Presented Design Procedure Research Articles

Seismic strengthening of isolated RC framed structures through orthogonal steel exoskeleton: Bidirectional non-linear analyses

The catastrophic effects of recent earthquakes around the world have highlighted the vulnerability of civil buildings; in Europe, most of the existing buildings were built after World War II and since they have largely exceeded their useful life, are characterized by a high vulnerability linked both to the durability of the materials and to the lack of seismic provisions in design. The current trend in constructional field is to design interventions aimed at the seismic and energy improvement of these structures jointly, in order to achieve a sustainable and integrated retrofit intervention. To this aim, the use of 2D orthogonal steel exoskeletons for the seismic strengthening represents a suitable solution, providing at the same time an enhancement in thermal insulation, through a ‘double-skin’ solution. Due to the growing interest in the design of steel exoskeleton interventions, a detailed dynamic characterization of this external strengthening solution is needed. In this framework, the present work, aims to investigate the effectiveness of the investigated strengthening solution by means of bi-directional non-linear dynamic analyses. Extensive numerical analysis was carried out. The selected case-study is an Italian existing pre-1980 s RC frame building located in Mugnano di Napoli (NA, Italy), which is a medium-high seismic hazard site in Italy (peak ground acceleration equal to 0.156 g). Two alternative strengthening solutions were numerically investigated by means of non-linear time-history and incremental dynamic analyses performed applying fifteen bidirectional ground motions on three-dimensional numerical models. The results of the dynamic non-linear analyses allow to quantify more appropriate performance indicators, both in terms of expected demand and overall collapse capacity, useful for the development of optimization strategy and design of exoskeleton system. The results highlighted that both the investigated strengthening scenarios allow to increase the stiffness of the existing building and allow it to meet the current code safety requirements reducing also the residual inter-storey drift. The obtained results are not strictly related to the investigated case study, but can be extended to all the structures retrofitted that follows the presented design procedure.

Design of Phase Shifters with Enhanced Selectivity and Miniaturized Size Using D-CRLH Resonator

This paper proposes and demonstrates a novel filtering phase shifter with a compact size and good frequency selectivity using two dual composite right/left-handed (D-CRLH) resonators. Firstly, the study analyzes the D-CRLH structure to gain insights into its unique properties, providing a physical understanding for subsequent design procedures. Then, an ad hoc systematic design procedure for the D-CRLH phase shifter is discussed in detail. Different from the traditional phase shifter, the innovative integration of D-CRLH structure in phase shifters enables its advantages in the flexible realization of good in-band frequency selectivity and compact size. This advantageous utilization of the D-CRLH structure distinguishes our proposed phase shifter from conventional implementations. Finally, to demonstrate the feasibility of the proposed structure, we design, fabricate, and measure a prototype of the filtering phase shifter with a 90° phase shift. The comparison between simulation and measurement results shows good agreement, thereby confirming the effectiveness of both the new filtering phase shifter and the presented design procedure. Through this comprehensive investigation, our work showcases a promising solution for achieving compact size, good frequency selectivity, and reliable performance in phase shifter design.

Reconfigurable biconcave lens antenna based on plasma technology

This article is focused on the application of plasma technology for the development of microwave lens antennas with electronically controllable radiation gain. With this aim, the analytical background and design procedure for designing a biconcave lens based on plasma dielectric material are presented. The procedure is used to design a plasma lens antenna with a pyramidal horn feed. The effect of switching the designed lens ON and OFF on the radiation gain of the lens antenna is investigated. It is also shown that the plasma frequency of the lens can be used to dynamically adjust the radiation gain. A one-dimensional version of the proposed plasma lens operating at 10 GHz has been developed to validate the concept. Experimentally measured characteristics of a fabricated prototype of the lens antenna based on commercially available fluorescent lamps confirm the presented design procedure and numerical results. The results also show that changing the plasma frequency of the lens can be used to adjust the radiation gain of the proposed lens antenna.

