Structural Forces Research Articles

Safety net of last resort: the evolution, determinants and adequacy of Dutch minimum income support

Dutch minimum income support provides a generous social safety net compared to most other European Union (EU) member states but has not been able to structurally reduce poverty. This inadequacy did not come about overnight but is the result of six decades of policy decisions. In this article, we aim to explain the current income shortfalls of people on minimum income support by studying the historical evolution and determinants of the Dutch minimum income scheme. We demonstrate that it has on average maintained a constant level of purchasing power over the period 1980–2023. This fits well with the notion that poverty is of an absolute nature, and that a social minimum should guarantee a stable level of purchasing power. It fits less well with relative or contextual approaches to poverty, and the view that a social minimum should adapt to changing norms when a society grows richer. To uncover the reasons for the growing gap between general prosperity and the minimum income benefit, we decompose it into smaller gaps by illustrating the evolution of prosperity, labour productivity, gross wages, collectively agreed wages, the minimum wage and the minimum income benefit. We show that each of these gaps matters and argue that this provides valuable insights into the structural, institutional and political forces that have shaped Dutch minimum income support since its introduction in 1965. Based on these results, we argue against the current ad hoc measures of the government and in favour of a more structural approach to supporting low-income households.

Variation in coral rubble cryptofauna is scale-dependent and driven by small-scale habitat characteristics

Motile cryptofauna living in dead coral rubble represent some of the greatest biodiversity and basal energetic resources on tropical coral reefs. Yet we know relatively little about how and why coral rubble cryptofauna communities change over space and time. As human impacts increase the degradation of living hard corals to dead coral rubble on many reefs worldwide, understanding the communities that will succeed in these degraded environments and the factors paramount to their success becomes increasingly central to coral reef ecology and conservation. Using a remote and uninhabited oceanic atoll in the Pacific Ocean, we quantified the natural spatial variability in motile cryptofauna diversity and community structure in coral rubble across scales (m to km) and tested whether variability at smaller scales could be explained by gradients in microhabitat. We show that coral rubble cryptofauna communities are most variable at intra-site scales (m) rather than inter-site scales (100s m) or between reef zones (km scales). We also show that a substantial amount of variation in cryptofauna density (55%) and phyla-level community structure (31%) is explained by small-scale habitat characteristics, specifically the substrate type below the rubble and the variability in macroalgal cover on individual rubble pieces. Our findings highlight the need to study small-scale processes that are relevant to motile cryptofauna and their community interactions if we are to elucidate the structuring forces of these diverse cryptic assemblages on coral reefs.

Wave forces and dynamic pressures on pile-supported breakwaters with inclined perforated plates under regular waves

The use of pile-supported breakwaters can be a cost-effective solution for wave energy dissipation when traditional rubble mound breakwaters are not suitable. For a cost-effective design of these barriers, it is essential to obtain accurate estimates of dynamic pressures and wave forces. Laboratory experiments were conducted to investigate the dynamic pressures and forces on a novel pile-supported breakwater with inclined perforated plates. The analysis focused on various wave and structural parameters, including incident wave height, wave period, plate porosity, and plate configuration. For double-layer configurations with the same porosity, dynamic pressures on the single-layer or front plate were significantly higher than on the rear plate, with rear plate forces being 20% to 60% less. The dynamic pressure on the rear plate exhibited a uniform vertical distribution. Varying plate porosity at different locations significantly impacted structural forces. Gradually decreasing porosity improved wave dissipation and reduced forces on the plates, with front and back plate forces reaching approximately 70% of those on single-layer plates. Optimal protection across various wave periods can be achieved by adjusting porosity and plate arrangement. These findings provide valuable insights for designing pile-supported breakwaters in coastal protection engineering.

