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.
This study examines land surface emissivity (LSE) variability within the Saint Ana volcanic crater, part of the Ciomad volcanic complex in the Eastern Carpathians. Using Landsat 9 OLI-2/TIRS-2 data, emissivity was estimated through a vegetation-index-based approach to evaluate spatial relationships between lithology, vegetation density, and surface radiative properties. The analysis reveals measurable emissivity contrasts between densely forested crater slopes and exposed volcanic substrates dominated by silicate-rich materials. Lower emissivity values are associated with rocky outcrops and sparsely vegetated areas, whereas higher values correspond to vegetated and moisture-retaining surfaces. The results confirm the sensitivity of emissivity retrieval to geological and ecological controls and support its relevance for thermal characterization in heterogeneous volcanic environments.
Conventional concrete pavers depend largely on cement, resulting in high carbon emissions. Although there has been an extensive study on individual pozzolanic materials and natural fibres, there exists a gap regarding their combined effect on the performance of paver blocks. This study investigates the mechanical and durability properties of the low-carbon concrete paver block made up of Rice Husk Ash (RHA) and sisal fiber for sustainable infrastructure applications. The RHA was used as replacement level of 5%-20% by weight of cement with the inclusion of sisal fiber at 0.25%-1%. It was observed showed that 10% RHA combination with 0.75% fiber demonstrated enhanced mechanical properties. The developed paver blocks reached an average compressive strength of 35.83 MPa, meeting the IS 15658:2006 standards for light-traffic applications with average water absorption was 4.88%, which is under the limiting value 15658:2006 standards, signifying strong durability. The findings concluded that the synergistic use of RHA and sisal fiber improves strength, durability, and sustainability, offering a practical sustainable option for infrastructure pavement applications.
In that study, first, the behaviour of insulated concrete form walls with and without openings were analysed numerically by Abaqus and Sap2000 under different axial pressure levels. In screen grid insulated concrete form wall specimens, the lateral load capacity varied between 152kN to 362.6kN. The lateral load capacity of flat insulated concrete form walls varied between 160.17kN (in zero axial pressure) to 593.42KN (under an axial pressure which is equal to 35% of characteristic concrete strength). Later, a three-story structure was considered, to be constructed using screen-grid insulated concrete forms, flat insulated concrete forms, and conventional walls. According to the pushover analysis, it was seen that the structures showed nearly a linear elastic behaviour and the structures are rigid. By using screen grid insulated concrete form walls, it's possible to have a lateral load capacity which is 56% of the capacity of structure with conventional walls. By using flat insulated concrete form walls the capacity increased to 69% of the capacity of structure with conventional walls. The ICF system can be considered as an alternative fast construction method if rigid structures are aimed to be designed.
A comparative machine learning-based methodology was adopted to predict the compressive strength of fly ash concrete using Multiple Linear Regression (MLR), Support Vector Regression (SVR), AdaBoost Regressor (ABR), Random Forest (RF), and Extreme Gradient Boosting models (XG). A dataset of 498 mix designs collected from published literature was used, considering cement, fine and coarse aggregate, fly ash content, water content, water-cement ratio, and curing period as input parameters. Model performance was evaluated using mean absolute error, root mean square error, and coefficient of determination. The Extreme Gradient Boosting model showed the best predictive capability (R & sup2; = 0.881; RMSE = 5.65 MPa). Sensitivity analysis identified curing period, cement content, and water content as the most influential variables. The results demonstrate reliable strength prediction and enable model comparison to support data-driven mix optimization for sustainable fly ash concrete (FAC).
Columns are essential structural elements that support the weight of a building. If they fail, the entire structure can become unstable. This study examines three different types of mortar to determine which is most effective for reinforcing and repairing damaged columns exposed to uniaxial compression. The research focuses on war-damaged buildings in Benghazi, Libya, aiming to find the best mortar Mix for structural rehabilitation. Each mortar mix was designed to strengthen columns under two stress conditions: one where the load is applied until cracks first appear and another where the load continues until total failure. The study evaluates key factors such as compressive strength and flexibility to determine how well each mortar Mix stabilizes damaged columns and prevents further deterioration.
