1. INTRODUCTION Tubular hollow sections are extensively used in industrial structures. These structures are often under imposed bending stresses during their service life. These elements sometimes contain surface defects, such as a dent, which may be caused due to a collision or during the transportation of the products. Very limited research has been conducted to evaluate the effect of surface defects on the loading capacity of such structures. As a result, no recommendations and design tips can be found in current design codes and guidelines to determine the tolerated size of surface defects in tubular sections. To this end, the present study assesses the post-collision integrity of such structures under bending. A literature review on the dented shell structures shows that previous studies have been carried out on various kinds of thin-walled structures under different loading conditions. Raviprakash Prabu et al. (2007) examined shells exposed to dent imperfection and subjected to compressive loads. It was found that buckling capacity dramatically decreased for the shells with both short and long dents. Raviprakash Prabu et al. (2012) studied the effect of the size and orientation of a Advances in Structural Engineering Vol. 18 No. 11 2015 1807 Experiments on Dented Steel Tubes under Bending Tohid Ghanbari Ghazijahani * , Hui Jiao and Damien Holloway School of Engineering and ICT, University of Tasmania, Hobart, Australia (Received: 22 August 2014; Received revised form: 15 October 2014; Accepted: 18 November 2014) Abstract: Steel tubular sections are extensively found in many kinds of civil and mechanical engineering structures such as columns and bracing elements, offshore industry, bridge elements, etc. Due to the extensive usage, a considerable amount of research has been carried out on such structural members. Although many studies focused on the bending stability of steel members, very little research can be found on the effect of surface defects, such as dent imperfection, on the bending behavior of such tubular members. This research aimed to evaluate the effect of dent-shaped defects on the flexural capacity of CHS members. The data obtained in this paper can be applied to evaluate the capacity of large scale CHS members with similar D/t ratio when a dent is formed on the tubes during the service life of such members. An interrelation between the capacity and the details of the dent, i.e. size and position of the dent, was proposed. Key words: thin-walled steel tubes, bending, dent imperfection, ultimate capacity. centrally located dent on the ultimate capacity of a thin steel plate under axial compressive loading. They mentioned that the load carrying capacity of the dented plate largely depended on the area of the dented plate excluding the area of DAR (dent affected region). In addition, it was pointed out that plates with a longitudinal dent had either equal or higher ultimate strength than the dented plates with a transverse dent of the same size. Theoretical and experimental investigation of damaged tubular members in offshore structures was studied by Taby et al. (1981) and Ellinas studied the ultimate capacity of damaged tubular bracing elements (Ellinas 1984). The mechanics of damage was examined as a parametric study which eventually led to design recommendations. Smith et al. (1979) investigated the buckling capacity and post- collapse response of bracing elements including damage effects. These authors studied the stiffness and residual strength of damaged steel bracing members as well as a respective study (Smith et al. 1981). The relationship between collision load and value of damage deformations was obtained in this study. Initiation of buckling propagation in pipes under denting loads was * Corresponding author. E-mail address: tohidghanbari@gmail.com, tohid.ghanbari@utas.edu.au; Tel: (+61) (0)469 311 896. Provided ONLY for academic NOT commercial or distribution use - All rights reserved to ASE DOI: http://dx.doi.org/10.1260/1369-4332.18.11.1807