Accurate Finite Element Model Research Articles

Experimental and numerical analysis on the post-fire flexural behavior of aluminum alloy gusset joints

Regarding the damage incurred by aluminum alloy latticed shells under fire loads, a crucial aspect in assessing structural integrity is examining the residual bearing capacity of aluminum alloy gusset (AAG) joints. Consequently, this paper conducted experimental and numerical analyses on the post-fire flexural behavior of AAG joints. Initially, twelve AAG joints underwent post-fire tests, revealing that the failure patterns differed between thin-plate joints (exhibiting block tearing of gusset plates) and thick-plate joints (exhibiting member buckling). Notably, the initial stiffness approximately remained constant, while a trilinear relationship emerged between the ultimate flexural bearing capacity and the maximum post-fire temperature. Subsequently, finite element (FE) analysis was carried out, and the accuracy of FE models was verified by comparing the FE results with the test results. A comprehensive parametric analysis, considering various plate thicknesses, post-fire temperatures, and aluminum alloy brands, was then conducted. Ultimately, employing statistical regression, theoretical equations were formulated to estimate both bending stiffness and bearing capacity for AAG joints after exposure to fire.

Experimental and numerical analysis of assembled steel beam to CFDST column joint

A novel assembled joint between the concrete-filled double-skin steel tubular (CFDST) column and steel beams is developed in this paper. The joint is connected by extended endplates and high-strength bolts, and it is designed to facilitate post-disaster repairs. The pseudo-static test was performed on four 1:2 scaled joints, the endplate thickness, column form, and inner tube configuration were considered. The experimental results suggested excellent seismic performance of the joints, including plump hysteretic curves, high displacement ductility coefficients, and significant energy dissipation values. Then, accurate finite element (FE) models were established. Comparative results showed that the FE models better simulated the failure modes of endplate bending, weld tearing, local buckling of the flanges, and bolt fracture. In addition, there was a small deviation between the lateral load-bearing capacity obtained from tests and FE simulations. Next, stress analyses showed that the joint's yielding mode is from the flanges and endplates yielding to the outer tube web yielding. The stress on the inner tube was always lower than the yield stress, indicating that the CFDST column had a significant reserve of lateral load-bearing capacity. The main findings of numerous numerical analyses were that higher-strength endplates and steel beams with wider flanges substantially increased the lateral load-bearing capacity of the joint. Finally, a proposal was made to enhance the installation of ribs at beam ends. It improved the load-bearing capacity and initial stiffness and alleviated the stress concentration.

Model updating of a shear‐wall tall building using various vibration monitoring data: Accuracy and robustness

SummaryAcceleration measurements are often used for model updating of civil engineering structures, especially in the case of seismic monitoring. It is yet unclear if accelerations alone would generate an accurate and robust finite‐element (FE) model. This study examines this notion and analyzes the possibility of using other vibration monitoring data for model updating of shear‐wall tall buildings. This study compares the accuracy and robustness of the FE models being optimized via accelerations, roof displacement, wall rotations, interstory drift ratios, and the linear combination of these measurements. A numerical case study is analyzed using Timoshenko beams for modeling the lateral vibration of a benchmark 42‐story building under seismic excitations. Results show that the acceleration response of the examined building is mostly governed by its higher vibration modes. Depending on the characteristics of ground motions, using accelerations alone may generate an FE model biased towards higher‐order modes without effectively capturing the lower‐order modes. For instance, the first modal frequency of the updated FE model could be 12.0% lower than the true value, and the reconstructed displacement and rotation responses are noticeably inaccurate. Employing multi‐source monitoring data for model updating, for example, the combinations of roof displacement and acceleration measurements, could reduce the normalized root‐mean‐square errors in displacements by more than 70%. This study also quantifies the robustness of the FE model under various measurement noise levels and 50 pairs of earthquake records. Finally, the effects of multi‐source data on FE model updating are validated via experiments on a 7‐story shear wall building. Analysis reveals that a more accurate and robust FE model can be determined via a combination of accelerations and top displacement than via acceleration alone.

