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Dynamic response analysis of vehicle–pavement-coupled system based on RIOHTrack full-size accelerated loading test

The interaction between vehicles and asphalt pavements can cause different degrees of damage to the pavement structure. Due to this interaction, deformation of pavement is commonly observed, potentially affecting ride quality and driving safety. Investigating the responses of the vehicle–pavement interaction to different pavement structures is therefore a curial task. To this end, we proposed a vehicle–pavement-coupled dynamic model, based on the accelerated loading test of the Research Institute of Highway MOT Track (RIOHTrack). This model is derived by coupling a heavy-duty truck vibration model and the well-known huge multi-layer rectangular plate model. The heavy-duty truck vibration model which describes a 3D vehicle–pavement dynamics system is constructed according to test conditions. We formulate the coupling based on the variable-order fractional Kelvin foundation and the random dynamic load. In particular, to obtain the random dynamic load, we first analyze the time domain equation of road roughness from the field data set of the RIOHTrack test track and then use the Galerkin method for numerical calculation. Using the proposed model, we simulated 19 types of pavement structures of the RIOHTrack test track, which characterize the primary features of the empirical data set. Furthermore, we discuss the bifurcation consensus of the dynamic response of the front and rear wheels under different loads and analyzes comprehensively the dynamic responses of different pavement structures. The results show that the vehicle–pavement-coupled dynamic response model proposed in this paper has better applicability to simulate deformation for different asphalt pavement structures and better reflects the history-dependent process and memory effect of pavement deformation.

Mountain gazelle optimisation‐based 3DOF‐FOPID‐virtual inertia controller for frequency control of low inertia microgrid

AbstractThe primary objective of the authors is to design a new robust and improved virtual inertia controller (VIC) for renewable energy dominated inverter interfaced low inertia microgrid (LIMG). Increasing penetration of inertia‐less renewable generation in microgrid leads to increased frequency deviation during and after a disturbance. To improve the frequency response of the LIMG, conventional VIC added with different second stage and third stage controllers are proposed in existing works. Higher degree‐of‐freedom (DOF) PID controller synchronised with fractional‐order (FO) operators are used with conventional VIC controllers. These controllers work in addition with conventional VIC and the multi‐stage controllers make the system more complex. To reduce the number of controller stages and, subsequently, reduce cost and complexity of the system, a single stage 3DOF‐FOPID controller is proposed to mitigate the frequency deviation after a disturbance in a LIMG. Performance of the proposed single stage controller is compared with that of the existing controllers to establish the advantages of the proposed controller. The parameters of the proposed 3DOF‐FOPID controller are optimised by Mountain Gazelle Optimsation. The robustness of this controller is also tested for random load fluctuation and renewable power variations in presence of system non‐linearities.

On the inadequacy of rate-dependent models in simulating asymmetric rate-independent hysteretic phenomena

Aim of this paper is to establish the limits of the common approach according to which, in oscillating systems, dissipative phenomena, often having an asymmetric rate-independent nature, are simulated by means of equivalent rate-dependent models relating forces and velocities. To this end we compare the time evolution of the generalized work and energy components of a Single Degree of Freedom (SDoF) hysteretic mechanical system including both conservative and non-conservative forces; in addition the generalized work of the non-conservative forces is related to the generalized internal energy of the system. To achieve such a result, we provide (closed-form) expression(s) to compute the path-dependent work performed by generalized rate-dependent (rate-independent) hysteretic forces, simulated by using the Seleemah and Constantinou (Asymmetric Bilinear) model. For the latter, we also provide a closed-form expression for the variation in internal energy associated with the generalized rate-independent work when a complete cycle of generalized displacement is applied. Such results are exploited to describe the behavior of symmetric, and asymmetric rate-independent hysteretic systems under loads of arbitrary nature, e.g., free vibration, harmonic load, and random load. Finally, the inadequacy of rate-dependent models in simulating asymmetric rate-independent hysteretic behaviors is assessed by showing that calibrating the former model according to the methodology usually suggested in the literature yields inaccurate results in terms of displacement and dissipated energy of the system.

