This study investigates the impact of perforations on the load-bearing capacity of C-section columns with different web stiffener configurations and proposes effective structural measures to mitigate capacity loss due to perforations. First, experimental tests were conducted on channel sections with a flat web, a V-shaped web stiffener, and a bow-shaped web stiffener. The specimens included unperforated columns as the control group, perforated columns, and perforated columns reinforced with batten panels. Subsequently, finite element modeling and parametric analysis were carried out based on the experimental results. Analysis of the experimental and finite element results indicates that flat-web C-section columns experience the least reduction in loadbearing capacity, while V-shaped web-stiffened C-section columns show significant stiffness degradation and the greatest reduction in load-bearing capacity after perforation, with reductions of up to 32.3% in the tests and 35.9 % in FEA. When transverse support is provided by batten panels, the distortional buckling of bow-shaped web-stiffened C-sections is suppressed, resulting in a substantial increase in load-bearing capacity, up to 50.9 % in the tests and 74.3 % in FEA. The load capacity evaluation reveals that the Direct Strength Method is conservative and reliable for flat-web C-section columns but tends to be non-conservative and less reliable for Csection columns with web stiffeners. Finally, this study introduces the perforation strength reduction factor to directly calculate the load-bearing capacity of perforated C-section columns, providing more reliable and less dispersed calculation values. Similarly, the strength enhancement factor proposed for batten panels can be used to directly calculate the load-bearing capacity of perforated, web-stiffened C-section columns, offering accurate, consistent, and reliable calculation results.

Assembling two or more channel sections is a common method to enhance the load-bearing capacities of thinwalled compression members in light gauge steel structures. However, perforations in these members redistribute stress across the section, reducing load-bearing capacity and increasing calculation complexity. This study combines experimental and finite element analysis to quantitatively examine: (1) the relationship between web perforations and the load-bearing capacities of built-up sections, and (2) the effectiveness of batten plates in compensating for the reduction in load-bearing capacities of perforated built-up sections. Specimens were categorized into three types: flat-web, V-shaped web-stiffened, and bow-shaped web-stiffened built-up sections. The analysis included specimens without holes, with web holes, and with web holes but reinforced with batten plates. Results indicate that flat-web built-up sections experience the least reduction in load-bearing capacity (average reduction of 5.4 % to 8.3 %) after perforations, while V-shaped web stiffener sections suffer the greatest loss (average reduction of 11.2 % to 15.6 %). Batten plates can compensate for the loss in flat-web built-up sections, resulting in a more uniform stress distribution. Notably, bow-shaped web-stiffened built-up sections can achieve load-bearing capacities with average increase up to 18 % after batten reinforcement, significantly exceeding those of unperforated built-up columns. Reliability analysis showed that the current direct strength method has low reliability and high variability. Therefore, this study proposes strength reduction factors for calculating the load-bearing capacities of perforated built-up sections, which are reliable and have low variability. Correspondingly, strength enhancement factors for batten-reinforced built-up sections are proposed, ensuring reliable and precise calculations with low variability.

This study investigates the effects of perforations on the buckling behavior and load-bearing capacity of advanced high-strength steel I-shaped built-up compression members. The built-up section was fabricated by connecting two identical lipped channel sections made of complex phrase steel HC700CP980 using pull rivets. The perforations were classified into two groups: holes in web and holes in both web and flanges. A comprehensive parametric study, combining both experimental results and finite element analysis, demonstrated the decrease in load-bearing capacity caused by the presence of perforations, particularly noticeable in specimens featuring holes in both web and flanges. The extend of the reduction is closely linked to the quantity and dimensions of the holes, with a higher hole-element width ratio resulting in a more substantial loss of load-bearing capacity. Additionally, the obtained test and FE results were used to evaluate the accuracy of direct strength method (DSM) for the examined advanced high-strength steel I-shaped built-up compression members. The evaluation findings highlight the limitations of the DSM in the design predictions for built-up columns featuring multiple web holes and holes on both web and flanges. Therefore, a modified calculation method was proposed, which integrated strength reduction factors to consider the influence of the position of holes relative to the flexural buckling axis of built-up sections. The modified method has shown notably improved design accuracy and consistency for the perforated advanced high-strength steel I-shaped built-up sections.

