Three-dimensional Finite Element Research Articles

Simulation study of a highly sensitive I-shaped Plasmonic nanosensor for sensing of biomolecules

This paper presents the design and simulation of an I-shaped metal insulator metal waveguide-based nanosensor for biosensing applications. The device’s sensing property is investigated using the three-dimensional finite element method. In the proposed design a I-shaped cavity is coupled to the main waveguide that serves as a resonator to generate the resonance peaks. The refractive index of the material to be sensed is filled inside the I-shaped cavity. This sensor operates in the near and mid-infrared wavelength ranges. The device can identify a variety of biomolecules, including cancer cells and bacterial samples. The simulation results reveal that device shows different resonance dips for different refractive indexes of cancer cells. The device can obtain sensitivity of 1550 nm RIU−1 and 1250 nm RIU−1 among refractive index of normal and cancerous cell for basal and hella cancer cells, respectively. Instead of all these biomolecules, the nanosensor shows different resonance dips in the transmittance spectrum for DNA, RNA, and ribonucleoprotein. Furthermore, the sensor has demonstrated potential applicability as an HB concentration detector and for sensing other blood components. Moreover, we improved the structure characteristics by varying the length and centre area of the cavity, demonstrating that modifying the device parameters can boost sensitivity. After making structural adjustments to the device, the maximum sensitivity of 3000 nm RIU−1 is achieved for some bacterial samples.

Investigation of torsion in asymmetric mid-rise structures on the pile-raft system considering soil-structure interaction

The adverse conditions of the soil such as soft soil can have seismic consequences that may either amplify seismic response or render the structure vulnerable. On one hand, the design and construction of asymmetric structures have become prevalent due to aesthetic considerations and structural space limitations. Studies indicate that structures with geometric irregularities are susceptible to seismic forces, leading to non-uniform distribution of floor drifts, excessive torsional behavior, and more, depending on the degree of irregularity. In this research, the main goal was to investigate the effect of soil and structure interaction on the torsion of asymmetric Mid-Rise Structures. To achieve this goal two asymmetric Steel moment frame system 15-story structures aim to address the effect of interaction between soil and structure on the seismic performance, one with a rigid base and the other with a flexible base, one with a rigid base and the other with a flexible base. To mitigate the settlement of soil-associated structures, a pile-raft system is employed, considering the softness of the soil. Additionally, to study the torsional behavior of these structures, their planes are asymmetrically designed in L-shape and C-shape configurations, subjected to four ground motion excitations in both far and near-field scenarios. Three-dimensional finite element numerical simulations are performed using Abaqus software. Various configurations of the pile-raft system for the asymmetric C-shape structure are examined to assess the effects of pile diameter and length on the torsional irregularity coefficient. The results show that the soil-structure interaction increases the maximum floor rotation angle, placing these structures in critical conditions concerning torsional irregularity under near-field and far-field seismic excitations.

3D electromagnetic assessment of bended CORC® cables

Conductor on round core (CORC®) cables have emerged as a leading contender in high-temperature superconducting (HTS) cable designs, offering exceptional performance with current densities surpassing 300 A/mm2 and the ability to withstand high axial tensile and compressive strain. Despite their remarkable properties, optimizing CORC® cables remains a challenge, particularly in accurately estimating their AC losses under real-world conditions, which necessitates advanced numerical modeling techniques. Building upon recent advancements in simulating straight CORC® cables, where Bean’s-like current profiles were observed across the actual thickness of wound superconducting tapes, we introduce a tailored computational approach to enhance the processing speed of three-dimensional (3D) finite element models of wound HTS tapes. This tailored approach is specifically designed to address the complexities of bent CORC® cables, which exhibit helicoidal winding and are subjected to varying mechanical strain. We focus on analyzing their electromagnetic performance by transitioning from idealized straight-former designs to more realistic scenarios where cable-formers are bent to accommodate flexible cable routing or coil configurations. Our simulations consider a typical cable design comprising three 4 mm-wide SuperPower tapes (SCS4050) with a twist pitch of 40 mm. We demonstrate the capability to accurately model the full electromagnetic behavior of bent CORC® cables without the reduction of degrees of freedom, providing valuable insights into their performance under bending conditions. Our findings contribute to the ongoing optimization of CORC® cable designs for a wide range of practical applications in high-current and high-magnetic field environments.