Random vibration of sandwich beam with a shear thickening fluid core

The dynamic performances of a sandwich beam with a shear thickening fluid (STF) core subjected to a random excitation are investigated. First, the STF is prepared and a new constitutive model is proposed based on the oscillatory rheological measurements. Next, a flexural vibration model of the sandwich beam with an STF core under random load is developed, and a parametric study is carried out. It is found that the response frequencies and damping ratios for the first three modes of the beam increase with the standard deviation of the external random excitation. The sandwich beam with STF provides better damping for larger broadband excitation. Additionally, the beam with an STF core will produce a response both inside and outside the load frequency domain. Furthermore, an optimal thickness ratio for the structure that maximizes the damping ratio of the structure is identified. It is important to note that this optimal thickness ratio of the structure varies with the order of vibration modes. This research provides valuable insights into the design of structures using STF and also contributes to the development of dynamic constitutive models for STF.

Fatigue reliability analysis for suspenders of a long-span suspension bridge considering random traffic load and corrosion

For suspension bridges, suspenders are critical load transferring components that connect girder to main cable, the safety of the suspenders conduces to maintain the structural integrity of the bridge. The cyclic stress and corrosion environment are the main reasons for the failure of suspenders. To evaluate the fatigue status of suspenders under the combined action of traffic load and corrosion, this paper presented a time-variant fatigue reliability analysis framework based on in-site measured traffic data and corrosive deterioration model for suspenders. First, the refined vehicle parameter models are established by statistical analysis. An elaborate random traffic flow model that involves car-following theory and Monte-Carlo method is developed. Then, a practical FEM-based method is used to simulate vehicle induced response time history. The fatigue loading effects, namely equivalent stress range and corresponding cyclic number are subsequently obtained. Finally, the time-variant fatigue reliability for suspenders considering corrosion and traffic growth is evaluated. A case study was performed for suspenders of an in-service sea-crossing suspension bridge in China. The results indicate that corrosion and growing traffic density would greatly shorten the service life of suspenders of a suspension bridge, among which corrosion has the most significant influence. Fatigue reliability index of the shortest critical suspender at 1/2 mid-span of the case bridge would lower than target value at the 18th service year in the most serious marine corrosion environment, which resulted in references for suspender maintenance and replacement.

A Unit-Load Approach for Reliability-Based Design Optimization of Linear Structures under Random Loads and Boundary Conditions

The low order Taylor’s series expansion was employed in this study to estimate the reliability indices of the failure criteria for reliability-based design optimization of a linear static structure subjected to random loads and boundary conditions. By taking the advantage of the linear superposition principle, only a few analyses of the structure subjected to unit-loads are needed through the entire optimization process to produce acceptable results. Two structural examples are presented in this study to illustrate the effectiveness of the proposed approach for reliability-based design optimization: one deals with a truss structure subjected to random multiple point constraints, and the other conducts shape design optimization of a plane stress problem subjected to random point loads. Both examples were formulated and solved by the finite element method. The first example used the penalty method to reformulate the multiple point constraints as external loads, while the second example introduced an approach to propagate the uncertainty linearly from the nodal displacement vector to the nodal von Mises stress vector. The final designs obtained from the reliability-based design optimization were validated through Monte Carlo simulation. This validation process was completed with only four unit-load analyses for the first example and two for the second example.

Fatigue strength analysis of semi-submersible platforms based on wide-band stress

As the focus of ocean resource exploitation shifts from shallow sea to ultra-deep sea, semi-submersible platforms are far away from the coastline for a long time. The semi-submersible platform structure is more prone to fatigue damage under complex sea conditions. The stress range and peaks are considered in the conventional frequency domain spectral method to obey the narrow-band distribution, which makes the results of fatigue assessment tend to be conservative. To solve the problems above, a wide-band fatigue assessment method based on Rice distribution is proposed from the perspective of stress distribution. Different methods are used to solve the error functions involved in fatigue calculations to obtain different approximate equivalent stress models. Finally, the broadband fatigue analysis of a semi-submersible platform in the South China Sea was carried out under different models, and the results showed that: The error of the wide-band fatigue calculation based on Rice distribution is related to the selected equivalent stress model, and a suitable model needs to be selected according to the bandwidth coefficient of the structure. The results obtained provide a reference for the safety assessment of pipelines in service. The research provides a reference for the fatigue assessment of semi-submersible platforms under random broadband loads.

