Multilayer Elements Research Articles

Failure analysis and curvature-based failure criterion of super large cooling tower under strong equivalent static wind load

More and more super larger cooling towers are used in recent years. However, investigations on super large cooling towers under strong wind are still insufficient and there is still no an agreement failure criterion. In this paper, we conducted the failure analysis of a super large cooling tower with 253 m height under the equivalent static wind load. The finite element analysis procedure incorporates the multi-layered shell element, the softening damage model of concrete and the two-level secant algorithm in one framework. The numerical results show that the nonlinear response of the tower can be divided into four stages, i.e., the initial linear stage, the nonlinear stage, the softening linear stage and the failure stage. The failure of the cooling tower is caused by the loss of the material strengths, i.e., the cracking of the concrete and the following yield of the meridian rebar. Finally, a curvature-based failure criterion is proposed to evaluate the failure of the cooling tower, in which the structure fails when the global curvature variation ratio ϰ reaches some definite values. ϰ is defined as the ratio of the total curvature variation with the initial total curvature of the cooling tower geometry. It can evaluate the total curvature variation in a global view. It is recommended that ϰ can be used as an index in the design of the cooling tower, and 1.0% and 3.5% can be deemed as the nonlinear and failure index, respectively. • The nonlinear response of the super large cooling tower can be divided into four stages. • The failure of the cooling tower is caused by the loss of material strengths, i.e., the yielding of the meridian reinforcement after the cracking of concrete. • A curvature-based failure criteria is proposed to evaluate the failure of the super large cooling tower, and the failure threshold is also recommended.

Using the Equivalent Plate Concept to Calculate Functionally Graded Plates by Numerical Method

Functional graded materials are based on two materials, with very different properties, which vary continuously, according to a material law, on their thickness (a beam or a plate). The concept of equivalent plate involves the replacement of the given plate, a plate made of FGM, with a homogeneous and isotropic plate, with the same geometric characteristics (shape and dimensions), with the same load, which is attributed material properties that lead to the same behavior with the given plate. The aim of the paper is to provide a way to solve a complex problem (mathematical and structural), as in the case of FGM plates, with available means, with known professional calculation programs, with common finite elements, without intervention in the structure of its program. of finite element matrices, in other words without dedicated calculation programs. The finite element method is applied using the Ansys program and one of the best known finite elements, the 3D Solid185 element, both in the common version (structural) and in the multilayer finite element version.

Fractal Impedance Element Synthesis Based on Multilayer Resistance-Capacitance Environment with C-R-Nc Layer Structure

The idea of fractural calculus appeared almost at the same time as the development of conventional differential calculus began. However, modern scientists became familiar with it only from pioneering works of B. Mandelbrot on fractal geometry of nature in 1980s. Since then, numerous scientific works were published on various aspects of fractural calculus and its application in science and engineering, and the interest to this area remains high. However, for physical implementation of fractural integration operators two-terminal elements with fractional power and frequency law (the fractural impedance elements - FIE) are required. Commercial FIE that could be produced industrially have not been developed so far. The greatest potential, in this case, have FIE built on the basis of multilayer resistance-capacitance element with distributed parameters (RC-distributed elements). One of the baseline designs of such FIEs with R-C-NR layer structure was manufactured as a prototype model. However, when manufacturing and testing of this element, flaws that may prevent its application were detected. The article suggests making FIE based on RC-distributed elements with dual C-R-NC layer structure where, as it is assumed, it is possible to avoid flaws found in FIE with R-C-NR layer structure. However, to solve this problem it is necessary to develop an algorithm and a program of structure synthesis of new type FIE enabling production elements with parameters not worse than those of the existing FIE with R-C-NR layer structure. For this purpose, an algorithm of frequency characteristic analysis of equivalent circuit FIE based on RC-distributed parameters having C-R-NC layer structure and being the component of synthesis algorithm, was developed. Principal stages of synthesis algorithm based on search optimization genetic algorithm were formulated. Ways of information coding of internal structure and parameter C-R-NC FIE were defined. Method of function calculation of individual fitness within population of object representation and ways of genetic operators (selection, crossing-over and mutation) realization in the process of genetic algorithm performance was described. Thereupon the synthesis program was developed and the results of its operation are given in the article. Synthesis result validity was verified by means of circuit simulation software OrCAD by application of Pspice-based C-R-NC-line model. The obtained FIE equivalent circuits integral C-R-NC structures, taking into account chosen materials and layer parameters, were designed. Comparative analysis results of synthesis program operation of C-R-NC FIE and R-C-NR FIE for synthesis FIE with the same requirements to frequency impedance FIE characteristics are given, showing that synthesizing C-R-NC FIE; the FIE with phase uniformity phase-frequency impedance characteristics from - 45° to about - 80° without galvanic coupling between poles and synthesizing R-C-NR FIE, the FIE with phase uniformity of phase-frequency impedance from -10° to about -45° with galvanic coupling between the pole are more likely to be realized.