Numerical Analysis of the Single-Directionally Misaligned Segment Behavior of Hydraulic TBM Tunnel

The misalignment of segments in installation is a common issue in the construction of TBM tunnels. This raises a question of whether misalignment affects the operation safety of a hydraulic TBM tunnel. Using a water transfer engineering project as an example, this paper built a three-dimensional finite element model composited with segment, grout layer and surrounding rock for the numerical analysis of the behavior of single-directionally misaligned segments. The crown or invert segment was separately misaligned towards to the center of segment ring in a value of 5 mm, 10 mm, 20 mm, 30 mm or 40 mm. The strength grade of the segment concrete was C50. A weaker surrounding rock composed of V-class rock was considered for the tunnel. The results indicate that the misalignment of the crown or invert segment, respectively, creates the tensile stress in the inner surface of the corresponding segment, the tensile stress will be over the limit of C50 concrete when the misalignment is over 30 mm, indicating a risk of concrete cracking. The contact surfaces of the segment ring basically remain in compression, and the locating pins between the segment rings exhibit an evident increase in tensile stress at misaligned positions. The key points that can be obtained from this study are that a special supervision is needed to ensure the accuracy of segment installation, and strengthening measures are needed for existing misaligned segments.

Effect of Excessive Clamping Force on Bolted CFRP Composite Plates

Friction-type bolted joints are widely used in both the civil and aerospace industries. Uncontrolled excessive bolt clamping force can cause damage to the laminated fiber-reinforced polymeric (FRP) composite through the thickness and damage the joint before applying the service loads. The effect of the friction coefficient (between 0 and 0.3), bolt clearance, joint type, and other parameters on failure modes and the maximum bolt clamping force of the carbon FRP lapped joint is studied. A three-dimensional finite element (FE) model consisting of a bolt, a washer, a laminate FRP composite plate, and steel plates was developed for the simulation of the double- (3DD) and single (3DS)-lapped bolted joint. The FE model was validated by using experimental results and was able to predict the experimental results by a difference of between 2.2 and 6.7%. The joint capacity of the clamping force was found to be greatly increased by adopting the double lap technique, which involves placing an FRP composite plate between two steel plates. Also, it was recommended to use an internal washer diameter less than or equal to the FRP composite plate hole diameter since a larger washer clearance can produce higher contact pressure and reduce the resistance by 22%. In addition, reducing the bolt head diameter can lead to a 65% reduction in the 3DS joint clamping strength.

Predicting Blast-Induced Damage and Dynamic Response of Drill-and-Blast Tunnel Using Three-Dimensional Finite Element Analysis

The significance of predicting the dynamic response and damage of an existing concrete tunnel during underground blasting has increased owing to the close proximity between the newly built and existing tunnels. Peak particle velocity (PPV) is a commonly used criterion in the assessment of blast-induced structural damage. However, such structural damage is also associated with the frequency content of the blast wave. Nevertheless, the recommended threshold PPVs, which are based on empirical criteria, predict conservative estimations. Using stringent and regulated blasting methods often results in project delays and escalates the total project expenditure. In this paper, a three-dimensional finite element model of an underground tunnel has been developed in LS-DYNA to analyze damage to the concrete tunnels under blast loading. A suite of analyses was performed to examine the potential damage induced in the underground tunnel. A lower frequency load was found to have a greater potential for producing damage compared with a high frequency blast load. The results showed that the location of the cracking within the tunnel, such as the arch foot or tunnel wall, was also influenced by the frequency of the blast wave. The maximum allowable PPV for the concrete tunnel was determined for a range of frequencies based on predicted free field PPV and additional factors of safety of 1.2 and 1.5 were established, depending on the safety needs and importance of the tunnel construction. Thus, our findings provide useful information for improving the evaluation of tunnel damage and guaranteeing the safety of underground tunnels.