Analysis of dynamic response of three-span bridge using vehicle load data from Road Administration Department IV in Vietnam

In many studies, the dynamic response of bridges is influenced by various factors. Multiple factors, such as vehicle loads, road roughness, vehicle-bridge interactions, and travel speed, impact the dynamics of a three-span bridge on highways. Because the mass of the vehicle, including the cargo, fluctuates randomly, a probabilistic methodology based on the Monte Carlo method is utilized to produce random anomalies for dynamic analysis. To examine the Song Gieng bridge, data from the Road Administration Department IV on heavy vehicle loads and overloaded vehicles are utilized to produce random vehicle loads. The analytical results indicate that there is a discrepancy in the probability distribution rules between the vehicle load (input random variable) and the dynamic impact factor (output random variable). This implies that their mapping connection is not monotone. Compared with the threshold values specified in the bridge design standards of Vietnam and the United States, the dynamic impact factor obtained in this study is significantly different. These findings can provide additional guidance for practicing engineers.

Multi-objective topology optimization design of truss structures based on evidence theory under limited information

Uncertainty information is often limited and has great discreteness, how to ensure the structure having good robustness under epistemic uncertainty becomes a technical problem for multi-objective topology optimization design. In this paper, the evidence theory is used to quantify the epistemic uncertainty; the plausibility measurement expressing upper limit of failure probability is applied to be a new evaluation of reliability. The total weight and the reliability of structures are taken as the optimization objectives, and a multi-objective robust topology optimization design model based on evidence theory is proposed. Parallelization technique based differential evolution for multi-objective optimization (DEMO) is preferable to search above robust Pareto front due to its merits of non-requirement of any gradient and superior mechanisms of non-dominate strategy. In order to verify the effectiveness of the proposed method, the multi-objective reliability optimization of a wood truss structure is implemented with considering elastic modulus and structural load as uncertain variables. According to the optimization results, six same truss specimens are made for the static random loading test. The failure probability of the truss structure is judged by the stress and node displacement obtained from the test, so as to verify the feasibility of the reliability optimization method based on evidence theory. The experimental results also indicate that the proposed method can avoid the deviation of the optimization results caused by the fluctuation of epistemic uncertainty, and provide a new method for designers to make the optimization results robust even when the data information is insufficient and the cognitive level is limited.

Experimental study on the energy dissipation and seismic behavior of RC columns due to repeated earthquakes including vertical excitation

The main innovation of this study is to carry out an experimental work focusing on the effects of seismic sequences on RC columns including vertical component of ground motions. The experimental behavior of RC columns under both standard cyclic loading and random earthquake loading is considered. To this purpose, standard cyclic lateral loading history under constant axial loading, standard cyclic lateral loading history under varying axial loading and random lateral and axial loading history to represent random earthquake loading are applied to test columns. Moreover, for random earthquake loading, not only horizontal component of ground motion excitation but also the vertical component is considered. The effect of repeating earthquake excitation on structural response is also investigated through two and three repetitive earthquakes. The effects of six different loading histories on displacement capacity, residual displacement at the end of test, maximum residual displacement measured during test, damage states and dissipated energy capacities are examined comparatively in the test program. It is found that, loading history especially variability in axial loading, plays a very important role on the response of columns.

