Finite Element Analysis on a Square Canister Piezoelectric Energy Harvester in Asphalt Pavement

A novel square canister piezoelectric energy harvester was proposed for harvesting energy from asphalt pavement. The square of the harvester was of great advantage to compose the harvester array for harvesting energy from the asphalt pavement in a large scale. The open circuit voltage of the harvester was obtained by the piezoelectric constant d33 of the piezoelectric ceramic. The harvester is different from the cymbal harvester which works by the piezoelectric constant d31. The finite element model of the single harvester was constructed. The open circuit voltage increased with increase of the outer load. The finite element model of the single harvester buried in the asphalt pavement was built. The open circuit voltage, the deformation difference percent and the stress of the ceramic of the harvester were obtained with different buried depth. The open circuit voltage decreased when the buried depth was increased. The proper buried depth of the harvester should be selected as 30 - 50 mm. The effects of structure parameters on the open circuit voltage were gotten. The output voltage about 64.442 V could be obtained from a single harvester buried under 40 mm pavement at the vehicle load of 0.7 MPa. 0.047 mJ electric energy could be gotten in the harvester. The output power was about 0.705 mW at 15 Hz vehicle load frequency.

Rutting Resistance of Asphalt Pavement Mixes by Finite Element Modelling and Optimisation

Asphalt pavement rtting is a major safety concem and is one of the main distress modes of asphalt pavement.Research into asphalt pavement mixes that provide strong resistance for nutting is considered of great significance as it can help provide extended pavement life and significant cost savings in pavement maintenance and rehabilitation.The objectives of this study are to develop numernical models to investigate the ntting of asphalt concrete pavements and to find optimal design of asphalt pave-ment mix for nutting resistance.Three-dimensional Finite Element mod-els were first developed to simulate both the axial compression and wheel track testing in which a visco elastic-plastic material model was used to predict the ntting of the asphalt concrete pavements.A strain hardening creep model with the material parameters developed from experimental testing was employed to model the time-dependent characteristics of the asphalt concrete pavements.The results were validated against the pre-vious experimental wheel track test results of different pavement mixes.Finally,optimisation techniques using the Design Of Experiments method were applied to the simulation rutting results by varying creep parameters to identify their effects on rutting resistance in order to obtain an optimal asphalt pavements mixes.The results of this paper clearly demonstrate an efficient and effective experimental-numerical method and tool set towards optimal design for asphalt concrete pavements for rutting resis-tance.

Mechanical Properties of Asphalt Pavement Structure in Highway Tunnel

A linear full 3D finite element method (FEM) was performed in order to present the key design parameters of highway tunnel asphalt pavement under double-wheel load on rectangular loaded area considering horizontal contact stress induced by the acceleration/deceleration of vehicles.The key design parameters are the maximum horizontal tensile stresses at the surface of the asphalt layer,the maximum horizontal tensile stresses at the bottom of the asphalt layer and the maximum vertical shear stresses at the surface of the as- phalt layer were calculated.The influencing factors such as double-wheel weight;asphalt layer thickness;base course stiffness modulus and thickness;and the contact conditions among the structure layers on these key design parameters were also examined separately to propose construction procedures of highway tunnel asphalt pavement.

Application of semi-analytical finite element method to analyze the bearing capacity of asphalt pavements under moving loads

To facilitate long term infrastructure asset management systems, it is necessary to determine the bearing capacity of pavements. Currently it is common to conduct such measurements in a stationary manner, however the evaluation with stationary loading does not correspond to reality a tendency towards continuous and high speed measurements in recent years can be observed. The computational program SAFEM was developed with the objective of evaluating the dynamic response of asphalt under moving loads and is based on a semi-analytic element method. In this research project SAFEM is compared to commercial finite element software ABAQUS and field measurements to verify the computational accuracy. The computational accuracy of SAFEM was found to be high enough to be viable whilst boasting a computational time far shorter than ABAQUS. Thus, SAFEM appears to be a feasible approach to determine the dynamic response of pavements under dynamic loads and is a useful tool for infrastructure administrations to analyze the pavement bearing capacity.

Application of semi-analytical finite element method coupled with infinite element for analysis of asphalt pavement structural response

A specific computational program SAFEM was developed based on semi-analytical finite element （FE） method for analysis of asphalt pavement structural responses under static loads. The reliability and efficiency of this FE program was proved by comparison with the general commercial FE software ABAQUS. In order to further reduce the computational time without decrease of the accuracy, the infinite element was added to this program. The results of the finite-infinite element coupling analysis were compared with those of finite element analysis derived from the verified FE program, The study shows that finite-infinite element coupling analysis has higher reliability and efficiency.