Redevelopment Mobility Dispositif, the Gwangju Complex Incident, and The Man Left as Nine Pairs of Shoes

The purpose of this article is to explore the interrelationship between mobility and unequal power relations by analyzing the Gwangju Complex Incident, which was centered on the placeness of Seongnam, in the framework of a mobility dispositif. When we confine the center of meaning to a place, we are apt to pass the heart of events. Mobility is another foundation of existence that is no less than a place. Like place mobility produces a meaning, and a meaning affects a representation. And this representation again affects the interpretation of a meaning. Yoon Heung-gil’s The Man Left as Nine Pairs of Shoes, the most wellknown among the literary representations that embody the Gwangju Complex Incident, organized the incident into a literary text and gave the incident a narrative. Therefore, this novel can be said to be another actor who has had a great influence on the way of understanding the Gwangju Complex Incident. Above all, The Man Left as Nine Pairs of Shoes is a novel that exquisitely captures the multi-layered mobility dispositif of the Gwangju Complex Incident. The unequal power relations and multilayered elements lying on the horizon of the Gwangju Grand Complex incident are refered to as as redevelopment mobility dispositif. The analysis of The Man Left as Nine Pairs of Shoes reveals a contingent necessity of the Gwangju Complex Incident by illuminating the interrelationship between mobility and power.

Multilayer diffractive optical element material selection method based on transmission, total internal reflection, and thickness

The polychromatic integral diffraction efficiency (PIDE) metric is generally used to select the most suitable materials for multilayer diffractive optical elements (MLDOEs). However, this method is based on the thin element approximation, which yields inaccurate results in the case of thick diffractive elements such as MLDOEs. We propose a new material selection approach, to the best of our knowledge, based on three metrics: transmission, total internal reflection, and the optical component's total thickness. This approach, called "geometric optics material selection method" (GO-MSM), is tested in mid-wave and long-wave infrared bands. Finite-difference time-domain is used to study the optical performance (Strehl ratio) of the "optimal" MLDOE combinations obtained with the PIDE metric and the GO-MSM. Only the proposed method can provide MLDOE designs that perform. This study also shows that an MLDOE gap filled with a low index material (air) strongly degrades the image quality.

Incorporating two-dimensional conduction modeling techniques into an energy simulation program: The EnergyPlus radiant system example

Due to the inherent complexity of multi-dimensional solutions for transient conduction in a multilayered building element, most heat balance-based algorithms assume that conduction occurs only in one dimension—through the building element between the inside and outside environments. Usually, since the length and width of the elements are much greater than the thickness of the element, this is a valid assumption. However, there are some cases such as hydronic radiant slabs where this assumption may not lead to an accurate estimate of the energy consumption of the system. In a hydronic radiant slab, water tubes are embedded in a slab, and hot or chilled water is circulated to meet any heating or cooling loads. The energy consumption of such a system will depend highly on the temperature of the water being sent to the slab (i.e., produced by the boiler or chiller). The temperature of the water that must be sent to the slab will depend on the spacing of the tubes, the multilayer construction of the building element, and the boundary conditions to which the construction is exposed. Thus, to accurately predict the energy consumption of such a system, a transient two-dimensional heat conduction model must be integrated with a heat balance-based simulation. This paper demonstrates the potential loss of accuracy associated with the one-dimensional radiant system models by providing a comparison of one- and two-dimensional solutions using EnergyPlus.

