Dynamic thermo-mechanical responses of road-soft ground system under vehicle load and daily temperature variation

A complete road-soft ground model is established in this paper to study the dynamic responses caused by vehicle loads and/or daily temperature variation.A dynamic thermo-elastic model is applied to capturing the behavior of the rigid pavement,the base course,and the subgrade,while the soft ground is characterized using a dynamic thermo-poroelastic model.Solutions to the road-soft ground system are derived in the Laplace-Hankel transform domain.The time domain solutions are obtained using an integration approach.The temperature,thermal stress,pore water pressure,and displacement responses caused by the vehicle load and the daily temperature variation are presented.Results show that obvious temperature change mainly exists within 0.3 m of the road when subjected to the daily temperature variation,whereas the stress responses can still be found in deeper places because of the thermal swelling/shrinkage deformation within the upper road structures.Moreover,it is important to consider the coupling effects of the vehicle load and the daily temperature variation when calculating the dynamic responses inside the road-soft ground system.

Quantification of the Vertical Load Applied to the Pavement during Cornering Maneuver of a Battery Electric Commercial Vehicle

The wheel loads of heavy trucks are the major source of pavement damage,given the repeated loadings imposed by them due to transient events and surface irregularities.While related studies focus on steady-state context regarding simplified vehicle’s parameters and ideal pavement conditions,this paper aims to analyze the vertical load applied to the pavement by considering cornering maneuver as a transient event,on a battery electric vehicle truck.In this concern,measurements were performed on a rigid truck,with two steering front axles,in a closed course proving ground.The relationship has been presented between vehicle’s speed,lateral acceleration and transferred vertical load for a given curve radius of 85.6 m and 3.7°of transversal slope.The measurements results indicated that for every 10 km/h increasing on the vehicle’s speed,additional 110 kgf will be transferred to the pavement on the outer side of the cornering radius.This value itself could not be considered high,but it will be also added to the static load,or overload in some truck applications.

Vehicle Routing Problem with Non-Full Loadof Less Freight Quantity

Freight quantity is usually less than the half of vehicle capacity,and the effectiveness of transportation utilizing a single vehicle is not satisfactory enough. In this paper,a sequential heuristic algorithm is presented, whichconsists of clustering and chaining. Lastly, the method is applied to a casestudy.

Electric Vehicle Charging Capacity of Distribution Network Considering Conventional Load Composition

At present,the large-scale access to electric vehicles(EVs)is exerting considerable pressure on the distribution network.Hence,it is particularly important to analyze the capacity of the distribution network to accommodate EVs.To this end,we propose a method for analyzing the EV capacity of the distribution network by considering the composition of the conventional load.First,the analysis and pretreatment methods for the distribution network architecture and conventional load are proposed.Second,the charging behavior of an EVis simulated by combining the Monte Carlo method and the trip chain theory.After obtaining the temporal and spatial distribution of the EV charging load,themethod of distribution according to the proportion of the same type of conventional load among the nodes is adopted to integrate the EV charging load with the conventional load of the distribution network.By adjusting the EV ownership,the EV capacity in the distribution network is analyzed and solved on the basis of the following indices:node voltage,branch current,and transformer capacity.Finally,by considering the 10-kV distribution network in some areas of an actual city as an example,we show that the proposed analysis method can obtain a more reasonable number of EVs to be accommodated in the distribution network.

A Novel Ultra Short-Term Load Forecasting Method for Regional Electric Vehicle Charging Load Using Charging Pile Usage Degree

Electric vehicle(EV)charging load is greatly affected by many traffic factors,such as road congestion.Accurate ultra short-term load forecasting(STLF)results for regional EV charging load are important to the scheduling plan of regional charging load,which can be derived to realize the optimal vehicle to grid benefit.In this paper,a regional-level EV ultra STLF method is proposed and discussed.The usage degree of all charging piles is firstly defined by us based on the usage frequency of charging piles,and then constructed by our collected EV charging transactiondata in thefield.Secondly,these usagedegrees are combinedwithhistorical charging loadvalues toform the inputmatrix for the deep learning based load predictionmodel.Finally,long short-termmemory(LSTM)neural network is used to construct EV charging load forecastingmodel,which is trained by the formed inputmatrix.The comparison experiment proves that the proposed method in this paper has higher prediction accuracy compared with traditionalmethods.In addition,load characteristic index for the fluctuation of adjacent day load and adjacent week load are proposed by us,and these fluctuation factors are used to assess the prediction accuracy of the EV charging load,together with the mean absolute percentage error(MAPE).

