Multilayer Elements Research Articles

Seismic behavior of composite shear walls with post-casting UHPC boundary elements and CRB600H steel bars

This study investigates the seismic behavior of composite shear walls reinforced with post-casting Ultra-High Performance Concrete (UHPC) boundary elements and Colded-Rolled Ribbed Bars (CRB600H). The research aims to explore the synergistic effects of UHPC and CRB600H bars on seismic performance. Six shear wall specimens with a shear span ratio of 1.56 were subjected to cyclic loading to evaluate their failure modes, crack patterns, hysteresis behavior, stiffness degradation, ductility, residual deformation, and energy dissipation capacity. The results demonstrated that the use of CRB600H bars in boundary elements of normal concrete specimens improved post-yield stiffness and reduced residual deformation. Conversely, incorporating UHPC in boundary elements enhanced load-bearing capacity and crack control but slightly reduced ductility due to the weaker interfacial connection between UHPC and the foundation. Additionally, CRB600H bars in the web region improved load-bearing capacity while maintaining ductility comparable to HRB400 bars. The findings suggest that substituting CRB600H for HRB400 in shear-dominant regions can enhance the seismic performance of shear walls. Finally, the multi-layer shell element numerical model validated by the experimental results was encouraged to conduct parametric analysis in the future. This research supports the development of more resilient building structures by integrating high-performance materials in key structural components.

Computational modeling of multi-track multi-layer laser directed energy deposition process

This study presents the development of a 3D fully coupled thermomechanical finite element model to evaluate the melt pool geometry, defects, and micro-hardness of multi-track multi-layer deposition in the powder feed laser-directed energy deposition (LDED) technique. Fabrication strategies can significantly affect the melt pool geometry and material behavior of the manufactured components. Understanding the effect of process parameters in a multi-track multi-layer LDED is important. Optimal process parameters are crucial for achieving high-quality deposition in terms of deposition geometry and integrity. The model can aid in mitigating issues such as inadequate inter-track or track-substrate fusion, porosity, cracks, and other defects. A multi-track multi-layer finite element model (FEM) can realistically predict melt pool evolution, mechanical properties, and defects in laser-LDED. This work focuses on the development of a fully coupled thermomechanical model for multi-track multi-layer deposition processes using ABAQUS®. The finite element framework employs Johnson-Cook’s flow stress model for constitutive behavior and the Koistein-Marburger equation for predicting hardness. Two tracks and two layers of SS316L powder are deposited on an SS304 substrate in finite element simulations and experiments. The model has been validated for the melt-pool depth in the substrate, deposition geometry, heat-affected zone, and hardness. It has been observed that there is a ∼10 % error in the prediction of melt pool geometry characterization and a ∼12 % error in hardness as compared to experimental results. The melt-pool width, depth, substrate dilution, and hardness have been characterized as a function of process parameters via simulations and experiments. The model is capable of predicting inter-track and interface defects. In addition, the effect of interlayer cooling on the melt-pool geometry and hardness has been studied.

Multilayer prefabrication in practice

Pre-cast reinforced concrete walls manufacturing is still associated in Poland with large-panel construction, all the advantages of which have been crossed out by technological imperfection, terrible workmanship and boring, repetitive architecture. Meanwhile, modern large-panel prefabrication provides almost unlimited creative possibilities and ensures much better quality than traditional construction. The article describes application of modern multi-layer pre-cast elements made of reinforced concrete and light-weight expanded clay concrete in construction with the incorporation of BIM technology. It presents the advantages of prefabricated construction on specific examples at various scales - from single-family houses to large residential and apartment buildings. It also presents in detail the implementation process from design, through BIM modelling, production and quality control of elements and assembly.

Effects of Magnetostatic Interactions in FeNi-Based Multilayered Magnetoimpedance Elements.

