Design Capacity Research Articles

Optimized Compound Layer Design for Highly Loaded Nitrided Gears

AbstractNitriding is a thermochemical surface hardening process, which can be used to improve the performance properties of gears. In particular, the tooth flank and tooth root load-carrying capacity can be significantly increased by nitriding. Previous work has shown that tribological dominated failure modes and limits, such as the micro-pitting and wear load-carrying capacity of gears, can be significantly increased by a suitable compound layer structure. In this work, the relationship between compound layer design and macro-pitting load-carrying capacity of nitrided gears is explored based on experimental investigations. For this purpose, the materials EN31CrMoV9 and EN42CrMo4 were nitrided under varying nitriding conditions to produce compound layers with different structures and properties. The characteristics of the compound layer such as phase composition, compound layer thickness and pore seam were extensively characterized by means of metallographic techniques, XRD, GDOES, and EBSD. Experimental investigations of the macro-pitting load-carrying capacity were carried out on an FZG back-to-back gear test rig with center distance a = 52 mm. It was shown that the pitting load-carrying capacity depends to a large extent on the characteristics of the compound layer, in particular on the formation of the pore seam. A minimum pore seam thickness of CLTP ≥ 1.8 µm has a positive effect on the pitting load-carrying capacity. The test results for the pitting load-carrying capacity are above (σH lim ≥ 1690 N/mm2) or, in some cases, significantly above (σH lim = 1979 N/mm2) the strength values specified in ISO 6336-5:2016 for nitrided nitriding steels (σH lim = 1450 N/mm2; material quality ME) and case-hardened alloy steels (σH lim = 1650 N/mm2; material quality ME).

Peculiarities of determining the capacity of land urban passenger transportation vehicles

Introduction. In the conditions of motorization growth the necessity to improve the quality of passenger service by public transport increases significantly. The determining factor for finding the design capacity of vehicles (TC) is the comfort provided to passengers. On the one hand, in order for public transport to be popular in comparison with private motor transport, it must provide comfortable travel conditions, which are ensured by the provision of free places for sitting and (or) the availability of sufficient space for standing. On the other hand, guaranteed provision of all passengers with seats with a comfortable interval between rows of seats, requires an increase in the number of vehicles to master the same volume of transportation and can lead to a sharp increase in the cost of transportation and fare, at which the economic advantages of public transport over private transport will be less obvious. The aim of the study was to find a compromise calculated occupancy rate of vehicles, at which public transport provides the necessary attractiveness and comfort for passengers and the required carrying capacity.Materials and methods. The methodological basis of the work was general scientific principles and research methods: empirical (expert evaluation) and theoretical (analysis, synthesis, systematization) methods. In order to achieve the set goal, the following tasks were solved: 1. The methods of determining the quality of occupancy quality of the vehicle interior were analyzed. 2. The maximum acceptable capacity of the considered public transportation vehicles was determined. 3. The proposals on the use of the calculated indicator of the density of standing passengers placement in determining the carrying capacity of public transportation are given.Discussion and conclusion. The conducted analysis of manuals on operation, repair, acting in corresponding periods of operation of the chosen vehicles shows that the capacity of vehicles according to norms of manufacturers of vehicles and social standard of the Ministry of Transport does not allow to reach the necessary quality of transportation. The performed research has allowed to establish a comfortable level of occupancy of vehicles for a passenger and a calculated indicator of the density of standing passengers.Practical significance. The established comfortable for passengers occupancy of vehicles can be used in the development and updating of social standards of the Ministry of Transport of the Russian Federation.Originality. There is an assessment of the travel conditions depending on passenger occupancy in different types of public transport vehicles operated in the Russian Federation and the Republic of Belarus.

