Elastic-plastic Interactive Buckling of Thin-walled Steel Compression Members

In the actual design codes the interaction formula for local and overall buckling modes of thin-walled steel compression (TWSC) members, the effect of local buckling. is introduced by means of effective strength of short members. This paper proposes to replace, into the Ayrton-Perry interaction formula, the short member effective strength, which is based on the effective width approach by the plastic strength evaluated by means of local plastic mechanism analysis. There are some papers by Murray et al. [1,2,3], in which the plastic mechanisms corresponding to the local buckling of plates and TWSC members in compression are analysed. On this basis, the local·overall interactive buckling modes can be regarded as interaction between local rigid-plastic mode and overall-elastic one, but until now it was difficult to couple these two modes into an adequate interactive equation. The paper shows the use of proposed plastic-elastic approach for the analysis of some series of plain and lipped channel specimens in compression. Comparisons with test and EUROCODE 3 results are presented

Plastic Strength of Thin-walled Members

Failure of thin-walled cold-formed members in compression is always characterized by a local plastic mechanisms, either a stub or slender column is referred. Starting from this observation, the authors suggest for the interactive local-overall buckling analysis to use instead of traditional effective section , the sectional plastic mechanism strength. This is a new approach and for this reason it is compared with another one, namely the Direct Strength Method. Experimental results and advanced FEM simulations are used to evaluate the two methods. Comparisons with European and American relevant design codes are also presented in the paper

Seismic Performance of Wall-stud Shear Walls

The ever-increasing need for housing generated the search for new and innovative building methods to increase speed, efficiency and enhance quality, one direction being the use of light steel profiles as load bearing elements and different materials for cladding. Wind and seismic behavior of these structures is influenced by the hysteretic characteristics of the shear wall panels. In this paper a review of actual research in the field and results of a full-scale shear test program on wall panels are presented. Based on tests, a numerical equivalent model for hysteretic behavior of wall panels working in shear was built to be used in 3D dynamic nonlinear analysis of cold-formed steel framed buildings

Cold-formed Steel Sections Experimental Data Base

Thin-walled cold-formed member critical load in the coupling point of overall/local buckling modes is defined, together with critical load erosion factor (ψ). A calibration method for (ψ) using an experimental database called DATACOST is presented

Dual-Steel Eccentrically Braced Frames with Bolted Links – Simulation of Safe Removal Process

Current seismic design philosophy is based on dissipative structural response, which implicitly accepts damage to the main structure and significant economic losses. Repair of the structure is often impeded by the permanent (residual) drifts of the structure. The proposed research aims at reducing the repair costs and downtime of a structure hit by an earthquake, and consequently more rational design approach in the context of sustainability. These objectives are to be attained through removable dissipative members and re-centring capability of the structure, concepts that are to be implemented in a dual structure, obtained by combining steel eccentrically braced frames with removable bolted links with moment resisting frames. The bolted links are intended to provide the energy dissipation capacity and to be easily replaceable, while the more flexible moment resisting frames would provide the necessary re-centring capability to the structure. The columns of the structure are to be realised from high strength steel, in order to keep these members in the elastic range even under strong seismic input. Practical solutions regarding order in which bolted links need to be replaced are proposed. In order that the link removal process to be a safe one, there is analyzed and chosen a solution that uses tension rods with viscous dampers mounted on the structure during link removal. Once the seismic link is removed from the structure, this system slowly releases the accumulated forces and the structure comes back to its initial position.JRC.G.4-European laboratory for structural assessmen

Factors affecting the response of steel columns to close-in detonations

[EN] Explosions produced in urban areas by the detonation of explosives are low-probability but high-impact events. When they occur in the immediate vicinity of buildings, the explosions can pose a high risk to the structural integrity (local/global failures) and to the occupants (risk of injury, death). Therefore, the design and the construction of the buildings should contain preventive measures to increase the robustness of the structures. The paper presents the results of recent research carried out on the safety of building structures under extreme actions. Blast tests performed on two identical 3D specimen extracted from a typical moment resisting steel frame structure, allow to calibrate the numerical models of a full scale building structural frame system and evaluate the consequences of close-in detonations on the structural elements. The data of the experimental testing, combined with the numerical modelling, allow to investigate different factors, such as dynamic factors that affect the local failure mechanism and the residual capacity of steel columns under different blast scenarios.This work was supported by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS/CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED2016-0962, within PNCDI III: “Experimental validation of the response of a full-scale frame building subjected to blast load” - FRAMEBLAST (2017-2018).Dinu, F.; Marginean, I.; Dubina, D.; Khalil, A.; De Iuliis, E. (2018). Factors affecting the response of steel columns to close-in detonations. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 873-880. https://doi.org/10.4995/ASCCS2018.2018.7186OCS87388

Experimental investigations on built-up cold-formed steel beams connected by resistance spot welding

[EN] The WELLFORMED research project, ongoing at the CEMSIG Research Center of the Politehnica University of Timisoara, proposes to study a new technological solution for built-up beams made of corrugated steel sheets for the web and thin-walled cold-formed steel profiles for the flanges, connected by resistance spot welding. Within the research project, the experimental work includes tensile-shear tests on the lap joint spot-welded specimens, were different combinations of steel sheets with various thicknesses were tested and, tests on full scale beams in bending. The study intends to demonstrate the feasibility of the proposed solutions, to assess their performance and to enlarge the knowledge by using numerical simulations for the optimization of the current solution and to define the limits of the solution’s applicability.This work was supported by a grant of the Romanian National Authority for Scientific Research and Innovation, CNCS/CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED2016-1684 / WELLFORMED - Fast welding cold-formed steel beams of corrugated sheet web, within PNCDI III.Ungureanu, V.; Both, I.; Burca, M.; Grosan, M.; Neagu, C.; Dubina, D. (2018). Experimental investigations on built-up cold-formed steel beams connected by resistance spot welding. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 205-212. https://doi.org/10.4995/ASCCS2018.2018.716920521

EXPERIMENTAL RESEARCH ON T-STUBS UNDER ELEVATED TEMPERATURES

Bolted end plate connections are widely used in multi-storey steel frame structures. Their design is based on the component method, which evaluates the behaviour of the basic components through equivalent T-stubs, to model the tension zone that constitutes the most relevant source of deformability. The paper presents the results of an experimental research on bolted T-stubs, tested under elevated temperatures, in normal and high strain rate loading conditions. The influence of the loading rate on the resistance and ductility of the T-stubs subjected to elevated temperatures is emphasized

Koiter asymptotic analysis of thin-walled cold-formed steel members

Abstract An imperfection sensitivity analysis of cold-formed steel members in compression is presented. The analysis is based on Koiter's approach and Monte Carlo simulation. If the modes interaction is correctly accounted, than the limit load and the erosion of critical buckling load can be easily evaluated. Thousands of imperfection can be analysed with very low computational cost and an effective statistical evaluation of limit performance can be carried out. The analysis is done on pallet rack uprights in compression, based on an intensive experimental study carried out at the Politehnica University of Timisoara

Numerical Study of Stability of Cold Formed Built-Up Columns

By means of numerical simulations using ANSYS program, the stability behavior of built-up columns made of back-to-back cold formed C sections, bolted together by C stitches, is analyzed. Comparison of the numerical analysis with the results obtained using two different design methods and experimental results are provided