Experimental and numerical investigation on out-of-plane ultimate strength of high-strength steel arches

This study presents an experimental investigation on the out-of-plane ultimate strength of high-strength-steel (HSS) I-section arches, which has not been reported previously. Fourteen I-section HSS arches having different yield strengths, cross-sectional dimensions, slendernesses, and rise to span ratios were tested under three-point symmetrical vertical loading. The corresponding out-of-plane deformation modes and strengths are identified. Subsequently, in order to predict the out-of-plane capacities of HSS arches, a finite element analyses is carried out, which takes into consideration residual stresses and initial geometrical imperfections. This analysis demonstrates a strong alignment with the experimental results, confirming the accuracy of finite element model and experimental results. Furthermore, the study comprehensively analyzes the influence of yield strength of steel, rise-span ratio, and slenderness on the ultimate bearing capacity of HSS arches. Through a parametric analysis, design formulas for the out-of-plane bearing capacity of HSS arches subjected to arbitrary compression forces combined with arbitrary bending moments are formulated. It is found that the out-of-plane ultimate strength of HSS arches is significantly influenced by the yield strength of the steel. Compared to a low strength steel (LSS) arch, the out-of-plane ultimate bearing capacity of the HSS arch increases with an increase in yield strength in the plastic stage, and the ultimate lateral displacement of the HSS arch decreases with an increase in yield steel strength due to the lower ductility of HSS. In addition, after reaching the out-of-plane ultimate bearing load of arch, the load-displacement curve of the HSS arch drops faster than the LSS arch. It is also found that the proposed design formulas can effectively predict the out-of-plane bearing capacity of HSS arches.

The Development of a 3D-Printed Compliant System for the Orientation of Payloads on Small Satellites: Material Characterization and Finite Element Analysis of 3D-Printed Polyetherketoneketone (PEKK)

This article focuses on the development of a 3D-printed 2-degree-of-freedom (DOF) joint for the payloads’ orientation on small satellites. This system is a compliant mechanism, meaning that this monolithic system composed of cross-axis flexural pivots (CAFPs) produces complex movements through the elastic deformation of its structure. Using fused filament fabrication (FFF), a demonstrator made of Polyetherketoneketone (PEKK) is printed to determine its potential compatibility with space conditions. Focusing on a segment of the joint, the CAFP, this study aims for an enhancement of its mechanical behavior through the study of its printing direction and the creation of an accurate finite element model of this compliant mechanism. First, material characterization of 3D-printed PEKK is achieved through differential scanning calorimetry tests of the filament and flexural and tensile tests of specimens printed in different printing directions. Then, these data are used to perform a finite element analysis of different CAFP designs and compare their mechanical response of their 3D-printed twin using digital image correlation software. Finally, the CAFP structures were observed by X-ray tomography. The results show that printing direction greatly influences both flexural and tensile strength. Voids induced by the FFF process could impact the mechanical behavior of 3D-printed parts as the simple CAFP design has a better test/model correlation than complex ones. This could influence its resistance to space environment.

Segment selection for fusion and artificial disc replacement in the hybrid surgical treatment of noncontiguous cervical spondylosis: a finite element analysis.