Multilayered [Cu(3 nm)/FeNi(100 nm)]5/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/[Cu(3 nm)/FeNi(100 nm)]5 structures were obtained by using the magnetron sputtering technique in the external in-plane magnetic field. From these, multilayer magnetoimpedance elements were fabricated in the shape of elongated stripes using the lift-off lithographic process. In order to obtain maximum magnetoimpedance (MI) sensitivity with respect to the external magnetic field, the short side of the rectangular element was oriented along the direction of the technological magnetic field applied during the multilayered structure deposition. MI sensitivity was defined as the change of the total impedance or its real part per unit of the magnetic field. The design of the elements (multilayered structure, shape of the element, etc.) contributed to the dynamic and static magnetic properties. The magnetostatic properties of the MI elements, including analysis of the magnetic domain structure, indicated the crucial importance of magnetostatic interactions between FeNi magnetic layers in the analyzed [Cu(3 nm)/FeNi(100 nm)]5 multilayers. In addition, the uniformity of the magnetic parameters was defined by the advanced technique of the local measurements of the ferromagnetic resonance field. Dynamic methods allowed investigation of the elements at different thicknesses by varying the frequency of the electromagnetic excitation. The maximum sensitivity of 40%/Oe with respect to the applied field in the range of the fields of 3 Oe to 5 Oe is promising for different applications.

Shaking table test of a full-scale lightweight bolt-connected concrete sandwich wall panel structure: Overview and seismic analyses

This study proposed a novel lightweight bolt-connected concrete sandwich wall panel structure with the advantages of thermal insulation, construction efficiency, demountability and remountability. The seismic design of the structure was employed a non-equivalent cast-in-place method, resulting in appropriate configurations of horizontal and vertical bolted joints. Subsequently, a shaking table test was carried out to investigate the damage pattern, dynamic characteristics and dynamic responses of a full-scale structure. The test results demonstrated that the overall damage was moderate, which exerted a few impacts on the structural capacity or integrity. The global responses, including small displacement response, minor torsion response, and high energy dissipation capacity were found, as well as local responses, such as small strains in the steel plates and a slight loss of bolt prestress. The maximum inter-story drift ratio was below the elastoplastic inter-story drift ratio limit θu = 1/120 defined in Chinese code GB 50011. In general, the structure presented high lateral stiffness and sufficient capacity against high-intensity ground motions. A numerical model was developed, wherein precast components were established by multi-layer shell elements and bolted joints were simulated by 3-DoF nonlinear springs. Linear modal and nonlinear time history analyses were performed and compared with the experimental results. The simulation results showed good agreement with the experimental ones, confirming the ability of the model to capture global responses.

New OpenSees material model for simulating reinforced concrete shear walls subjected to coupled axial tension and cyclic lateral loads

In high-rise buildings, reinforced concrete (RC) shear walls, particularly those forming part of coupled wall systems or core wall systems, may be subjected to coupled axial tension and cyclic lateral loads during strong seismic events. A new two-dimensional material model named the “Fixed Angle Model Considering Crack Sliding” (FAM-CS) was proposed for simulating the nonlinear behavior of RC walls subjected to axial tension and cyclic lateral loads. The proposed model was implemented in the OpenSees platform. Nonlinear constitutive models for shear aggregate interlock effects of concrete and dowel action of rebars were incorporated into the proposed model to represent the shear transfer mechanisms along concrete cracks. The proposed model was validated against the test data of six wall specimens subjected to coupled axial tension and cyclic lateral loads. The results indicated that the proposed model reasonably predicted the lateral strength capacity (an average error of 6.2 %) and the residual strength at the maximum drift loading (an average error of 12.3 %) of the specimens. For comparison, three other commonly used models, the Shear-Flexure Interaction Multiple-Vertical-Line-Element-Model, the multi-layer shell element model and the Cyclic Softened Membrane Model were adopted for the simulation of the specimens. Compared with the three existing OpenSees models, the newly implemented material model provided improved predictions of the wall hysteretic behavior with respect to lateral strength capacity, lateral strength degradation, pinching characteristics and cyclic stiffness degradation. In addition, the proposed model reasonably captured the localized failure pattern as well as the energy dissipation characteristics of the test specimens. Finally, a mesh sensitivity study was conducted to assess the robustness of the proposed model. The results revealed that the proposed model was robust regarding the lateral load-drift responses of RC walls, with a mesh size ranging from approximately one to three times the average crack spacing.