Harvesting Energy from Asphalt Pavement by Piezoelectric Generator

This paper presents the way to harvest mechanical energy from asphalt pavement by piezoelectric generator. Results show that the potential energy in asphalt pavement can be up to 150 kW/h per lane per kilometre. Part of the mechanical energy can be harvested by piezoelectric transducers. The performance of seven typical transducers is examined through finite element analysis. Results show that PZT piles and multilayer, cymbal and bridge can work in asphalt pavement environment. PZT piles and multilayer have higher energy converting rate, However, the total harvested energy is small if these transducers are embedded directly in pavement. A prototype pavement generator is developed using PZT piles to increase the harvested energy. The generator can harvest more than 50 kW/h energy from the pavement under heavy traffic. 8-16 PZT piles are recommended for one generator. Round shape is suggested for the PZT piles to reduce the concentration of stress. And multilayer structure is recommended for PZT piles to decrease the electric potential of generator. The generator can be extended as sensor in the asphalt pavement, which can be used to monitor the traffic, pavement stress and temperature.

Test and Analysis of Bridge Transducers for Harvesting Energy from Asphalt Pavement

Part of energies in asphalt pavement caused by vehicle can be converted into electric energy by piezoelectric transducer.A bridge-shaped transducer is selected to harvest energy because of its reasonable efficiency and moderate stiffness close to asphalt pavement.This paper is to compare the performance of Bridge transducers with trapezoidal,arc and arch structure through finite element analysis(FEA)and laboratory test.Results show that the arch Bridge has higher energy conversion efficiency and the trapezoidal Bridge has stronger ability to resist pressure.For arc and trapezoidal Bridge,the maximum tensile stress and shear stress are both in the inner corner of contact area between cap and PZT(lead zirconate titanate)disk.They were broken because of the cracking of PZT at the stress concentrations area.For arch Bridge,the maximum tensile stress increases with thickness of metal cap but decrease with modulus,and maximum shear stress decreases first and increases later with increasing thickness and modulus of metal cap.In laboratory test,its cracking area is shifted from edge to inner corner of contact area between cap and PZT disk with increasing thickness of metal cap.The electric potential generated by arch Bridge decreased with increasing thickness and modulus of metal cap.Under the load of 0.7 MPa,the electric potential is about 286 V for an arch Bridge transducer with 0.4mm thickness of stainless steel cap,and its storage electric energy is 0.6 mJ.The designed arch Bridge transducer is suggested as the optimum one for harvesting energy from asphalt pavement.

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.

多轮荷载作用下的高模量沥青道面力学响应特性

飞机起落架多轮荷载作用下,道面内部应力应变等力学响应将产生叠加与干涉。针对高模量沥青机场道面,通过ABAQUS有限元软件开展道面结构力学响应计算,分析飞机多轮荷载对道面力学响应敏感性,研究高模量沥青混合料在机场道面中的应用效果。结果表明:在飞机主起落架的六轮荷载作用下,道面结构层中产生的应力与路表弯沉的峰值最大,且道面的疲劳寿命最小,在进行道面结构计算与材料组成设计时,应以六轮荷载作为最不利荷载工况;机轮荷载分布的对称性越强,结构内应力与路表弯沉的峰值点位置越靠近荷载包围区域中心;沥青道面变形有一定的时间滞后,卸载后路表弯沉不能立即恢复并存在残余变形,且主起落架轮数越多,滞后时间越长,保留的残余变形越大;中面层采用的高模量沥青混合料可降低道面各层拉应力、压应力、剪应力的应力水平,进而有效地减少机场沥青道面轮辙与疲劳开裂。

移动荷载下道路病害的弯沉盆特性

移动荷载作用下道路弯沉盆蕴含路基、路面的病害信息,充分利用移动弯沉盆信息开展道路病害快速无损检测受到行业重要关注。该文通过分析道路病害的弯沉盆特性,为移动弯沉车开发道路病害检测方法提供技术参考。首先建立半刚性基层沥青路面有限元模型,通过设置不同类型和程度的病害有限元模型,分析在移动荷载作用下路表弯沉盆的连续变化情况。结果表明:荷载移动到病害区域时,各病害模型中路表弯沉盆的中心弯沉值均会变大;路面结构层出现横向裂缝时,弯沉盆的形状会发生明显变化,贯通性横向裂缝对弯沉盆形状的影响最明显;基层与底基层局部松散对弯沉盆形状的影响比面层松散对弯沉盆的影响更明显;土基顶部出现空洞时,弯沉盆形状变化不明显;路基唧泥病害会严重影响路表弯沉盆形状与大小。

