Improved Design Procedure Research Articles

Seismic design of concrete structures for damage control

Recent earthquakes have demonstrated that code-conforming modern (i.e. post-1970s) reinforced concrete (RC) buildings can satisfy life safety performance objectives. However, the accumulated earthquake damage in these modern buildings raised concerns about their performance in future events, contributing to widespread demolition and long-term closure of damaged buildings. The economic and environmental impacts associated with the demolition and long-term closure of modern buildings led to societal demands for improved design procedures to limit damage and shorten recovery time after earthquakes. To address societal demands, this study proposes a damage-control-oriented seismic design approach that targets functional recovery by ensuring structural component demands do not exceed the damage-control limit state (DLS) under design-level events. Herein, DLS is defined as the post-earthquake state beyond which the strength and deformation capacity of a structural component is compromised, and its performance in a future event cannot be relied upon without safety-critical repair. This study proposes a methodology to determine component deformation limits for the design of structures for damage control. Using the developed methodology, we propose component rotation limits for RC beams, columns, and walls. The seismic performance and capability of buildings designed using the proposed design approach to satisfy recovery-based performance objectives is demonstrated through nonlinear response history and recovery analyses (using the ATC-138 methodology) of four archetype frame buildings, designed per New Zealand standards to different beam deformation limits. The analyses show that building codes can achieve functional recovery using the proposed component deformation limits without the need for sophisticated recovery analyses.

Mono-objective Optimization of Retaining Wall Using Genetic Algorithm

Abstract This paper examines the importance of geotechnical optimization techniques for soil engineering applications, with a particular emphasis on evaluating geotechnical structures. Due to its prevalence in civil engineering, the complex interplay of geotechnical, structural, and financial considerations necessitates a trial and error approach. The study focuses on design elements, geometric dimensions, and volume considerations in order to highlight the economic viability of reinforced concrete retaining walls. Three code files are created using MATLAB to analyze their impact on active and passive thrusts and, as a result, the structure’s volume. The slope angle, backfill overload, and friction angle are varied. The results demonstrate the effectiveness of using evolutionary algorithms to precisely optimize a single goal and demonstrate that this approach can enhance the design of retaining walls in reinforced concrete. This method demonstrates the ability to improve design procedures in this crucial area, which makes it an invaluable resource for structural engineering researchers and civil engineers.

An Improved Design Procedure for a 10 kHz, 10 kW Medium-Frequency Transformer Considering Insulation Breakdown Strength and Structure Optimization

Medium-frequency transformer (MFT) is an essential device in the smart solid-state transformer (SST) prototype. Compared with the well-defined principle design of magnetic core and windings in MFT, insulation issues are barely concerned. This article focuses on improved design optimization of an MFT, considering the main insulation strength and structure. Dielectric breakdown characteristics of epoxy resin insulating material were studied. An obvious reduction of dielectric strength occurred at high frequency and high temperature in thick samples, which is used for the design of insulation clearance and margin. Moreover, a modified insulation loss evaluation was used, involving the square wave with spike voltages. Through introducing a strategy of multilayered insulation in the windings, the insulation structure is optimized. A 10-kW, 10-kHz, 1-kV/750-V MFT used in the 10-kV SST system was designed by considering the insulation research. Finally, experimental verifications of the MFT performance were carried out by a resonant dc–dc converter. It appears that the optimized MFT exhibits low electric field, small temperature rise, and high efficiency at a 10-kW load. This research provides the basic principles for insulation design in high-voltage and high-power MFT.

Extenics enhanced axiomatic design procedure for AI applications

Abstract This paper introduces a method to improve the design procedure of axiomatic design theory (AD) with Extenics. A comprehensive review of the AD indicates that the powerful principle of AD has been widely studied and applied to many areas, however, inexperienced practitioners of the AD theory still find it difficult to follow or apply the principles in their design which inadvertently often leads to misunderstanding and skepticism. The lack of definitive descriptions for all the elements and specific approaches to guiding the mapping process restricts the development and application of AD theory. This paper improves the design procedure of AD with Extenics. The elements in AD domain are expressed by basic-elements of Extenics, and the formulations are generated. The mapping process based on AD and Extenics is developed. The improved design procedure provides designers with a theoretical foundation based on the logical and rational thought process, meanwhile the solution space can be expanded and innovative designs are inspired. Based on the proposed design procedure, a computer-aided system is developed, which makes the complex and fuzzy design activity clear and easy to follow by filling in the blanks in a step-by-step manner. An example of a novel corn harvester header design scheme is considered to illustrate the validity of the improved design procedure.