This paper explores the corrosion resistance of stainless steel clad carbon steel plate (SCSP) in simulated marine environments. The hot-rolled steel plate, composed of stainless steel (304) exteriors and a carbon steel (Q235) core, underwent a salt spray test for 24 to 1344 h. The study focused on three sections: the transverse section, the core layer of carbon steel, and the outer layer of stainless steel. Using mass loss method, electrochemical methods, and microscopic and compositional analysis, it was found that stainless steel showed significantly better corrosion resistance than carbon steel. The carbon steel's corrosion rate was initially high but stabilized over time due to alpha-FeOOH in the rust layer. The transverse section exhibited a similar but slightly higher corrosion rate. XRD analysis identified alpha-FeOOH in the rust layer, while SEM, EDS, and 3D scanning indicated significant galvanic corrosion at the stainless and carbon steel interface, causing deep pits. Overall, the corrosion rate of the transverse section over longer exposure is influenced by both the rust layer's resistance and the galvanic corrosion at the bi-metallic section.

This paper presents an experimental investigation of the post-fire behavior of double-sided stainless-clad bimetallic steels (DSSCBS), which is a new type of high-efficiency material and is promising to be used in cold-formed structures. A total of 48 tensile coupon specimens were extracted from two types of DSSCBS plates, with 316L stainless steel as the cladding material and Q235 or Q345 carbon steel as the substrate material. The specimens were heated up to various temperatures up to 1000°C and subsequently cooled down to ambient temperature via air-cooling or water-cooling methods, to evaluate the effect of different cooling approaches. Additionally, the influence of in-fire stresses, which reflects the load ratios of structural members in fire hazards, was also examined. Stress-strain curves as well as key mechanical properties including the elastic modulus, yield strength, ultimate strength, ultimate strain and fracture strain were obtained and fully reported. Moreover, the measured post-fire retention factors were compared with existing prediction equations for carbon steel and stainless steel, as well as the prediction curves for single-sided stainless-clad bimetallic steel to assess their applicability to this novel material. New predictive rules for retention factors of DSSCBS in post-fire conditions were proposed with stress-strain models advanced to offer a reference for future numerical simulation and assessment of the post-fire behavior of members and structures of DSSCBS.

Superabsorbent polymers are new functional polymeric materials that can absorb and retain liquids thousands of times their masses. This paper reviews the synthesis and modification methods of different superabsorbent polymers, summarizes the processing methods for different forms of superabsorbent polymers, and organizes the applications and research progress of superabsorbent polymers in industrial, agricultural, and biomedical industries. Synthetic polymers like polyacrylic acid, polyacrylamide, polyacrylonitrile, and polyvinyl alcohol exhibit superior water absorption properties compared to natural polymers such as cellulose, chitosan, and starch, but they also do not degrade easily. Consequently, it is often necessary to modify synthetic polymers or graft superabsorbent functional groups onto natural polymers, and then crosslink them to balance the properties of material. Compared to the widely used superabsorbent nanoparticles, research on superabsorbent fibers and gels is on the rise, and they are particularly notable in biomedical fields like drug delivery, wound dressing, and tissue engineering.

This paper examines the influence of perforations on the buckling instability and load-bearing capacity of advanced high-strength steel channel section (C-section) columns. Experimental tests were first conducted on 19 column specimens made of complex phrase steel HC700CP980 under axial compression, followed by finite element (FE) analysis. Two section types, the flat web C-section and the web-stiffened C-section, were considered, with perforations categorised as web-only or both web and flanges. Material tests and initial imperfection measurements were conducted and reported. Using test results, finite element models were established and parameter analysis was carried out. Analysis of test results and finite element data revealed that perforations had a noticeable impact on the buckling deformation of flat web C-sections but had a minor effect on load-bearing capacity. In contrast, web-stiffened C-sections exhibited intensified deformation post-perforation, significantly reducing their axial stiffness and load-bearing capacity. The Direct Strength Method (DSM) was assessed based on combined test and FE data. It revealed that the DSM resulted in a high level of inaccuracy and scatter in the load-bearing capacity predictions of high-strength steel C-sections after perforation. To address this, a modified method incorporating a perforation strength reduction factor was proposed, offering straightforward and intuitive calculations with improved design accuracy and consistency.

This paper presents a numerical investigation and design of cold-formed steel built-up closed section columns with web stiffeners. A finite element model (FEM), considering the initial geometric imperfections and nonlinear material properties, was developed to simulate the structural behaviour of fixed-ended built-up closed section compression members. The comparison between the numerical results and the available test results show that this FEM can provide good predictions for both the ultimate strength and the failure modes of the test specimens. The verified FEM was used to conduct an extensive parametric study for the investigation on the structural behaviour of cold-formed steel built-up closed sections with web stiffeners. The parametric study was designed to investigate the effect of web stiffeners as well as to evaluate the current design method. The column strengths obtained from the finite element analysis and the test results were compared with the design strengths calculated using the direct strength method in the North American Specification and the Australian/New Zealand Standard for cold-formed steel structures. Design curves modified from the current direct strength method are proposed for flexural, local and distortional buckling. The reliability analysis was used to assess the current design rules and the modified design curves. It is shown that the modified direct strength method is generally conservative and reliable for the design of cold-formed steel built-up closed section compression members.