Trial Design of a Truss Bridge Prefabricated Using a Rectangular Steel Tube—Ultra-High-Performance Concrete Composite

In order to promote the development of bridge assembly technology and accelerate the application of rectangular steel-tube–concrete composite truss bridges, this study focuses on the Yellow River Diversion Jiqing Main Canal Bridge as the engineering example and conducts a numerical analysis of a rectangular steel-tube–concrete composite truss bridge. Based on the results of the analysis, structural optimization is achieved in three dimensions—structural design, construction methods, and force analysis—leading to the establishment of key design parameters for through-type ultra-high-performance rectangular steel-tube–concrete composite truss bridges. The results show that filling the hollow sections with ultra-high-strength concrete can significantly enhance the load-bearing capacity. Additionally, employing prestressed concrete components addresses the bending and tensile load capacity challenges of composite structures, thus maximizing the material strength advantages. The proposed preliminary design scheme incorporates prestressed PBL-reinforced tie rods filled with ultra-high-performance concrete with optimal design parameters, such as high span ratios, wide span ratios, and ideal segment lengths, are suggested to ensure that the strength, stiffness, and stability comply with relevant standards. While ensuring that the structure meets safety, applicability, and durability criteria, the preliminary design scheme reduces steel usage by 23.5%, concrete usage by 11.6%, and overall costs by 17.29% compared to the original design. The proposed design demonstrates distinct advantages over the original in terms of mechanical performance, construction efficiency, economic viability, and durability, highlighting its promising application potential.

Large-scale turbulence effects on flow dynamics around and aerodynamic forces on a square cylinder

Turbulence effects on the aerodynamics of a square cylinder have been widely investigated due to their fundamental significance in both flow physics and engineering applications. However, the influence of large-scale turbulence on shear layer unsteadiness, and its consequences on flow structure and aerodynamic forces has received insufficient attention. The present study explores these effects, considering turbulent flows with turbulence intensities up to 20% and integral length scales up to four times the characteristic length of the obstacle. A reduced-order model and measurable indicators of flow dynamics are employed to investigate the underlying mechanisms quantitively. The findings reveal that large-scale, high-intensity freestream turbulence amplifies the root mean square (rms) flapping amplitudes of shear layers by provoking and superposing a set of low-frequency unsteadiness with energy levels comparable to that of Karman vortex shedding. The alteration in shear layer behavior results in (1) an extended region of high rms pressures around the square cylinder and (2) intermittent shear layer reattachment, followed by an intermittent weakening of the vortex shedding. These effects lead to a significant increase in rms pressure coefficients on the lateral and leeward surfaces, as well as an intermittent suppression of lift forces. Two new flow patterns were observed during periods of weakened flow dynamics: (1) vortices forming above the lateral surfaces shed downstream directly without interacting with the shear layer on the other side; and (2) Karman vortices in the wake region break down before shedding downstream.

Simulation analysis of the internal flow field in single screw compressor using local re-meshing method

Abstract The single screw compressor (SSC) is considered an excellent competitor to the twin screw compressor due to its symmetrical structure and balanced gas forces on the screw rotor. To enhance the performance of SSC, it is crucial to have a thorough understanding of the internal flow field, particularly in the leakage channels. Nevertheless, the vertical relationship between the star wheel axis and the screw axis leads to mesh distortion, which presents technical challenges for mesh division in CFD simulations. In this paper, the method of local re-meshing is employed to simulate the comprehensive flow field using the Forte software. The mesh is regenerated near the motion boundary, while the mesh in the remaining areas remains unchanged. The pressure and temperature distribution of the internal flow field of the compressor are obtained, as well as its variation during operation. The results indicate a noticeable pressure gradient change in the leakage gap. The pressure and temperature of gas gradually increase along the axis direction of the screw, reaching the maximum value in the exhaust channel. The research can provide support for the future optimization design of the SSC.

A State-of-the-Art Review on Vortex Induced Vibrations Phenomenon Bladeless Wind Turbine Technology

Vortex bladeless wind turbine (VBWT) is a new wind power extraction technology that is dependent on the Aero-elasticity phenomenon that is called vortex induced vibrations – VIV – which is derived from the study of flow induced vibrations, it is the phenomenon that arises from the interaction of inertial, structural and aerodynamic forces over a bluff body. it has been found that when Air – ideal gas - flows around a body an induced oscillatory motion can be established by vortex shedding. By leveraging the induced oscillatory motion resulting from VIV, Vortex Bladeless aims to generate power in a novel way. The absence of traditional blades sets this technology apart from conventional wind turbines and introduces different dynamics in the extraction of wind energy. VBWT devices are particularly advantageous in low to moderate wind situations, where traditional turbines may prove inefficient or unfeasible. Moreover, their reduced noise levels and compact size render them suitable for urban or ecologically sensitive regions. The selection of this new technology to be investigated and studied will play an important role in wind energy field of study opening a new chapter in the development of this kind of renewable energy, leading to generate power with a lesser cost than that produced by the conventional wind turbines by 40 %. Nonetheless, the efficacy of VBWT may be constrained in high-wind conditions where conventional turbines thrive, and their performance is significantly influenced by certain design and resonance attributes.

