Design Procedure Research Articles

Development of functionally graded structure for hip endoprosthesis stem based on lattice-type metamaterial

The paper reports on design and studies of a promising configuration of a hip endoprosthesis stem. The femoral component of the endoprosthesis is constructed based on a metamaterial produced by additive technologies, representing a periodic porous structure of variable topology. The central goal of the design procedure was to numerically determine the spatially graded relative density of the lattice structure within the implant volume by solving the optimization problem. The first stage of development comprised finite element modeling of a system with a solid implant attached, i.e., the optimization space, for seven different loading scenarios. These scenarios were constructed to represent the most typical cases of human motor activity. The second step was to determine the optimal spatial distribution of relative density of the lattice structure in the implant volume, obtained by solving the topological optimization problem under the given loading. After the optimization problem was solved, the distribution of the relative density of the lattice structure was obtained, serving as a basis for constructing a geometric model of a functionally graded porous scaffold for implantation. This result allows achieving an optimal ratio of stiffness and mass properties under the given loading conditions. The approach was verified by direct finite element modeling of the constructed lattice geometry of the implant under specific loading scenarios. Analyzing the stress fields in the volume of the endoprosthesis, we concluded that there were no critical regions in the developed structure, so the approach taken to develop the metamaterial-based endoprosthesis can be deemed correct.

Replacement of conventional aggregates and fillers with steel slag and palm kernel shell ash in dense-graded asphalt mixtures

Large quantities of steel slag and palm kernel shell ash (PKSA) – waste products from steel production and palm oil milling, respectively – are generated annually in several countries, and their disposal is challenging. Meanwhile, the over-reliance on conventional rock aggregates for asphalt mixture production poses increasing sustainability challenges. This study investigated the potential of entirely replacing granite aggregates with steel slag and PKSA in a dense-graded asphalt mixture. Two sets of asphalt mixtures were prepared; the control mixture contained crushed granite aggregate and hydrated lime, while the other set incorporated steel slag as coarse aggregate and PKSA as fine aggregate and filler. Both mixture types utilized AC-30 viscosity-graded asphalt binder. The properties of the waste materials met the quality standards required for aggregates in asphalt mixture production. Both mixture types were designed according to the Marshall design procedure and were evaluated for durability (Cantabro abrasion loss), fatigue cracking Resistance, rutting Resistance, and moisture damage susceptibility. The Cantabro abrasion loss test indicated that the waste-based mixture was 3% less durable than the control. However, the cracking Resistance of the waste-based mixture was approximately twice that of the control. Even though the rapid rutting test indicated that the control mixture was slightly superior in rutting Resistance, the Marshall quotient suggested otherwise. Both mixture types exhibited similar moisture damage resistance. Overall, the steel slag and PKSA samples have shown high potential to replace virgin granite aggregates and lime in asphalt mixtures fully and are, thus, recommended for field performance evaluation and possible adoption.

Design of Stabilizing Network for Capacitive Power Transfer Transmitter Operating at Maximum Power Transfer Limiting the Voltage Gain in Resonant Capacitors

Capacitive power transfer (CPT) is a technology that is emerging as an alternative to inductive power transfer (IPT) in applications requiring low to medium power. A great interest has been developed in the implementation of CPT systems in battery charging systems, where a condition to compete with IPT systems is the need to increase the power transfer in the CPT systems without significant losses. This paper puts forth a design methodology for a stabilizing network, which has been applied to a CPT system. This methodology has been developed through impedance analysis of the circuit, in order to achieve maximum power transfer, with total gains of voltage and current reaching a value close to unity. The methodology allows for the calculation of the value of the components of the stabilizing network, which has been designed with the objective of stabilizing the resonant frequency against changes in the capacitance of the transmission plates. To validate the design procedure, an experimental prototype was developed at 25 W and an operational frequency of 1.55 MHz. The results obtained validate the design methodology.

Pixelated slot-based dual-broadband tunable graphene metasurface absorber design through excitation of coupled modes in terahertz regime

This work presents a dual-broadband metasurface absorber (DBMSA) design inspired by the pixel-based slot patterning of the top graphene sheet (Gpat). Complimentary design procedure using slots ensures an inbuilt DC connection among graphene patterns, which makes tuning of chemical potential μc highly practical. A DBMSA provides an absorptivity (Af) ≥ 90 % from 4.46 to 5.6 THz (22.66 %) in the lower band and from 7.52 to 8.68 THz (14.32 %) in the upper band. At the same time, variation in μc (Top) from 0.5 to 1 eV leads to the coverage of an ultra-wideband (UWB) terahertz (THz) spectrum from 3.62 to 9.1 THz with Af≥ 90 % due to the overlapping of bands. The absorber is polarization-insensitive due to the symmetricity in the design of the unit cell and provides stable Af for incidence angle ≤ 60° under both transverse magnetic and electric polarization. The DBMSA is compact and ultra-thin, having periodicity and thickness of λ0/6.72 and λ0/26.9, respectively. The developed ECM model closely predicts the working principle of the metasurface. In conclusion, the proposed DBMSA can be used for several applications in the THz gap regime, such as THz shielding, radar cross-section (RCS) reduction, sensing, imaging, etc.