移动荷载作用下沥青路面的力学响应数值模拟

掌握沥青路面在移动荷载作用下的力学响应,是更为合理地进行路面结构设计的重要基础。该文基于有限元建立了移动荷载作用下沥青路面力学响应的数值模拟方法,讨论了移动荷载作用下沥青路面结构不同层位的竖向位移、应力与应变等力学响应特征,系统研究了轴载、车速及温度对沥青路面力学响应的影响,为优化路面结构设计提供参考。结果表明:移动荷载作用下,沥青路面各层的竖向位移随路面深度增加逐渐增大,且随轴载与温度增加而增大,而受车速影响较小;沥青路面各层所受应力包括竖向压应力与剪切应力,其压应力与剪切应力均随着轴载增加而显著增加,而受温度与车速的影响较小;相应的各层竖向压应变与剪切应力均随轴载与温度增加而增加,受车速影响较小。路面结构内部的应力与应变情况复杂,在设计中,应控制各结构层最不利应力及应变,满足设计要求。

分层变模量下的沥青路面车辙预估模型

为建立分层变模量下沥青路面车辙预估模型,修正动态模量变化引起沥青路面永久变形预估的偏差。根据沥青混合料动态模量试验和室内三轴动态蠕变试验,验证沥青混合料动态模量(|E^(*)|)与其抗高温变形能力的相关性;采用Abaqus有限元软件分析不同时间沥青路面随深度、温度的动态模量和竖向压应力变化规律,提出各亚层在不同动态模量下的竖向压应力修正因子(m);根据“亚层变形叠加”思想,运用SPSS软件回归分析,建立包含温度、沥青层厚度、竖向压应力、修正因子和荷载作用次数等因素的分层变模量沥青路面车辙预估模型。结果表明,建立的车辙预估模型可更为准确地预估沥青路面的永久变形,可将中、下面层车辙预估精度分别提高6.03%和10.34%,沥青层整体提高5.19%。

基于沥青混合料动态模量主曲线参数的沥青路面结构分析

为研究沥青混合料动态模量主曲线参数变化以及交互作用对沥青路面结构响应的影响,采用有限元方法建立沥青路面结构三维模型,并开展半刚性基层和柔性基层沥青路面结构计算;以动态模量主曲线参数δ、α、β、γ为影响因素,以沥青层底最大拉应变、路基顶面竖向压应变为响应目标,采用响应面法(RSM)建立动态模量主曲线参数与沥青路面关键结构响应的响应面模型,分析主曲线参数及其交互作用对沥青路面结构关键响应的影响。结果表明:动态模量主曲线参数对结构关键响应的影响受响应类型和路面结构类型的共同影响,其中参数δ的影响最大,α次之,β、γ的影响相对较小。半刚性基层路面结构的沥青面层层底拉应变和路基竖向压应变不受参数间的交互作用影响,参数α和β的交互作用对柔性基层路面结构的路基竖向压应变影响显著。

基于XFEM的再生复合路面反射裂缝扩展研究

为了探究裂缝扩展路径及在不同条件下的扩展规律,该文基于ABAQUS软件中扩展有限元方法(extended finite element method,XFEM)模拟分析沥青混凝土半圆弯曲断裂试验中的裂缝扩展规律。通过对比他人试验及数值模型数据,验证了基于XFEM的有限元模型分析裂缝扩展的有效性。此外,该文建立干法油石分离再生复合路面二维模型,研究模型中施工缝宽度、预埋裂缝长度、偏转角及预设位置对裂缝尖端应力影响,结果表明尖端应力随着裂缝长度、偏转角增加而增大,而随着施工缝宽度增大呈现先减小后增大趋势,随着偏移距离变大则先增大后减小。该文研究结果有助于复合路面反射裂缝定量分析与表征,为复合路面设计及后期养护提供了参考与依据。

基于足尺试验环道的沥青路面有限元模型

有限元技术的发展使得精细化路面结构仿真计算成为可能,但通过软件建立符合实际的有限元模型尤为重要.基于此,依托交通运输部公路科学研究院正在开展的足尺环道试验,采用大型通用有限元软件ABAQUS建立环道上3种典型沥青路面结构的有限元模型,研究模型尺寸、边界条件、荷载形式、网格划分等参数对路面力学响应结果的影响,通过与BISAR软件得到的解析解进行对比,确定合理的有限元建模方法和参数,为后续的沥青路面结构有限元分析提供建模依据.