Shear-bearing capacity prediction of concrete-infilled double steel corrugated-plate shear walls

The concrete-infilled double steel corrugated-plate shear wall (CDSCW), consisting of two corrugated plates, infilled concrete, and two boundary elements, is a highly efficient force-resistant structural component under axial compression, in-plane bending, and shear loading. Previous research has primarily focused on the structural performance of CDSCWs under axial compression and bending loads. However, there is still a lack of a sufficiently accurate design method for predicting the shear-carrying capacity of CDSCWs. This paper presents numerical investigations into the shear buckling behavior of corrugated plates and proposes the shear strength design method of CDSCWs. Firstly, the shear elastic bilateral buckling behavior of corrugated plates subjected to lateral constraints of high-strength bolts is explored, considering influences of the bolt arrangement, the bolt spacing, and the dimensions of the plates. The formulas involving various buckling modes are established as a foundation for the further elastoplastic buckling capacity prediction. Then, by applying the normalized slenderness ratio, this study suggests the shear-carrying capacity design of the corrugated plates considering the bolt constraints and unilateral concrete constraint on the plates. Moreover, the shear-carrying mechanism of the CDSCWs is revealed: when CDSCWs experiences shear failure, the corrugated plates are primarily subjected to the shear load, with the boundary elements acting as constraints on the corrugated plates. Finally, a design method is proposed for the CDSCWs’ shear-carrying capacity prediction, which shows good accuracy and offers foundations for the stability design of corrugated plates under shear loads.

The Operational Data Analytics (ODA) for Service Speed Design

We develop the operational data analytics (ODA) framework for the classical service design problem of [Formula: see text] systems. The customer arrival rate is unknown. Instead, some historical data of interarrival times are collected. The data-integration model, specifying the mapping from the arrival data to the service rate, is formulated based on the time-scaling property of the stochastic service process. Validating the data-integration model against the long-run average service reward leads to a uniformly optimal service rate for any given sample size. We further derive the ODA-predicted reward function based on the data-integration model, which gives a consistent estimate of the underlying reward function. Our numerical experiments show that the ODA framework can lead to an efficient design of service rate and service capacity, which is insensitive to model specification. The ODA solution exhibits superior performance compared with the conventional estimation-and-then-optimization solutions in the small sample regime. This paper was accepted by David Simchi-Levi, operations management. Funding: Z. Jiang’s research is supported by the National Natural Science Foundation of China [Grant 71931007]. Supplemental Material: The online appendix is available at https://doi.org/10.1287/mnsc.2023.00655 .

Life cycle techno-economic-environmental optimization for capacity design and operation strategy of grid-connected building distributed multi-energy system

Distributed multi-energy systems (DMS) have received increasing attention. Many studies have optimized the capacity and operation strategies of DMS based on multiple objectives, but these studies must discuss the weights of different objectives and have not considered the internal coupling between different objectives. Besides, existing studies have not considered the changes in the actual value of environmental impacts. To address these shortcomings, this paper constructs a technology-economic-environmental optimization model by mixed-integer linear programming. Based on life-cycle assessment, the model quantifies the value of system life-cycle environmental impacts by introducing carbon price. The case results show that the proposed optimization model can reduce the total cost by 28.83 % and the life cycle environmental cost by 3.39 % compared to the traditional model. To reduce the strain on the grid, a new operation pattern (The grid provides fixed electricity to the system throughout the year.) is proposed. The electricity interaction of the system with the grid under the new operation pattern is more than 70 % lower than the system without electricity purchased quantity constraint. Sensitivity analysis shows the total system cost is more sensitive to natural gas and electricity price than carbon price. But carbon price volatility helps reduce system carbon emissions.

Planning of Production Capacities of Precast Construction Plants under Conditions of Changes in Demand for Products

The main criterion for a feasibility study of the production efficiency of precast construction plants, analysis of internal production reserves and optimal production volume is the production capacity indicator. Thus, the study of various Factors influencing the production capacity indicators is an important task. The results of research of the influence of the number of storeys and the set of block sections in the configuration of industrial residential buildings on changes in the ratio of product types in the range of the production programme of plants are presented in the paper. Fluctuations in the ratio of product types during the construction of different types of houses have been established. Based on the obtained results, the dependence of the production capacity plants on fluctuations in the ratio of product types has been constructed. It has been determined that the main reason for the revealed facts of a decrease in production capacity is the uneven loading of production lines with fluctuations in the ratio of product types in the range of production programs of precast construction plants. Taking into account the known facts of the dependence of production capacity on the concrete capacity of block sections of houses, the results of a comparison of the degree of influence of concrete capacity on the production capacity and the ratio of the main types of products in the range of production programs of plants are presented in the paper. It has been established that a key influence on the indicators of production capacity is exerted by changes in the ratio of product types. On the basis of the conducted research, optimal reserves of production capacity have been determined with a high share of different types of houses in the production programs of the plants. Taking into account the established indicators of production capacity reduction, their optimal reservation is within 20–25 % of the design capacity of the plants, which should serve as a reference point when planning the functioning of the production management system under the conditions of changes in demand for products.