Research on Temperature Distribution and Gradient Prediction of U-Shaped Girder Bridge under Solar Radiation Effect

With the development of bridge engineering, U-shaped girder bridges have been applied in numerous bridge designs due to their structural characteristics. However, the U-shaped girder bridge is sensitive to solar radiation effects, leading to uneven temperature distributions that can affect the service performance of the structure. Thus, this study proposes an analysis method for the temperature distribution of U-shaped girder bridges and develops a prediction model to estimate temperature gradients. First, an improved ASHRAE clear sky model is proposed to calculate the structural shadow areas under sunlight, which provides a basis for the numerical simulation of U-shaped girder bridges under solar radiation effect. Then, a three-dimensional finite element model of the U-shaped girder bridge is established, and its correctness is verified by comparing with the actual temperature data. The temperature distribution of the U-shaped girder bridge under solar radiation is simulated using the verified model to obtain the maximum temperature difference and temperature variation characteristics. Finally, a prediction model for the temperature gradient is developed using nonlinear fitting approaches, and its accuracy is confirmed through comparison with actual data. The results indicate that the temperature distribution of the U-shaped girder bridge has minor changes along the longitudinal direction, while there are significant changes in the transverse distribution; the temperature distribution exhibits nonlinear changes in the height direction of the two side webs and the lateral direction of the bottom slab, with the maximum temperature difference reaching 17 °C; the fitting effect of the prediction model is very good, the correlation coefficients of the fitting curve and the actual data are all greater than 88%, providing a basis for the analysis of the temperature effects on U-shaped girder bridges and its application in design specifications.

Numerical investigation on the deformation of railway embankment under normal faulting

Active faults in the earthquake region are consistently regarded as a potential geological hazard to the construction and operation of railway engineering. However, the effects of normal faulting on railway embankments have not been investigated thoroughly. For bridging this knowledge gap, three-dimensional finite element analysis considering the influence of faulting offset, the soil layer’s thickness, the fault dip angle and the embankment cross-fault angle are conducted to clarify the normal faulting effects on the railway embankment. Emphasis is given to the stress and strain characteristic in the fault rupture outcropping regions on the embankment, the deformation of the embankment centerline for design purposes, and the determination of the affected zones for railway embankment preservation. The analysis shows that the normal fault rupture outcropping regions on railway embankment are tensile yield in most cases. The existence of the soil layer and its thickening would widen the affected zones and the regions where the fault ruptures outcrops. The fault dip angle and the cross-fault angle of the embankment have a complex effect on the behaviors of the crossing embankment. The depth of the subsidence zone of the embankment would increase with the decrease of the fault dip angle and the large fault dip angle would change the primary fault rupture to be a compressive one directly above the fault line. If the embankment crosses the fault line obliquely, the curvature radius of the centerline would hardly meet the design code.

Effect of sagittal alignment on spinal cord biomechanics in the stenotic cervical spine during neck flexion and extension.

Spinal cord stress and strain contribute to degenerative cervical myelopathy (DCM), while cervical kyphosis is known to negatively impact surgical outcomes. In DCM, the relationship between spinal cord biomechanics, sagittal alignment, and cord compression is not well understood. Quantifying this relationship can guide surgical strategies. A previously validated three-dimensional finite element model of the human cervical spine with spinal cord was used. Three models of cervical alignment were created: lordosis (C2-C7 Cobb angle: 20°), straight (0°), and kyphosis (- 9°). C5-C6 spinal stenosis was simulated with ventral disk protrusions, reducing spinal canal diameters to 10mm, 8mm, and 6mm. Spinal cord pre-stress and pre-strain due to alignment and compression were quantified. Cervical flexion and extension were simulated with a pure moment load of 2Nm. The Von Mises stress and maximum principal strain of the whole spinal cord were calculated during neck motion and the relationship between spinal cord biomechanics, alignment, and compression was analyzed using linear regression analysis. Spinal cord pre-stress and pre-strain were greatest with kyphosis (7.53kPa, 5.4%). Progressive kyphosis and stenosis were associated with an increase in spinal cord stress (R2 = 0.99) and strain (R2 = 0.99). Cervical kyphosis was associated with greater spinal cord stress and strain during neck flexion-extension and the magnitude of difference increased with increasing stenosis. Cervical kyphosis increases baseline spinal cord stress and strain. Incorporating sagittal alignment with compression to calculate spinal cord biomechanics is necessary to accurately quantify spinal stress and strain during neck flexion and extension.