This paper presents an experimental investigation conducted on cold-formed steel built-up closed section columns with web stiffeners. To fabricate a built-up closed section, the single open sections were formed by brake press operation with high strength steel plate of thickness of 0.48 and 1.0 mm, then two identical sections were connected together face-to-face by self-tapping screws. After the measurements of material properties and the initial geometric imperfections were made, the built-up closed section specimens with inward or outward stiffeners at the web were tested between fixed-end boundary conditions with various column lengths ranging from 300 to 3200 mm. The tested specimens were failed by local buckling and interaction between local and flexural buckling. The ultimate strengths of the specimens were used to compare with the column strengths predicted using direct strength method, which is adopted in the North American Specification and Australian/New Zealand Standard for cold-formed steel structures. In addition, a reliability analysis was performed for this design method to access its reliability with cold-formed steel built-up closed section compression members. The results show that the direct strength method is applicable for the design calculation of cold-formed steel built-up closed section compression members with web stiffeners. (C) 2017 Elsevier Ltd. All rights reserved.

This paper describes an experimental investigation of cold-formed steel built-up closed sections compressed between fixed ends. Two built-up closed section types, one with inward web stiffeners, and the other with outward web stiffeners, were tested. The test specimens were firstly brake-pressed from high strength zinc-coated steel sheets. Then, two of the same sections were connected face-to-face by self-tapping screws to form a built-up closed section. The members had the nominal thicknesses of 0.48 and 1.0 mm. The column length of the test specimens varied from 300 to 3200 mm, with an increment of approximately 600 mm. The material properties were obtained by tensile coupon tests. The failure modes including local buckling and interaction of local and flexural buckling were observed in the tests. The appropriateness of the direct strength method in the North American Specification and Australian/New Zealand Standard for cold-formed steel structures was evaluated based on the test results. It is shown that the direct strength method can be used for cold formed steel built-up closed sections with web stiffeners.

A built-up I-section with longitudinal stiffeners is expected to have better performance to resist against local and distortional buckling compared to conventional built-up I-section by simply connecting two plain channels back-to-back. This paper presents a non-linear finite element analysis to investigate the behaviour of cold-formed steel built-up open section columns with edge and web stiffeners. A finite element model was firstly developed and verified against tests of cold-formed steel built-up compression members, in which the initial geometric imperfections and material properties of the test specimens were included. Secondly, the verified finite element model was used for an extensive parametric study of fixed-ended cold-formed steel built-up open section columns. The parametric study was designed to investigate the effect of edge and web stiffeners in the built-up open sections. The finite element results together with the test results were compared with the design predictions calculated from the current design rules in the North American Specification and the Australian/New Zealand Standard. Furthermore, design rules of the current direct strength method were modified. It is shown that the design strengths predicted by the modified direct strength method are generally in good agreement with the ultimate loads of the built-up open section columns. In addition, the current design rules and the modified direct strength method were evaluated by reliability analysis.

A series of column tests on cold-formed steel I-shaped open sections with edge and web stiffeners has been conducted. The test specimens were firstly brake-pressed from high strength zinc-coated steel sheets and then two of the same members were connected back-to-back by self-tapping screws to form an I-shaped section with edge and web stiffeners. The members had the nominal thicknesses of 0.48, 1.0 and 1.2mm. The column length of the test specimens varied from 300 to 3200mm with an increment of approximately 600mm. The column specimens were compressed between fixed ends. Tensile coupon tests were also conducted to obtain the material properties at both flat and corner portions of the sections. Initial local and overall geometric imperfections were measured. The columns were failed by local, distortional, flexural buckling and the interaction of these buckling modes. The failure modes and ultimate strengths of the column specimens were presented. The direct strength method in the North American Specification and the Australian/New Zealand Standard was used to calculate the design strengths of the I-shaped open section columns. The appropriateness of the direct strength method for I-shaped open sections with edge and web stiffeners was evaluated. In addition, the reliability of the direct strength method for the I-shaped open sections was evaluated using reliability analysis. It is shown that the direct strength method can be used for cold-formed steel I-shaped open sections with edge and web stiffeners.