Design Equations Research Articles

Erratum for “Evaluation of Design Equations for Critical Properties of Reinforced Elastomeric Bearings and Recommended Revisions”

Erratum for “Evaluation of Design Equations for Critical Properties of Reinforced Elastomeric Bearings and Recommended Revisions”

Intra-organizational knowledge sharing, ambidexterity and firm performance: evaluating the role of knowledge quality

PurposeThis study aims to examine how knowledge sharing contributes to organizations’ ambidexterity, their overall performance and the role of knowledge quality in this relationship. Knowledge sharing is conceptualized based on tacit and explicit dimensions, and ambidexterity is viewed as comprising exploitative and explorative capabilities.Design/methodology/approachThis study uses a cross-sectional survey-based research design and structural equation modeling to test the proposed model of knowledge sharing and knowledge quality in organizational ambidexterity and the related hypotheses.FindingsThe results indicate that tacit knowledge sharing has a significant, direct impact on the exploitative and explorative capabilities of the organization and indirectly impacts both dimensions of ambidexterity (i.e. exploitative and explorative) through knowledge quality. In contrast, explicit knowledge sharing does not have a significant impact on knowledge quality and affects only the exploitative extent of ambidexterity. Both exploitative and explorative capabilities significantly impact organizational performance.Originality/valueTo the best of the authors’ knowledge, this study is the first study to empirically examine the role of knowledge quality in the context of knowledge sharing for ambidexterity, especially within the context of organizations in the United Arab Emirates.

Compressive load capacity of CHS X-joints: The Efficacy of doubler plates

This study explores the effects of doubler plates and alterations in joint configuration, on the static characteristics of X-joints made from circular hollow sections (CHS) with slender walls, concentrating on how they withstand compressive forces applied to the braces. A detailed finite element analysis (FEA) was launched. Its accuracy verified through experimental tests carried out by the research team and by comparing it with existing studies. The investigation included an extensive parametric analysis (by generating 204 models) to evaluate changes in initial stiffness, load capacity, and modes of failure, with a focus on the importance of interactions between the chord and plates and the impact of geometric and material nonlinearities. Findings revealed that the doubler plates significantly improve the maximum load bearing capacity and failure modes under various joint geometrical scenarios. While the benefits of doubler plates in enhancing the durability of X-joints are clear, their effectiveness under axial load was not studied. Based on these insights, the research introduces a new theoretical design equation, based on yield volume theory and nonlinear regression, to accurately forecast the ultimate load capacity of the joints.

Compact Ultra-Wideband Wilkinson Power Divider in Parallel Stripline with Modified Isolation Branches.

An efficient design method for a compact and ultra-wideband multi-stage Wilkinson power divider in a parallel stripline (PSL) is proposed. To enhance the frequency bandwidth of the proposed power divider while reducing its size, the isolation branch is modified; that is, two capacitors are connected to both sides of a resistor at each isolation branch. For an efficient design process, the PSL power divider is equivalently represented by two microstrip power dividers, and the design equations are derived. Based on the design equations, an in-house algorithm is utilized to optimally determine the design parameters, including the line impedance, resistance, and capacitance of each stage. For example, a three-stage PSL power divider is designed with three λ/4 transmission lines at a base frequency of 5 GHz. To verify the accuracy of the design procedure, 3D EM simulations and measurements are performed, and the results show good agreement. Compared with the conventional three-stage Wilkinson power divider, the proposed PSL power divider achieves a wider frequency bandwidth of 1.16 to 6.51 GHz (139.5%) and a 23% shorter transmission line length of 207°, while exhibiting an insertion loss of 0.7 to 1.4 dB.

Unveiling the veil: exploring how wellbeing motivations shape anonymous and public prosocial behavior in Indonesia.