Introduction: The treatment of skip-level cervical degenerative disease (CDD) with no degenerative changes observed in the intervening segment (IS) is complicated. This research aims to provide a reference basis for selecting treatment approaches for noncontiguous CDD. Methods: To establish accurate finite element models (FEMs), this study included computed tomography (CT) data from 21 patients with CDD (10 males and 11 females) for modeling. The study primarily discusses four cross-segment surgical approaches: upper (C3/4) anterior cervical discectomy and fusion (ACDF) and lower (C5/6) cervical disc arthroplasty (CDA), FA model; upper CDA (C3/4) and lower ACDF (C5/6), AF model; upper ACDF (C3/4) and lower ACDF (C5/6), FF model; upper CDA (C3/4) and lower CDA (C5/6), AA model. An initial axial load of 73.6 N was applied at the motion center using the follower load technique. A moment of 1.0Nm was applied at the center of the C2 vertebra to simulate the overall motion of the model. The statistical analysis was conducted using STATA version 14.0. Statistical significance was defined as a p value less than 0.05. Results: The AA group had significantly greater ROM in flexion and axial rotation in other segments compared to the FA group (p < 0.05). The FA group consistently exhibited higher average intervertebral disc pressure in C2/3 during all motions compared to the AF group (p < 0.001); however, the FA group displayed lower average intervertebral disc pressure in C6/7 during all motions (p < 0.05). The AA group had lower facet joint contact stresses during extension in all segments compared to the AF group (p < 0.05). The FA group exhibited significantly higher facet joint contact stresses during extension in C2/3 (p < 0.001) and C6/7 (p < 0.001) compared to the AF group. Discussion: The use of skip-level CDA is recommended for the treatment of non-contiguous CDD. The FA construct shows superior biomechanical performance compared to the AF construct.

A novel systematic approach for robust numerical simulation of carbon fiber-reinforced plastic circular tubes: Utilizing machine-learning techniques for calibration and validation

Developing a reliable and robust finite element model of a carbon fiber-reinforced plastic (CFRP) composite structure is investigated by using the LS-DYNA solver and Python. This study tries to provide a systematic numerical approach to cover the principal impediment to adaptation of composite energy absorbers, that is the lack of a reliable predictive method. The proposed procedure aims to further the understanding of advanced composite structures’ behavior during the crash phenomenon by developing an accurate finite element model. To do so, the mechanical properties of the material were extracted from American Society for Testing and Materials (ASTM) standard test methods, followed by experimental investigation of circular CFRP tubes undergoing quasi-static loading. A numerical simulation framework was then utilized to scrutinize the effectiveness of simulation parameters on the crushing mechanism. Finally, a systematic approach based on machine learning techniques was performed to adjust non-physical modeling parameters for further calibration and validation. In this regard, a versatile Python code was developed to automate pre-processing, processing, and post-processing steps. The code also provides a groundwork to perform machine learning techniques. Interestingly, the numerical and experimental results were highly correlated with a correlation coefficient of almost 90%. Additionally, several non-physical numerical parameters were found to be inactive, while some else were identified as effective parameters, and their corresponding effectiveness was quantitatively extracted and discussed for the first time in the literature.

Multichannel multimodal piezoelectric middle ear implant concept based on MEMS technology for next-generation fully implantable cochlear implant applications

This paper introduces a unique multimode, multichannel piezoelectric vibration sensor for the next-generation fully implantable cochlear implant (FICI) systems. The sensor, which can be implanted on the middle ear chain to collect and filter the ambient sound in eight frequency bands, comprises an array of 4 M-shape multimode and 11 single cantilevers. Finite element (FE) analysis indicates a 2.05-fold improvement in capturing frequency information for the multimodal sensor compared to its single-mode counterpart. Under an acoustic excitation at 100 dB SPL, the sensor, mounted on an artificial tympanic membrane, yielded a peak output voltage of 546.16 mVpp and a peak sensitivity of 285.28 mVpp/Pa at 1613 Hz. The extrapolated acoustic results indicated a dynamic frequency range between 300 Hz and 6 kHz, even at 30 dB SPL. Furthermore, a lightweight titanium coupler, employing a two-sided clipping structure with a maximum wall thickness of 70 μm, is micromachined for surgical attachment of the transducer to the middle ear chain. A commercial accelerometer, implanted on the incus short process (SP) of a cadaver using the titanium coupler, successfully recorded 0.1 g for 100 dB SPL at 500 Hz, revealing the potential feasibility of the coupler for vibration sensor implantation. Moreover, the presented anatomically accurate FE model of the middle ear, exhibiting a high correlation coefficient (R2) of 0.97 with the cadaveric experiment, suggests an efficient numerical approach for evaluating the implantation of middle ear prostheses. In this regard, the study holds great promise for clinical application in the field of implantable hearing aids.