Research on the expansion of energy-saving boundary for CCHP system under all operating conditions based on collaborative integration

In this study, the impact of load demands on the energy-saving characteristics of the systems was analyzed, and the mathematical model was derived for the relationship between the load supply and demands under different capacity design modes and operation strategies, and the influence of the key parameters (load demands, load rate, matching degree) on system integration and operation characteristics in different energy use scenarios was quantitative analyzed to elucidate the inherent mechanism of energy saving characteristics. Furthermore, the impact of energy-matching degree and system efficiency on the energy saving rate (ESR) was discussed, and based on the load demands, an universal system boundary of the ESR was constructed. Based on this, the coupling mechanism between the system and users from a global perspective was reconstructed, and an collaborative integrated method based on centralized energy supply systems, CCHP systems, and load demands was proposed to expand the energy-saving boundary under all operating conditions. Finally, a case analysis and method verification were conducted using typical summer days at Beijing hotel as an example. The results show that this method universally characterizes the coupling matching relationship and energy-saving characteristics. Through collaborative integration, the ESR increase of 5% can be achieved.

Monotonic testing of brace assemblies for piping systems and considerations for capacity design

Distributed nonstructural elements (NSEs), such as piping systems, are restrained against seismic actions using proprietary or, at times, custom-designed braces. The strengths of these elements are provided in the component brochures published by the manufacturers, with no information on their deformation capacities. Previous research on the seismic performance of NSEs provide several formulations to calculate possible reductions in design force by relying on ductility capacity of their seismic restraints. However, designers require a realistic estimate of the ductility capacity of the seismic restraints to use these formulations. This paper discusses the results of a test program on the behavior of brace assemblies under monotonic tensile and compression loading. The results are used to identify the potential failure modes of the tested brace assemblies and to quantify their ductility capacity. Further, design examples are presented to highlight the need for the use of capacity design principles in the design of brace assemblies and their anchors.

A probabilistic model for residential community heating load calculation based on occupancy patterns

Ensuring precise prediction of community heating loads is crucial for optimizing the performance of district heating systems. However, the currently prevalent methods, like the simultaneous usage coefficient method and the area index method (AIM), which heavily rely on practical engineering experience, may not be suitable for ultra-low energy residential buildings (UERBs). Applying these methods to UERBs may result in overcapacity of the heating system, which increases energy consumption and costs. This study aims to enhance the accuracy of heating load calculations for UERB communities. A probabilistic model for heating load calculation was proposed, considering the “part time, part space” spatiotemporal distribution characteristics of residents. Typical occupancy patterns in cold zones of China were identified through questionnaire surveys and K-means cluster analysis, and typical models of UERBs were established, with both the building models and survey data validated. The residential building energy model (RBEM) was applied to a case community in Dalian, analyzing the impact of occupancy patterns on heating loads. The results indicate that the RBEM method increased the system's heating load factor by 6.9 % and reduced its design capacity by 32.9 % compared to the AIM. The proposed method might guide the development of management strategies in the energy planning stage of district energy systems.

Capacity design in school choice

We study a new variant of the school choice problem in which capacities can be altered by distributing additional seats across schools in response to students' reported preferences. We show that heuristic solutions to this capacity design problem can be inefficient, even if they focus on allocating seats to the most demanded schools. We introduce a simple class of algorithms that, in the problem where additional seats can be distributed, characterizes the set of efficient matchings among those that respect priorities. We also investigate the incentive properties of this class of efficient algorithms.