Wideband Circularly Polarized Cavity-Backed Dielectric Resonator Antenna With Low RCS for Aerial Vehicle Communications

This letter explains the design of a wideband circularly polarized dielectric resonator antenna (DRA) with a dual-cylindrical conformal cavity for aerial applications. The proposed dielectric resonator (DR) element uses multilayer cross-shaped elements of varying dimensions with an off-centered circular slot that is inserted inside the DR geometry. Combining the wideband DRA with a conformal cavity (bending angle, α = 5°) that provides wider impedance bandwidth of 111% from 5.02 to 17.52 GHz and axial ratio bandwidth of 32.29% from 6.18 to 8.56 GHz. The proposed antenna provides a higher gain of 10.77 dBi at 8.5 GHz, gain values better than 7.21 dBi, and radiation efficiency better than 90% for the complete band. Also, the proposed antenna provides good radar cross-section reduction mechanism for the entire working band.

Microflow multi-layer diffraction optical element processed by hybrid manufacturing technology.

Traditional planar diffractive optical elements (DOEs) are challenged in imaging systems due to diffraction efficiency and chromatic dispersion. In this paper, we have designed a microfluidic diffractive optical element (MFDOE), which is processed by digital micromirror device (DMD) maskless lithography (DMDML) assisted femtosecond laser direct writing (FsLDW). MFDOE is a combination of photoresist-based multi-layer harmonic diffraction surface and liquid, realizing diffraction efficiency of more than 90% in the visible band. And it shows achromatic characteristics in the two bands of 469 nm (±20 nm) and 625 nm (±20 nm). These results show that MFDOE has good imaging performance.

Experimental and numerical investigation on seismic performance of semi-precast concrete sandwich shear wall

This study investigated the seismic performance of an innovative semi-precast concrete sandwich shear wall (SCSSW) system. The system consists of two precast reinforced concrete (RC) wythes, a core cast-in-place RC wythe, a core thermal insulation layer, the fiber reinforced polymer connectors and the steel trusses. A total of three RC shear wall specimens were fabricated and tested under in-plane cyclic load. They consists of one conventional cast-in-place RC shear wall, one structural wythe of SCSSW (i.e., the assemble of a precast and a cast-in-place RC wythe), and one typical SCSSW. The failure mode, hysteretic curve, ductility and energy dissipation of the three specimens were studied and compared. Furthermore, numerical simulation based on multi-layer shell element was conducted to reproduce the test, and parametric analysis was conducted to facilitate a better understanding on the SCSSW. It was concluded that the SCSSW presented a ductile failure behavior; the seismic performance of the SCSSW including hysteretic curves, skeleton curves, stiffness degradation and the energy dissipation was similar to that of the cast-in-place RC shear wall, while the ductility of the SCSSW was slightly lower; and the facade precast RC wythe contributed few effect on the seismic performance of the SCSSW.

Analysis of the design of ultrasonic electronic generators

The design and operation of electronic generators for ultrasonic intensification of processes in gaseous and liquid media will be considered. General requirements and new approaches to electronic generators have been developed based on the analysis of the characteristics of modern piezoelectric vibration systems that perform large amplitude oscillations (quality factor, multi-frequency, multilayer piezoelectric elements). Continuous monitoring of system parameters and setting of optimal operating modes of the electronic generator were studied.

Hybrid ray-tracing/Fourier optics method to analyze multilayer diffractive optical elements.

The performance (paraxial phase delay) of conventional diffractive optical elements is generally analyzed using the analytical scalar theory of diffraction, based on thin-element approximation (TEA). However, the high thickness of multilayer diffractive optical elements (MLDOEs) means that TEA yields inaccurate results. To address this, we tested a method based on ray-tracing simulations in mid-wave and long-wave infrared wave bands and for multiple f-numbers, together with the effect of MLDOE phase delay on a collimated on-axis beam with an angular spectrum method. Thus, we accurately generate optical figures of merit (point spread function along the optical axis, Strehl ratio at the "best" focal plane, and chromatic focal shift) and, by using a finite-difference time-domain method as a reference solution, demonstrate it as a valuable tool to describe and quantify the longitudinal chromatic aberration of MLDOEs.