Indonesia is often regarded as a country with a strong inclination toward prosocial behavior, with both public and anonymous acts of kindness being commonplace. However, there is a notable gap in related research regarding the predictors of such behaviors. Previous studies have highlighted how individuals with diverse motives for wellbeing are inclined to either assist or hinder others. The present study explored the role of eudaimonic, hedonic, and extrinsic motives for wellbeing in predicting public and anonymous prosocial behavior. Using convenience sampling, 254 Indonesian undergraduate students (18-25 years old) from a private university participated in an online survey. The data were analyzed with correlational design and structural equation modelling. The findings revealed that the eudaimonic motive for wellbeing positively predicted anonymous prosocial behavior. Interestingly, no significant impact of hedonic motives on either public or anonymous prosocial behavior was observed. On the other hand, the extrinsic motive for wellbeing emerged as a positive predictor of public prosocial behavior. The absence of a discernible effect of the hedonic motive on either form of prosocial behavior highlights the need for further research into the complex interplay between motives for well-being and altruistic actions. This research represents a pioneering exploration into the distinct impacts of individuals' pursuit of wellbeing on their approaches to altruistic actions, providing valuable insights for understanding and promoting prosocial behavior in society.

Exploring primary school teachers’ idea generation during the STEM instructional design process

ABSTRACT Background Instructional design is essential for the implementation and quality of STEM education. However, it remains challenging to help teachers acquire pedagogical content knowledge and come up with novel instructional design ideas in STEM. education. Purpose Guided by the full-perspective learning theory, this study proposed a conceptual model that was constructed by teaching needs assessment (TNA), internal meditation (IM), external interaction (EI), and idea generation in instructional design (IGID). Sample A total of 1,727 primary school technology teachers (51.8% female, 48.2% male) who had conducted STEM learning activities participated in this study. Design and methods Structural equation modeling was used to verify the relationships between variables. Results The results indicated that (1) TNA, IM, and EI were positively related to IGID; and (2) both IM and EI were positively related to IGID. In addition, through the multiple group analysis, it was observed that there were significant gender differences in the idea generation process. Conclusion The findings implied that male teachers performed better than female teachers in TNA, and were more motivated to seek ideas through IM and EI after TNA. Female teachers were more likely to obtain novel ideas through IM. The research provides some ways to facilitate the acquisition of ideas on STEM instructional design, which can be used to guide course design for instructors and course designers in STEM fields.

Monte Carlo Simulations for Global and Local Interaction Buckling of Welded Box-sections

The present study focuses on investigating the interaction behavior of local and global buckling resistance of welded box-section columns by using stochastic analysis. Previous studies mainly investigated this failure mode using experimental or numerical investigations but using deterministic approaches. The current research employs Monte Carlo simulations as a robust numerical tool to estimate the interaction buckling resistance. Stochastic variables are defined, encompassing variabilities in geometrical and material properties, as well as local and global imperfections. To facilitate these simulations, a rigorously validated numerical model is employed, utilizing geometrical and materially nonlinear analysis with imperfections (GMNIA). This advanced modeling approach accounts for the complex nonlinearities inherent in the behavior of welded box-section columns. The characteristic resistance derived from the Monte Carlo simulation is compared to 1. test results, 2. analytical buckling resistance according to the Eurocode design approach, and 3. previously proposed deterministic approaches. Within the research program, an improved generalized design formula is developed to estimate the buckling resistance for pure local, global, and interaction buckling modes. The new design equation is compatible with the design rules of the Eurocode and enhances the ease of use of the standard regulations.