Modelling, simulation, and measurement of solar power generation: New developments in design and operational models

The discrepancy between the operating and design capacities of solar plants in eastern Uganda is alarming; about 35 % underperformance in solar power generation is observed. The goal of the current study is to minimize this disparity by improving the design models. Considering only cell temperature in the power generation model is responsible for the observed difference in design and operational solar power generated, the present study used a thermocouple to directly measure cell temperature, an anemometer to measure wind speed, and a solar power meter to measure irradiance. These extrinsic factors were used to modify the power generation model based only on cell temperature through the direct correlation of cell temperature, wind speed, and irradiance with solar power generation. Thus, the absence of extrinsic factors (wind speed and irradiance) in the design models is responsible for the colossal drop in solar power generated. Empirically, the missing extrinsic factors were used to transform the implicit solar power model into an explicit model. The development of a solar power generation model, multiple differential models, simulation and experimentation with a pilot solar rig served as alternate model for the prediction of solar power generation. The second-order differential model validated well with empirical solar power generated in Busitema, Mayuge, Soroti, and Tororo study areas based on RMSEs (0.6437, 0.6692, 0.2008, 0.1804, respectively), thus, narrowing the gap between the designed and operational solar power generated. Mayuge and Soroti recorded the highest solar power generation of 9.028 MW compared to Busitema (8.622 MW) and Tororo (8.345 MW), suggesting that it has a conducive site for installing future solar plants. The above results support the use of empirical explicit (triple) and second-order differential models for the design and operation of power plants.

Confinement effects within the seismic design of reinforced concrete frames: reliability assessment and comparison

The current Italian code “NTC2018” and Eurocode “EC8” provide specific design requirements in terms of flexural overstrength factors for reinforced concrete (RC) buildings in seismic areas. This study proposes to improve the design methodology by including explicitly the confinement effects within the seismic design of a new regular RC frame due to their influence on the capacity design principles (at structural and member level). Specifically, the seismic performance of a RC frame designed according to codes is compared, in reliability terms, with the one of the same frame designed including the concrete confinement effects. Moreover, a comparison between three constitutive models for confined concrete is performed. Selecting L’Aquila (Italy) as reference site, the two design methodologies combined with the three confinement models are numerically implemented. Scaling 30 non-frequent natural ground motions to increasing seismic intensity measures, according to the site seismic hazard, non-linear incremental dynamic analyses (IDAs) have been developed. Assuming the interstory drift indices as engineering demand parameters, the peak responses have been fitted through log-normal distributions to define IDA curves. Subsequently, appropriate limit state thresholds have been adopted to define the seismic fragility curves. Finally, through the convolution integral and Poisson model, the seismic reliability curves have been derived showing the importance of the proposed design methodology. In fact, for the frame under investigation, the seismic performance strongly improves in terms of ductility respecting all the reliability objective levels if the confinement effects are explicitly considered in the seismic design. Furthermore, the different confinement models provide similar results when the proposed seismic design is adopted, implying a reduction of the model uncertainty.

Research Progress, Trends, and Updates on STEM Learning-ESD: A Bibliometric Analysis

The aim of this paper is to analyse research trends and address knowledge gaps in order to improve STEM-ESD learning. Technical terms are explained upon first use, and sentence structure is clear and unambiguous. The bibliometric review examines current research progress, trends, and updates related to STEM-ESD learning. The study used the Scopus database to select documents and VOSviewer software to investigate bibliometrics. STEM-ESD research shows an upward trend based on the analysis of 19 collections of STEM and ESD learning papers from 2010 to 2023. Indonesia leads in conducting STEM-ESD research, with the highest number of publications on this theme in 2022. In 2010, the significance of STEM-ESD research was its application in the STEM curriculum. STEM-ESD research has facilitated the inclusion of various social science topics in the learning process. This fosters 21st-century skills in students through a project-based learning model. Further STEM-ESD research can be advanced by improving pedagogical design capacity, biodiversity, sustainable development goals, formal and initial teacher training, biology education, and sustainable learning. This will lead to more innovative research.

Location and allocation of primary and backup shelters in transboundary disasters

Disaster management is plagued by uncertainty and chaotic situations, often crossing boundaries and affecting multiple jurisdictions. Collaboration in these settings is complicated, especially when authorities face failure in the infrastructure available leading to facilities operating over capacity and/or vulnerable people left without support. There are records about those experiences globally. There is a broad literature on shelter location/allocation, but few articles consider the potential failure facilities and none of those contributions consider the collaboration between multiple jurisdictions. This article introduces a novel bi-objective formulation for shelter location-allocation considering backup facilities for operations involving multiple jurisdictions. This approach is applied to a set of numerical examples and a real case of volcanic eruptions in Mexico. The results show the influence of transboundary coordination on the support provided to disaster victims, the value of backup facilities and the capacity of the model design to provide relevant alternatives in practice.