Assessment of Power System Resiliency with New Intelligent Controller and Energy Storage Systems

This research investigates the role of various energy storage systems (ESS) in improving the power system resiliency. Different ESS configurations are analyzed individually and in combination to assess their impact on system performance. Additionally, a fuzzy-based controller (PIλDN + FFOPI) is proposed as a secondary controller for load frequency control, with control parameters optimized using an improved Volleyball Premier League algorithm (IVPL). This algorithm leverages the powerful synergy of opposition-based learning and the versatility of the VPL algorithm, resulting in a highly effective and innovative approach. To validate the proposed approach, the modified Kundur’s 2-area test system under deregulation is first utilized, and its effectiveness is confirmed through testing with both step and random load disturbances. Sensitivity analysis is conducted to evaluate system performance across a wide range of parameter variations. Furthermore, the modified IEEE 39 bus system is utilized to assess compatibility and scalability. Results demonstrate the effectiveness of combined ESS configurations and the fuzzy-based controller in enhancing system stability and reliability. This research contributes to power system engineering by offering insights into the benefits of energy storage systems for dynamic response enhancement. The proposed fuzzy-based control strategy, tuned by the IVPL algorithm, presents a promising approach for improving power system performance and stability.

Impact of a Redox Flow Battery on the Frequency Stability of a Five-Area System Integrated with Renewable Sources

Energy storage devices are imperative to damp out the oscillations caused by sudden magnified disturbances occurring in a power system. The presence of a small rating of storage device in each area can alleviate the system oscillations effectively. Therefore, in this work, redox flow batteries (RFBs) have been integrated in each area of a five-area interconnected system for effective load frequency control (LFC). The RFB pumps up the active power into the system quickly to meet the short-time overload; in turn, the efficacy of the LFC in the system is boosted. Despite the presence of the RFB in the power system, a secondary controller is necessary to quench the deviation of frequency and tie-line power caused by the power mismatch between demand and generation. In this perspective, a cascade controller incorporated with a fractional operator (FO) has been endorsed and designed through a nascent selfish herd optimizer technique to evaluate the transient response of the system. Besides this, the unprecedented performance of fractional-order cascade controllers has been compared with one-stage classical controllers with and without a fractional operator. Further, the robustness of the proposed controller has been inspected through subjecting it to a random load in the presence/absence of an RFB and parametric variation. Finally, the proposed model has been simulated in the OPAL-RT-4510 platform to validate the performance of the proposed controller that has produced in the MATLAB environment.

Digital twin-driven fatigue life prediction framework of mechanical structures using a power density theory: Application to off-road vehicle front axle housing

Accurate fatigue life prediction is beneficial for fatigue maintenance of complex mechanical structures of off-road vehicles. For fatigue life prediction of mechanical structures subjected to non-stationary random loads during operation, this paper proposes a digital twin-driven fatigue life prediction method for mechanical structures. The core consists of improved fatigue theory, stress online measurement, and fatigue damage verification. In this study, a digital twin (DT) prediction framework containing multiple correction factors is established, in which the actual stress values in the physical world and the stress predictions of the estimated twin model can be obtained in real time. The remaining strength degradation of the structure and material can be compared to correct the prediction accuracy of fatigue analysis. In addition, based on the power density theory, combined with the short-time Fourier transform, a fatigue life analysis method that can comprehensively calculate the effect of load amplitude and frequency on fatigue is proposed. A test case has been demonstrated using a front axle housing of the off-road vehicle. The difference between the results predicted by the method in this paper and the actual fatigue results in failure time is only 2.65 h, with a relative error of only 3.95 %. In terms of failure location, the relative error is only 3.15 %.

Battery safety issue detection in real-world electric vehicles by integrated modeling and voltage abnormality

Detecting battery safety issues is essential to ensure safe and reliable operation of electric vehicles (EVs). This paper proposes an enabling battery safety issue detection method for real-world EVs through integrated battery modeling and voltage abnormality detection. Firstly, a battery voltage abnormality degree that is adaptive to different battery types and working conditions is defined. Then an integrated battery model is developed by combining an electrochemical model, an equivalent circuit model (ECM), and a data-driven model to evaluate the normal voltage. To ensure normality of input current, a current processing model is presented. The performance of the proposed scheme is examined under random loading profiles using operating data collected from real-world EVs. The results show that the integrated battery model can precisely predict normal battery terminal voltage, with mean-squared-errors of 1.034e−4 V2, 7.221e−5 V2, and 4.612e−5 V2 for driving, quick charging, and slow charging, respectively. The accuracy in classifying faulty and normal batteries is verified based on the operating data collected from 20 EVs.