Seismic design of acceleration-sensitive non-structural elements in New Zealand: State-of-practice and recommended changes

Acceleration-sensitive non-structural elements not only constitute a significant portion of a building’s component inventory, but also comprise components and systems that are indispensable to the operational continuity of essential facilities. In New Zealand, Section 08 of the seismic loadings standard, NZS 1170.5: Earthquake Actions, and a dedicated standard, NZS 4219: Seismic Performance of Engineering Systems in Buildings, address the seismic design of non-structural elements. This paper scrutinizes the design provisions for acceleration-sensitive non-structural elements in NZS 1170.5 and NZS 4219, and provides an international perspective by comparing with the design provisions for non-structural elements specified in ASCE 7-16, the latest ATC approach and Eurocode 8. This is followed by a detailed discussion on the improvements required for component demand estimation, the need for design criteria that are consistent with performance objectives, definition of realistic ductility factors, and recommendations for the future way forward in the form of an improved design procedure and its application through a new seismic rating framework.

Acoustic absorption modeling of single and multiple coiled-up resonators

This work proposes an improved design procedure of sound absorption metamaterials consisting of acoustic coiled-up quarter-wave resonators that fit into a limited space, in order to broad the range of possible applications even in the low-frequency regime. Different types of models were used to understand the propagation of sound in long, narrow, and square-section tubes, including the visco-thermal loss within the structures for accurate modeling. An analytical model, which includes the definition of the different loss contributions with equivalent fluid models, has been developed: the Johnson-Champoux-Allard model for inlet losses and the “Narrow Region” model for visco-thermal loss along the tubes. A geometric parameterization procedure, for maximizing acoustic absorption at certain target frequencies, was carried out. To validate the theoretical acoustic absorption predictions, the 3D printing technique was used to fabricate samples in a plastic material (PLA) for normal incidence sound absorption coefficient measurements. Moreover, systems containing several quarter-wave resonators of different dimensions coupled in parallel or in series were designed, with the aim of broadening the absorption band; in this case, for practical reasons, only the medium-high frequency regimes were experimentally investigated.

Electromagnetic Bearings With Power Electronic Control for High-Speed Rotating Machines: Review, Analysis, and Design Example

This article reviews electromagnetic bearings with power electronic control for high-speed machinery, which are termed active magnetic bearings (AMBs). AMB is a contactless-type bearing, which uses magnetic force to support the rotor. This is suitable for high-speed applications, harsh operating conditions, and also clean environments. However, the AMB has nonlinear characteristics and is inherently unstable. Due to recent advancements in fast-switching power devices, high-switching-frequency power converters, high-bandwidth current control, nonlinear control strategies, advanced digital controllers, and sensors, AMBs have become promising for high-speed aerospace, industrial, and energy applications. This article contains a brief tutorial on the AMB, covering its operating principle, system-level block diagram, magnetic-circuit-based analysis, dynamic load due to rotor mass unbalance, load capacity, force slew rate, and response to large force disturbance. Furthermore, a design example of an eight-pole AMB with four excitation coils is presented to achieve a load capacity of 180 N. A preliminary design, based on magnetic circuit analysis, is seen to fall short in terms of load capacity. Iterative changes to the AMB dimensions achieve the required load capacity, but the characteristics are still nonlinear. Finite-element analyses bring out the effects of magnetic saturation on load capacity, linearity between force and current, force slew rate, and relationships between maximum force generated and AMB dimensions. An improved design procedure is presented to achieve both desired load capacity and linear characteristics, while balancing the compactness requirement. The improved design also achieves the desired slew rate besides faster response and improved stability.

Out-of-plane buckling of boundary regions in planar RC structural walls: an approach to prevent instability

Despite the slenderness that usually characterizes planar RC structural walls, these structural elements effectively resist significant in-plane earthquake demands. However, during the 2010 Chile and 2011 New Zealand earthquakes, some medium to high-rise buildings exhibited out-of-plane buckling instability, a failure mode that had only been observed in experiments. This failure mode was first studied in the 1980s; however, it was just after the recent earthquakes that several studies arose to improve design procedures to avoid future damage. Parameters as the height-to-thickness ratio, reinforcement content, material properties, and the hysteretic behavior of the longitudinal steel have been identified as critical for the onset of buckling instability. In this paper, the influence of the concrete cover was studied through a fiber-based element parametric analysis conducted on 120 RC prisms that simulate boundary elements of special RC walls. The prisms were subjected to incremental axial cyclic loading that mimics the effects of in-plane lateral displacements. As a result, a new approach is presented to limit tensile strains developed in the longitudinal reinforcement of boundary zones to prevent the onset of out-of-plane buckling instability.