Flight Loads and Dynamics of Flexible Air Vehicles

Based on the equations of motion of flexible air vehicles includingrigid-body modes and elastic structural modes, and applying influence coefficients of linearaerodynamics, a set of equations are derived and a method is presented for analysis of flight loadsand dynamic characteristics. The problems in the fields of flight mechanics and aeroelasticity suchas static aeroelastic divergence, trim and deformation, aerodynamic loads distribution, flutter andflight dynamics can be solved by the procedure. An airplane with high aspect ratio wings isanalyzed, and the results show that the coupling between rigid -body modes and elastic modes isdistinct and should not be overlooked.

Dynamic reliability analysis of supercavity vehicle with stochastic parameters under impact loads

With dynamic reliability problems of stochastic parameters,supercavity vehicle is subject to impact loads.The supercavity vehicle is modeled by using eight-node super-parametric shell elements.The tail impact loads of supercavity vehicle structures are simplified into two stationary random processes with a certain phase difference,and the random excitations are transformed into sinusoidal ones in terms of the pseudo excitation method.The stress response of stochastic structure can be obtained through combining Newmark method with pseudo excitation perturbation method,and then all required digital features for dynamic reliability of supercavity vehicle have be calculated.The expressions of the mean value and the variance of dynamic reliability of supercavity vehicle with stochastic parameters are educed on the basis of the Poisson formula of calculating dynamic reliability.Finally,the influence of the randomness of structural parameters on the dynamic reliability is analyzed.And the feasibility and availability of this method were validated by comparing with the Monte Carlo method.

Test and numerical investigations on static and dynamic characteristics of extra-wide concrete self-anchored suspension bridge under vehicle loads

The present work is aimed at studying the mechanic properties of the extra-wide concrete self-anchored suspension bridge under static and dynamic vehicle loads. Based on the field test using 12 heavy trucks and finite element simulations, the static deformations of different components, stress increments and distributions of the girder, as well as the vibration characteristics and damping ratio of the Hunan Road Bridge were analyzed, which is the widest self-anchored suspension bridge in China at present. The dynamic responses were calculated using the Newmark-β integration method assisted by the simulation models of bridge and vehicles, the influences on the dynamic impact coefficient(DIC) brought by the vehicle parameters, girder width, eccentricity travel and deck flatness were also researched. The spatial effect of the girder is obvious due to the extra width, which performs as the stress increments distribute unevenly along the transverse direction, and the girder deflections and stress increments of the upper plate change as a "V" and "M" shape respectively under the symmetrical vehicle loads affected by the shear lag effect, cross slope and local effect of the wheels, the maximum of stress increments are located in the junctions with the inner webs. The obvious girder torsional deformation and the apparent unevenness of the hanger forces between the two cable planes under the eccentric vehicle loads, together with the mode shapes such as the girder transverse bending and torsion which appear relatively earlier, all reflect the weakened torsional rigidity of the extra-wide girder. The transverse displacements of towers are more obvious than the longitudinal ones. As for the influences on the DIC, the static effect of the heavier vehicles plays a major role when pass through with a higher speed and the changes of vehicle suspension stiffness generate greater impacts than the suspension damp. The values of DIC in the vehicle-running side during the eccentric travel, affected by the restricts from the static effects of the eccentric moving trucks, are significantly smaller than the vehicle-free side, the increase in the road roughness is the most sensitive one among the above influential factors. The results could provide references for the design, static and dynamic response analysis of the similar extra-wide suspension bridges.

Anti-slip security assessment between main cable and saddle of the middle pylon under extreme vehicle loads

The traffic condition of Taizhou Yangtze River Bridge is obtained to a certain extent, according to the traffic investigation nearby Taizhou Bridge. The statistical characteristics of the traffic conditions are acquired by statistical analysis. Simulation of the extreme vehicle loads and the sensitive analysis of load parameters are carried out based on these data complemented, which would guide the determination of the frictional coefficient between the main cables and the saddle.