Behaviour of large-diameter high-strength bolted shear connections for prefabricated composite beams

This paper presents an experimental investigation into the structural behaviour of a new proposed shear connection incorporating high-strength large-diameter steel bolts in conjunction with steel fibre reinforced concrete blocks. A detailed account of fourteen large-scale push-out tests is provided with the aim of examining and quantifying the full deformational characteristics of these shear connections. The results include the load-slippage responses, shear resistances, and failure modes for the various specimens. It is shown that the proposed connection configuration is suitable for prefabricated composite beams in highway bridges and can be detailed to provide high stiffness over 1500 kN/mm, large shear resistance exceeding 1000 kN, and slippage at failure greater than 6.0 mm. The proposed connection can also be easily assembled on site and provides significant resistance against pull-out forces. Based on the experimental results, complementary design procedures are proposed to enable a prediction of the shear resistance of the connections. A simplified load-slippage relationship for the shear connections is also suggested and shown to represent closely the full deformation characteristics. Overall, the proposed shear connection configuration is shown to offer considerable stiffness, resistance, and ductility, and can be readily installed on site for joining steel beams and precast slabs in combination with high performance in-situ concrete. This connection form contributes to an enabling construction technology for promoting effective prefabrication of composite bridge structures.

Concept and Experimental Validation of Using Titanium Alloy Bars (TiABs) as Flexural Reinforcing in Concrete Beams

The research focuses on the use of Titanium Alloy Bars (TiABs) in concrete cap beams. TiABs offer good ductility, high strength, lightweight, superior corrosion resistance, lower overstrength, and better fatigue performance. TiABs have recently been used in several existing bridges in Oregon and Texas in the United States to increase shear and flexural capacities of concrete beams. While TiABs have been implemented in retrofitting of existing bridges in the United States, their application in new structures have not been tested and compared against conventional steel rebars. The research in this paper proposes concept for an innovative cap beam reinforced with longitudinal TiABs. The cap beam integrates both structural performance and durability. Flexural and shear design procedures for the cap beam in accordance with the AASHTO LRFD Design are discussed. To investigate structural performance, a large-scale cap beam reinforced with longitudinal grade 5 titanium alloy (Ti-6Al-4V) is tested under three-point bending test protocol. The results are compared against a benchmark cast-in-place beam with normal rebars under the same testing arrangement and loading protocol.

Compact dual-band enhanced bandwidth 5G mm – wave MIMO dielectric resonator antenna utilizing metallic strips

A compact dual-band Multiple-Input Multiple-Output Dielectric Resonator Antenna with improved bandwidth for 5G mm-wave applications is presented. Two rectangular DRAs mounted on a substrate backed ground plane are excited by microstrip feed through aperture coupling. Notches cut out from center of the DRAs helps to achieve a dual-band response with improved bandwidth by exciting several modes. The isolation between the DRAs is achieved by appropriately positioning metallic strips on walls on of the DRAs. A dual-band response with enhanced bandwidth and mutual coupling reduction. The impedance bandwidth for the proposed design is between 26.5–30 GHz (12.4 %) and 34.2–40 GHz (15.6 %). The maximum isolation achieved in the lower band is 32 dB and above 45 dB in the upper band. The overall size of the design is 1.88λo x 0.94λo x 0.20λo. The design procedure is described, and the role of decoupling strips are explained. A prototype is fabricated and measured to validate the proposed design.