Development of multiple input supply based modified SEPIC DC–DC converter for efficient management of DC microgrid

The development of DC microgrids is reliant on multi-input converters, which offer several advantages, including enhanced DC power generation and consumption efficiency, simplified quality, and stability. This paper describes the development of a multiple input supply based modified SEPIC DC–DC Converter for efficient management of DC microgrid that is powered by two DC sources. Here Multi-Input SEPIC converter offers both versatility in handling output voltage ranges and efficiency in power flow, even under challenging operating conditions like lower duty cycle values. These features contribute to the converter's effectiveness in managing power within a DC microgrid. In this configuration, the DC sources can supply energy to the load together or separately, depending on how the power switches operate. The detailed working states with equivalent circuit diagrams and theoretical waveforms, under steady-state conditions, are shown along with the current direction equations. This paper also demonstrates the typical analysis of large-signal, small-signal, steady-state modeling techniques and detailed design equations. The proposed configuration is validated through the conceptual examination using theoretical and comprehensive MATLAB simulation results. Detailed performance analysis has been done for different cases with various duty ratios. Finally, to show the competitiveness, the multi-input SEPIC topology is compared with similar recent converters.

A Broadband Three-Way Series Doherty Power Amplifier with Deep Power Back-Off Efficiency Enhancement for 5G Application

This article presents a new broadband three-way series Doherty power amplifier (DPA) topology, which enables a broadband output power back-off (OBO) efficiency enhancement of up to 10 dB or higher. The proposed DPA topology achieves Doherty load modulation and three-way power combining through a transformer, which requires only a low coupling factor, thus facilitating its implementation in double-sided PCBs or monolithic microwave integrated circuit (MMIC) processes. The design equations for the proposed DPA topology are proposed and analyzed in detail. A proof-of-concept PA at the 2.1–2.8 GHz band using commercial GaN transistors was designed and fabricated to validate the proposed concept. Within the operating frequency band, it achieves a saturated output power (Psat) of 44.5–46.5 dBm with a peak drain efficiency (DE) of 60–72%, and 43–52% DE at 10 dB OBO. Moreover, under a 20 MHz long-term evolution (LTE)-modulated signal, the PA demonstrates a 36.8–37.5 dBm average output power (Pavg) and 47–53% average drain efficiency (DEavg). Notably, the adjacent channel leakage ratio (ACLR) is as low as −35–−28.2 dBc without any digital predistortion (DPD).

Assessing the Effect of Compensation Packages, Work-Life Balance Policies, and Career Development Opportunities on Employee Retention: A Case Study of MSME Employee

In today's competitive business environment, Micro, Small, and Medium Enterprises (MSMEs) face significant challenges in attracting and retaining top talent. This study examines the impact of compensation packages, work-life balance policies, and career development opportunities on employee retention within MSMEs. Using a quantitative research design and Partial Least Squares Structural Equation Modeling (PLS-SEM), data from 300 respondents were analyzed to explore the relationships between these factors. The findings reveal significant positive relationships between compensation packages, work-life balance policies, career development opportunities, and employee retention. These results highlight the importance of strategic investments in human capital and the creation of conducive work environments to foster employee loyalty and commitment within MSMEs.

The relation between lateral thinking and inquiry skills of higher education students: A path analysis

AbstractThe aim of the study is to examine the relations between higher education students' lateral thinking dispositions and inquiry skills. Survey design and Structural Equation Modelling were used in the study. The sampling of the study consisted of 975 prospective teachers attending three faculties of education in three different state universities in Turkey. Inquiry Skills Scale and Lateral Thinking Disposition Scale were used to collect data. The collected data were analysed using R Studio programme. It was observed in the study that students' inquiry skills and lateral thinking dispositions were high. It was revealed in the study that inquiry skills predicted lateral thinking dispositions. Inquiry skills account for 31% of lateral thinking disposition. Thus, it can be concluded that lateral thinking dispositions of higher education students' depend on their inquiry skills at a percentage of 31%.