Steel Baffles as a Rockfall Protection Measure for Mountainous Urban Settings

A form of steel baffles, which is made of steel poles encased in concrete and embedded into the ground, are introduced in this article. This type of protective installation is to be located on previously identified/designed catchment at multiple levels up the hillslope to fence off large fallen boulders during landslides or rockfalls. These baffles are intended to serve as added-on protection to filter barriers (array of baffles) that have recently gained popularity as a means of filtering out coarse debris. The aforementioned protective devices are to be installed in strategic positions close to unstable rocks (noting that the velocity of impact can be much reduced at the upstream end of the rockfall trajectory). The proposed design involves only a simple hollow steel section, which is embedded into the ground. The installation process involves manually excavating a hole in the ground to accommodate the baffle, followed by backfilling with concrete. A straightforward calculation method, which is found on the established principles of structural dynamics and soil mechanics, has been developed to determine the section sizes and embedment depths for a given impact scenario. Based on the presented design procedure, a set of design charts have been developed for expediting the design and analysis process. The presented calculation methodology based on use of design charts have been validated by comparison with data generated by LS-DYNA simulations.

Synthesis of Orbital Angular Momentum Antennas for Target Localization

AbstractThe exploitation of Orbital Angular Momentum (OAM) is proposed to design circular‐support continuous aperture distributions and concentric‐ring arrays for target‐localization applications. The proposed approach allows generating a single isolated null of the field in the target direction, which is of interest with respect to common techniques leading to a line (or perpendicular lines) of power‐pattern zeroes in the spectral plane. In the presented design procedure, the optimal continuous aperture source is first identified by resorting to the most suitable OAM vortex and effective tools such as the Singular Value Decomposition of the involved operator and a smart Convex Programming optimization. Then, by exploiting fast deterministic algorithms, this continuous source is discretized into circular‐ring arrays emulating it at best. Relevant applications including equispaced arrays, sum‐difference reconfigurable arrays, and isophoric sparse arrays are presented. The proposed approach is also compared with the state‐of‐the‐art techniques and assessed through full‐wave electromagnetic simulations.

Assessment of the seismic behavior of self-centering eccentrically braced frames with vertical link-beam

Conventional eccentric braced frames often sustain large residual deformations and significant damages after strong earthquakes which may lead to heavy damages or even destruction of the structure. This paper proposes a self-centering, Y-inverted, eccentrically braced frame (SC-YEBF) which combines the lateral load resisting benefits of YEBF including strength, stiffness and energy dissipation capacity with the re-centering capacity of post-tensioned (PT) high strength steel strands used at beam-to-column connections. A design procedure is presented assuming that all the seismic input energy is dissipated through inherent damping and plastic deformations of the link-beams. Thus, in the presented design procedure, only the link-beams yield under the design earthquake and any other structural failure is prevented under the maximum considered earthquake (MCE). The feasibility of the proposed idea is checked first by cyclic loading analysis of a one-bay, one-story, SC-YEBF system using finite element models. Then, a simplified numerical approach for modeling such a system is presented. A series of nonlinear dynamic analyses are performed for a four-story steel frame equipped with SC-YEBF system under seven ground motions recorded on site classes C and D according to ASCE 7-16. The results indicate that the proposed system achieves the desired performance goals and sustains very small residual displacements. Also, the post-earthquake structural damage of main members including floor-beams, columns, and braces remains negligible.

Simplified Procedure for Capacity Check of Historic Monolithic Glass Windows under Soft-Body Collision/Bird-Strike