A Novel MARS-Based Design Procedure for Anchored Wall Systems in Urban Excavations

A Novel MARS-Based Design Procedure for Anchored Wall Systems in Urban Excavations

An improved flexural design procedure of steel plate I‐girders considering elastic lateral torsional buckling at elevated temperatures

AbstractIn the present study, an improved design method is proposed for the flexural design of steel plate I‐girders at elevated temperatures. The proposed method accounts for two important phenomena accompanying the temperature increase in steel I‐girders: (1) alteration of the failure mode and (2) degradation of the material properties. The main strategy of the proposed procedure is to find the ambient‐temperature‐equivalent design parameters of steel I‐girders at elevated temperatures. The basic design relationships are adopted from the flexural design provisions of AISC 360‐16 and then modified to accommodate the elevated temperatures and instability conditions of I‐girders. To evaluate the accuracy and efficiency of the proposed method, a comprehensive finite element study is conducted using ABAQUS. To this aim, 54 numerical models of steel plate I‐girders with different cross‐section slenderness parameters were investigated. All the simulated I‐girders were prone to fail in elastic lateral‐torsional buckling mode at both ambient temperature and elevated temperatures. To corroborate the numerical modeling and analysis process at ambient and elevated temperatures, the results were verified against the available experimental data. Based on the results, the maximum absolute deviation of the ultimate flexural strength obtained from the proposed method from the finite element predictions was 9%.

From CAD to representations suitable for isogeometric analysis: a complete pipeline

AbstractNext generation CAD/CAE systems shall integrate design and analysis procedures as a means to simplify workflows, boost performance, and speed up time to market. In the present paper we demonstrate a proof of concept of such a unification using subdivision surfaces and the enabling technology of isogeometric analysis. In particular, we present a complete pipeline to convert CAD models into smooth $$G^1$$ G 1 spline representations, which are suitable for isogeometric analysis. Starting from a CAD boundary representation of a mechanical object, we perform an automatic control cage extraction by means of quadrangular faces, such that its limit Catmull-Clark subdivision surface approximates accurately the input model. We then compute a basis of the $$G^1$$ G 1 spline space over the quad mesh in order to carry out least squares fitting over a point cloud, acquired by sampling the original CAD geometry. The resulting surface is a collection of Bézier patches with $$G^1$$ G 1 regularity. Finally, we use the basis functions to perform isogeometric analysis simulations of realistic PDEs on the reconstructed $$G^1$$ G 1 model. The quality of the construction is demonstrated via several numerical examples performed on a collection of CAD objects presenting various challenging realistic shapes.

Optimizing multivariate alarm systems: A study on joint false alarm rate, and joint missed alarm rate using linear programming technique

In modern complex industrial systems, multiple process variables interact with one another. The role of alarm systems in ensuring the safety of these systems is of utmost importance. Consequently, there is an increasing value placed on the assessment of the performance of multivariate alarm systems. As the dimensions of the system and the number of variables grow, designing optimal parameters for the multivariate alarm system using traditional approaches such as probability density function estimation becomes increasingly convoluted. In this paper, an approximate method is proposed for calculating two indices known as the Joint False Alarm Rate (JFAR) and Joint Missed Alarm Rate (JMAR), which are used to evaluate the performance of multivariate alarm systems. These indices are computed using the multivariate Markov chain method. The Markov chain is constructed by solving an optimal Linear Programming (LP) problem. Subsequently, joint indices are defined based on steady state estimations of a multivariate Markov chain. To validate the theoretical results obtained on the JFAR and JMAR and to demonstrate the proposed performance assessment and alarm system design procedures, numerical example and an industrial case study are provided.

Feasibility study on additive-manufactured honeycomb sandwich structural solutions for a Fast Patrol Vessel

This work represents a significant step toward integrating additive-manufactured honeycomb sandwiches into ship hull structures. The sandwich structure consists of two continuous fibre-reinforced thermoplastic faces and a regular honeycomb core made of chopped fibre-reinforced thermoplastic. The primary goal is to create optimal manufacturing and design methods to determine to which extent the sandwich solution that has been analysed may be used as a structural component of a fast patrol vessel. The core of the design procedure is a purposely developed evolutionary multiobjective optimisation routine suited to evaluate the flexural response of the structure under investigation. The analytical formulations utilised to predict the structural response of an additive-manufactured honeycomb sandwich subjected to 3-point bending have been derived using a combined analytical and experimental approach. A fast patrol vessel made of steel has been taken as a reference to demonstrate the capabilities of the proposed solution. A steel primary stiffener and its associated plate have been extracted from the midship section and replaced by an additively manufactured honeycomb sandwich. By maintaining the same structural encumbrances, it has been found that a pseudo-optimal combination of the mechanical properties of the sandwich base materials can accomplish an exceptional weight reduction of three times.