Stress Concentration Factors of Concrete-Filled Double-Skin Tubular K-Joints

Tubular joints are important connecting parts of a welded steel tube structure. The S-N curves based on the hot spot stress (HSS) method are often used to evaluate the fatigue life of tubular joints in practical engineering. The stress concentration factor (SCF) is a key parameter to calculate HSS. In this paper, stress concentration tests of hollow-section and concrete-filled double-skin tubular (CFDST) K-joints were carried out, respectively, and then finite element models of K-joints considering the weld were established. The developed models were validated with the experimental results. The influence of key geometrical parameters, such as the diameter ratio of brace to chord β, the diameter to thickness ratio of chord γ, the wall thickness ratio of brace to chord τ, brace angle θ, and hollow section ratio ζ on the distribution and key position of SCFs along the weld toe, was discussed. Parametric studies were conducted to obtain the calculating equations for the SCF values of CFDST K-joints. The results demonstrate that infill concrete can effectively reduce SCFs along the weld on the chord. When the hollow section ratio was reduced to 0.317, the SCF was reduced by 77.2%. Notably, the SCF reduction rate was sensitive to γ and θ, with a decrease observed as γ increased. The hollow section ratio ζ had a less pronounced effect on SCF distribution patterns, but as ζ decreased, the chord’s stiffness improved, suggesting a potential approach to enhance joint performance. The distribution of SCFs is similar for joints of the same type but different geometric configurations. The innovatively integrated hollow section ratio in the CFDST design equation significantly simplifies and enhances the precision of SCF calculations for CFDST K-joints.

Strength design of built-up radially battened columns subject to axial compression and arbitrary directional bending moment

Built-up radially battened columns (RBCs), comprising several identical circular steel tubes interconnected by multiple radial-shaped battens, represent an innovative column design that combines aesthetic appeal with exceptional load-bearing capacity. This makes them well-suited for architectural applications in large public buildings such as stations and airports. The axial compressive strength design methods for the built-up RBC have been extensively explored in the authors' prior studies. However, in real-world engineering applications, built-up RBCs may experience simultaneous axial compression and varying directional bending moments, particularly when considering potential eccentric compression or wind and earthquake loads in public buildings. Currently, strength design methods for this loading condition are still lacking. To address this deficiency, this paper primarily delves into the failure mechanism and strength design methods for built-up RBCs experiencing combined axial compression and arbitrary directional bending moments. Initially, the sectional strength of the built-up RBC is investigated by using a shell finite element model (FEM) for the built-up RBC. It is revealed that the compression-bending sectional strength of the built-up RBC exhibits significant differences with varying bending directions and tube numbers. Moreover, in some bending directions, the M-N sectional strength curve of the built-up RBC exhibits convexity. By integrating theoretically derived equations grounded in the principles of materials mechanics with FEM numerical calculations, concise and practical design equations are proposed for accurately predicting the sectional strength of the built-up RBC under combined axial compression and arbitrary directional bending moments. Subsequently, The buckling strength of the built-up RBC is studied using the FEM, considering initial geometrical imperfections consistent with first-order flexural buckling and accounting for geometric nonlinearity. It is noted that the bending direction of the built-up RBC may deviate during loading. Besides, the M-N buckling strength curve of the built-up RBC is not as convex as its M-N sectional strength curve. Based on calculations from numerous examples, practical design equations for predicting the buckling strength for the built-up RBC under axial compression and any directional bending moments are introduced. The key findings of this paper contribute to the compression-bending strength design of RBCs, enriching RBC design theory and promoting the widespread application of built-up RBCs in actual engineering projects.

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.

A Simplified Method for Determining Fire Resistance of RC Columns Using Fire-Resistance-Column-Curves Approach