Axial compressive behaviors of multi-cavity concrete-filled double-skin tubular stub columns

The axial compressive behaviors of multi-cavity concrete-filled double-skin steel tubular (MCFDST) stub columns are investigated using experimental and numerical methods in this study. The MCFDST columns comprise two concentric steel tubes (circular hollow section (CHS) inner and square hollow section (SHS) outer), sandwiched concrete filled between them, and four strips connecting outer and inner tubes. Fourteen MCFDST stub columns and two concrete-filled double-skin steel tubular (CFDST) (CHS inner and SHS outer) stub columns are fabricated and tested. Experimental results are used to validate the accuracy of finite element models of MCFDST and CFDST stub columns, and based on which, extensive parameter analyses are conducted. The analysis results show that the strips delay the local buckling and change the buckling mode of outer steel tube, as well as improve the bearing capacity and ductility of stub columns. Observed failure modes are controlled by the local buckling of the outer tube associated with the crushing of filled concrete. In addition, the axial compressive performance of MCFDST stub columns can be improved by reducing the width-to-thickness ratio of outer tube, increasing the steel yield strength of outer tube and concrete strength, and adding strips. The hollow ratio has a negligible effect on the axial compressive behaviors when it ranges from 0.26 to 0.56. Furthermore, the predicted results by European, Japanese, British, and Chinese codes are compared with the experimental and FE results, suggesting that the formula in the European code has the best accuracy when predicting the load-bearing capacity of MCFDST stub columns.

Research on the initial tensile stiffness of T‐stub based on correlation

AbstractSemi‐rigid steel and composite joints are widely used in steel structures for their effectiveness and low constructional costs and mechanical property research on the semi‐rigid connections could not be ignored. There are still limitations to the performance analysis of mechanical components in connections based on component method, such as T‐stub. This study mainly focuses on the modification of the stiffness formula of T‐stub. Ten groups of different sizes of T‐stub were designed for monotonic loading tests and accurate finite element models were established for comparable study with the experimental results. Parametric analysis was performed on the finite element models, and the influence of each parameter on the tensile stiffness of T‐stub was analyzed. Finally, based on the correlation between tensile stiffness and the parameters, using the probabilistic design system (PDS) module, a T‐stub initial tensile stiffness theoretical formula which has a wide range of application and easier to use is proposed.

Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)

Abstract Due to a variety of reasons, including the water retained inside and the intrinsic weight of the dam itself, dam constructions have the ability to move both horizontally and vertically. If these displacements exceed a crucial limit, a dam’s structural integrity is jeopardized. Concrete buttress dams in particular may be susceptible to high-frequency vibrations because of their slender structure, especially when the flow of water is involved. The Khassa Chi Dam, which is located northeast of Kirkuk City, is the subject of this study’s attempt to offer an alternative since the constructed dam is an embankment dam. In this research, a concrete buttress dam design was studied as an alternative dam to the constructed one. Such designs exemplify one form of gravity dams widely implemented on diverse soil types. Finite element model (FEM) was employed to simulate the behavior of the dam. The simulation utilized DIANA FEA, which relies on governing equations. There are several steps involved in developing an accurate FEM that faithfully simulates the actual behavior of a dam and predicts its future responses. The model is evaluated in later analyses in terms of stress and displacement. In this context, RSA was conducted on the modeled buttress dam. The outcome of the displacement analysis of the buttress dam exhibited its safety across all load combinations after undergoing linear dynamic analysis. This analysis included Eigenvalue Analysis and RSA. The response remained low at seismic frequencies below 3 Hz, and the extent of displacement correlated with the frequency values.