The harmonization between nature and construction, in the context of the development of human society, is a desideratum for protecting the environment; the advantages of a sustainable construction industry are reflected economically by increasing energy efficiency, reducing pollutants, and the consumption of natural resources while respecting the legislation and norms in the field. Climate change is mainly determined by the increase in the concentration of greenhouse gases released into the atmosphere, as a result of human activities in all fields, with particular emphasis on the construction sector. On the other hand, the construction sector is one of the most important pillars of economic growth in Romania. According to provisional data from the I.N.S., the construction sector represents almost 8% of GDP (Agerpres, 2025), being the largest share in the European Union (according to Eurostat data). The locality of S & acirc;ntandrei in Bihor County is located in a strategic peri-urban development area, in the west of Oradea municipality, being one of the most dynamic communes in Bihor County. The development of the locality and its favorable location have attracted real estate investors in rapid and dynamic urban development. In order to become a model of sustainable and intelligent economic development, for S & acirc;ntandrei the issue of renewable energies, sustainability and environmental protection represents a central point of urban development. The rapid population growth requires the application of a coherent strategic vision in accordance with Romanian and European norms regarding the construction of new, sustainable, ecological and efficient housing.
The main causes of damage in hydraulic structures are cavitation, vibration, and crushing. Cavitation, a phenomenon that occurs at high velocities, can damage hydraulic structures. It occurs when the pressure of the water flow drops below its vapor pressure. Flow aeration in hydraulic structures is known to reduce cavitation damage. Bottom outlet aeration is one example of this. The high-velocity flow in the bottom outlet is a mixture of air and water. This airflow results from the sub-atmospheric pressure downstream of the gate. The air vent supplies the air entrained by the high-velocity flow. Without a sufficient air supply, the pressure drop downstream of the gate will cause cavitation. This study investigates the cavitation index of bottom outlets with a sluice gate and three different outlet cross-sections. The results indicate that the cavitation index decreases with an increasing Froude number. The geometry of the bottom outlet cross-section did not significantly affect the cavitation index. An equation is also presented that relates the cavitation index to the Froude number, the gate opening rate, and the ratio of the hydraulic radius to the bottom outlet length.
The geographical position of Romania at the end of European Union, the Schengen Area and on the Eastern Flank of North Atlantic Treaty Organization creates the context of a highly exposed area. The European Union framework of organisation applied in Romania generated Regions and Macro Regions that are more punctually exposed. The paper approaches the most populated region of Romania - Development Region of Romania number three - North East Development Region, part of Macro Region Two of Romania for which the evolution of resident population is presented. The exposed region is researched in detail regarding the ecological transport infrastructure connections and critical points along the routes. The mapping of each critical point is being made for the region and extended to neighbouring regions to ensure a comprehensive view of the discovered critical routes for passengers and freight transport. Finally, discussion is made and conclusions are drawn, from which the most important resulted the need of an atlas of critical points along the ecological transport infrastructure of the region and lately, for the entire country.
Hydropower plants are increasingly required to provide fast-response balancing services to compensate for the variability of wind and solar generation. However, frequent start-up and shutdown cycles impose severe mechanical and hydraulic stresses, reducing the mean time between failures (MTBF) and increasing unplanned outages. This paper investigates the Drăgan–Iad Hydropower Development (Romania), analyzing Reliability–Availability–Maintainability (RAM) indicators, vibration and cavitation monitoring, and the techno-economic potential of integrating Battery Energy Storage Systems (BESS). Results show that BESS can reduce torque peaks by 20–40%, lower cavitation intensity by 25–30%, and extend MTBF by 13–15%. Economic evaluation indicates annual savings of EUR 50,000–90,000 from avoided outages, with a payback period of 5–6 years. Beyond technical benefits, hybrid hydro–BESS systems contribute to the sustainable modernization of hydro-technical infrastructures, prolong equipment and structural lifetime, and improve grid flexibility in renewable-dominated systems.