Investigating the etiology of non-carious cervical lesions: Novel µCT analysis

ObjectivesThe etiology of non-carious cervical lesions (NCCLs) is not fully understood, limiting treatment and prevention. Our aim was to evaluate the effect of mechanical loading and acid exposure on the cervical tooth region using a random spectrum loading model that simulates the nature of oral mastication. MethodsThirty extracted human premolars were divided into three experimental groups: 1) unloaded teeth immersed in acid (erosion group: Er), 2) loaded teeth immersed in acid (erosion with spectrum loading group: Er-SL), and 3) loaded teeth immersed in distilled water (spectrum loading group: SL). Random spectrum loading with loads ranging from 100 to 500 N was performed. All teeth were scanned using micro-CT. A novel 3D analysis was developed to evaluate the circumferential cervical tissue loss and regions under tension and compression. For parametric and non-parametric comparisons, one-way ANOVA with Tukey post-hoc tests and Kruskal-Wallis with Bonferroni post-hoc tests were used. ResultsA significant difference was observed in the circumferential volumetric loss, with the Er-SL exhibiting the greatest volume loss (p < 0.001). Moreover, in the loaded groups (Er-SL and SL), regions subjected to tension showed significantly greater loss (p < 0.001, p = 0.007) compared with regions subjected to compression. ConclusionsThe novel high-resolution micro-CT analysis provided new insights into the etiology of NCCLs. The results suggested that the cumulative effect of mechanical loading and acid exposure may play a major role in NCCL formation. Clinical significanceThis study investigates the etiology of NCCLs by examining the combined effects of occlusal loads and acid exposure on cervical tissue loss. Understanding the pathogenesis of NCCLs paves the way for the development of improved preventative measures and treatment strategies to prevent tooth structure degradation.

Dynamic Response of a Long-Span Double-Deck Suspension Bridge and Its Vibration Reduction

This paper presents a dynamic analysis of a long-span double-deck suspension bridge subjected to random traffic loading using a Finite Element (FE) model. During this study, the influence of various traffic parameters, such as vehicle speed, traffic volume, traffic weight, and the location of the passing girder, on the longitudinal movement of the girders was investigated. The results reveal that schemes with double girders passing can lead to greater longitudinal displacement of the girder as compared to a long-span bridge with a single passing girder. However, the incorporation of fluid-viscous dampers at the ends of the girders significantly reduces the displacement range of each node. For instance, at the left end of the bridge, the original model (without dampers) exhibits a displacement range of approximately 0.01–0.056 m, whereas the constrained model (with dampers) shows a range of 0.025–0.033 m. A quantitative analysis demonstrates that higher damping coefficients (or smaller damping exponents) can further mitigate the girder’s movement.

Characterizing fatigue damage behaviors of concrete beam specimens in varying amplitude load

In this paper, the random and nonlinear mechanical characteristics of the composition distribution of concrete in each phase are investigated to solve the difficulty of fatigue damage test of concrete beam specimens under variable amplitude loading. A three-dimensional (3D) concrete composite random aggregate meso-model of concrete beam specimens is built with Digimat as a composite modeling tool. Subsequently, the bending-tensile strength and fatigue life of the model under four-point bending loading is analyzed and calculated using Abaqus finite element analysis model based on the concrete elastic-plastic damage criterion. The mechanical behaviors of concrete materials under static load failure, multistage fatigue loading, and random fatigue loading are studied. Finally, compared with the test results, the following conclusions are obtained. The random aggregate model and elastoplastic damage mechanics model of concrete composite constructed by concrete in Abaqus and Digimat can better describe the geometric and distribution characteristics of composite structure and aggregate in concrete beams and the mechanical behavior of fatigue and static load failure. The difference is 4.08 % with the experimental results, which verifies the validity and reliability of the numerical simulation model, and the fatigue life of concrete beams under random loading Sra and Srb is 1622 and 164 times, respectively. The research results have certain guiding significance and reference value for accurate calculation of bending and tensile strength of concrete beams under specified raw material and mix ratio and prediction of fatigue damage cracking in airport cement concrete pavement structure.