Delamination model of an epoxy-impregnated REBCO superconducting pancake winding

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes are promising for high-energy and high-field applications. In epoxy-impregnated REBCO superconducting windings, during the cooling process, the delamination induced by thermal mismatch stress significantly threatens stable operation due to the weak c-axial strength of REBCO CC tapes. In this study, a two-dimensional axisymmetric multilayer delamination finite element model with main layers of REBCO CC tapes and insulation materials was developed based on the bilinear cohesive zone model. Based on the proposed model, the stress distribution and delamination properties of an epoxy-impregnated REBCO winding induced during the cooling process were investigated. Furthermore, the effects on the structural configuration on the delamination and optimisation schemes of fabrication are discussed. The model results indicate that during the cooling process of the REBCO winding, when the radial tensile stress induced by the thermal mismatch stress is greater than the delamination strength, interface cracking will occur. Interface failure occurs in regions containing several turns of coils and not just a single-turn coil. Our analyses indicate that structural failure caused by delamination depends on the radius ratio of the outer to the inner winding, where a small radius ratio is preferred to reduce the risk of delamination. An excessive radius ratio can result in multiple delamination failures during the cooling process. The optimisation scheme, which divides the winding into several sub-windings with a consistently small radius ratio, is an effective method for mitigating the risk of delamination failure, which is consistent with available experimental results. Additionally, by reducing the thermal expansion coefficient of the epoxy resin, the risk of delamination failure during cooling can be significantly reduced. For the winding structure considered in this study, if the coefficient of thermal expansion of the epoxy resin is reduced to 5 ( K−1), then delamination failure caused by thermal mismatch will be eliminated. Our model results are consistent with those of several valuable experimental phenomena and numerical calculated in the literature.

Broadband Radar Cross Section Reduction Binary Metasurface With a High-Efficiency Intraband Transmission Window

In this letter, a broadband radar cross section (RCS) reduction binary metasurface with a high-efficiency intraband transmission window is proposed and implemented based on multilayered elements combining the Jerusalem cross and cross-slot patterns. Electromagnetic responses of such structures are investigated by the equivalent circuit method. The results indicate that the metasurface consisting of elements with two types of Jerusalem crosses can invoke diffused scattering to reduce the RCS of metallic targets. Meanwhile, the metasurface has a high-efficiency transmission window since the bandpass cross-slot pattern is deployed here. The simulation results indicate that the metasurface can achieve a −10 dB RCS reduction from 3.5 to 11.5 GHz and transmission with an insertion loss of 0.72 dB at 8.4 GHz. The performances of the proposed metasurface are verified experimentally. Our design may find potential applications in the low-RCS antenna or the stealth radome for wireless facilities.

Optimization of Synthetic Vocal Fold Models for Glottal Closure.

Synthetic, self-oscillating models of the human vocal folds are used to study the complex and inter-related flow, structure, and acoustical aspects of voice production. The vocal folds typically collide during each cycle, thereby creating a brief period of glottal closure that has important implications for flow, acoustic, and motion-related outcomes. Many previous synthetic models, however, have been limited by incomplete glottal closure during vibration. In this study, a low-fidelity, two-dimensional, multilayer finite element model of vocal fold flow-induced vibration was coupled with a custom genetic algorithm optimization code to determine geometric and material characteristics that would be expected to yield physiologically-realistic frequency and closed quotient values. The optimization process yielded computational models that vibrated with favorable frequency and closed quotient characteristics. A tradeoff was observed between frequency and closed quotient. A synthetic, self-oscillating vocal fold model with geometric and material properties informed by the simulation outcomes was fabricated and tested for onset pressure, oscillation frequency, and closed quotient. The synthetic model successfully vibrated at a realistic frequency and exhibited a nonzero closed quotient. The methodology described in this study provides potential direction for fabricating synthetic models using isotropic silicone materials that can be designed to vibrate with physiologically-realistic frequencies and closed quotient values. The results also show the potential for a low-fidelity model optimization approach to be used to tune synthetic vocal fold model characteristics for specific vibratory outcomes.