Thermal Model of the AGR-5/6/7 Experiment with Offset Gas Gaps

Because of their high impact on calculated temperatures, the offset gas gaps between the graphite holder and capsule wall are evaluated for the thermal model of the Advanced Gas Reactor 5/6/7 (AGR-5/6/7) irradiation experiment. Fuel compact temperatures are a crucial factor in assessing the irradiation performance of tristructural isotropic (TRISO)-coated-particle fuel for use in high-temperature gas-cooled reactors. TRISO fuel irradiation performance is a core tenet of the U.S. Department of Energy’s Advanced Gas Reactor Fuel Development and Qualification Program, conducted in the Advanced Test Reactor at Idaho National Laboratory. Specifically, the irradiation experiments were intended to provide irradiation performance data to support fuel process development, qualify fuel for normal operating conditions, support the development of fuel performance models and codes, and provide irradiated fuel and materials for postirradiation examination and safety testing. The thermal model used to predict the fuel compact temperatures was a three-dimensional finite element model that was subject to uncertainty. The most dominant factor in the uncertainty pertaining to calculated fuel temperatures is the gas gap uncertainty, which is caused by the graphite holder nub-to-capsule wall clearance. In AGR-5/6/7 capsules, the graphite holders can be shifted away from being perfectly centered inside the stainless steel capsule walls. This is due to irradiation-induced graphite shrinkage or to insufficient nubs on the graphite holder leading to azimuthally varying gas gaps during irradiation. A method was developed to find the best offset magnitude and direction at the top and bottom of the graphite holders in Capsules 1 and 2, which experienced higher temperatures than originally predicted among the five AGR-5/6/7 axially dispersed capsules irradiated between 2018 and 2020. The differences between the calculated and the measured temperatures of thermocouples (TCs) placed in the graphite holder near the fuel compacts were used as the basis for the holder offset determination. The best-fit offset assumes that the root-mean-square error between the measured and calculated TC temperatures is a minimum value. Typical offsets in the range of 0.002 to 0.004 in. increase the fuel compact temperatures in the range of 100°C to 200°C when compared to the zero offset for Capsules 1 and 2. Additionally, because of irradiation-induced changes in the capsule geometries, the holder offsets change throughout the irradiation period.

The role of the foundation flexibility on the seismic response of a modern tall building: Vertically incident plane waves

The soil-structure interaction (SSI) is an integral part of the seismic response of structures. The knowledge about its effects is based largely on numerical simulations involving simplified models. In this paper, we examine the consequence of several assumptions in SSI models of buildings, with emphasis on the rigid foundation assumption. To this end, we analyze several variants of a linear three-dimensional finite element model of the structure and soil corresponding to a uniquely instrumented 50-story skyscraper, with a basement on a pile foundation, located in southwest China. The models are excited by triaxial motion due to a vertically incident plane wave. The most realistic model (with basement and piles, both with bond contact with the soil), predicted an 8 % reduction of the apparent frequency and a 30 %–50 % increase in the apparent damping ratio of the 1st mode of vibration, relative to the model with fixed basement. The model with a rigid foundation (basement) embedded in the soil underestimated the reduction in apparent frequency by a factor of two. The SSI effects were the most pronounced for the model with flexible basement and no piles (16 %–19 % reduction in apparent frequency and 73 %–86 % increase in apparent damping ratio). The basement-structure interaction reduced the apparent frequency by 5 %–8 % depending on the direction. It is concluded that, for such a building, a detailed model of the structure and its foundation is needed to predict reliably the SSI effects.