The present paper presents some of the results of the experimental research carried out by the authors in order to obtain construction materials, mortars in particular, which are more environmentally friendly, less polluting, while aiming to obtain new materials that also help to increase the energy efficiency of buildings. The study includes the realization and testing of several mortar samples with different compositions in order to reduce the consumption of cement, a polluting material by its way of obtaining but a main component of mortars. The mortar samples had cement and perlite in different dosages and some of them also had lime in different quantities. They have been mechanically tested, determining bending tensile strengths and compressive strengths. At the same time, there are some physical characteristics for the mortars obtained, namely the density of the samples and their mass loss over time. The interpretation of the results obtained helps us to obtain useful information regarding the composition of mortars with the addition of perlite, an ecological material, difficult to degrade, with special physical properties and the possibilities of their use in constructions in order to increase the energy efficiency of buildings, reduce energy consumption and in identifying new efficient and sustainable solutions for constructions and for the built environment.
Mortar and concrete are the mostly used construction material composed of a mixture of cement, water, aggregates (such as sand, gravel, or crushed stone), and often additional additives or admixtures. It is widely used in the construction industry for various applications due to its strength, durability, and versatility. Key characteristics of concrete include strength, durability, versatility, fire resistance, cost-effectiveness, weather resistance, insulation, and decorative options. Concrete plays a vital role in the construction industry, providing the foundation for most buildings, infrastructure, and many other structures worldwide. Its composition and properties can be tailored to meet specific project requirements, making it an indispensable material in modern construction. Various fibers can be used to enhance the mechanical and bonding properties of concrete. Additionally, waste fibers after recycling can reduce the environmental burden. Keeping in this view, glass powder sodium silicate glass (SSG) is used as a replacement of cement with different percentages 0%,5%,10%, and 15% in combination of guar gum (GG) 1% for all mixes to prepare Glass Powder–Guar Gum Concrete (GPGGC). An experimental study is conducted to investigate the mechanical and durability properties of concrete by performing compression test, flexural test, alkali silica reactivity test, sulfate resistivity test and drying shrinkage test. For this, forty-eight concrete cylinders are prepared for compression test, twelve concrete prisms for flexural test and twenty-four mortar bars of four mixes are prepared for durability testing. Workability is checked of fresh concrete during the pouring of concrete cylinders. Poured cylinders’ samples are left for 7, 14, 21 and 28 days of curing. Various tests are performed on hardened concrete and mortar samples to evaluate the mechanical and durability properties. Results concluded that workability of four mixes lies between 62-94mm and the compressive strength of concrete has been improved using glass powder (SSG). Optimum results have been achieved at 15% as compared to other mixes 5% and 10% of concrete samples. Fibrous material is used as a binding agent and fibrous concrete is suitable for humid environments where high strength and voidless concrete are required. Quantity of cement can be reduced by using different fibers as a replacement of cement. Research recommended that recycled glass powder can be used in concrete as construction material and 15% replacement is suitable for optimum results.
When a water jet passes through a layer of air and plunges into a pool of water, it is well known that it entrains a significant amount of air into the pool. This forms a submerged, two-phase region with a large surface area at the air-water interface. This process is called plunging water jet entrainment and aeration. This paper describes an experimental study of the air entrainment ratio of two-hole circular nozzles. Depending on which air holes were opened on the circular nozzles, negative pressure was created. The resulting aeration of the jet affected its expansion, shape, and roughness; consequently, it also affected the air entrainment ratio. The investigation showed that the maximum air entrainment ratio was achieved with a nozzle length four times the diameter of the nozzle. Higher air entrainment ratios were observed for air holes with diameters greater than 2 mm. Additionally, a design equation was developed to estimate the air entrainment ratio of two-hole circular nozzles. This equation considers the ratio of the nozzle diameter to the air hole diameter, the water jet length, the circular nozzle length, and the jet velocity at the nozzle inlet.