Capacity of Reinforced/Prestressed Concrete Compression Members Strengthened/Repaired Using Ultra-High-Performance Concrete Encasement

Currently, 36% of bridges in the United States need major repair work or replacement and 7% of them are classified as structurally deficient. Most of these bridges can be repaired or strengthened to meet the current load demands and withstand the environmental impacts for the remaining service life. Ultra-high-performance concrete (UHPC) has shown immense potential as a repair and strengthening material thanks to its exceptional characteristics such as high workability, excellent strength and durability, and remarkable energy absorption capacity. This paper presents an analytical approach to predict the capacity of reinforced or prestressed concrete compression members with UHPC encasement (jacket) under combined axial and bending effects. The approach is based on strain compatibility and uses idealized UHPC material models in tension and compression according to the new AASHTO Guide Specifications. The approach uses integration to develop accurate interaction diagrams for any section with complex geometry, which overcomes the approximations of the lamina approach. The paper also provides a comprehensive literature review on UHPC usage in repairing and strengthening concrete bridge columns and piers. A design example of a circular reinforced concrete column is presented to illustrate the proposed approach and to calculate the nominal and design capacities of the composite section. This example has shown that increasing the thickness of the UHPC jacket has a prominent effect on enhancing the axial capacity but only a slight effect on the flexural capacity of compression members.

A dimensionless capacity design method for combined cooling, heating, and power (CCHP) systems based on energy matching performance

In this study, a capacity design factor was defined to evaluate the system design and off-design operation strategy, and the mathematical model was derived for the relationship between the load supply and the users' demands under different capacity design modes and operation strategies, and the influence of the key parameters (load demands, load rate, matching degree) on system integration and operation characteristics under different capacity design scenario was quantitative analysised. Furthermore, the impact of energy-matching degree and system efficiency on the energy saving rate (ESR) was discussed, and based on the user demands, an universal system boundary of the ESR was constructed. Finally, the energy saving potential in different scenarios was clarified, and a case study was conducted using a data centre as an example, and the optimal capacity design mode was demonstrated.

A ductile seismic design strategy for the cross-aisle direction of racking systems

Due to their lightness and simple connectivity, steel racking systems are typically considered as “low-dissipative” structures, which is reflected in the modern seismic codes by the absence of capacity design and the adoption of low behaviour factors. This limited capability of stress redistribution significantly increases the vulnerability of racks under beyond-design seismic hazards and raises the demand for more resilient designs. Along these lines, the proposed Plastic Ovalization Strategy (POS) attempts to increase the ductility of the individual upright frames comprising the cross-aisle direction of racks, and at the same time to preserve their low-cost and easy-to-assemble nature. This is achieved by tasking the bearing failure mechanism of the diagonal bolt hole to absorb seismic deformations, while capacity design is employed to keep the rest of the structure in the elastic zone. Following a detailed discussion on the motives and basic principles of the strategy, two high-rise racking systems are designed twice by professional engineers, once using standard approaches and then by additionally employing the proposed POS rules. Finally, the two design solutions are compared by conducting a comprehensive seismic assessment, which employs a phenomenological macro-model comprising elastic elements and nonlinear springs to simulate the bearing failure mechanism.

Assessment of organizational factors affecting utilization of Monitoring and Evaluation results in delivering government programs: A case of Ministry of Education and Sports (MoES), Uganda

