Thermomechanical analysis of cold formed steel sections

This work presents an experimental study about cold formed steel elements submitted to compression loads. The sections analyzed are C and Z sections made of steel sheet with 1.5 and 2 [mm] thick and three different cross section heights. The compression tests were made at ambient and elevated temperatures. In both cases a pined support was developed and used. The member resistance at ambient temperature was determined by applying an increasing compression load until the member collapse was achieved. The fire tests were performed in a fire resistance furnace, using the same type of end supports, and a mechanical load given by a specific degree of utilization that is maintained constant during the fire test. These tests allow the determination of the fire resistance time and member critical temperature. The experimental results are compared with the ones obtained with the Eurocode simplified models.info:eu-repo/semantics/publishedVersio

Thermomechanical analysis of cold formed steel sections

This work presents an experimental study about cold formed steel elements submitted to compression loads. The sections analyzed are C and Z sections made of steel sheet with 1.5 and 2 [mm] thick and three different cross section heights. The compression tests were made at ambient and elevated temperatures. In both cases a pined support was developed and used. The member resistance at ambient temperature was determined by applying an increasing compression load until the member collapse was achieved. The fire tests were performed in a fire resistance furnace, using the same type of end supports, and a mechanical load given by a specific degree of utilization that is maintained constant during the fire test. These tests allow the determination of the fire resistance time and member critical temperature. The experimental results are compared with the ones obtained with the Eurocode simplified models.info:eu-repo/semantics/publishedVersio

Thermomechanical analysis of cold formed steel sections

This work presents an experimental study about cold formed steel elements submitted to compression loads. The sections analyzed are C and Z sections made of steel sheet with 1.5 and 2 [mm] thick and three different cross section heights. The compression tests were made at ambient and elevated temperatures. In both cases a pined support was developed and used. The member resistance at ambient temperature was determined by applying an increasing compression load until the member collapse was achieved. The fire tests were performed in a fire resistance furnace, using the same type of end supports, and a mechanical load given by a specific degree of utilization that is maintained constant during the fire test. These tests allow the determination of the fire resistance time and member critical temperature. The experimental results are compared with the ones obtained with the Eurocode simplified models.info:eu-repo/semantics/publishedVersio

Experimental study of cold-formed ferritic stainless steel hollow sections

Stainless steel is gaining increasing use in construction because of its durability, favorable mechanical properties, and aesthetic appearance, with the austenitic grades being the most commonly used. Austenitic stainless steels have a high nickel content (8–11%), resulting in high initial material cost and significant price fluctuations; this, despite its desirable properties, represents a considerable disadvantage in terms of material selection. Ferritic stainless steels, having no or very low nickel content, may offer a more viable alternative for structural applications, reducing both the level and variability of the initial material cost while maintaining adequate corrosion resistance. There is currently limited information available on the structural performance of this type of stainless steel. Therefore, to overcome this limitation, a series of material, cross section, and member tests have been performed, covering both the standard EN 1.4003 grade (similar to the chromium weldable structural steel 3Cr12) and the EN 1.4509 grade (441), which has improved weldability and corrosion resistance. In total, 20 tensile coupon tests, 16 compressive coupon tests, eight stub column tests, 15 flexural buckling tests, and eight in-plane bending tests were carried out. Precise measurements of the geometric properties of the test specimens, including the local and global geometric imperfections, were also made. The experimental results are used to assess the applicability of the current European (EN 1993-1-4) and North American (SEI/ASCE-8) provisions to ferritic stainless steel structural components. In addition, the relative structural performance of ferritic stainless steel to that of more commonly used stainless steel grades is also presented, showing ferritic stainless steel to be an attractive choice for structural applications

Connection in Joints for Thin-Walled Steel Sections and Sheeting

Thin-walled cold-formed members are thin, this will give rise to behavioural phenomena, which are not usually encountered in the more familiar hot-rolled sections. When compared to hot-rolled steel sections, cold-formed thin-walled steel sections are more likely to fail in local buckling, distortional buckling, various global buckling and shear buckling. This paper will discuss types of connection in Jjoints for coldformed thin-walled sections and steel sheeting. Bolts, screws, blind rivets or cartridge fired pins are commonly used in joints for coldformed thin-walled sections or steel sheet connections. Fasteners in light gauge steel tend to be relatively less stiff than their counterparts in heavier construction so that connection flexibility can be significant in certain assemblies. Furthermore, as in any load-bearing structure, it is important that connections are not brittle and this implies that there should be adequate deformation capacity