Effect of forefoot transverse arch stiffness on foot biomechanical response--based on finite element method

BackgroundThe plantar vault, comprising the transverse and longitudinal arches of the human foot, is essential for impact absorption, elastic energy storage, and propulsion. Recent research underscores the importance of the transverse arch, contributing over 40% to midfoot stiffness. This study aimed to quantify biomechanical responses in the ankle-foot complex by varying the stiffness of the deep metatarsal transverse ligament (DTML).MethodsUsing CT image reconstruction, we constructed a complex three-dimensional finite element model of the foot and ankle joint complex, accounting for geometric complexity and nonlinear characteristics. The focus of our study was to evaluate the effect of different forefoot transverse arch stiffness, that is, different Young’s modulus values of DTML (from 135 MPa to 405 MPa), on different biomechanical aspects of the foot and ankle complex. Notably, we analyzed their effects on plantar pressure distribution, metatarsal stress patterns, navicular subsidence, and plantar fascial strain.ResultsIncreasing the stiffness of the DTML has significant effects on foot biomechanics. Specifically, higher DTML stiffness leads to elevate von Mises stress in the 1st, 2nd, and 3rd metatarsals, while concurrently reducing plantar pressure by 14.2% when the Young’s modulus is doubled. This stiffening also impedes navicular bone subsidence and foot lengthening. Notably, a 100% increase in the Young’s modulus of DTML results in a 54.1% decrease in scaphoid subsidence and a 2.5% decrease in foot lengthening, which collectively contribute to a 33.1% enhancement in foot longitudinal stiffness. Additionally, doubling the Young’s modulus of DTML can reduce the strain stretch of the plantar fascia by 38.5%.ConclusionPreserving DTML integrity sustains the transverse arch, enhancing foot longitudinal stiffness and elastic responsiveness. These findings have implications for treating arch dysfunction and provide insights for shoe developers seeking to enhance propulsion.

Seismic mitigation performance of a periodic foundation for nuclear power structures considering soil-structure interactions

Periodic structures may be designed as periodic foundations to reduce the seismic response of engineering structures. The periodic foundation is more suitable for the seismic mitigation of nuclear power structures because of its wide attenuation domain. Based on the dispersion relationship of infinite periodic structures, this research constructs a one-dimensional layered periodic foundation using rubber and concrete materials, determines the attenuation domain frequency band gap that meets the seismic design requirements of nuclear power structures, and optimizes the raft design of nuclear power structures. At the same time, with the scarcity of bedrock sites, the site selection of nuclear power structures is inevitably shifted to soft rock sites. Therefore, this paper also considers the influence of the soil-structure interaction (SSI) on the seismic response of nuclear power structures. A three-dimensional finite element model of the nuclear power structure-periodic foundation-site system was established, and a detailed parameter analysis of the seismic performance of the periodic foundation of nuclear power structures considering the SSI effect was carried out. The results show that the seismic response of nuclear power structures can be significantly reduced by designing the attenuation domain of the periodic foundation.

A numerical analysis of the mechano-electrochemical effects on localised corrosion in pipelines using a multi-physical field coupling approach

In this study, we used a multi-physics coupling approach integrating the electrochemical and solid mechanics fields to develop a three-dimensional finite element model. This model was specifically designed to investigate the effects of mechano-electrochemical (M-E) effects on pipeline corrosion. The boundary conditions for the finite element simulation were established using experimental data, enabling the model to effectively predict the corrosion potential and current density, which aligned well with the experimental findings. Subsequently, the validated model was applied to examine the M-E effects near the pipe corrosion defects, considering various depths of corrosion defects and axial strain. Our results indicate that the stress concentration at the core of the defect increases with increasing axial tensile strain and deepening corrosion. The investigation of the correlation between the corrosion potential and net current density revealed that mechanical forces significantly impact metal corrosion rates, thus influencing pipeline longevity. When the metal structure of the pipeline is deformed within the elastic deformation range, the impact of the M-E effects on corrosion is minimal. However, when a tensile strain is applied or the defect geometry induces plastic deformation at the defect site, a notable increase in the local corrosion activity is observed.