Power Quality Issues Concerning Photovoltaic Generation and Electrical Vehicle Loads in Distribution Grids

The high utilization level of renewable generation including residential photovoltaic (PV) systems together with the uncontrolled charging of electric vehicles (EVs) can have a significant impact on load characteristics in distribution networks. Harmonic content of PV generation, EV charging loads, and their influence on power quality indicators in residential distribution networks are discussed in this paper. For investigating likely power quality scenarios, PV generation and EV charging measurement results including current harmonic amplitude and phase angle values are used and compared with present load characteristics. Different modelling scenarios are analysed and a simplified model of harmonics in PVs and EVs is offered. The results of the study show moderate additional harmonic distortion in residential load current and voltage distortion at the substation’s busbar when PV generation and EV loading are added. The scenarios presented in this paper can be further used for modelling the actual harmonic loads of the PVs and EVs in distribution networks.

Cost Impact of Increasing Heavy Vehicle Loads on Bridges

This study aimed to investigate the cost impact of meeting the increase in freight demand by doubling the truck weight （AS 1 ）, doubling the traffic volume （AS2）, or legalizing a new-proposed-truck of 97-kip weight instead of the currently legal 80-kip truck （AS3）. The State of Michigan＇s average daily traffic database of year 2001 has been used as a case study. The study was applied only on the very common US Bridge with RC （reinforced concrete） deck over steel girder. Sampling criteria also includes the age of the bridges. The study covered the four-cost-impact categories provided by the NCHRP （National Cooperative Research Program）. The current truck weight and double traffic volume （AS2） show the best scenario to meet the increase in freight demand. However, doubling the truck weight with the current traffic volume （AS 1） was the worst scenario. The use of the proposed 97-kip truck with the current traffic volume （AS3） compromises both, meeting the increase in freight demand and the cost impact.

Critical load position for cavities beneath CRCP slab under vehicle loading

In order to study the critical load position that causes cavities beneath the continuously reinforced concrete pavement（ CRCP） slab under vehicle loading, the elliptical load is translated into the square load based on the equivalence principle.The CRCP slab is analyzed to determine the cavity position beneath the slab under vehicle loading. The influences of cavity size on the CRCP slab＇s stress and vertical displacement are investigated. The study results showthat the formation of the cavity is unavoidable under traffic loading, and the cavity is located at the edge of the longitudinal crack and the slab corner.The cavity size exerts an obvious influence on the largest horizontal tensile stress and vertical displacement. The slab corner is the critical load position of the CRCP slab. The results can be used to assist the design of CRCP in avoiding cavities beneath slabs subject to vehicle loading.

Deflection and stress of hollow CRCP slab under concentrated vehicle load

Based on the equivalence principle of deflection and stress, the concentrated vehicle load which acts on the center of continuously reinforced concrete pavement （CRCP） is translated into the equivalent half-wave sine load by the Fourier transform. On the basis of this transform and the small deflection theory of elastic thin plates, the deflection and stress formulae of CRCP under the concentrated vehicle load with a hollow foundation are put forward. The sensitivity of parameters is analyzed. The results show that maximum deflection is directly proportional to the concentrated vehicle load and the slab width, and inversely proportional to the lateral bending stiffness and slab thickness. The effects of slab width and thickness are significant with regard to maximum deflection. Maximum stress is directly proportional to the concentrated vehicle load and the slab width as well as inversely proportional to slab thickness. The effect of slab thickness is significant with regard to maximum stress. According to the calculation results, the most effective measure to reduce maximum deflection and stress is to increase slab thickness.

Reflective cracking viscoelastic response of asphalt concrete under dynamic vehicle loading

In order to investigate the mechanical response of reflective cracking in asphalt concrete pavement under dynamic vehicle loading, a finite element model is established in ABAQUS. The viscoelastic behavior is described by a prony series which is calculated through nonlinear fitting to the creep test data obtained in the laboratory. Based on the viscoelastic theory, the time-temperature equivalence principle, fracture mechanics and the dynamic finite element method, both the Jintegral and the mix-mode stress intensity factor are utilized as fracture evaluation parameters, and a half-sine dynamic loading is used to simulate the vehicle loading. Finally, the mechanical response of the pavement reflective cracking is analyzed under different vehicle speeds, different environmental conditions and various damping factors. The results indicate that increasing either the vehicle speed or the structure damping factor decreases the maximum values of fracture parameters, while the structure temperature has little effect on the fracture parameters. Due to the fact that the vehicle speed can be enhanced by improving the road traffic conditions, and the pavement damping factor can become greater by modifying the components of materials, the development of reflective cracking can be delayed and the asphalt pavement service life can be effectively extended through both of these ways.