Differing from present structural design procedures, most of the existing glass windows and even historic components in traditional/old buildings are not specifically designed to resist possible accidental loads. Rather thin monolithic ordinary annealed glass panels can be found in vertical non-structural envelopes, where they are often arranged to cover large surfaces. As such, an accidental glass fracture could originate even from rather common and moderate impact events and result in severe risk for people, due to propagation of dangerous shards from these vulnerable and fragile building components. To assess potential risks and support possible mitigation strategies, the present study is focused on the bird-strike analysis of existing/historic linearly restrained non-structural glass windows, based on a parametric Smoothed-Particle Hydrodynamics (SPH)–Finite Element (FE) model. Starting from a 1 m–wide and 1.5 m–high configuration, the attention is first given to various influencing parameters, such as impactor features (mass, 0.35–1.81 kg; impact speed, 0–40 m/s; and, thus, impact energy) and the target window (glass thickness, 4–6 mm; impact point; and, thus, glass stiffness). Local and global effects due to parametric localized bird-strikes are discussed based on non-linear dynamic numerical analyses and in terms of expected deflections, tensile stress peaks, and damage extension/severity (i.e., D1 to D3 damage levels). Scale effects are also examined for a case-study historic envelope (≈7 m in total size, 5 mm in thickness), and one of its 2.58 m × 3.3 m large glass components. Furthermore, a simplified empirical approach based on analytical formulations and normalized charts is proposed for a preliminary vulnerability assessment of historic monolithic glass envelopes, including parameters to account for impactor features and glass panel size/thickness, based on vibration-frequency considerations.

An Analytical Design Method of PI and PID Controllers for Industrial Series Cascade Processes With Time Delay Under Robustness Constraints

In this paper, an analytical method is proposed to design Proportional-Integral (PI) and Proporional-Integral-Derivative (PID) controllers for two-stage industrial series cascade processes with transport delay under robustness constraints. The main rationale behind using series cascade control structure is that the disturbances in the inner loop are suppressed by the secondary controller before being transmitted to the outer loop. The presented design procedure consists of two steps: In the first step, the controller Cb(s) in the inner loop is designed, while in the second step the controller Ca(s) in the outer loop is obtained. The obtained controller is of PI or PID-type structure depending on the number of selected terms used in Maclaurin’s approximation of the transfer function of the high-order controller. By specifying the robustness constraints within design procedure one define values of adjustable parameters to achieve compromise between robustness and performance indicators. The result is efficient suppression of load disturbances, evaluated by the integral of the absolute error (IAE). The step reference response can be additionally reshaped by using Two Degree of Freedom – 2DoF control structure via suitable selection of set-point weighting factor b, 0≤b≤1, which acts on the control signal through displaced proportional action of the controller. The proposed design method is analyzed with simulations on wide class of typical representatives of industrial processes including stable, integral and unstable processes with time delay. A comparison with recent studies shows the effectiveness of the proposed tuning method for industrial cascade processes.

A gradient-descent-based method for design of performance-scaled rotor for floating wind turbine model testing in wave basins

When performing the model testing of floating wind turbine (FWT) in wave basins, using geometric-scaled rotors is unable to achieve the desired thrusts due to the dramatic reduction of Reynolds number experienced by model-scaled blades. Alternatively, a performance-scaled rotor (PSR) is usually utilized. In the present study, a gradient-descent-based method, named as CCB-GD method is proposed to conduct the PSR design for FWT model testing in wave basins. Different from existing methods, the proposed method aims to mimic the radial distribution of normal aerodynamic loads along the blade, rather than the total thrust. This is achieved by combining the blade element momentum theory with gradient descent optimization algorithm. In the present design procedure, a new airfoil with good aerodynamic performance at low Reynolds number is first selected, the optimal radial distribution of twist angles and chord lengths are then determined separately and sequentially based on the gradient-descent optimization algorithm. Additionally, high-order Bezier curves are used to smooth the radial distribution of twist angle and chord length. The proposed method is demonstrated by two case studies, in which the PSR design of the NREL 5 MW wind turbine and the DTU 10 MW wind turbine are conducted and compared with existing methods. Results show that the present method can design the PSR with good accuracy. Besides, the present method is robust, generic and also applicable in the PSR design of MW-scale wind turbines for FWT model testing in the wave basin.