Multi-layered solid element for seismic analysis of rubber bearings considering stress continuity based on finite particle method

Rubber bearings are crucial components in seismic isolation systems to mitigate the damaging effects of earthquakes on structures. Rubber bearings generally consist of alternate layers of steel and rubber bonded together. Simplified two-point spring models omit this layered construction and have limitations in adaptability and programmability, while refined multiple solid models lead to substantial computational costs. This study presents an effective and efficient approach to simulate rubber bearings by using multi-layered solid element based on the finite particle method (FPM). The traditional “Zigzag” shape function is extended into the 3D situation to reflect the serrated deformation within the layered construction. Based on the simplified assumption of stress continuity, an iterative approach is presented for the deformation gradient to achieve the force continuity between layers in dynamic nonlinear scenarios. The multi-layered solid models for both natural rubber bearings (NRBs) and lead rubber bearings (LRBs) are proposed based on this element. The errors of the hysteresis curves of rubber bearings are below 3.1 % between the numerical results obtained by using the multi-layered solid model and the experimental results. The computational speedup ratio of the proposed multi-layered solid model is verified to be 19 relative to the refined multiple solid model. The proposed method is applied to a base-isolated frame structure to demonstrate its effectiveness in structural seismic analysis.

Cyclic Behavior of Partially Prefabricated Steel Shape-Reinforced Concrete Composite Shear Walls: Experiments and Finite Element Analysis

Due to the higher lateral stiffness, load-carrying, and energy dissipation capacities compared with traditional reinforced concrete (R.C.) shear walls, steel shape-reinforced concrete (SRC) shear walls, in which steel profiles are encased in the boundary elements, have been widely applied in high-rise buildings. In order to simplify the on-site construction procedure, this paper proposes a novel partially prefabricated steel shape-reinforced concrete (PPSRC) shear wall using throat connectors. Based on the pseudo-static tests of two large-scale specimens, the effect of construction methods (prefabricated or cast in place) on the cyclic behavior of PPSRC shear walls was investigated by the hysteretic loops, skeleton curves, stiffness degradation, energy dissipation, and deformation decomposition. The test results indicated that PPSRC shear walls could exhibit a comparative cyclic response with the cast-in-place SRC shear walls, and the proposed throat connectors could effectively transfer the stress of the longitudinal reinforcements. Finally, a macro-modeling of PPSRC shear walls based on the multi-layer shell elements in OpenSees 3.3.0 was established and validated by the test results, and the parametric analysis of the axial compression, steel ratio, and concrete strength of prefabricated and cast-in-place parts was then conducted.

Thermomechanical Collaborative Design and Experimental Verification of a Sandwich Structure with a Polyimide Foam Core

This paper introduces the technology and performance of a new sandwich structure consisting of carbon fiber composite face sheets, a polyimide foam core, and an aluminum honeycomb panel with both heat insulation and load-bearing functions. The heat-resistant performance of the sandwich structure was evaluated. The vacuum thermal conductivity of the sandwich structure in the vertical direction ranges from 0.54 to 0.92 (W/[m⋅K]) with increasing temperature from −170 to 135°C. A multilayer finite element model of carbon fiber cloth, polyimide foam, and aluminum honeycomb was established. Finally, a comprehensive evaluation of the mechanical and thermal insulation performance of the sandwich structure was conducted through random vibration testing and thermal vacuum testing. The results showed that the sandwich structure had good stiffness and thermal insulation performance, successfully verifying the effectiveness of the collaborative design.