Expansive soils exhibit considerable volumes changes in response to humidity fluctuations, swelling upon water absorption and shrinkage during desiccation. This recurrent volumetric instability can induce differential settlements, often resulting in structural distress such as cracking in lightly loaded constructions. This study aims to analyse the behaviour of expansive soils under shrink-swell cycles by means of direct shear tests, oedometer tests and finite elements analysis. Hereby, number of cyclic drying-wetting of N=0, N=1, N=2, N=3, N=4, N=5, N=6, N=7, N=8 was investigated for more 200 undisturbed expansive soils from 6 locations in the study area. The soil samples exhibited a pronounced volumetric expansion of approximately 10% during the first two drying–wetting cycles. Beyond this stage, the swelling amplitude progressively diminished with each subsequent cycle, stabilizing at about 1% by the eighth cycle (N = 8). However, the shrink magnitude increased approximately from 10% to 50% as the number of swell-shrink increases. extent of cracking progressively increased with the number of swell-shrink cycles, resulting in an enlargement of the mesopore volume within the samples. Results from the direct shear tests performed under unconsolidated–undrained (UU) conditions showed that both the angle of internal friction and the cohesion underwent a pronounced reduction during the first two cycles. Thereafter, these parameters converged toward residual values corresponding to approximately 30% and 35% of their initial internal friction angle and cohesion, respectively. Exponential decay functions are derived from the test data, that describe the degradation of the shear strength, the angle of internal friction and the cohesion with increasing numbers of drying–wetting cycles. Furthermore, a finite element model has been developed by means of the software Abaqus for analysing the response of pavement resting on expansive soil under to repeated shrink-swell. The finite elements model has been validated with the in-situ results of falling weight deflectometer. The numerical results demonstrated that the pavement deflection and shear strain increase with increasing cyclic drying-wetting. As a result, cracks can occur in the pavement and compromising the serviceability limit state and the integrity of the pavement structure.
This study investigates the cyclic friction properties of asphalt pavements under repeated loading by developing a custom-designed testing apparatus, which was rigorously calibrated to ensure stability and experimental reliability. Results show that both the frictional force and surface roughness decrease with increasing cycles, exhibiting a clear linear correlation. SEM analysis reveals the formation and accumulation of discrete abrasive particles on the tire surface, identified as a key factor contributing to frictional instability. Based on elastoplastic contact theory, the reduction in surface roughness is attributed to stress concentrations at the boundary layer, leading to material removal and wear particle generation. Furthermore, a spring-slider numerical model was established, and its initial results qualitatively match experimental findings. By adjusting the roughness parameter, the model demonstrates that friction force gradually decreases and stick-slip behavior weakens with increasing cycles, consistent with the experimental trends.
This study examines the performance and the durability of the geocomposite obtained by replacing cement by rice husk ash (RHA)-based geopolymer in stabilizing laterite soil for the use in pavement construction. For that laterite soil was first characterized through tests such as Atterberg limits, compaction test, Californian Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS), and X-ray diffraction. Thermogravimetry (TG) coupled with differential (DTG) and X-ray diffraction analysis showed that the calcination of rice husk power (RHP) at 800°C leaded to amorphous silica needed for the geopolymer synthesis. It was found that the optimum geopolymer formulation 80%MK+20%RHA presents the best physical and mechanical performance, achieving a density of 1.61 t/m 3 , a water accessible porosity of 20% and an unconfined compressive strength of 24.6 MPa. The optimum geopolymer formulation was used to stabilize the laterite soil for base layer of pavement. Unconfined compressive strength of geopolymer-stabilized laterite soil is approximately 8% larger than that of cement-stabilized laterite soil. Unconfined tensile strength of geopolymer-stabilized laterite soil is approximately 20% larger than that of cement-stabilized laterite soil. Furthermore, the durability analysis showed that the unconfined compressive strength and the bending strength of geopolymer-stabilized samples decrease up to 70% of the initial compression strength and 75% of the initial bending strength with increasing cyclic wetting-drying, respectively. However, the unconfined compressive strength and the bending strength of geopolymer-stabilized laterite soil are approximately twice those of cement-stabilized laterite soil for a given cyclic number of wetting-drying. The FE simulations of pavement under traffic loading showed that the base layer stabilized with geopolymer and the base layer stabilized with cement present comparable performance regarding the vertical and shear deformation.