Analysis of the Seismic Behavior of a Wall Pier of a Covered Bridge Based on the Multi-Layer Shell Element

To investigate the seismic behavior of the wall pier of a covered bridge, the multi-layer shell element in OpenSEES was used to carry out the numerical analysis under a horizontal low cyclic loading in the weak axis direction. The effects of the mesh divisions of the wall pier models were evaluated and the hysteretic curves, skeleton curves, bearing and energy dissipation capacity, stiffness degradation and displacement ductility of the wall pier with different lateral loading modes were mainly researched. The results demonstrate that the discretization of layers along the thickness direction of the multi-layer shell element model has a very limited effect on the hysteretic and skeleton curves. The mesh division of the horizontal direction depends on that of the vertical, and the vertical mesh spacing shall be longer than the plastic hinge with a length of 0.5744 m. The arrangement of the loading points is critical for the seismic behavior of the wall pier. The pier suffering the force from the five points presents a relatively strong energy dissipation and larger ductility, but this layout may cause a more concentrated force at the local position. When the loading points are evenly distributed, the capacity and displacement changes sharply and the ductility diminishes. Successively, the seismic performance indexes at the local position of the wall pier tend to be more consistent with the increasing loading points. The deformation and energy dissipation capacity of the nearby position with the denser side loading points becomes larger, but this has a minor impact on the seismic performance of the position far from the points. The wall pier without the bent cap and with three bearings set is supposed to be more reasonable for the covered bridge through the overall analysis of seismic performance.

A Three-Dimensional Finite Element Analysis Model of SAW Torque Sensor with Multilayer Structure

A three-dimensional finite element analysis model of surface acoustic wave (SAW) torque sensor based on multilayer structure is proposed in this paper. Compared with the traditional saw torque sensor with quartz as piezoelectric substrate, the SAW torque sensor with multilayer structure has the advantages of fast propagation speed and high characteristic frequency. It is a very promising torque sensor, but there is very little related research. In order to successfully develop the sensor, it is essential to understand the propagation characteristics and torque sensing mode of SAW in multilayer structure. Therefore, in this study, we first established a multi-layered finite element analysis model of SAW device based on IDT/128° Y-X lithium niobate/diamond/Si (100). Then, the effects of different film thicknesses on the characteristic frequency, electromechanical coupling coefficient, s parameter, and mechanical quality factor of SAW device without changing the wavelength are analyzed. Then, based on the finite element analysis, a three-dimensional research model of a new SAW torque sensor suitable for small diameter torsion bar (d = 10 mm) is established, and the relationship between saw device deformation and torque under the condition of small torque (±40 Nm) is tested. The shape variable is introduced into the finite element analysis model of multi-layer SAW device. Finally, the relationship between saw torque sensor with multi-layer structure and torque is established by using the deformation relationship, which shows the perfect curve of sensor performance.

Seismic performance assessment of high-rise steel moment frame building with Reinforced Concrete (RC) core wall based on nonlinear time history analysis

This paper focuses on seismic responses of a 30-story high-rise building with a dual lateral system of Reinforced Concrete (RC) core shear wall and steel moment frame. To assess the seismic performance of the building, a nonlinear finite element model is built by using the OpenSees software. This three-dimensional model is created by using the fiber-beams for members and multi-layer shell elements for RC core walls. The numerical simulation has been examined under the thirteen sets of strong ground motion records which are scaled with the design and maximum seismic levels, Design-Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) level hazards respectively. In consequence, the desirable performance of high-rise steel moment frame building with RC shear core consisting of coupling beams and rectangular shear walls is shown. The outcome of nonlinear time history analyses reports the acceptable seismic performance of tall buildings designed. Results showed that maximum inter-story drift is significantly lower than allowable drift. Also, the RC core wall absorbed almost two-third of the total shear forces from the base level to one-third of height. However, the shear values of the core wall were significantly reduced by increasing the height while the shear values of the steel moment frame stayed constant.

