Assessment of the Bending Moment Capacity of Naturally Corroded Box-Section Beams

Abstract

The steel constructions of mine shaft steelwork are particularly exposed to aggressive environments, which cause large, nonuniform corrosion loss throughout the steel members. A correct assessment of corrosion loss and load-carrying capacity of shaft steelwork is crucial for its maintenance and safe operation. In this article, we present the results of laboratory, numerical, and analytical investigations conducted on naturally corroded steel guides disassembled from shaft steelwork. The steel guides considered had a closed profile formed by welding two hot-rolled channel sections. Laboratory bending tests were carried out on beams with various levels of corrosion loss, corresponding to compact, non-compact, and slender cross sections. Multiple detailed measurements of the thicknesses of naturally corroded walls were used in order to reproduce their nonuniform geometry in finite element (FE) models. The results of numerical simulations of five bending tests showed good agreement with laboratory measurements and replicated the observed failure modes, therefore confirming the applicability of this modeling approach for assessing the moment capacity of highly corroded steel beams when the deteriorated geometry is known. For the purpose of generalization, a series of derived models reflecting the natural corrosion pattern was then developed, and moment capacity statistics were collected through multiple simulations. They showed that the mean moment capacity is determined by the mean wall thickness. However, the minimum moment capacity is strongly affected by corrosion loss variation, particularly for the highly corroded beams. A simplified, analytical modeling approach was also examined, providing fairly good assessments of the mean; however, the minimum moment capacity could not be estimated. This study contributes to the body of knowledge on the mechanical behavior of highly corroded hot-rolled box-section beams.

Structural Safety Assessment of Shaft Steelwork – A Review

“…the results of the load-carrying capacity numerical simulations (Fig. 8) were consistent with the laboratory test results in the study by Fiołek and Jakubowski [46,47]. they proved the accuracy of the standard formulas for moment resistance assessment of highly corroded guides.…”

“…laboratory tests (Fig. 7) performed on guides subjected to chemical etching to represent uniform cl [46] and naturally corroded guides [47] confirmed this particular change in the load capacity with the cl. the results of the load-carrying capacity numerical simulations (Fig.…”

“…by contrast, the standard formulas resulted in significant disagreements for extremely high wear (70% and more). based on many Fem numerical simulations, Fiołek and Jakubowski [47] showed that the influence of natural corrosion heterogeneity significantly affects the load-carrying capacity only for extremely corroded profiles, in which corrosion leads to wall perforation. otherwise, corrosion can be accurately estimated based on the average wall thickness.…”

“…otherwise, corrosion can be accurately estimated based on the average wall thickness. [47] and (b) uniformly corroded model [46] The main members, guides, and buntons of a structure determine its load-carrying capacity. khan and krige [35] conducted a load-carrying capacity analysis and forecasted further operation for two shafts in an advanced state of corrosive deterioration.…”

“…11) [49]. the resistance assessment considered the sensitivity to local buckling [44,46,47] and the uncertainty of the steel strength properties [52]. The load effects and resistance probability distributions enabled a probabilistic shaft steelwork reliability analysis.…”