Mode conversion of fundamental guided ultrasonic wave modes at part-thickness crack-like defects

Guided ultrasonic waves can be employed for efficient structural health monitoring (SHM) and non-destructive evaluation (NDE), as they can propagate long distances along thin structures. The scattering (S0 mode) and mode conversion of low frequency guided waves (S0 to A0 and SH0 wave modes) at part-thickness crack-like defects was studied to quantify the defect detection sensitivity. Three-dimensional (3D) Finite Element (FE) modelling was used to predict the mode conversion and scattering of the fundamental guided wave modes. Experimentally, the S0 mode was excited by a piezoelectric (PZT) transducer in an aluminum plate. A laser vibrometer was used to measure the out-of-plane displacement to characterize the mode-converted A0 mode, employing baseline subtraction to achieve mode and pulse separation. Good agreement between FE model predictions and experimental results was obtained for perpendicular incidence of the S0 mode. The influence of defect depth and length on the scattering and mode conversion was studied and the sensitivity for part-thickness defects was quantified. The maximum mode conversion (S0-A0 mode) occurred for ¾ defect depth and the amplitude of the mode-converted A0 and scattered S0 modes mostly increased linearly as the defect length increased with an almost constant A0/S0 mode scattered amplitude ratio. Similar forward and backward scattering amplitude was found for the mode converted A0 mode. The mode conversion of the S0 to SH0 mode has the highest sensitivity for short defects, but the SH0 mode amplitude only increased slightly for longer defects. Employing the information contained in the mode-converted, scattered guided ultrasonic wave modes could improve the detection sensitivity and localization accuracy of SHM algorithms.

Cracking modes and force dynamics in the insertion of neural probes into hydrogel brain phantom

Objective. The insertion of penetrating neural probes into the brain is crucial for advancing neuroscience, yet it involves various inherent risks. Prototype probes are typically inserted into hydrogel-based brain phantoms and the mechanical responses are analyzed in order to inform the insertion mechanics during in vivo implantation. However, the underlying mechanism of the insertion dynamics of neural probes in hydrogel brain phantoms, particularly the phenomenon of cracking, remains insufficiently understood. This knowledge gap leads to misinterpretations and discrepancies when comparing results obtained from phantom studies to those observed under the in vivo conditions. This study aims to elucidate the impact of probe sharpness and dimensions on the cracking mechanisms and insertion dynamics characterized during the insertion of probes in hydrogel phantoms. Approach. The insertion of dummy probes with different shank shapes defined by the tip angle, width, and thickness is systematically studied. The insertion-induced cracks in the transparent hydrogel were accentuated by an immiscible dye, tracked by in situ imaging, and the corresponding insertion force was recorded. Three-dimensional finite element analysis models were developed to obtain the contact stress between the probe tip and the phantom. Main results. The findings reveal a dual pattern: for sharp, slender probes, the insertion forces remain consistently low during the insertion process, owing to continuously propagating straight cracks that align with the insertion direction. In contrast, blunt, thick probes induce large forces that increase rapidly with escalating insertion depth, mainly due to the formation of branched crack with a conical cracking surface, and the subsequent internal compression. This interpretation challenges the traditional understanding that neglects the difference in the cracking modes and regards increased frictional force as the sole factor contributing to higher insertion forces. The critical probe sharpness factors separating straight and branched cracking is identified experimentally, and a preliminary explanation of the transition between the two cracking modes is derived from three-dimensional finite element analysis. Significance. This study presents, for the first time, the mechanism underlying two distinct cracking modes during the insertion of neural probes into hydrogel brain phantoms. The correlations between the cracking modes and the insertion force dynamics, as well as the effects of the probe sharpness were established, offering insights into the design of neural probes via phantom studies and informing future investigations into cracking phenomena in brain tissue during probe implantations.

Crash analysis of glass mat thermoplastic (GF/PA6) tubes considering splaying failure mode and energy absorption

Glass mat thermoplastic tubes are potential materials for improving crashworthiness owing to their excellent crash energy absorption capability due to their splaying failure mode of glass mat thermoplastic tubes, which must be considered in the crash analysis to accurately predict their crash performance. This study investigates the crash analysis of glass-mat thermoplastic composite tubes to realize the splaying failure mode and crash energy absorption capability. We evaluated the mechanical properties and fracture toughness of advanced glass mat thermoplastics, termed multi-layered hybrid mats, and employed the result in a 3D Hashin-type continuum damage model implemented with a user material subroutine. For the crash analysis of glass mat thermoplastic tubes, a three-dimensional finite element (FE) model, including cohesive elements in the middle layer of the tube to simulate the splaying failure mode, was constructed. In addition, in the process of the efficient FE modeling of the crash tube, the fracture toughness correction factor was proposed and optimized to calibrate the energy absorption in conjunction with crash test results, as interlaminar fracture modeling causes a difference in energy absorption between the actual test and simulation. As a result, the proposed crash analysis predicted the energy absorption capacity and a splaying failure mode of glass-mat thermoplastic tubes, demonstrating strong concordance with experimental results.