荒漠区沥青路面拱胀病害机理及影响因素分析

针对阿勒泰荒漠区S21阿乌高速出现的沥青路面拱胀病害问题,对其机理及影响因素进行分析。经现场调查与室内试验,分析沥青路面拱胀病害成因。以调查结果为基础,运用Kirchhoff薄板理论与有限积分变换法理论推导基层拱胀临界应力计算公式,分析沥青路面拱胀病害力学机制,确定基层拱胀临界应力值。应用Abaqus建立道路有限元模型,分析基层施工温度、膨胀系数、回弹模量及路表最高温度等因素对基层纵向最大应力与路面最大拱起高度的影响,并基于基层拱胀临界应力值给出相应建议。研究认为:S21阿乌高速沥青路面拱胀病害是水泥稳定砾石基层在过大的温度应力作用下发生拱起破坏的结果。考虑实际道路情况,S21阿乌高速水泥稳定砾石基层拱胀临界应力值为3.49 MPa。当基层纵向最大应力大于基层拱胀临界应力值时,基层将会发生拱起失稳破坏。基层施工温度、膨胀系数及路表最高温度均为基层纵向最大应力与路面最大拱起高度的敏感因素,而基层回弹模量对路面最大拱起高度无明显影响。建议将基层膨胀系数控制在2.8×10^(-5)℃^(-1)以内,基层回弹模量控制在1400~2200 MPa以内。

Long-term performance of fiber-grid-reinforced asphalt overlay pavements: A case study of Korean national highways

The objective of this study was to verify the effect of fiber grid reinforcement on the longterm performance of asphalt overlay pavements by performing field investigation, laboratory test, and finite element analysis. Crack, rutting, roughness, and other miscellaneous distresses of fiber-grid-reinforced overlay sections and ordinary overlay sections were compared. Pavement conditions of fiber grid overlay sections before and after the overlay were also compared. Cores were obtained from the fiber-grid-reinforced and ordinary sections to measure bonding shear strength between the intermediate and overlay layers.Fracture energy, displacement after yield, and shear stiffness of the cores were also obtained by analyzing the test results. Finite element analysis was performed by using the test results to validate the effect of the fiber grid reinforcement on the long-term performance of asphalt overlay pavements. Rutting and fatigue cracking were predicted for three cases: 1) fiber grid was not used;2) glass fiber grid was used;and 3) carbon fiber grid was used. The cracking ratio of fiber-grid-reinforced sections was much smaller than that of ordinary sections. The results of field investigation, laboratory test, and finite element analysis showed that the fiber grid reinforcement improved the long-term performance of asphalt overlay pavements.

桥梁无缝化改建对接界沥青路面受力影响

为研究服役期内的既有中小跨径桥梁的快速、低成本、低影响无缝化改建对桥头搭板区域沥青路面温度响应的影响,选取了温度场、台后填土摩阻系数为研究参数,进行了有限元力学仿真建模分析并进行了工程验证。研究及应用工程长期监测的结果表明,既有中小跨径桥梁在完成快速、低成本、低影响的无缝化改建后,通过搭板端部的特殊构造及多项加强加韧措施,在循环隐形缝范围内路面的使用性能及耐久性良好,可有效延缓改建区域接界沥青路面反射裂缝的产生时间。研究可为服役期内的既有桥梁无缝化改建的结构设计与应用以及后续养护维修工作提供理论和数据上的支撑。

考虑路面摩擦性能的自动驾驶汽车安全制动策略

针对现有自动驾驶研究大多忽略路面摩擦性能的问题,制备了5种不同级配的沥青混合料车辙板试件,基于Persson表面分形摩擦理论和轮胎‒路面三维有限元模型,求解沥青路面的动摩擦系数和附着系数,表征其摩擦性能,并使用Matlab/Simulink软件建立自动驾驶汽车的动力学控制模块,根据车辆期望制动减速度和道路摩擦性能逆向反推求解轮缸的制动压力值,实现自动驾驶汽车的制动过程。使用CarSim软件和Matlab/Simulink进行联合仿真,设定了下坡制动和曲线制动工况,分析了纵向坡度、弯道半径和道路超高等影响因素对自动驾驶车辆制动效能的影响。

隧道复合式路面层间抗裂性能研究

反射裂缝是隧道复合式路面结构的一大突出问题,严重影响路面使用性能。本文采用加纤改性沥青作为层间抗裂材料,成型了基层预设接缝的复合试件,基于室内弯曲试验和轮碾试验研究其层间抗裂性能,并通过有限元数值分析探究加纤改性沥青对复合式路面沥青面层应力分布情况的影响。结果表明:加纤改性沥青具有良好的层间抗裂性能,能够增强复合试件的抗弯曲能力,减缓反射裂缝的发展,延长复合试件疲劳寿命;有限元分析结果表明加纤改性沥青能够有效吸收沥青面层底部因基层接缝导致的集中应力,大大降低沥青面层底部的最大拉应力和最大剪应力。研究成果可为加纤改性沥青层间抗裂材料在隧道复合式路面中的应用与推广提供理论依据和技术支撑。