Detailing Redundant Pattern–Induced Failures in Transmission Line Towers

Transmission line (TL) towers may fail prematurely during mandatory testing for many reasons, even though they were designed based on the provisions of different standards. Five premature failures observed during full-scale testing at the Tower Testing and Research Station, Structural Engineering Research Centre [Council of Scientific and Industrial Research (CSIR)-SERC], Chennai, India, are grouped into two categories and studied in detail. The first two towers failed due to improper and inadequate redundant patterns and design. The third tower failed due to the detailing not matching the design assumptions. The fourth tower failed due to insufficient bolts in the stitch plates, and the fifth tower due to improper detailing. All the failures are modeled using general-purpose finite-element software. The test and analytical results are compared with the design code provisions. This study emphasizes the importance of detailing and the secondary member design.