Protection performance of a novel anti-collision guardrail with recycled foamed concrete under vehicle collision

Highway guardrails play an important protective role in transportation. However, most traditional highway guardrails are poor at buffering and energy absorption, which cannot guarantee the safety of passengers in traffic accidents. To address this problem, recycled foamed concrete (RFC) was combined with thin-walled steel shells to prepare a novel recycled foamed concrete anti-collision guardrail (RFCG) in current study. The energy absorption and protection performance of the guardrail were evaluated by full-scale model impact tests and numerical simulations. The results revealed that compared with standard guardrail (SG), RFCG performed better in buffering and energy absorption, yielded less damage to vehicles, exhibited a peak impact force reduction rate of 54.46%, and reduced the manufacturing cost by 5.5% per kilometer. A finite element model for the guardrail was proposed. The numerical simulation results matched well with the experimental results and the accuracy of finite element model was validated.

Design of battery shell stamping parameters for vehicles based on fusion of various artificial neural network models

The application of neural network model in engineering prediction is frequent. The BPE shell material was optimized, and the reliability of the new material was verified by modal simulation. The accuracy of finite element modeling was ensured by constrained mode experiments, and all variables were preprocessed by Latin hypercube sampling. The design parameters were determined by Monte Carlo simulation. Four different neural networks, including back propagation (BP), radial basis function (RBF), extreme learning machine (ELM) and wavelet neural network (WNN), are used to train and learn the dataset. The BPE weight reduction ratio was 14.3%, the stress was reduced by 18.6%, deformation displacement was reduced by 14.2%, and the first-order mode was increased by 29.1%.

A Novel X-ray Diffraction Procedure for Determining Residual Stresses Around Cold Expanded Holes

The continued interest in developing more accurate finite element models of the cold expansion process has driven the need for better measurement methodologies. This work details an x-ray diffraction (XRD) procedure explicitly designed to determine the residual stresses around a cold expanded hole. Aluminum coupons from two different alloys (2024-T351 and 7075-T651), with nominally 12-mm-diameter holes, were cold expanded to two different levels of applied expansion and measured using XRD. The results of a limited interlaboratory study highlight the reproducibility that one may expect to achieve by its application. For the majority of data points, the residual stresses characterized at each of the two laboratories were in agreement within the bounds of the residual stress determination experimental uncertainties, which were generally ± 15 MPa or less. After examining the differences between results obtained at each laboratory as a function of radial distance from the hole, it was found that no significant systematic error exists between data sets. Thus, the proposed novel procedure appears to provide a more precise and accurate determination of the residual stresses around cold expanded holes with a significant reduction in measurement uncertainty compared to conventional XRD measurement procedures. The results obtained using this novel procedure will be useful in calibrating new computational material models of the expansion process.

Cross-Scale Reliability Analysis Framework for LNG Storage Tanks Considering Concrete Material Uncertainty

The reliability of liquefied natural gas (LNG) storage tanks is an important factor that must be considered in their structural design. Concrete is a core component of LNG storage tanks, and the geometric uncertainty of concrete aggregate material has a significant impact on their reliability. However, owing to the significant size difference between the concrete aggregate compared to the LNG storage tank, structural analysis using an accurate finite element model that includes all the geometric characteristics of the aggregate incurs significant analytical costs. In particular, for reliability analysis requiring a large number of samples, the computational costs incurred by finite element models are infeasible. Therefore, a dual acceleration strategy based on the asymptotic homogenization method and surrogate model technology is proposed to improve the efficiency of LNG storage tank reliability analysis. In the cross-scale analysis of a LNG storage tank based on asymptotic homogenization, order reduction of the LNG storage tank analysis model was realized. Based on this, a surrogate model construction method with the aggregate fraction and mass moment as inputs was proposed to further accelerate the reliability analysis of LNG storage tanks. Subsequently, a Monte Carlo method was used to perform a reliability analysis of the LNG storage tank considering the uncertainty of the concrete aggregate geometry and distribution under the action of liquid weight and wind load. The analysis showed that the wind load has a significant influence on the safety of the design of the roof of a LNG storage tank. The directionality of the wind load has a significant impact on the distribution of the sample point response for reliability analysis and the failure mode of the LNG storage tank. Owing to the directionality of the wind load, the response distributions of the maximum displacement and maximum stress of LNG were more concentrated, and the reliability of the LNG storage tank decreased after considering the wind load. In particular, the stress reliability of the tank decreased by 5.86%. When only the liquid load was considered, the maximum displacement and stress exhibited asynchronous failure, and the two almost never occurred simultaneously. When the wind load was considered, the failure mode of the LNG storage tank was dominated by the maximum stress. Moreover, the numerical example also demonstrated that the degree of freedom involved in structural analysis, as well as the time of structural analysis can be significantly reduced. So, the proposed cross-scale analysis framework can significantly improve the efficiency of reliability analysis. The conclusions established in this study provide theoretical and methodological guidance for the reliable design of LNG storage tanks.