Study on Error Influence Analysis of an Annular Cable Bearing-Grid Structure

Manufacturing errors of cable length, external node coordinates and tension force by the passive tension method are inevitable, which will inevitably affect the prestressing of cable bearing-grid structures, while existing studies lack the error analysis of error influences in this area. This paper proposes a method for analyzing random errors in constructing annular cable bearing-grid structures. An error control index and a normal distribution-based random error model, considering the impact of cable and ring beam length errors on cable force, were established afterwards. Taking the roof of the Qatar Education City Stadium as an example, the influence of the length errors of the radial cable, ring cable, and outer pressure ring beam on the structural cable force and stress level was analyzed, and the coupling error effect analysis was carried out. The results show that ring cable force and radial cable force are less affected by the length error of each other’s cables, while they are more affected by the length error of the outer ring beam. Stress levels exhibit greater sensitivity to outer ring beam errors compared to cable length errors. As the error limits of outer ring beam increase, radial and ring cable error ratios and outer ring beam stress errors also rise.

Moratorium? Youth experiences of waiting on South Africa’s ‘platinum belt’

ABSTRACT The extraction of platinum group metals in South Africa's rural territories has increased the hope for development and employment opportunities among local residents. However, despite the increase in mining activities over the past decades, poverty and unemployment persist. Drawing on detailed ethnographic research conducted in a platinum-rich community on South Africa's rural ‘platinum belt' – the Bafokeng – this article explores the experiences of unemployment and waiting among the local youth. Recent studies have highlighted the active agency of unemployed youth in devising and deploying strategies to engage with local and outside structural forces of waiting. The analysis, however, reveals the complex power relations in the local social landscape. The article shows that deliberate actions by platinum mining corporates working in cahoots with the traditional authorities (the chiefs) in the Bafokeng community result in the ‘social moratorium’ of the youth.

Gradual Failure of a Rainfall-Induced Creep-Type Landslide and an Application of Improved Integrated Monitoring System: A Case Study.

Landslides cause severe damage to life and property with a wide-ranging impact. Infiltration of rainfall is one of the significant factors leading to landslides. This paper reports on a phase creep landslide caused by long-term rainfall infiltration. A detailed geological survey of the landslide was conducted, and the deformation development pattern and mechanism of the landslide were analyzed in conjunction with climatic characteristics. Furthermore, reinforcement measures specific to the landslide area were proposed. To monitor the stability of the reinforced slope, a Beidou intelligent monitoring and warning system suitable for remote mountainous areas was developed. The system utilizes LoRa Internet of Things (IoT) technology to connect various monitoring components, integrating surface displacement, deep deformation, structural internal forces, and rainfall monitoring devices into a local IoT network. A data processing unit was established on site to achieve preliminary processing and automatic handling of monitoring data. The monitoring results indicate that the reinforced slope has generally stabilized, and the improved intelligent monitoring system has been able to continuously and accurately reflect the real-time working conditions of the slope. Over the two-year monitoring period, 13 early warnings were issued, with more than 90% of the warnings accurately corresponding to actual conditions, significantly improving the accuracy of early warnings. The research findings provide valuable experience and reference for the monitoring and warning of high slopes in mountainous areas.

