A six-node triangular shell element was developed to study the geometrically non-linear behaviour of open-section members. The present formulation is free from shear and membrane locking due to use of mixed interpolation of tensorial components scheme. Due to model thin-walled section, an improvement is considered to update the normal vectors of elements which are located at the angle between flange and web of section. In other words, an average of director vectors is employed for these elements in updating formulation. Moreover, the total Lagrangian formulation is employed to consider large displacement and rotation. An incremental iterative technique named generalised displacement control method is utilised to solve the governing equation. Several numerical examples are studied to illustrate the accuracy and predictability of the proposed formulation.

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