Integration of Swin UNETR and statistical shape modeling for a semi-automated segmentation of the knee and biomechanical modeling of articular cartilage

Simulation studies, such as finite element (FE) modeling, provide insight into knee joint mechanics without patient involvement. Generic FE models mimic the biomechanical behavior of the tissue, but overlook variations in geometry, loading, and material properties of a population. Conversely, subject-specific models include these factors, resulting in enhanced predictive precision, but are laborious and time intensive. The present study aimed to enhance subject-specific knee joint FE modeling by incorporating a semi-automated segmentation algorithm using a 3D Swin UNETR for an initial segmentation of the femur and tibia, followed by a statistical shape model (SSM) adjustment to improve surface roughness and continuity. For comparison, a manual FE model was developed through manual segmentation (i.e., the de-facto standard approach). Both FE models were subjected to gait loading and the predicted mechanical response was compared. The semi-automated segmentation achieved a Dice similarity coefficient (DSC) of over 98% for both the femur and tibia. Hausdorff distance (mm) between the semi-automated and manual segmentation was 1.4 mm. The mechanical results (max principal stress and strain, fluid pressure, fibril strain, and contact area) showed no significant differences between the manual and semi-automated FE models, indicating the effectiveness of the proposed semi-automated segmentation in creating accurate knee joint FE models. We have made our semi-automated models publicly accessible to support and facilitate biomechanical modeling and medical image segmentation efforts (https://data.mendeley.com/datasets/k5hdc9cz7w/1).

Structural Damage Detection Based on Static and Dynamic Flexibility: A Review and Comparative Study

Material damage in structures must be detected in a timely manner to prevent engineering accidents. Damage detection based on structural flexibility has attracted widespread attention in recent years due to its simplicity and practicality. This article provides a detailed overview of damage detection methods based on structural flexibility. Depending on the calculation method and data used, flexibility-based methods can be divided into the following categories: flexibility difference, flexibility derivative index, flexibility sensitivity, flexibility decomposition, static flexibility, and combinations of flexibility with other methods. The basic principles and main calculation formulas of various flexibility methods are explained, and their advantages and disadvantages are analyzed. For the method using flexibility difference, the advantage is that the calculation is very simple and does not require the construction of a finite element model of the structure. The disadvantage is that it requires the measurement of modal data of the intact structure, and this method cannot quantitatively assess the degree of damage. For the method using the flexibility derivative index, the advantage is that it only requires the modal data of the damaged structure to locate the damage, but this method is particularly sensitive to noise in the data and is prone to misjudgment. For methods based on flexibility sensitivity and flexibility decomposition, the advantage is that they can simultaneously obtain the location and degree of damage in the structure, but the disadvantage is that they require the establishment of accurate finite element models in advance. Static flexibility methods can compensate for the shortcomings of dynamic flexibility methods, but they usually affect the normal use of the structure during static testing. Combining flexibility-based methods with advanced intelligent algorithms and other methods can further improve their accuracy and efficiency in identifying structural damage. Finally, this article discusses the challenges that have not yet been solved among damage detection methods based on structural flexibility.