Research on Influence Mechanism of Nozzle Structure on Properties of Thick Carbon Steel Plate by Laser Cutting

Aiming at problems such as slow cutting speed, poor cutting quality and inability to cut thick plates effectively with traditional single-layer nozzle structure, it is proposed to add an outer ring core to form a double-layer nozzle structure on the basis of the single-layer nozzle structure to improve its cutting performance. The three-dimensional entity of single- and double-layer nozzle is established, and the simulation model of auxiliary gas flow field is established by using N-S equation and SST k-ω turbulence model assisted by laser cutting in this paper. The simulation results show that under the same cutting parameters, the auxiliary gas flow rate, oxygen concentration, mass flow rate, shear force and dynamic pressure of the double-layer nozzle structure are higher than those of the single-layer nozzle structure. In addition, compared with the single-layer nozzle structure, the double-layer nozzle structure can effectively improve the attenuation of oxygen concentration in the direction of sheet thickness. Two nozzle structures were used to laser cutting carbon steel plates with a thickness of 20 mm in the experiment, and the experimental parameters of cutting speed were 1.2–1.6 m/min. The comparison results show that the cutting speed and cutting section quality of the double-layer nozzle are better than those of the single-layer nozzle, and the results of simulation analysis are consistent with the cutting test results.

Experimental and numerical investigation of failure modes in RC frame structures designed using the equivalent linearization method

The codes of many countries currently employ the column-to-beam flexural strength ratio (CBFSR) based on frequent earthquake internal forces to achieve the expected strong-column-weak-beam (SCWB) ductile failure mode. However, real earthquake damage indicates a general failure to achieve SCWB. The design method based on frequent earthquake internal forces struggles to consider factors such as internal force redistribution and variable axial forces under rare earthquakes. Therefore, developing a seismic design method directly based on rare earthquake internal forces is crucial. The equivalent linearization method is a practical approach for obtaining the internal forces of RC frame structures under strong earthquakes without extensive nonlinear computations. In this paper, nonlinear finite element analyses of RC frame structures with expected SCWB failure modes under various structural parameters were conducted to obtain ductility coefficients under rare earthquakes. Using the equivalent linearization method based on secant stiffness, the equivalent stiffness and damping of beams and columns were calculated. Simplified parameters were determined for engineering applications to facilitate seismic design based on rare earthquake internal forces. Two RC frame structures were designed using both the equivalent linearization method and the CBFSR code method, and then subjected to pseudo-static low-cycle reciprocating loading tests. The study investigated failure modes and hysteretic energy dissipation, as well as overall stiffness and bearing capacity under earthquake conditions. Results showed that the equivalent linearization method can effectively direct RC frame structures to achieve the expected strong earthquake failure mode.The dynamic time history analysis was performed on finite element models of different heights, and the results indicated that the equivalent linearization method significantly reduced plastic hinge occurrences and ductility coefficients of column ends, resulting in improved seismic performance compared to the CBFSR code method.

Democratisation in Southern Europe: a contingent or inevitable process?

ABSTRACT Debates on democratisation often struggle to reconcile structural and agency approaches. Structural explanations highlight factors like economic development, natural resources, inequality, and international power shifts. Agency-based explanations focus on the choices of political actors, including elites and social movements, and their interactions leading to democracy. This study compares Greece, Portugal, and Spain, harmonising these perspectives. Structural and agency forces are not contradictory when temporal scope conditions are clearly defined. Despite differing democratisation paths, Southern European countries experienced rapid modernisation, and political, social, and economic convergence during the consolidation phase. Modernisation favoured liberal democracy and democratic consolidation through varied events and actor combinations. Our analysis underscores the importance of considering both structural and agency-based factors in understanding democratisation processes.

Investigation of the Durability of the Regulating Junction of the Christmas Tree Throttle

Objective: In the research work, the issue of ensuring the stability of its details wasconsidered by studying the voltage distribution mode in the throttle control node. SolidWorks software was used to perform force analysis of the improved throttle. Theoretical Framework: The research draws upon theories and simulations related to regulatory constructions and wear prevention. Methodology: In the research work, the performance criteria of the improved throttle have been studied. The force analysis of the proposed throttle's regulating node was carried out using modern methods and Solidworks simulations. Results and Discussion: The analysis of the wear occurring at the tip of the improved throttle shows that the wear resistance of this equipment is ensured, and the wear of the saddle-cutter pair, which has a hardness of HRC=55-66, amounts to 0.040...0.050 mm after 500 forward-backward cycles intended for the throttle. This is also twice smaller than the allowable limit. The processing of the conducted force analyses has proven that the performance of the improved throttle is ensured. Research Implications: The structural force analysis of the improved throttle shows that its performance is ensured. An analytical expression has been obtained to determine the maximum value of the radial stresses occurring at the tip of the throttle. It has been found that the safety factor for bending stress in the central zone of the throttle tip is equal to 2.5. Originality/Value: Based on simulations and analytical calculations, the radial stresses generated at the tip of the nozzle were investigated, and the longevity of the improved nozzle was enhanced based on new approaches.