Evaluating gantry crane-way pavement performance: An inverse approach

Gantry-crane pavements and foundations are significant assets within intermodal facilities. The performance of these pavements, which are subjected to highly-variable loads, is critical to safe operations. Traffic interruptions and costs associated with maintaining and rehabilitating distressed or failed pavements in associated areas are of particular importance. The purpose of this study was to evaluate structural behavior and improve design procedures for gantry crane way pavement used at intermodal facilities by assessing interactions among pavements, subgrades, and operational loading conditions. The performance of the gantry crane pavements and foundations was assessed using a finite-element (FE) model, while pavement structural response to a crane load was measured using strain gages installed in the field. Measuring material properties using in-situ/laboratory tests was not possible in this work due to the limited resources, restricted access to intermodal facilities, and tight schedule of rail freight transport(i.e. tight schedule of cranes). To verify the materials properties and ensure a consistent behavior of the developed FE model with respect to the field measurements, an inverse design approach was implemented. Because of the significant cost of FE simulation, the gradient-based solver used in this study is based on a trust region algorithm. The verified model was used to predict the critical responses of Portland cement concrete (PCC) layer, base course, and subgrade soil. These parameters were then used to conduct a pavement fatigue damage analysis, parametric analyses of material strength and slab geometry were carried out based on Model Code, and resulting fatigue-life recommendations for improved designs were made. The developed FE model along with the inverse approach create a framework that can be used in further health monitoring problems when a specific parameter cannot be directly observed.

Design and Optimization of Double Balanced Gilbert Cell Mixer in 130 nm CMOS Process

An improved design procedure for double balanced Gilbert cell mixer is proposed for specific gain and power requirements at various license exempted frequency ranges for a variety of wireless equipment in India. The down conversion mixer design is aimed to carry out in 130 nm CMOS process. At 2.5 mW d.c power, a conversion gain of over 10 dB and a noise figure under 10 dB is intended at minimum overdrives for transconductance and switching stages of the mixer. Several optimization techniques for enhancement of gain, linearity and noise performances of the designed mixer are presented. An improvement in linearity about 10 dBm is targeted for 1-dB gain compression as well as third order intercept points introducing a unique criterion to integrate and exhaustively explore the enhancement techniques while preserving the gain as well as noise performance of the mixer.

Finite-element modelling of laterally loaded piles in a stiff glacial clay till at Cowden

The PISA project was a combined field testing/numerical modelling study with the aim of developing improved design procedures for large-diameter piles subjected to lateral loading. This paper describes the development of a three-dimensional finite-element model for the medium-scale pile tests that were conducted in Cowden till as part of the PISA work. The paper places particular emphasis on the consistent interpretation of the soil data determined from the available field and laboratory information. An enhanced version of the modified Cam clay model was employed in the numerical analyses, featuring a non-linear Hvorslev surface, a generalised shape for the yield and plastic potential surfaces in the deviatoric plane and a non-linear formulation for the elastic shear modulus. Three-dimensional finite-element analyses were performed prior to the field tests. Excellent agreement between the measured and simulated behaviour for a range of pile geometries was observed, demonstrating the accuracy of the numerical model and the adequacy of the calibration process for the constitutive model. The developed numerical model confirmed the premise of the PISA design method that site-specific ground characterisation and advanced numerical modelling can directly facilitate the development of additional soil reaction curves for use in new design models for laterally loaded piles in a stiff clay till.

Planar Transformers in LLC Resonant Converters: High-Frequency Fringing Losses Modeling

Fringing losses play a detrimental role in high-frequency transformers. The tendency toward higher power density and miniaturization of power converters leads to higher switching frequency and enforces the use of low-profile components such as gapped planar transformers. Due to the air gap, lower magnetizing inductance and better regulation of LLC (L $_m$ , L $_s$ , C $_s$ ) can be achieved, but fringing fluxes can also be induced, resulting in extra magnetic losses and more hotspots. These losses are highly dependent on the frequency and the core material, so it is critical to model them for gapped planar transformers in LLC resonant converters, which operate at high frequencies and use ferrite material. In this article, fringing losses for gapped ferrite transformers in LLC converters are thoroughly modeled in order to provide a precise prediction regardless of the materials and core geometries. The proposed method provides an accurate and compact formula for predicting the fringing losses of planar transformers. This formula is obtained based on the finite-element method so as to consider and evaluate different design parameters. An LLC resonant converter with different planar transformers is implemented to show the compatibility of the proposed model. Experimental results show the higher accuracy of the proposed model compared to traditional ones and confirm that the proposed loss model can be applied to diverse core shapes. In addition, the gradient descent method is used to calibrate the theoretical and experimental results. Moreover, temperature deviations of the transformer due to the fringing losses are measured and evaluated both experimentally and theoretically to show the accuracy of the proposed loss formula. Due to the proposed model's higher accuracy, an improved design procedure for planar transformers is obtained, adding substantial value for design engineers.