Experimental and numerical investigations of the shear performance of reinforced concrete deep beams strengthened with hybrid SHCC-mesh

This paper investigates the shear strengthening of simply supported deep beams using welded wire mesh and glass fiber mesh filled with strain-hardening cementitious composites (SHCC) concrete. Nine reinforced concrete (RC) deep beams were tested in this study to investigate different shear-strengthening techniques including the type of mesh (glass fiber mesh and welded steel wire mesh), number of layers (single and double), and the effects of additional anchor using high-strength bolts on the shear performance of RC deep beams. The results showed the SHCC-mesh jackets increased the ultimate load of the deep beams by up to 82 %, cracking load by up to 73 %, elastic stiffness by up to 457 %, and energy absorption by up to 380 % compared to the unstrengthen control beam. Furthermore, the welded wire mesh provided greater enhancements of strength, stiffness, and energy absorption than the glass fiber mesh. In addition, anchoring the jackets further improved the strengthening efficiency. Advanced nonlinear three-dimensional finite element models were also simulated to capture the structural responses of the RC deep beams strengthened using welded wire mesh and glass fiber mesh. It was found that the numerical models accurately predicted the behavior of the beams upon validation against the experimental results.

The Evaluation and Prediction of Flame Retardancy of Asphalt Mixture Based on PCA-RBF Neural Network Model.

Warm mix flame retardant asphalt mixture can reduce the energy dissipation and harmful gas emissions during asphalt pavement construction, as well as mitigate the adverse effects of road fires. For this, this paper studies the design and performance of a mixture modified with a combination of warm mix agent and flame retardant, and the pavement performance and flame retardancy of the modified mixture are evaluated. Additionally, a flame retardancy prediction model based on the radial basis function (RBF) neural network model is established. On this basis, the principal components analysis (PCA) model is used to analyze the most significant evaluation indicators affecting flame retardancy, and finally, a three-dimensional finite element model is developed to analyze the effects of loading on the pavement structure. The results show that compared to virgin asphalt mixture, the modified mixture shows a reduction in mixing and compaction temperatures by approximately 12 °C. The high-temperature performance of the mixture is improved, while the low-temperature performance and moisture stability slightly decrease, but its flame retardancy is significantly enhanced. The RBF neural network model revealed that the established flame retardancy prediction model has a high accuracy, allowing for precise evaluation of the flame retardancy. Finally, the PCA model identified that the combustion time has a significant effect on the flame retardancy of the asphalt mixture, and the finite element model revealed that the displacements of the warm mix fire retardant asphalt mixture were lower than virgin asphalt mixture in all directions under the loading.

Nonlinear Analysis of Electric Potential in a Piezoelectric Thin Plate as Pressure Sensor

Piezoelectric materials are widely applied in electronic components due to their ability to couple electric and mechanical fields. For the piezoelectric thin plate as a pressure sensor, we extend the modified first-order piezoelectric plate theory to explore the nonlinear solution of electric potential and discuss the relevant regulation mechanisms. Based on the piezoelectric effect, the electric potential generated by deformation is not linear with thickness. A quadratic function of electric potential across thickness is introduced. However, the electric potential on upper and lower electrodes is an unknown constant, which can be determined by the nonlinear complementary equation based on the Gauss theorem. It is shown that the nonlinear results of electric potential are consistent with outcomes by the three-dimensional finite element method. Furthermore, relevant regulation mechanisms are discussed on electric potential, including supported conditions, plate thickness, and load area. In addition, the influence of load locations on the electric potential response is analyzed. It is expected that these findings will be instructive to the structural design of piezoelectric pressure sensors.