Application of an analytical method for the design for robustness of RC flat slab buildings

• Design for robustness of multi-story RC frame with RC flat slabs. • The analytical strip method was validated with experimental and NLFE results. • The capability of the analytical method to predict the behaviour at the catenary stage was proved. • The analytical method provides the ultimate bearing capacity and the failure modes of a large variety of flat slabs. • The paper provides, in the form of design nomographs, the maximum load in accidental design situation. Nowadays the structural engineering community needs reliable and design-oriented methods for the design of low and medium-rise reinforced concrete (RC) buildings with regard to progressive collapse. In this context, the current work aims to validate and apply a new analytical method suitable for the design for robustness of RC buildings characterised by the presence of flat slabs falling in low and medium consequence classes. The analytical method presented in this study is an extension of a method recently proposed by some of the authors for the analysis of two-way slabs in which flexural capacity and punching and post-punching failure criteria are added to reproduce the ultimate behaviour of flat slabs. In this paper, the design for robustness is applied together with the design for ultimate and serviceability limit states in the framework of the partial safety factor method of verification for RC flat slabs. The analytical method is applied as a direct method to evaluate the level of robustness of RC flat slabs to sustain a localised failure simulated by considering an internal column removal scenario. First, the method is validated by comparing the analytical results with both experimental data available in the literature and nonlinear finite element results obtained by adopting a multi-layered shell element approach and the PARC_CL 2.0 crack model. The comparison of the results demonstrates the reliability of the analytical approach in reproducing the ultimate load and ultimate chord rotation of flat slabs with a good approximation by considering the effect of tensile membrane action (TMA). Second, in strategies based on unidentified accidental actions, the analytical method is used to carry out a parametric analysis in the context of an internal column loss scenario. The parametric analysis allows the level of robustness to be evaluated by varying the main geometrical properties that affect the failure mode, resistance and ductility of RC flat slabs. Finally, the paper presents—for a given span and span-to-depth ratio—the required reinforcement ratios, design load in the accidental load combination and ultimate chord rotation in the form of design nomographs useful for engineering.

Numerical Modeling and Shake Table Test for Seismic Response Evaluation of an Auxiliary Building in NPP with Reinforced Concrete Shear Wall

The dynamic responses of three storied auxiliary building of a nuclear power plant (NPP) constructed with a monolithic reinforced concrete shear wall are investigated in this study. The dynamic characterization is weighed through a shake table test and evaluated the efficiency of various structural modeling systems for evaluating seismic responses. The shear wall was subjected to a collaborative research round-robin analysis conducted by the Korea Atomic Energy Research Institute to forecast seismic responses of the auxiliary building in the NPP using a shake table test. The shake table test was performed with five different levels of intensity measures of the base excitation to obtain acceleration responses from different positions of the building in one horizontal direction (front-back). The main motivation of this study is to develop a nonlinear numerical model and examine the efficiency of various modeling approaches for evaluating the performance under seismic loading. Three numerical modeling approaches, i.e., multi-layer shell element modeling (MLSM), fiber beam-column element modeling (FBCM), and beam-truss element modeling (BTM), are generated to simulate the seismic response behaviors of the auxiliary building structure. Modal analysis, floor response spectra, acceleration amplification factor along with height, and story shear force of the building are compared as they are critical responses for evaluating the seismic vulnerability of the structure. The comparison shows that all the nonlinear numerical modeling approaches, i.e., MLSM, FBCM, and BTM, can predict the complex behavior of a shear wall system for low earthquake level, but for high earthquake level, MLSM shows better agreement with the shake table experiment. So, it is recommended to use MLSM modeling for nonlinear analysis with an earthquake intensity measure of 1 g or more.

Experimental and numerical analysis of a novel curved sandwich panel with pultruded GFRP strip core

Curved sandwich structure made of glass fiber-reinforced polymer (GFRP) composite is emerging in the construction of non-linear architectures and wind turbine blades. In this work, a novel curved sandwich panel with pultruded GFRP strip core was proposed and studied. Compared with the common core materials such as foam and wood, pultruded GFRP strips can provide a higher stiffness and strength, particularly when used in large-scale sandwich structures. The proposed sandwich panel was manufactured through vacuum-assisted resin transfer molding process. A series of three-point bending tests was conducted to study the flexural behavior. The effect of surface thickness on the load-carrying capacity and failure mode was addressed. Then, a finite element analysis was conducted via ABAQUS and validated by the experimental results. The parametric study was performed to address the key design parameters. Both experimental and numerical results indicated that with the increased surface thickness, the failure mode could transition from the damage of glue seam to the transverse cracking inside the pultruded GFRP strip. Moreover, the load-carrying capacity can be improved with the thickened face sheet. In the end, this work successfully demonstrated the use of multilayer shell elements in the finite element modelling of the cracking behavior of glue seams.