Experimental Study on Shear Capacity of High Strength Reinforcement Concrete Deep Beams with Small Shear Span-Depth Ratio.

This study aimed to investigate the shear capacity performance for eight deep beams with HTRB600 reinforced high strength concrete under concentrated load to enable a better understanding of the effects of shear span–depth ratio, longitudinal reinforcement ratio, vertical stirrup ratio and in order to improve design procedures. The dimension of eight test specimens is 1600 mm × 200 mm × 600 mm. The effective span to height ratio l0/h is 2.0, the shear span–depth ratio λ is 0.3, 0.6 and 0.9, respectively. In addition, the longitudinal reinforcement ratio ρs is set to 0.67%, 1.05%, 1.27%, and the vertical stirrup ratio is taken to be 0%, 0.25%, 0.33%, 0.5%. Through measuring the strain of steel bar, the strain of concrete and the deflection of mid-span, the characteristics of the full process of shear capacity, the failure mode and the load deflection deformation curve were examined. The test results showed that the failure mode of deep beams with small shear span–depth ratio is diagonal compression failure, which is influenced by the layout and quantity of web reinforcement. The diagonal compression failure could be classified into two forms: crushing-strut and diagonal splitting. With decreasing of shear span–depth ratio and increasing longitudinal reinforcement ratio, the shear capacity of deep beams increases obviously, while the influence of vertical web reinforcement ratio on shear capacity is negligible. Finally, the shear capacity of eight deep beams based on GB 50010-2010 is calculated and compared with the calculation results of ACI 318-14, EN 1992-1-1:2004 and CSA A23.3-04, which are based on strut-and-tie model. The obtained results in this paper show a very good agreement with GB50010-2010 and ACI 318-14, while the results of EN 1992-1-1:2004 and CSA A23.3-04 are approved to be conservative.

Steel Structures Research Update: Advances in Design with Hollow Structural Steel Members

Recent advances in design of steel-frame systems with hollow structural steel (HSS) members are highlighted. The featured work includes new and updated design guides that are co-authored by Jeffrey Packer and Jason McCormick. Dr. Packer’s experimental, numerical, and analytical research informs the design of HSS for various loading conditions, with a bias toward code/specification-related issues and guidance for practicing engineers. Dr. McCormick’s research on HSS members and connections ranges from research on steel HSS-based seismic moment frames to the use of innovative materials (e.g., polymer foam) to control the structural response of HSS members under seismic and wind loads. Selected studies are featured along with a preview of the new design guides. Research on HSS columns under axial and lateral loads fills knowledge gaps in seismic behavior and design. Foam-filled brace and bending member experiments show improved seismic performance with a light-weight polyurethane fill. Field tests, laboratory experiments, and numerical modeling are used to study behavior and develop design methods for hollow and concrete-filled HSS subject to blast and impact loading. Research on single-sided fillet welds of HSS members leads to improved design recommendations. Improved design procedures are also recommended based on research on HSS connections that are in branch compression, near chord ends, or offset laterally.

Improved design procedure for battened cold-formed steel built-up columns composed of lipped angles

The present paper reports the numerical parametric study on the structural behaviour of battened cold-formed steel built-up box columns composed of four lipped angles. The validated numerical model with the experimental results reported by the author in the comparison paper was employed to carry out parametric studies to produce numerical data over a wider range of global column slenderness by varying the sectional compactness of the lipped angle section, batten spacing, and global column slenderness. The numerically derived results were employed to check the accuracy of the current design rules. The results of the assessment revealed the limitation of the current design rules in the prediction of the capacity of the CFS built-up battened box columns, which was mainly associated with the influence of unbraced chord slenderness and interconnector stiffness on the buckling behaviour. Therefore, improved design procedure was proposed in the framework of AS/NZS specifications (AS/NZ 4600:2018) and European standards (EN1993-1-3:2006) for the safe, less scattered and reliable design strength predictions of battened CFS built-up columns composed of four lipped angles.