A comparative investigation of thermodynamic performance and flow field structure of a modified Collins cycle-based helium turboexpander system

The optimum design of radial expansion turbine and nozzle (turboexpander) have a remarkable effect on the thermophysical performance of gas liquefaction cycles. The present study proposes a new mean-line design, sensitivity analysis, and optimization method to develop three turboexpander systems for a modified Collins cycle-based helium liquefaction system. The proposed method deals with the real gas equation of state to determine the turboexpander configurations and their performance at off-design conditions. The mean-line design approach integrated with different loss correlations has been performed using an in-house code in Matlab® environment. Furthermore, sensitivity analysis and artificial neural network-based optimization process of thirteen design coefficients and non-dimensional variables has been carried out which improves the off-design performance of the turboexpander up to 4.43%, 12.57%, and 16.36% for total-to-static efficiency, total losses, and power output respectively. Applying the aforementioned procedure, three turboexpanders have been designed. After that, a three-dimensional transient blade-row turbulent flow simulations have been carried out to stimulate the rotor-stator interaction at different operating conditions (25 bar & 80 K, 7 bar & 50 K, and 25 bar & 30 K) and rotational speeds (2.84 × 105, 1.61 × 105, and 2.75 × 105 rpm) using k-ω shear stress transport turbulence model. The commercial Navier-Stokes finite volume solver ANSYS CFX® has been used to study a comparative thermodynamic performance and flow field structures at different streamwise and spanwise directions of the entire flow passage. Additionally, the present numerical results have been validated with available experimental and computational data in the open literature. The present design, optimization, and numerical procedure presented herein will be advantageous for the future development of efficient small-scale turboexpander systems subjected to wide operating ranges.

Time-of-flight mass spectrometry of aluminium plasma: investigation of multiply charged ions and clusters

Ionic species in laser-produced plasma plume are generally analyzed by the time-of-flight method using a charge collector placed near to the target surface. One of the shortcomings of these methods is sacrifice of the important information for large mass cluster ions and the different charge states of atomic ions. In the present manuscript, design, development, and optimization procedure of a modified Wiley–McLaren type time-of-flight mass spectrometer (TOFMS) for the diagnostics of ions and cluster distribution in laser produced plasma (LPP) plume is presented. Second harmonic (532 nm) from a pulsed Nd:YAG laser is used to ablate aluminium disk in a vacuum chamber evacuated to base pressure of 7 × 10−8 mbar. The mass spectrometric results of aluminium (Al) plasma are presented and discussed in detail. To minimize the degradation in detection and mass resolution of spectrometer due to the wide angular and energy spared of the ions in the plasma plume, optimization of the TOF spectrometer in different configurations, single as well as a double field, is also discussed. Cluster ions as large as and multiply charged ions (MCI) up to Al11+ are observed in the mass spectra. The possible pathways for the production of MCI and cluster ions are discussed on the basis of the Coulomb explosion mechanism. The dependence of ion distribution on the laser fluence is also discussed.

Zero Voltage Switching Condition in Class-E Inverter for Capacitive Wireless Power Transfer Applications

This paper presents a complete design methodology of a Class-E inverter for capacitive wireless power transfer (CWPT) applications, focusing on the capacitance coupling influence. The CWPT has been investigated in this paper, because most of the literature refers to inductive power transfer (IWPT). However, CWPT in perspective can result in lower cost and higher reliability than IWPT, because it does not need coils and related shields. The Class-E inverter has been selected, because it is a single switch inverter with a grounded MOSFET source terminal, and this leads to low costs and a simple control strategy. The presented design procedure ensures both zero voltage switching (ZVS) and zero derivative switching (ZDS) conditions at an optimum coupling coefficient, thus enabling a high transmission and conversion efficiency. The novelties of the proposed method are that the output power is boosted higher than in previous papers available in the literature, the inverter is operated at a high conversion efficiency, and the equivalent impedance of the capacitive wireless power transfer circuit to operate in resonance is exploited. The power and the efficiency have been increased by operating the inverter at 100 kHz so that turn-off losses, as well as losses in inductor and capacitors, are reduced. The closed-form expressions for all the Class-E inverter voltage and currents waveforms are derived, and this allows for the understanding of the effects of the coupling coefficient variations on ZVS and ZDS conditions. The analytical estimations are validated through several LTSpice simulations and experimental results. The converter circuit, used for the proposed analysis, has been designed and simulated, and a laboratory prototype has been experimentally tested. The experimental prototype can transfer 83.5 W at optimal capacitive coupling with operating at 100 kHz featuring 92.5% of the efficiency, confirming that theoretical and simulation results are in good agreement with the experimental tests.