Eurocode-2 (EC2) empirical equation for fire resistance of RC columns is very sensitive to the value of column capacity at normal temperature conditions NRd\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_{Rd}$$\\end{document}. Techniques to determine NRd\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N_{Rd}$$\\end{document} accurately for eccentric slender columns are difficult and computationally demanding; thus, adopting simplifications leads to unsatisfactory results in many column cases. Another shortcoming of EC2 equation is that it does not include an explicit term regarding the effect of load eccentricity on fire resistance. In this paper, a simplified method, as an attempt to overcome EC2 method defects, is developed to determine the fire resistance of RC columns using fire-resistance-column-curves. A rational numerical model is used to analyze various series of RC columns with different geometric, material, and loading properties at elevated temperatures. The results of the numerical study are utilized to construct different fire-resistance-column-curves from which simplified design equations are developed to predict the fire resistance of fixed- and pinned-end RC columns. The validity of the method is established with the aid of experimental data and it was found that in most cases, there is good agreement between assessed and test columns. It was also found that the proposed equations provide sufficiently safe predictions when appropriate material safety factors are adopted. The applicability of the proposed method to fire resistance design of RC columns is illustrated through numerical examples.

Numerical studies of pull-through failures in cold-formed steel battens at sub-zero temperatures

Cold-formed steel (CFS) roof and wall cladding systems comprising thin, high strength steel battens and claddings are popularly used in the building industry worldwide. These cladding systems have been observed to encounter failures under combined snow and strong wind actions during blizzards. Significant damage is caused by the disengagement of the entire roof/wall cladding when localised pull-through failures occur in thin-walled steel battens at the batten to truss/rafter screw connections due to a splitting mechanism around the screw head. This study uses detailed finite element analyses of the pull-through failures of a range of batten configurations under combined wind and sub-zero temperature conditions. Suitable finite element models capable of simulating the pull-through failures of battens were developed and validated using experimental results, followed by detailed numerical parametric studies. The main outcomes of this study are accurate design equations and capacity reduction factors essential for predicting the pull-through capacities of CFS battens at sub-zero temperatures.

Effect of BFRP ties on the axial performance of RC columns reinforced with BFRP and GFRP rebars

The adoption of fiber-reinforced polymer (FRP) bars in lieu of traditional steel reinforcement for concrete structures has gained prominence. Nevertheless, prevailing international standards have not incorporated provisions to assess the significant contribution of FRP materials to the axial capacity and deformability of compression members. This study investigates the impact of Basalt (BFRP) ties on the axial performance of full-scale concrete columns reinforced with BFRP and Glass (GFRP) rebars, alongside traditional steel longitudinal rebars. Ten columns were subjected to concentric loading, with parameters including the type of longitudinal rebars (BFRP, GFRP, and steel), spacing of BFRP ties (180 mm, 120 mm, and 60 mm), and diameter of steel rebars (16 mm and 20 mm). Varied steel rebar diameters aimed to discern the influence of axial stiffness on column behavior. Results indicate an 18 % to 26 % higher axial load capacity in steel-reinforced concrete (RC) columns compared to FRP-RC columns. Both types of FRP rebars contributed approximately 12 % to the axial capacity. Reducing BFRP tie spacing from 180 mm to 60 mm significantly increased deformability by up to 250 % in FRP-RC columns and ductility by up to 14 % in steel-RC columns. The study highlights conservative predictions in existing design equations (ACI 440.11–22 and CSA S806-12) for the axial load capacity of BFRP and GFRP RC columns, underestimating by 14 % to 20 %, as they neglect the contribution of FRP rebars. Utilizing a concrete crushing strain of 3,000 µε and 3,500 µε as the ultimate FRP compressive strain produced predictions closest to the experimental axial load capacity.

Ultimate strength and design of CFDST columns with intermittent welded plate stiffeners

