System reliability analysis of cold-formed steel lipped channel section panel

Abstract

Transmission Line (TL) systems and the TL tower as support structures are the vital infrastructure facilities. Conventionally these towers are fabricated using Hot Rolled Steel (HRS) angle sections. Nowadays, the use of Cold- Formed Steel (CFS) is gaining popularity in construction of general steel structures due to its cost effectiveness and numerous other advantages. An attempt has been made in this research work to carry out the experimental investigations on X-bracing panel replicating substructure of a TL tower made of CFS lipped channel sections. Prior studies by the authors on probabilistic analysis of capacity/resistance of CFS columns suggested the distribution of resistance, with modelling error as random variable seems to follow lognormal distribution irrespective of the design standards, and COV for simulated resistance with modelling error, as random variable is 0.3. The results of experimental investigations on CFS panel indicated that the individual member capacities calculated as per ASCE 10-15 (2015) standard are higher as compared to the member forces corresponding to panel failure load. Hence, it is proposed to carry out the system reliability analysis considering the possible uncertainty parameters. Present studies brought out the importance of consideration of the modelling error associated with the member strength estimation models given in design standards along with the variations present in material properties and loading. Further, estimations of component reliabilities for the panel members may not provide actual failure probability for the system and hence it is necessary to carry out system reliability analysis. While evaluating the safety margins for various failure modes, in order to determine the overall reliability of structural system, it is important to consider the correlations arising from the common sources of loading and common material properties. In this study failure probability has been estimated considering the series system for critical members contributing to overall failure of panel.