Ka-Band Wide-Angle Scanning Phased Array with Dual Circular Polarization

A wide-angle scanning phased array with dual circular polarization in the Ka-band is presented in this paper. To improve the scanning capability of the phased array, the microstrip element is modified by loading many metal posts at its center and periphery. In addition, a stripline coupler is designed to achieve dual circularly polarized (CP) radiation, and the inner conductor of the subminiature micro-push-on (SSMP) connectors for feeding the coupler is extended to the top layer of the multilayer element by introducing an open stub, which simplifies the assembly process between the SSMP connector and multilayer printed circuit board (PCB) due to through-hole soldering instead of blind-hole soldering. The proposed element can cover a frequency range from 28 GHz to 30.5 GHz with a relative bandwidth of 8.5% in the Ka-band. An 8 × 8 phased array is constructed based on this proposed element, and a wide-angle scanning range from −65° to +65° is obtained for the dual circular polarization. The proposed array has a gain fluctuation of 5.1 dB and an axial ratio (AR) of less than 3.3 dB during beam-steering. The prototype is fabricated and measured, with a good agreement between the measured and simulated results. The proposed phased array can be applied in a Ka-band millimeter-wave (MMW) communication system.

Numerical Study on Mechanical Behavior and Electromechanical Properties of Solder-Jointed REBCO-Coated Conductors.

As the second-generation high-temperature superconducting conductors, rare earth-barium-copper-oxide (REBCO) coated conductor (CC) tapes have good potential as high-field and high-energy superconductors. In superconducting applications, several joints are required for conjugating comparatively short REBCO CC tapes. Soldering lap joints are the simplest and most commonly applied REBCO CC joints. In addition to joint resistance, the mechanical behavior and electromechanical properties are also crucial for superconducting applications. In this paper, the electromechanical properties and mechanical behaviors of soldering lap joints at 77 K under a self-field were studied. The mechanical behavior was addressed by using a full three-dimensional multilayer elastic-plastic finite element model (FEM) with REBCO CC tape main layers and solder connecting layers. Then, the electromechanical properties were analyzed by using Gao's strain-Ic degradation general model on the basis of the FEM results. Both the mechanical behavior and electromechanical properties were verified by experimental results. The effects of soldering lap conditions including lap length, soldering thickness and lap style on the electromechanical properties and mechanical behaviors were discussed. The results indicate that shorter overlap lengths and a thinner solder can reduce the premature degradation of Ic due to stress concentrations nearby the joint edges; moreover, the irreversible critical strain is significantly higher in the back-to-back joint approach compared to the widely used face-to-face joint approach.

Seismic behavior of reinforced concrete shear walls using a combined model of multi-layer shell and fiber beam elements

Seismic behavior of reinforced concrete shear walls using a combined model of multi-layer shell and fiber beam elements

Influence of HTS tape arrangement on the transverse compression performance of copper former CORC cables

CORC cables are subject to large transverse compression electromagnetic forces in fusion projects. Unfortunately, the electromagnetic force exceeding its critical transverse compression load will cause an irreversible decrease in its critical current. Therefore, it is particularly important to enhance the critical transverse compression load to ensure that the critical current does not decrease during operation. The winding method of high temperature superconducting (HTS) tape on the central former is variable. So the experimental study on how to increase the critical transverse compression load of CORC cable by changing the winding method of HTS tape is carried out in this paper. Firstly, the influence law of parameters of the number of HTS tapes per layer and the number of HTS tape layers on their transverse compression performance are analysed independently. The results indicate that increasing the number of HTS tapes per layer and the number of HTS tape layers can both improve the transverse compression performance of CORC cables. Whereas, in the case of a cable with a certain critical current demand (the same total number of HTS tapes), increasing the number of HTS tape layers necessarily reduces the number of HTS tapes per layer. Therefore, in order to compare the degree of influence of the above two parameters, we conducted transverse compression experiments on multiple groups of CORC cables with different winding methods (more layers with few tapes per layer or few layers with more tapes per layer) under the same critical current demand. The results show that under the same critical current demand, choosing the winding method that reduces the number of HTS tape layers and increases the number HTS tapes per layer can effectively improve the transverse compression performance of CORC cables. A 3D multilayer CORC cable transverse compression finite element model is also established to explain the inherent reasons for the differences in transverse compression performance of CORC cables under different HTS tape winding methods.