PV Microgrid Design for Rural Electrification

There are high numbers of remote villages that still need electrification in some countries. Extension of the central electrical power network to these villages is not viable owing to the high costs and power losses involved. Isolated power systems such as rural microgrids based on renewables could be a potential solution. Photovoltaics (PV) technology is particularly suited for countries like India due to factors such as the available solar resource, the modularity of the technology and low technology costs. It was identified that unlike larger isolated power systems, rural microgrids have a low energy demand as the loads are mainly residential and street lighting. Hence, these microgrids could be of a single-phase configuration. At present, the typical procedure followed by planners of rural networks does not consider the importance of PV source siting and optimisation of network structure. An improved design procedure is introduced in this work based on the use of centres of moments for central PV system sizing, simulated annealing for network structure optimisation and load flow based parametric analysis for confirming the PV microgrid structure before detailed software-based PV design. Case studies of two remote villages are used to inform and illustrate the design procedure.

Uncertain Saturated Discrete‐Time Sliding Mode Control for A Wind Turbine Using A Two‐Mass Model

AbstractThe aim of this paper is to propose a new design variable speed wind turbine control by discrete‐time sliding mode approach. The control objective is to obtain a maximum extraction of wind energy, while reducing mechanical loads and rotor speed tracking combined with an electromagnetic torque. For this application, we designed a discrete time sliding mode control using the equivalent discrete time reaching law. Furthermore, a systematic and improved design procedure for uncertainties discrete‐time sliding mode control (SMC) with saturation problem is provided in this paper. The saturation constraint is reported on inputs vector. LMI technique and polytopic models are used in the design of the switching surface. To achieve some performance requirements and good robustness, in the sliding mode, the pole clustering method is investigated. Based on the unit vector control approach, a robust control is developed, then, to direct and maintain the system states onto the sliding manifold in finite time. Finally, a systematic design procedure for DSMC required to achieve a given performance level is provided and its effectiveness is varied by applying it to variable speed wind turbine systems.

Experimental determination of mechanical parameters in sensorless vector-controlled induction motor drive

High-performance industrial drives widely employ induction motors with position sensorless vector control (SLVC). The state-of-the-art SLVC is first reviewed in this paper. An improved design procedure for current and flux controllers is proposed for SLVC drives when the inverter delay is significant. The speed controller design in such a drive is highly sensitive to the mechanical parameters of the induction motor. These mechanical parameters change with the load coupled. This paper proposes a method to experimentally determine the moment of inertia and mechanical time constant of the induction motor drive along with the load driven. The proposed method is based on acceleration and deceleration of the motor under constant torque, which is achieved using a sensorless vector-controlled drive itself. Experimental results from a 5-hp induction motor drive are presented.

Improved Design Procedures for Ground Improvement using Pre- Fabricated Vertical Drains

Background/Objective: Ground improvement for soft saturated clay soil is often achieved by preloading combined with vertical drains. Use of vertical drains gives rise to smear zone and well resistance, which hinders consolidation. However, Indian code of practices doesn’t consider this aspect. Method: Computation of optimum spacing for vertical drains is iterative and tedious procedure. Therefore, an automate procedure using goal seek function of MS Excel is developed which gives optimum spacing instantly. Using developed spreadsheet, effect of smear zone has been studied by comparing field data to that obtained by using theoretical equations. Findings: Time estimates for target value of consolidation required in a project are better predicted by considering smear effects. Based on these findings it has been suggested to incorporate the effect of smear zone in Indian Codes for rational design of PVD. Application/Improvement: Using proposed modifications in Indian code of practices realistic estimate for desired consolidation can be found quickly.

Seismic retrofit of RC building structures with Buckling Restrained Braces

The search for passive control systems has increased in some high seismicity areas of the world, especially in terms of the strengthening of existing RC or steel building structures designed without earthquake-resistance considerations (pre-code structures) or with outdated structural codes. One of the most promising techniques consists of adding steel Buckling Restrained Braces (BRBs) to the existing structure. This paper presents an applicability study of these devices in the retrofit of a typical existing RC pre-code school building structure. The effectiveness of the retrofit solution, initially designed according to Kasai et al. (1998) formulation, was assessed through non-linear static and dynamic numerical analyses. The results of these analyses, led to the design method being developed with the purpose of optimising the dimensions of the steel dampers at different storeys and therefore improving the structural performance. This development is based on a simplified method of predicting the response of a passive system, by devising a single degree of freedom system. The effectiveness of the seismic retrofit solution designed through the improved design procedure was confirmed, showing that the studied strengthening solution results in a significant increase in strength, deformation and energy dissipation capacity, thereby limiting damage in the original structure to admissible levels.