Numerical evaluation of the slab effective width in steel-concrete composite box girder bridges

ABSTRACT: Bridges are structures built to overcome obstacles and allow continuity of transport routes. In the search for efficient construction systems, steel-concrete composite structures, especially box girder bridges, emerged. The American AASHTO and European EN 1994-2-2 standards present design procedures for this type of bridge, but there are still doubts about which portion of the concrete slab contributes to each web strength in composite section (effective width). The present paper aims to evaluate, by numerical analysis in the Abaqus® software, the concrete slab effective width and to verify whether the expressions for its calculation in composite I-girder bridges are valid for box girder sections. After analyzing the results, it was found that the standards recommendations for composite I-girder cannot be applied directly to box girders. Finally, based on the numerical analysis, an equation was proposed to calculate the effective width of steel-concrete composite box girder bridges.

Design of Simple Steel Connections under Fire Temperatures

A methodology is developed for designing simple steel connections (shear tab and double angle) subjected to fire. The proposed methodology is based on quantifying the strength and stiffness of steel framed simple connections at elevated temperatures. To achieve this, first, a stiffness-based model that characterizes the rotational stiffness of simple steel connections when subjected to fire temperatures is developed. The model is capable of predicting the behavior of two widely used simple steel connections (shear tab and double angle) when subjected to fire temperatures. It incorporates the connection rotation of key component elements and the nonlinear behavior of both bolts and base materials at elevated temperatures. The model is validated against experimental results available in the literature under steady-state temperature analysis. The model covers all possible limit states and governing failure modes under different loading and temperature conditions. It can be considered a practical tool for designing simple steel connections for professional structural fire engineers in the United States. Step-by-step design examples of simple steel connections in an isolated frame are provided to illustrate the incorporation of the developed stiffness model in a fire design procedure. The presented design procedure accounts for the additional load demand on the connection during fire. This includes the load demand due to thermal expansion and beam sagging.

Proračun pomičnih okvirnih konstrukcija modificiranim Crossovim postupkom

An original procedure for static design of movable in-plane frame structures is presented in the paper. The presented design procedure was derived using the modified traditional Cross procedure (TCP). The introduction of the TCP modification has resulted in significant improvement of the design algorithm of movable frame structures as compared to TCP, especially as to elimination of the need to conduct greater number of individual iteration procedures, and to solve linear algebraic equation systems.

Noise‐power‐area optimised design procedure for OTAs with complementary input transistors for neural amplifiers

Simultaneous measurement of neural bio-potentials from a large number of neurons is finding applications in a diverse range of areas such as healthcare and brain-machine interfacing. Neural amplifiers used for these measurements have a tight specification of low-power, low-noise and small area. Most of the reported neural amplifiers use operational transconductance amplifier (OTA) based capacitive feedback amplifiers to meet these requirements. In this study, for the first time, a novel systematic noise-power-area optimised design procedure, for complementary input transistor based OTAs, used frequently in neural amplifiers is proposed. By applying the proposed design procedure, the authors have presented a neural amplifier design that is split into two stages to reduce area requirement and enhance linearity at the expense of slight degradation in noise efficiency factor. The presented design achieves noise in the integration bandwidth of 0.2 Hz–8 kHz with 7.7 μA total current in a die area of in 180 nm CMOS technology. The presented design procedure is inherently technology agnostic. The novelty lies not in the architecture of the proposed neural amplifier, but in the proposed design procedure to optimise the noise-power-area trade-off in CMOS amplifier circuit design.