Axial Flow Fan Performance in a Forced Draught Air-Cooled Heat Exchanger for a Supercritical Carbon Dioxide Brayton Cycle

Abstract An axial flow cooling fan has been designed for use in a concentrated solar power plant. The plant is based on a supercritical carbon dioxide (sCO2) Brayton cycle, and uses a forced draft air-cooled heat exchanger (ACHE) for cooling. The fan performance has been investigated using both computational fluid dynamics (CFD) and scaled fan tests. This paper presents a CFD model that integrates the fan with the heat exchanger. The objective is to establish a foundation for similar models and to contribute to the development of efficient ACHE units designed for sCO2 power cycles. The finned-tube bundle is simplified, with a Porous Media Model representing the pressure drop through the bundle. Pressure inlet and -outlet boundary conditions are used, meaning the air flowrate is solved based on the fan and tube bundle interaction. The flowrate predicted by the CFD model is 0.5% higher than the analytical prediction, and 3.6% lower than the design value, demonstrating that the assumptions used in the design procedure are reasonable. The plenum height is also found to affect the flowrate, with shorter plenums resulting in higher flow rates and fan efficiencies, and longer plenums resulting in more uniform cooling air flow.

Surface Disinfection Systems with UV-C Lamps – Verification Measurements and Design Procedure Proposal

ABSTRACT Ultraviolet radiation in the UV-C range is widely applied to disinfect surfaces, air, and water. UV-C (germicidal) lamps are commonly used, and their application is reliable, scientifically proven, and efficient to inactivate various types of bacteria, viruses, and fungal spores, including the SARS-CoV-2 virus. This research aims to develop a UV-C irradiance design procedure for germicidal devices disinfecting surfaces in rooms. This procedure considers the required values of UV-C radiation doses that disinfect rooms efficiently. For this purpose, it has been proposed to apply the DIALux evo software to design the appropriate UV-C irradiance on disinfected room surfaces using different germicidal devices. The measurements verified the accuracy of the simulation performed in the DIALux evo software, which also considered the reflection of the ultraviolet radiation from the principal planes of the room. Two rooms with different dimensions were selected to verify the computational accuracy of the developed design procedure for the disinfection system. Ultraviolet lamps were placed in the rooms, and irradiance measurements were taken at the selected measuring points. The results of the irradiance measurements were compared. The comparative analysis of the disinfection device proved that it was possible to adapt the DIALux evo software to make the calculations for designing room disinfection systems. The research made it possible to determine a suitable design procedure for surface disinfection systems, which prevents errors in proper surface disinfection after implementing UV-C lamps in the room.

Design procedure of reach stacker control system

Reach stackers are efficient and maneuverable machinery for an overload of overall containers in cargo terminals and ports today. Such machinery design determines the practical interest of the engineering industry specialists. However, the lack of information in open sources about structural or kinematic diagrams of equipment control mechanisms and recommendations for their calculation does not allow an effective approach to the creation and update of reach stackers. We developed the design procedure of the reach stacker control system, which considers the kinematic and geometric parameters of the container spreader, as a result of the conducted research. It can be used in the design stages of mechanisms for spreader lateral displacement, extension of the spreader sections, spreader inclination in the vertical plane, container fixation by spreader, spreader rotation, lifting-lowering and telescoping of the boom, as well as during the real operation modes of reach stackers in cargo terminals and ports.

H∞ optimum design and nonlinear seismic performance assessment of tuned-mass-damper-inerter (TMDI) supported by an auxiliary structure

Tuned Mass Damper Inerter (TMDI) and its simplified form, Tuned Inerter Damper (TID), are highly effective in mitigating seismic responses in buildings, particularly when rigidly connected to the ground. However, practical constraints often limit the feasibility of this ideal setup. This study introduces a novel configuration: the AS-type TMDI, which connects the TMDI to an auxiliary structure (AS) adjacent to the main building to simulate a ground connection. To design the AS-type TMDI, this research builds upon insights from studies on TMDIs in adjacent buildings and develops an analogous 3-DOF model representing the TMDI-linked adjacent-building system. This model incorporates two buildings of different heights, allowing the TMDI to be connected at any floor level. Utilizing fixed-point theory, the study derives an analytical solution for the optimal design of TMDI systems within this novel configuration. Additionally, a method is introduced to determine the optimal stiffness and design procedure for the AS itself. The performance of the proposed AS-type TMDI is evaluated through comprehensive nonlinear seismic analysis of a benchmark nine-story steel frame structure, accounting for material and geometric nonlinearities. Results demonstrate that the AS-type TMDI performs comparably to a virtually grounded TMDI in effectively reducing the seismic responses. Furthermore, this innovative configuration outperforms both a conventional retrofitting technique, where the building is rigidly connected to the AS, and a system where a viscous damper alone connects the main building to the AS. This highlights the AS-type TMDI's potential to significantly improve the building’s seismic performance.