Experimental study on hydrodynamic performance and structural forces of curved and vertical front face pile-supported permeable breakwaters

This paper presents an experimental study on the hydrodynamic characteristics and structural forces of pile-supported permeable breakwaters under regular wave conditions. The study evaluates three distinct configurations: one featuring a vertical superstructure, another with a permeable curved superstructure, and a third that combines a permeable curved superstructure incorporating a perforated diaphragm. Experiments were conducted under regulated wave conditions, focusing on pressures, forces, and hydrodynamic scattering coefficients associated with each structural form. Results from the experiments indicate that, under the conditions tested in this study, the curved permeable superstructure significantly reduces wave reflection coefficients and forces acting on critical elements. The curved permeable superstructure maintains reflection coefficients below 0.3 while ensuring low transmission coefficients. Moreover, the study explores dynamic water pressure on an inclined perforated plate and identifies an asymmetric double-peak phenomenon in the pressure time series, signifying the transition from regular waves to breaking waves. The critical wave steepness for the occurrence of double peaks was found to be lower than the breaking limit steepness. Filter analysis elucidates the generation mechanism and evolution pattern of this double-peak phenomenon, revealing the influence of relative water depth, with second-order harmonics dominating near the bottom and second- and third-order harmonics prevalent at the free water surface. This research contributes to the understanding of the hydrodynamic performance of pile-supported permeable breakwaters and underscores the benefits of the curved permeable superstructure design in reducing wave reflection and structural forces. The findings provide valuable insight for the further development and application of pile-supported breakwater structures.

Clashing Gender in the Age of Transnational Infrastructural Capitalism: The Vocational Education and Subject Making of China's Future Workers

Accompanying the “China Dream” as a symbol of the advent of Chinese transnational infrastructural capitalism, a new project of subject making is emerging: an increasing number of Chinese youth, especially those from working-class backgrounds, have entered the expanded urban vocational education system for training as future workers. As a national project attempting to (re)invent educated, skilled labor subjects to serve the state goal of industrial upgrading, vocational education is geared toward entrance into the labor market, producing valuable “marketable subjects” specifically for the enhancement of the export manufacturing sector and a new service sector now increasingly extending to overseas markets. Engaging in a participatory action project in vocational schools between 2016 and 2019, this article’s authors studied students’ learning experiences and examined how the larger structural, political, economic, and cultural forces shape the girls’ and boys’ educational and occupational decisions. To understand the subject making of young Chinese workers, the concept of “clashing gender” is used to illustrate how gender plays a central yet conflicted role, torn between forces of state, market, school, and individual desire, during these young people’s years of vocational training. The article thus illustrates how the postsocialist state’s linking of China’s new economic sectors into the circuits of transnational capitalism produces intimately gendered and subjective effects for working-class youth.

Research on Coordinated Relationship Between Deformation and Force in Shaft Foundation Pit Support Structures

In order to investigate the coordinated relationship between lateral deformation of the diaphragm wall and axial force of the internal strut, this paper first carried out a scaled model test on the mechanical features of a foundation pit support system based on a novel axial force servo device. Then, a finite element model was established to simulate the scaled model test, and the correctness of the finite element modeling approach was validated by comparing test results. After that, the same finite element modeling method was used to analyze the coordinated relationship between axial force and lateral deformation in the prototype foundation pit support structure. The results show that the axial force of the inner strut is negatively correlated with the lateral deformation in the diaphragm wall. The initial maximum lateral deformation in the diaphragm wall of the shaft foundation pit occurs at the bottom of the foundation pit, so changing the length of bottom strut simultaneously is the most effective way to adjust the mechanical behavior of the support structure. Under various support conditions, the maximum lateral deformation of the diaphragm wall in the prototype project is 0.59~0.66‰ of the total excavation depth of the foundation pit, and the maximum axial force of internal support is 11~30% of the yield load of a single steel strut.