Effect of high-pressure rolling followed by laser processing on mechanical properties, microstructure and residual stress distribution in multi-pass welds of 304L stainless steel

Multi-pass fusion welding by a filler material (wire) is normally carried out to join thick steel sections used in most engineering applications. Multiple thermal cycles from a multi-pass weld resulted in a variable distribution of residual stress field across the weld and through the thickness. Presence of tensile residual stresses can be detrimental to the integrity and the service behaviour of the welded joint. In addition to a complex distribution of residual stress state, multi-pass welds also form dendritic grain structure, which are repeatedly heated, resulting in segregation of alloying elements. In this research, microstructural refinement with modification of residual stress state was attempted by applying post-weld cold rolling followed by laser processing and then cold rolling. The residual stress was determined non-destructively by using neutron diffraction. Post-weld cold rolling followed by laser processing was carried out to induce recrystallization of the cold rolled grains. Microstructural characterisation indicates a significant grain refinement near the capping pass. However, post-weld cold rolling followed by laser processing reinstates the lock-in stress. In this study, it was demonstrated that a complete recrystallized microstructure with compressive state of stress can be formed when a further cold rolling is applied on the laser processed, recrystallized microstructure

Design of new cold rolled purlins by experimental testing and Direct Strength Method

New cold roll formed channel and zed sections for purlins, namely UltraBEAM™2 and UltraZED™2, have been developed by Hadley Industries plc using a combined approach of experimental testing, finite element modelling and optimisation techniques. The new sections have improved strength to weight ratio by increasing the section's strength through the use of stiffeners in the section webs. The European standard, Eurocode 3 [1], uses the traditional Effective Width Method to determine the strength of a cold formed steel member. However, the design of the new sections UltraBEAM™2 and UltraZED™2 using this method is very complicated in calculating the effective section properties as these sections contain complex folded-in stiffeners. In addition, the incorporation of competing buckling modes such as distortional buckling of these sections can be difficult to analyse. To overcome difficulties of using Eurocode 3 or such a standard with the Effective Width Method for determining the strength of these sections, the Direct Strength Method is adopted in this paper. Four-point beam bending tests were carried out to determine the buckling and ultimate bending capacities of the UltraBEAM™2 and UltraZED™2 sections. Results from both experimental testing and Finite Element analysis were initially used as validation for the design using the Direct Strength Method. The Direct Strength Method's results were then compared with the experimental test results for a broader data in which the UltraBEAM™2 and UltraZED™2 sections had a range of different width-to-thickness ratios. It showed an excellent agreement between test and Direct Strength design values suggesting that the Direct Strength Method is a powerful tool for the design and optimisation of the new cold roll formed channel and zed purlins.N/

Virtual testing against experiment for post-buckling behaviour of coldformed steel columns

Cold-formed steel has already started to replace hot rolled companions in some structural applications. Advantages of cold-formed steel originate from its high strength over weight ratio and ease of manufacturing and construction compared to hot rolled heavy sections. Moreover, cold-formed columns have significant post-buckling reserve which has the potential to be exploited in design process. Therefore, it is essential to predict the response of cold-formed columns by means of high fidelity engineering techniques. Herein an in depth study which links experimental testing and non-linear computational capabilities is undertaken to address the failure behaviour of cold-formed columns. Experimental program comprises coupon tests to specify material properties and compression testing of fixed end cold-formed columns. Thereafter, measured material properties are utilized to generate a stress-strain curve for finite element models. Boundary conditions imposed into simulation models in such a way that would represent test conditions. Creating a suitable mesh for different cross sectional dimensions, different shapes of initial imperfections are introduced into models to compare contributions to performance of columns. Predicted collapse loads and modes via finite element models are assessed against test results. Mesh and initial imperfection sensitivities on failure characteristics are discussed. Finally a general assessment is made for the deployed testing and simulation to generate knowledge for the design evaluation of cold-formed steel columns. Key findings and discussions of present study have the potential to lead to develop promising cold-formed steel column virtual test models