Theoretical model of ultimate shear capacity and flexural capacity design method of boundary elements for reinforced concrete frames with steel plate shear walls

AbstractThe steel plate shear walls (SPSWs) have been proven effective in reinforced concrete frames (RCFs) as a lateral force‐resistant structure. Despite of advancements, accurately predicting the ultimate shear capacity of RCFs with SPSWs remains challenging using current simplified models. Additionally, the flexural capacity design procedure for the boundary elements (beams and columns) in previous studies of RCF‐SPSWs involved intricate iterative procedures, hindering its widespread implementation. To address the two issues, this paper investigates the pushover responses and the plate‐frame interaction (PFI) of an RCF‐SPSWs system using theoretical and numerical methods. There are three main contributions. First, a theoretical model of ultimate shear capacity for RCF‐SPSWs is proposed, which can also be used to predict shear contributions of boundary frames in RCF‐SPSWs. Calculation errors for ultimate shear capacity of RCF‐SPSWs and shear contribution from the boundary frame are only 3.7% and 6.7% respectively, which are reduced dramatically compared with the traditional model. A simplified schematic diagram for the global collapse mechanism (uniform distribution of plastic hinges within a structure) of RCF‐SPSWs is developed to facilitate the calculation of internal work and reaction forces. Secondly, a flexural capacity design method for the boundary elements to avoid in‐span plastic hinges is proposed. The proposed method enables the achievement of direct estimation of the flexural demands that could trigger a global collapse mechanism, all without intricate iterative procedures. The applicability of current assumptions for the design of steel boundary frame in RCF‐SPSWs system is discussed, and engineering suggestions are provided to ensure safer and more economic designs. Comparison results confirmed the applicability of the proposed design method, which can be adopted to achieve the global collapse mechanism for RCF‐SPSW system. Thirdly, impacts of yielding panel actions on the flexural capacity of boundary elements of RCF‐SPSWs are clarified. Comparison results demonstrated that adding SPSWs to an RCF alters the axial force on boundary elements and significantly impacts the flexural capacity. A design suggestion is made to emphasize the importance of avoiding the balanced failure of boundary elements. The proposed theoretical model can be used to economize the cross‐section of boundary elements in RCF‐SPSWs system under seismic loads due to accurate prediction of their shear contribution; the proposed flexural capacity design method can achieve a global collapse mechanism, and thus the structural safety and energy dissipation capacity are improved; moreover, the building design efficiency is also improved due to avoidance of intricate iterative procedures.

Gothic Design Procedures in Three Early Hawksmoor Churches

Gothic Design Procedures in Three Early Hawksmoor Churches

State-of-the-Art Power Factor Correction: An Industry Perspective

On 1 January 2001, the IEC 61000-3-2 regulation became effective. Since then, mitigating current harmonics has been essential to ensure that electronic equipment connected to single-phase power distribution lines conforms to electromagnetic compatibility directives. Today, high-quality rectification, commonly known as power factor correction (PFC), is a well-established technique widely adopted by the industry for powering various devices from the ac line. The topic has been studied by academia and industry since the mid-1980s; thus, an enormous amount of research has been published and countless solutions have been proposed since then. However, only a few of those solutions have encountered wide industrial usage. So, it is not the authors’ intention to provide a comprehensive review, but to take stock of the most used PFC techniques from an industry perspective. This paper will review the power factor theory with non-sinusoidal currents, the practical and regulatory aspects of using PFC, and the most common industry solutions for power factor correction in equipment operated from the single-phase, public, low-voltage supply system, with a special focus on boost PFC pre-regulators, their control methods, design procedures, and issues.

Flexural behaviour and design of hybrid cold-formed steel built-up I-section beams

The current study investigates the flexural performance and design of hybrid cold-formed steel built-up I-section beams, which are increasingly popular in the construction industry. These beams combine the benefits of both an "I" section and a closed-box section in their cross-section profile. They are constructed from two identical plain channels placed back-to-back with space between them and top and bottom cover plates, fastened together by screws. A nonlinear finite element (FE) model was developed to consider initial geometric imperfections, material and geometric non-linearities. The model was validated against the test results of cold-formed steel (CFS) built-up beams from the companion paper and literature. Once validation was successful, a comprehensive parametric study using finite element modelling was conducted to generate data on hybrid cold-formed steel built-up I-section beams across a broader range of cross-sectional slenderness, hybrid ratio, aspect ratio of the cross section and thickness of the cover plates. The parametric results were used to analyse the influence of key parameters on the moment carrying capacity and buckling modes. The applicability of the current Direct Strength Method in the AISI S100–16 specifications was evaluated based on these results, revealing that it is unconservative. Additionally, modified design procedures and equations were suggested for hybrid CFS built-up I-section beams vulnerable to local buckling in major axis bending, which were then evaluated through reliability analysis.