Uniaxial ratcheting behavior and microstructure evolution of 316H stainless steel under the random cyclic loads

In this study, the Computational Fluid Dynamics (CFD)-Finite Element Method (CFD-FEM) were used to simulate the transient stress response of the structure surface under thermal striping environment, and a uniaxial random cyclic loading (RCL) method was used to reveal the mechanical properties and initial microstructure evolution of 316H austenitic stainless steel (SS) under random stress induced by thermal striping. The experimental results showed that 316H exhibited a lower saturation ratcheting strain rate at 334.44 MPa, along with stronger cyclic hardening effects and resistance to plastic accumulation at loading rate of 100 Hz. Random loading tests with different cycles were performed at σpeak=334.44MPa and fRCL=100Hz, and ratcheted specimens were characterized to investigate the effect of the micro-mechanism on cyclic softening/hardening. The geometrically necessary dislocation (GND) density increases and then decreases with cyclic loading, which is mainly attributed to the deformation twin (DT) and multi-dislocation slip mechanisms. The deformation mechanism during the ratcheting cycle from 1000 to 3000 cycles is mainly dominated by the twinning reduction, where the dislocation migration accelerated the transformation from dislocation walls to subgrain boundaries; the twinning increase dominates from 3000 to 9000 cycles, where the subgrain boundary grew into boundaries with high angle misorientations.

Multi-type dynamic load identification algorithm in continuous system: A numerical and experimental study based on SSM-Newmark-β

Dynamic load identification based on structural responses is an important problem in the field of engineering and plays an important role in the condition assessment of mechanical structures. Current popular load identification methods such as the state-space method (SSM) and the Green's kernel function method (GKFM) are implemented on discrete systems with outstanding performance, but when dealing with complex continuous systems, there are some limitations such as low efficiency and inaccuracy. In this paper, a continuous system load identification algorithm based on SSM and Newmark-β is proposed for the first time. Using modal coordinate transformation and modal truncation methods, the number of infinite vibration differential equations of a continuous system in physical space are converted to a finite number of vibration differential equations in modal space, where the modal truncation order and the optimal layout of the sensors are combined by modal strain energy. The Newmark-β method in modal space is derived and thus combined with SSM to obtain a load identification model Y=HF called SSM-Newmark-β method, which reduces the size of the transfer matrix H. The solution time of the proposed algorithm is 0.38 s for continuous systems, which is rather shorter than that for discrete systems. Furthermore, the simulations show that it has better accuracy and noise immunity than SSM and GKFM in the identification of sinusoidal load, impact load, and random load. The effect of time step is also discussed which reveals that the larger time step has less effect on the proposed algorithm. An experimental study is carried out on a cantilever beam system. The result verifies that the SSM-Newmark-β algorithm has better accuracy in load identification for the continuous system. This research provides a new sight for the real-time identification of dynamic loads for complex structures.

Longitudinal displacement control of a long-span suspension bridge under random traffic loads using a polyimide friction damper

This paper proposes a novel method to control the cumulative displacement of the girder end of a long-span suspension bridge caused by traffic loads using friction dampers. Friction dampers have Coulomb damping characteristics and high initial stiffness, providing a significant damping force at low speed to suppress the longitudinal deformation of the girder end. The working mechanism of the friction damper is explained, and the performance of the proposed polyimide (PI) friction damper is tested. A random traffic load model of a long-span suspension bridge is established, and the longitudinal displacement, reaction force time history, longitudinal peak displacement, and cumulative longitudinal displacement (CLD) under different yield forces of the PI friction damper are analyzed. We propose the excess ratio δ of the yield displacement to determine the optimum yield force. The influences of different vehicle speeds and traffic flows on the performance of the PI friction damper are discussed. The results show that the PI friction damper substantially reduces the longitudinal displacement, longitudinal peak displacement, and CLD of the girder end; the reduction rate of the CLD exceeds 57% when the yield force of the PI friction damper is 1000 kN. The vehicle speed and traffic flow have negligible influences on the CLD of the long-span suspension bridges equipped with PI friction dampers in the normal working range.