Universal three-dimensional finite element for analyzing of elastic inhomogeneous shells under thermomechanical loads

The work is devoted to the development of a new modification of the finite element intended for the calculation of inhomogeneous composite shells of thin and medium thickness. The element is constructed on the basis of a universal three-dimensional isoparametric 8-node multilayer finite element of a continuous medium. The layers of the modified finite element are made of composite materials reinforced with continuous unidirectional fibers. Within the framework of a finite element model of a multilayer shell of stepwise variable thickness, a technique for modeling the properties of a unidirectional fibrous composite material has been developed, based on a method for structuring material inhomogeneities iby thickness and by plan. The shell can consist of an arbitrary number of layers of varying thickness bonded into a single piece. Each layer can have its own type of material: traditional or composite. Effective physical and mechanical characteristics of the layer material are determined using known micromechanical methods for predicting the thermoelastic constants of a fiber composite through the known physical characteristics of the matrix and fiber. The fibrous material of the layer is presented as homogeneous transversely isotropic with planes of isotropy normal to the direction of reinforcement. Additional variable parameters of the "basic" universal finite element are supplemented with new attributes that determine the thermoelastic properties of the composite components. The new parameters are related to the choice of the type of fibrous composite material in the layer of the finite element, to the setting of structural micromechanical parameters of its components, and to the setting of the reinforcement orientation angle. This allows the calculations to use both traditional and fiber-composite materials in layers of inhomogeneous shells. Numerical examples demonstrate the effectiveness of the developed approach.

Stress distribution in multilayer structural element subjected to skew bending

Results of researches on strength and stiffness of diagonally bending sandwich girders having geometric and/or stiffness asymmetry have been given. A mathematical module for calculation of normal strain (strength) and stiffness on bending at any cross-section point of sandwich girder has been proposed. The kinetics of stiffness on bending and strength variation dependences when geometric parameters of a cross-section and tension modulus ratios of girder layers are changing have been examined. It has been established that the strength of a diagonally bending sandwich girder on the whole depends on the position of the centre of stiffness and the position of the neutral plane.

Research on the dynamic behavior of flexible drilling tools in ultrashort-radius radial horizontal wells

A flexible drilling tool is a special drilling tool for ultrashort-radius radial horizontal wells. This tool is composed of many parts and has the characteristics of a multibody system. In this paper, a numerical method for the dynamic analysis of flexible drilling tools is proposed. The flexible drill tool is discretized into spatial beam elements, while the multilayer contact of the flexible drilling tool is represented by the multilayer dynamic gap element, and the dynamic model of the multibody system for the flexible drilling tool’s multilayer contact is established, considering the interaction force between the drill bit and the rock. The nonlinear dynamic equation is solved using the Newmark method and Newton–Raphson method. An analysis of the dynamic behavior of a flexible drilling tool is conducted. The results indicate that the flexible drilling tool experiences vortex formation due to the interaction between the flexible drilling pipe and the guide pipe, leading to increased friction and wear. This situation hinders safe drilling operations with flexible drilling tools. The collision force of the flexible drilling tool near the bottom of the hole is more severe than that of the other tool types, which may lead to failure of the connection.

Modelling reaction transfer velocities in disconnected compact heterogeneous multilayer reactive material systems

The tuning of the self-propagating reaction is studied theoretically by introducing a non-reactive material between two reactive material elements. For the study, the Ni/Al bilayer system was chosen. The Ni/Al elements were placed on a silicon wafer covered with a 1-µm-thick silicon dioxide. The spaces between the multilayer reactive material elements were filled with different non-reactive materials covering a wide range of thermal properties. On top of this heterogeneous layer, a 1-µm-thick sealing layer was placed consisting of the filler material. The carried out two-dimensional simulations demonstrated that embedding material allows to scale the ignition transfer time and the heat propagation velocity. For example, for a transfer length of 1 µm, the ignition time can be tuned from nano- to microseconds. Consequently, in contrast to previous results embedding materials allow scaling the properties of the self-propagating reaction in heterogeneous reactive material systems.Graphical abstract