A Comprehensive Design of the Thyristor-Based Crowbar for Vacuum Tube High-Voltage DC Power Supplies

High-voltage power supplies (HVPSs) are widely used to drive vacuum tubes, inherently susceptible to vacuum arc faults. Owing to the considerable cost of vacuum tubes, the HVPS should enjoy a reliable, fast protection mechanism. A common protection mechanism against vacuum arc faults is the shunt crowbar. The crowbar diverts the energy stored in the elements of the HVPS through itself as a parallel path, thereby protecting vacuum tubes from irrecoverable damages. Among all types of the shunt crowbar, the thyristor-based crowbar along with the fault current limiter (FCL) resistors attracts more attention because of its more reliable operation. The absence of the comprehensive design procedure providing an insight into selecting the key components of the crowbar is strongly felt. This article presents a comprehensive design procedure for selecting these components. All constraints which should be satisfied by the protection mechanism and key components are elaborated. By doing so, the upper and lower limits of the FCL resistors, the thyristor specifications, and their series inductance are specified. It is shown that thyristors with high nominal peak current cannot contribute to the operation of the crowbar. The intersection area of the constraints and optimum values are determined for one case study. The simulations and experimental tests are exploited to evaluate the effectiveness of the presented design procedure.

RBFNN-Based Minimum Entropy Filtering for a Class of Stochastic Nonlinear Systems

This paper presents a novel minimum entropy filter design for a class of stochastic nonlinear systems, which are subjected to non-Gaussian noises. Motivated by stochastic distribution control, an output entropy model is developed using a radial basis function neural network, while the parameters of the model can be identified by the collected data. Based upon the presented model, the filtering problem has been investigated, while the system dynamics have been represented. As the model output is the entropy of the estimation error, the optimal nonlinear filter is obtained based on the Lyapunov design, which makes the model output minimum. Moreover, the entropy assignment problem has been discussed as an extension of the presented approach. To verify the presented design procedure, a numerical example is given, which illustrates the effectiveness of the presented algorithm. The contributions of this paper can be summarized as follows: 1) an output entropy model is presented using a neural network; 2) a nonlinear filter design algorithm is developed as the main result; and 3) a solution of the entropy assignment problem is obtained, which is an extension of the presented framework.

Corner reinforced slopes: Required strength and length of reinforcement based on internal stability

This paper develops an analysis procedure for turning corner in Geosynthetic-Reinforced Soil Structures (GRSS's). The procedure includes the calculations of the required strength and length of the reinforcement for internal stability. The calculations are based on the variational limit equilibrium analysis of three-dimensional (3D) stability of slopes. Seismic effects are also considered using the pseudo-static method. Results are presented in a condensed form of design charts, providing a simple tool to determine the required tensile strength and embedment length of the reinforcement. Two examples are given to demonstrate the use of the design charts. Compared with the conventional design based on plane-strain analysis, the presented design procedure yields longer reinforcement for the 3D internal stability of the corners. Generally, 3D design requires longer reinforcement than 2D as the seismic acceleration increases. The trend of obtained result is in good agreement with performance observations related to corners reported in commentary of AASHTO.

Analysis and circuit sizing performance of a differential amplifier using HPSO algorithm

This paper presents an analysis of thermal noise of differential amplifier and automated sizing procedure with thermal noise incorporation, in addition to various design specifications, as constraints in the design process. Human behaviour-based particle swarm optimisation (HPSO), a swarm intelligence (SI)-based optimisation algorithm is used to perform the sizing task to obtain optimal value of design variables value subject to a satisfying set of constraints, with the main objective of designing a low-noise amplifier with minimum circuit area. The presented design procedure gives an option of considering both width and length of MOS transistor as design variables, which in turn can tune trade-off circuit performance parameters. The computational analysis is performed in MATLAB and CADENCE tool with UMC 180 nm parameters technology is used to validate the presented design procedure. Further, the performance of the purposed automated design methodology is compared with previous design methodology to check its efficiency in terms of speed, time and robustness.