A Study on the Influence of Hydraulic Compactor Reinforcement on the Force Law of an Independent Foundation Under a Column and Its Safety Standard

Due to the complexity of the actual geotechnical environment, the backfill compaction design theory and calculation method are not reflected in the current specification. Therefore, in order to investigate the effect of the hydraulic compactor on the foundation structure during the treatment of the backfill of an independent foundation under a column, the Menard formula was modified. At the same time, relying on an independent foundation project under a column in Jinan, the dynamic model of compactor tamping backfilling soil was established. The applicability of the calculation formula is verified by simulating the single-point multiple tamping on the backfill directly above the foundation tie beam, and the influence law of two factors, the thickness of the backfill and the tamping energy, on the force of the foundation tie beam is elucidated. The results show that after reaching the optimum number of tamping, the cumulative soil settlement and the effective reinforcement depth of tamping show a stable trend, and their simulation results are in good agreement with the analytical solution, which provides a supplement to the relevant safety standards. At this critical point, the force on the tie beams peaked and showed up and down fluctuations under the subsequent ramming action. The tamping action of the compactor has a significant effect on the structural forces within the effective reinforcement range, and there is a negative correlation between the magnitude of the structural forces and the thickness of the backfill. According to the numerical calculation results to choose the best construction programme, the on-site monitoring shows that under 42 KJ tamping energy and 1.5 m single backfilling thickness, the tie beam reinforcement stress reaches 18.5~55.5% of the specification warning value, which meets the safety standard. The research results of this paper can provide important guidance for the hydraulic tamping treatment of an independent foundation backfill project.

Numerical Study of Vortex-Excited Vibration of Flexible Cylindrical Structures with Surface Bulge

This study conducted numerical simulations of three-dimensional vortex-induced vibrations (VIV) on cylindrical bodies with various surface protrusion coverage rates, systematically investigating the impact of coverage and protrusion height on the vibrational response of flexible cylinders. The fluid forces on the surface of the riser were resolved using the finite volume method, while the structural forces were solved with the finite element method. A strongly coupled approach was employed for iterative updates between the flow field and structural field data, achieving a bidirectional flow–structure coupling simulation of VIV in a marine environment. The study further explored the performance of surface protrusions in suppressing VIV and considered protrusion heights of 0.1 times the cylinder diameter (0.1D) under coverage rates (CR) of 0%, 10%, 20%, 30%, and 40%, as well as seven different protrusion heights of 0.05D, 0.1D, and 0.15D at a 20% coverage rate. The mechanism of VIV suppression by surface protrusions was identified as altering the separation point of the shear layer and the frequency of vortex shedding through the vortices formed between the surface protrusions. It was found that a 20% coverage rate with a protrusion height of 0.01D (CR20) effectively suppressed the VIV of the cylinder, showing the best performance in VIV suppression, with an efficiency of 30.04%. These results provide a theoretical basis for designing more efficient VIV suppression devices and contribute to enhancing the resistance of marine structures against vortex-induced vibrations.

Image charge effects under metal and dielectric boundary conditions.

Theimage charge(IC)effect is a fundamental problem in electrostatics. However, proper treatment at the continuum level for many-ion systems, such as electrolyte solutions or ionic liquids, remains an open theoretical question. Here, we demonstrate and systematically compare the IC effects under metal and dielectric boundary conditions (BCs), based on a renormalized Gaussian-fluctuation theory. Our calculations for a simple 1:1 symmetric electrolyte in the point-charge approximation show that the double-layer structure, capacitance, and interaction forces between like-charged plates depend strongly on the types of boundaries, even in the weak-coupling regime. Like-charge attraction is predicted for both metal and dielectric BCs. Finally, we comment on the effects of a dielectricallysaturated solvent layer on the metal surface. We provide these results to serve as a baseline for comparison with more realistic molecular dynamics simulations and experiments.