Stochastic model updating for analysis of a nuclear containment vessel under internal pressure

The prestressed concrete containment vessel (PCCV) is a critical safety measure for nuclear power plants. In the analysis of PCCV, the parameters of PCCV are usually determined through experience and a small number of experiments, which are highly accidental, and this paper provides a new idea for clarifying the scope of PCCV material parameters and clarifying some parameters that are important to PCCV based on the Bayesian updating method. Finite element models consisting of multilayer shell elements were established based on the 1:4 PCCV experiment conducted at Sandia National Laboratories (SNL) in this paper. The model was used to identify the most influential 5 parameters during the late loading stage, and a Bayesian model updating method was applied to adjust these parameters. The finite element model, incorporating the modified posterior parameters, effectively predicted the displacements of measurement points and failure mechanisms of the model.

Capacity assessment of uncorroded and corroded dapped‐end beams by NLFE and strut‐and‐tie based methods

AbstractThe verification of dapped‐end beams degraded by corrosion is a problem, especially for existing bridges in service. This paper proposes a nonlinear finite element (NLFE) modeling procedure and a simple strut‐and‐tie based procedure for predicting the response of dapped‐end beams subjected to chloride corrosion. Firstly, the finite element modeling strategy, based on the adoption of multilayer shell elements and the PARC_CL 2.1 crack model is described. Then, the degradation effects on concrete, rebars, and steel‐to‐concrete interaction are defined as a function of the propagation period of corrosion. In particular, the effects of corrosion on the reinforcement are modeled by applying a reduction of tensile strength that considers for both the reduction of cross‐section and the ultimate strain caused by pitting. Concrete splitting cracking due to volume expansion during rust formation is modeled by reducing the mechanical properties of concrete. Corrosion effects in steel‐to‐concrete interaction are modeled by applying a bond strength decay to the spring elements connecting corroded rebars—modeled with truss elements—and concrete multilayer shell elements. The proposed finite element procedure is used to study two scenarios based on different spatial distributions of corrosion‐prone areas. Subsequently, a simplified analytical approach based on the strut‐and‐corroded tie method—called S&CT method—is proposed and compared with the finite element outcomes. Finally, the validations of the two proposed methods are presented with respect to a corroded dapped‐end beam, showing that corrosion of rebars affects the resistance mechanisms of the dapped‐end beam, by reducing both resistance and ductility. The proposed simplified analytical S&CT method provides conservative and safe results compared to the numerical NLFE model and to experimental data.

Micromesh reinforced strain sensor with high stretchability and stability for full‐range and periodic human motions monitoring

AbstractThe development of strain sensors with high stretchability and stability is an inevitable requirement for achieving full‐range and long‐term use of wearable electronic devices. Herein, a resistive micromesh reinforced strain sensor (MRSS) with high stretchability and stability is prepared, consisting of a laser‐scribed graphene (LSG) layer and two styrene‐block‐poly(ethylene‐ran‐butylene)‐block‐poly‐styrene micromesh layers embedded in Ecoflex. The micromesh reinforced structure endows the MRSS with combined characteristics of a high stretchability (120%), excellent stability (with a repetition error of 0.8% after 11 000 cycles), and outstanding sensitivity (gauge factor up to 2692 beyond 100%). Impressively, the MRSS can still be used continauously within the working range without damage, even if stretched to 300%. Furthermore, compared with different structure sensors, the mechanism of the MRSS with high stretchability and stability is elucidated. What's more, a multilayer finite element model, based on the layered structure of the LSG and the morphology of the cracks, is proposed to investigate the strain sensing behavior and failure mechanism of the MRSS. Finally, due to the outstanding performance, the MRSS not only performes well in monitoring full‐range human motions, but also achieves intelligent recognitions of various respiratory activities and gestures assisted by neural network algorithms (the accuracy up to 94.29% and 100%, respectively). This work provides a new approach for designing high‐performance resistive strain sensors and shows great potential in full‐range and long‐term intelligent health management and human–machine interactions applications.image