Study on Tightening, Anti-Loosening, and Fatigue Resistance Performances of Bolted Joints with Different Anti-Loosening Washers and Nuts

Loosening failure of bolted joints often occurs in a vibration environment. This may induce the separation of clamped components and even result in catastrophic consequences in certain situations. Various anti-loosening bolted connections have been developed and widely applied to prevent loosening. Tightening and fatigue resistance performances are also two important characteristics of anti-loosening bolted connections. However, a comprehensive comparison study of the tightening, anti-loosening, and fatigue resistance performances of typical anti-loosening bolted connections is lacking, meaning that there is a lack of material to assist in the selection of anti-loosening bolted connections in engineering. In this study, accurate three-dimensional finite element models of typical anti-loosening bolted connections with the forms of washers or nuts are established. The processes of tightening, vibration-induced loosening, and fatigue are simulated via finite element analysis (FEA). Based on the results of FEA, the tightening, anti-loosening, and fatigue resistance performances of regular bolted joints and several anti-loosening bolted connections are comprehensively compared. The results reveal that bolted joints installed with both a variable-diameter nut and an eccentric double nut are difficult to tighten. We confirm that the researched structures all have superior anti-loosening capacities compared to regular bolted joints. Additionally, the results show that the regular bolted joint achieved the worst fatigue resistance performance, i.e., the application of anti-loosening bolted connections improves fatigue resistance. Finally, the effects of preload distributions on the two nuts in bolted joints with double nuts are discussed in terms of tightening, anti-loosening, and fatigue resistance performances.

Accurate finite element modeling of multilayered flexible piezoelectric energy harvesting devices with strong coupling of structure, piezoelectricity, and circuit

Multilayered flexible piezoelectric energy harvesting devices (FPEDs) are a new future harvesting technology which are highly flexible and lightweight than familiar cantilever piezoelectric energy harvesters. This mechanical vibration driven FPED is a strongly coupled multiphysics phenomena that involve complex natural three-way interaction among the composite piezoelectric structure, the electric charge accumulated in the piezoelectric material, and a controlling electrical circuit attached to it. Efficient and accurate computational solution approaches are essential for analyzing these mechanical vibration-driven FPEDs to capture the main physical aspect of the coupled phenomena and to accurately predict the output voltage. While there are some numerical models for simple familiar cantilever type piezoelectric energy harvester reported in the literature, a fully three-dimensional strongly coupled model for complex material distributed, complex geometry, and multilayered FPED involving strong coupling of structure, piezoelectricity, and circuit phenomena has not yet been developed. A partitioned iterative algorithm is developed using a hierarchical decomposition approach wherein the coupled three fields are solved separately and coupled through loop union integration techniques that provide an efficient and accurate simulation of FPEDs. The simulation results matched the experiment results very well. This study provides a basis for the natural extension of partitioned iterative finite element coupled algorithm to simulate the future piezoelectric energy harvesting technologies involving a strong coupling of structure, piezoelectricity, and circuit phenomenon.

Reinforced concrete columns strengthened with near-surface mounted and hybrid FRP under compression with or without eccentricity: Experimental study and finite element modeling

The utilization of FRP in strengthening of reinforced concrete (RC) columns has garnered significant attention in the past two decades. Researchers have proposed the use of near-surface mounted (NSM) FRP bars with (hybrid) or without FRP jackets alongside the conventional approach of column strengthening through jacketing particularly in the presence of load eccentricity. In the realm of static loading scenarios, a significant focus has been directed toward the evaluation of the NSM, jacketing, and hybrid methodologies, while comparatively less attention has been given to the impact of various parameters on the capacity. In this article, a total of 22 RC column specimens with medium slenderness were tested under axial compressive loads with or without eccentricity to study the effect of the parameters the number and type of NSM FRP bar, the number of layers and type of FRP jacket, and the groove size for FRP bar mounting. The experimental results reveal the beneficial effects of using FRP jackets, increasing their layers and groove dimensions, and augmenting the number of NSM FRP bars on column capacity and ductility up to 36% and 197% respectively. Additionally, an accurate Finite element model has been developed and role of corbel in eccentricity application is investigated. The results showed that the corbel is not capable of transmitting the desired eccentricity.