The field of Monitoring and Evaluation (M&E) is often restricted to the technical aspects of conducting M&E. However, it is increasingly being acknowledged that organizational factors of entities are regularly more influential as far as mainstreaming the adoption and utilization of M&E is concerned. This study sought to assess the organizational factors affecting utilization of M&E results, specifically by analyzing how information availability, information processing skills and organizational culture affect utilization of M&E results in MoES. The study methodology entailed grounded theory and quantitative research methods and covered a sample of 191 respondents. The study’s key findings, among others, include: M&E information is often stored as manual paper records which subjects the information to wastage through poor handling and physical deterioration; and, poorly presented M&E results have a negative effect on their utilization. The study generated a number of recommendations, which inter alia include MoES should: design and implement a mind–set change programme for all staff of the Ministry to embracing and utilize of M&E results; design and implement regular capacity building and retooling programmes for all staff involved in the generation and utilization of M&E results; and, migrate its M&E records and management procedures from paper–based systems to digital systems. The study's conclusions inform various government MDAs about the relevance of using M&E results for planning, budgeting, and policy making. The study findings will enable MoES appreciate the need for installation of appropriate information management systems necessary for improved uptake of M&E results utilization. The study suggests a number of areas for further investigation, such as, examining the influence of political direction and choices on the application and usefulness of M&E results in government organizations, and analyzing the impact of information dissemination on demand and utilization of M&E results in Government agencies.

Numerical Modeling and Performance Evaluation of Carbon Fiber-Reinforced Polymer-Strengthened Concrete Culverts against Water-Induced Corrosion

Culverts fulfill the vital function of safely channeling water beneath railway tracks, highways, and overpasses. They serve various purposes, including facilitating drainage in areas such as watercourses, drainage zones, and regions with restricted ground-bearing capacity. Precast reinforced concrete (RC) box culverts are a popular choice because they are strong, durable, rigid, and economical. However, culverts are prone to corrosion due to exposure to a range of environmental factors and aggressive chemicals. Therefore, enhancing the design and construction of this crucial infrastructure is imperative to effectively combat corrosion and to adhere to modern standards of reliability and affordability. In this study, carbon fiber-reinforced polymer (CFRP) was used to strengthen corroded culverts, with promising potential to improve safety and longevity in these structures. This study compared the behavior of corroded RC box culverts to CFRP-strengthened ones using the finite element method (FEM). It explored the impact of varying the damage thicknesses owing to corrosion, ranging from 0 mm to 20 mm, on the structural performance of the box culverts. The results showed that the CFRP model exhibited a substantial 25% increase in the capacity and reduced the damage compared to the reference model. Moreover, a parametric study was conducted for establishing a cost-effective design, in which numerous CFRP strip configurations were examined for a damaged-culvert model. The results indicated that a complete CFRP sheet was most effective for the maximum design capacity and repair effectiveness. The study’s outcomes provide valuable insights for professionals engaged in enhancing the strength of box culverts, aiming to increase the capacity, enhance the stability, and strengthen corroded culverts.

Numerical and experimental studies on bending behavior of circular aluminium-concrete-steel double skin tubular cross-sections and bending capacity design approach

Considering the excellent corrosion resistance of aluminium alloy, a new-type aluminium-concrete-steel double skin tubular (ACSDST) member is proposed by replacing the outer steel tube of concrete-filled double skin steel tubular members with an aluminium alloy tube to improve structures' corrosion resistance and durability. Until now, no literature has been available on ACSDST cross-section in bending. This paper presents experimental and numerical investigations on the flexural behaviour of circular ACSDST cross-sections in bending. Broad parameters are examined in this research, including varying diameter-to-thickness ratios of the outer tube (20–120), hollow ratio (0.2–0.75), concrete compressive strength (30–70 MPa) and steel yield strength (235–355 MPa). The experimental results show that the final failure is controlled by the tensile rupture of aluminium alloy tubes, but it generally happens after the maximum moment, and the composite section behaves in good curvature ductility. The parametric analysis based on the developed finite element (FE) model discloses the different influences of diameter-to-thickness ratios of the outer tube, hollow ratio, and concrete and steel strengths on the bending moment capacity. Among them, the diameter-to-thickness ratio of the outer tube and hollow ratio significantly affect the bending moment capacity. The design equations for bending moment capacity are induced based on the plastic stress distribution method. Those equations are safe and accurate for the maximum moment (a widely used definition of bending moment capacity) within a certain range of parameters. However, a reduction factor 0.9 is proposed for the equations to predict the moment at a longitudinal flexural tensile strain of 1% (another widely used definition of bending moment capacity). Moreover, the cross-section slenderness limit for the compact ACSDST section is recommended based on the analysis of the experimental and FE results.