This study conducts an experimental investigation and formulates a finite element model and design equation to determine the ultimate strength of concrete-filled double-skin tubular (CFDST) short columns. These columns are equipped with intermittent welded plate stiffeners, and the welding is performed on the inner surface of the outer tube through pre-drilled holes at intervals of 10 t, 20 t, 30 t, and 40 t, where “t” represents the thickness of the outer tube. The study investigates the behaviour of the CFDST column influenced by the presence of plate stiffeners, determines the axial strength of eighteen CFDST specimens and discusses the load-displacement curve, deformation and ultimate strength. The findings demonstrated that the ultimate load of the plate-stiffened CFDST columns is between 24% and 42% higher than the unstiffened CFDST columns. The plate-stiffened CFDST columns also exhibited higher ultimate strength at the smallest weld spacing of 10 t. The experimental results showed that the plate stiffeners influenced the distribution of the internal forces, which changed the effective confinement area of the concrete. The investigated force distribution provides a fundamental theoretical basis for computing the confinement area for the finite element model (FEM) and design model. This study developed a verified nonlinear FEM that employed ABAQUS to replicate the behaviour of the plate-stiffened CFDST columns. Finally, this study proposes a new design model that considers the effective cross-sectional area of the concrete confined in CFDST columns with intermittent welded plate stiffeners. The strength predictions of the plate-stiffened CFDST columns were accurate compared to the experimental results.

Single-Phase Robust Charger with High Power Quality for Electric Vehicle Application

The widespread use of electric vehicles (EVs) necessitates the development of a robust charging infrastructure. The goal of this research paper is to create a high-quality, single-phase charger for electric cars. The purpose of this design is to provide a charger that is both fast and efficient but also protects against power quality problems including harmonics, power factor correction, and voltage variations. A single-phase–single-stage improved power quality EV charger for small and medium power applications has been designed and simulated. A single DC-DC converter is utilized for constant charging and improved power quality operation. The charger presented exhibits improved power quality as sinusoidal current is drawn from the utility grid supply with the total harmonic distortion (THD) in compliance with the IEEE 519 and IEC 61000-3-2 standards. In order to charge the battery of an electric vehicle, most two-stage converters first use a boost converter for power factor correction (PFC), and then they use a DC-DC converter that can accept any input voltage. These two-stage conversions are inefficient and use more parts than necessary. This work proposes a PFC converter based on a single-stage switching inductor Cuk converter, which has the advantages of high step-down gain, low current stress, high efficiency, and a small number of components. The suggested converter’s operational analysis and design equations are performed in continuous current mode. The proposed converter is the subject of extensive mathematical modelling, analysis, simulation, and experimentation presented in this study. With both constant voltage (CV) and constant current (CC) loads, the proposed converter’s performance is analysed with regard to power quality indices like voltage total harmonic distortion (THD), current THD, and total power factor. Additionally, in CV mode and CC mode, the suggested converter’s dynamic performance with battery charging is evaluated in relation to the extensive supply changes. The developed charger presents a reliable and efficient solution for EV charging, fostering the transition to a cleaner and more sustainable transportation system.

Member capacity of cold-rolled aluminium alloy channel columns – Part II: Numerical investigation and design

The paper first presents the development of detailed finite element (FE) models for investigating the member capacity of cold-rolled aluminium alloy 5052-36 channel columns. The numerical non-linear FE models are developed using the commercial FE software package ABAQUS to simulate laboratory experiments and calibrated against the test results. The experimental program was performed by the authors at the University of Sydney and the detailed test results are fully described in a companion paper. The calibrated numerical FE models with actual mechanical properties and measured geometric imperfections in analyses accurately predict the experimental results and behaviours, including flexural and flexural-torsional buckling as well as local-global interaction buckling failure modes. A parametric study is subsequently performed to extend the data range by varying cross-section dimensions and member lengths. The effects of loading eccentricity positions and initial geometric imperfections are also considered in the parametric study. The experimental and numerical results are compared with design strength predictions from current Australian/New Zealand, American and European specifications for aluminium structures in the companion paper. In this paper, the Direct Strength Method (DSM) for the design of compression members as per the Australian/New Zealand standard AS/NZS 4600 for cold-formed steel structures is adopted for comparison. The DSM design rules for cold-formed steel compression members are found to provide more accurate predictions than those of current specifications for aluminium structures and therefore used to propose improved design equations for cold-rolled aluminium alloy columns. Finally, a reliability analysis is performed to evaluate the safety level of current design specifications and the proposed design rules.