Abstract The use of diverse material combinations in engineering structures is witnessing growing interest, particularly in sectors such as transportation, due to the improvements it offers in design efficiency and overall performance compared to single-component materials. Ultrasonic welding (USW) is a promising modern technique for joining thin sheets of similar and dissimilar non-ferrous metals, such as aluminum and copper, without the need for fillers. This study analyses the effect of using a zinc intermediate layer on the development of the microstructure and mechanical properties of dissimilar aluminum/copper joints resulting from ultrasonic spot welding. This study focuses on the mechanical properties of asymmetric aluminum-copper joints created using ultrasonic welding. These joints typically exhibit high strength and resistance to various mechanical loads and stresses. Recent studies have investigated the relationship between the tensile strength of welded joints and key operating parameters, such as welding pressure, welding time, and fixation period. The results show that increasing the welding pressure while extending the process time enhances the bond strength between the welded plates. Furthermore, the use of intermediate layers, particularly zinc layers, has been shown to effectively improve mechanical performance by increasing the tensile and shear strength of the joints. The shear strength of ultrasonically welded aluminium/copper joints, both with and without zinc interlayers, initially increased by 35%, while fracture energy decreased threefold during the formation of the aluminium-zinc/copper-zinc phase. However, it declined when subjected to an input energy of 1000 J. Additionally, this review article systematically examines the mechanical behaviour of ultrasonic-welded sheets, interface characteristics, performance outcomes, and the influence of system parameters applies on a selected material combination.
This paper presents a comparative study of several design approaches for evaluating the lateral-torsional buckling resistance of steel girders with doubly symmetric I and H cross-sections, both hotrolled and welded. The investigated methods include the general method and alternative approaches specified in EN 1993-1-1:2006 and EN 1993-1-1:2022, as well as simplified procedures that avoid the explicit evaluation of the elastic critical moment Mcr. A numerical application on an IPE 400 beam is used to quantify the influence of the chosen method on the resulting non-dimensional slenderness, reduction factors and design bending resistances. The results highlight the difference between methods, show that the direct simplified procedure leads to the most conservative resistance, and underline the conditions under which simplified approaches may become unconservative for lateral-torsional buckling verification.
The paper deals with solving the instability phenomenon of a diluvial clay slope. The flysch deposits that predominate in the Curvature Subcarpathians are frequently affected by slope instability phenomena. The large volume of sediments entrained in movement requires that the stabilization method result as a consequence on the one hand of the scale effect, which implies a reduction of the mechanical parameters, and on the other hand due to cost constraints. Due to the fact that they generally have a creep character and do not have a visible catastrophic effect, they are analyzed as being of low risk, but their stabilization represents a major challenge from a technical point of view. The study case presents a stabilization method with minimal costs that has proven its effectiveness by acting on the entire unstable mass through superficial drainage and modifying the geometry of the slope by creating terraces and in the last instance a punctual intervention through support structures. After six years the aspect of the slope is still stable, uniform, clean, without irregularities.
Structures composed of lattice beam subassemblies are commonly used for constructing pedestrian bridges with medium spans. These structures are typically equipped with wind bracing at the top. Another scenario where lattice walls are employed is in box girders with concrete decks. During the installation phase, these girders are fitted with upper flange bracing to ensure overall structural stability. For composite decks or those with orthotropic steel plating, lattice bracing may also be arranged at the bottom. Truss walls can be transformed into plate beams using the transformed beam method, which simplifies efficiency analysis, particularly for torsional stresses. This case study presents an example of equating a truss structure with a plate structure under torsional loading. The efficiency of closed sections compared to open sections for pure torsional resistance is analysed.
The European Union has long prioritized the enhancement of energy efficiency in buildings, aligning with the nZEB (nearly Zero Energy Building) standard, with the ambitious target of achieving Zero Energy Buildings (ZEB) by 2030. This article aims to showcase the use of passive technologies for achieving a Zero Energy Building on a historic building located in Bucharest, with a volumetric design worth emphasizing dating back to the post-war period. This study underscores the challenges architects and engineers encounter in upgrading the energy efficiency of such structures while preserving both their aesthetic coherence and the architectural integrity of the period. Various passive technologies are employed to boost the energy efficiency of the selected building. These include measures such as: thermal bridge reduction, thermal envelope and window details for capturing solar energy and reducing the overheating. The active technologies that remain include ventilation and heating in a small percentage. To assess and quantify the energy efficiency achieved through these interventions, the Passive House Institute's methodology is adopted. Also, for calculating the solar gain, custom more detailed methods are applied. By showcasing the successful integration of passive technologies in a historic building, this paper contributes to a sustainable architecture and offers practical insights for architects, engineers and stakeholders for achieving ZEB status while respecting the unique characteristics and the heritage of historic structures.