Investigation on nonlinear rolling dynamics of amphibious vehicle under wind and wave load

Nonlinear amphibious vehicle rolling under regular waves and wind load is analyzed by a single degree of freedom system.Considering nonlinear damping and restoring moments,a nonlinear rolling dynamical equation of amphibious vehicle is established.The Hamiltonian function of the nonlinear rolling dynamical equation of amphibious vehicle indicate when subjected to joint action of periodic wave excitation and crosswind,the nonlinear rolling system degenerates into being asymmetric.The threshold value of excited moment of wave and wind is analyzed by the Melnikov method.Finally,the nonlinear rolling motion response and phase portrait were simulated by four order Runge-Kutta method at different excited moment parameters.

A Novel Load Balancing Strategy of Software-Defined Cloud/Fog Networking in the Internet of Vehicles

The Internet of Vehicles(IoV)has been widely researched in recent years,and cloud computing has been one of the key technologies in the IoV.Although cloud computing provides high performance compute,storage and networking services,the IoV still suffers with high processing latency,less mobility support and location awareness.In this paper,we integrate fog computing and software defined networking(SDN) to address those problems.Fog computing extends computing and storing to the edge of the network,which could decrease latency remarkably in addition to enable mobility support and location awareness.Meanwhile,SDN provides flexible centralized control and global knowledge to the network.In order to apply the software defined cloud/fog networking(SDCFN) architecture in the IoV effectively,we propose a novel SDN-based modified constrained optimization particle swarm optimization(MPSO-CO) algorithm which uses the reverse of the flight of mutation particles and linear decrease inertia weight to enhance the performance of constrained optimization particle swarm optimization(PSO-CO).The simulation results indicate that the SDN-based MPSO-CO algorithm could effectively decrease the latency and improve the quality of service(QoS) in the SDCFN architecture.

Analysis of permanent deformations of railway embankments under repeated vehicle loadings in permafrost regions

By large-scale dynamic tests carried out on a traditional sand-gravel embankment at the Beilu River section along the Qinghai-Tibet Railroad, we collected the acceleration waveforms close to the railway tracks when trains passed. The dynamic train loading was converted into an equivalent creep stress, using an equivalent static force method. Also, the creep equation of frozen soil was introduced according to the results of frozen soil rheological triaxial tests. A coupled creep model based on a time-hardening power function rule and the Druker-Prager yield and failure criterion was estab- lished to analyze the creep effects of a plain fill embankment under repeated train loads. The temperature field of the embankment in the permafrost area was set at the current geothermal conditions. As a result, the permanent deformation of the embankment under train loading was obtained, and the permanent deformation under the train loads to the total embankment deformation was also analyzed.

Method for secondary spring load equalization of railway vehicles with two-stage spring suspension: Modeling and optimal regulation

To ensure running safety,the secondary spring loads of railway vehicles must be well equalized.Due to the coupling interactive effects of these hyper static suspended structures,the equalization adjustment through shimming procedure is quite complex.Therefore,an effective and reliable method in application is developed in this paper.Firstly,the best regulation of spring load is solved based on a mechanical model of the secondary suspension system,providing a target for actual adjustment.To reveal the relationship between secondary spring load distribution and shim quantity sequence,a forecasting model is constructed and then modified experimentally with consideration of car body’s elastic deformation.Further,a gradient-based algorithm with a momentum operation is proposed for the load optimization.Effectiveness of the whole method has been verified on a test rig.It is experimentally confirmed that this research provides an important basis for achieving an optimal regulation of spring load distribution for multiple types of railway vehicles.

Finite Element Modeling and Parametric Analysis of Pavement Dynamic Responses under Moving Vehicle Load

This paper intends to develop finite element models that can simulate vehicle load moving on pavement system and reflect the pavement response of vehicle and pavement interaction.We conduct parametric analysis considering the influences of asphalt concrete layer modulus and thickness,base layer modulus and thickness,and subgrade modulus on pavement surface displacement,frequency,and strain response.The analysis findings are fruitful.Both the displacement basin width and maximum value of dynamic surface displacements are larger than those of static surface displacements.The frequency is positively correlated with the pavement structure moduli,and negatively correlated with the pavement structure thicknesses.The shape of dynamic and static tensile strain is similar along the depth of the pavement structure.The maximum value of dynamic tensile strain is larger than that of static tensile strain.The frequency of entire pavement structure holds more significant influence than the surface displacement and strain do.The subgrade modulus has a significant effect on surface displacement,frequency and strain.