3-Stepped foundation with dense sand.

Keywords: Transmission Line Tower, Suspension and Tension Tower, Isolated Foundation, Different soil conditions

| DOI: 10.17148/IARJSET.2021.8538