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This paper proposes the application and manufacturing of piezoelectric devices based on pile and arc-bridge transducers to harvest mechanical energy from concrete pavement. Multi-scale experiments are conducted to clarify the influence of electrical connection, load resistance, traffic speed, and loading times on the electrical properties of the harvesters. The reduced-scale test shows that the transducers should be connected to rectifiers before being connected as an array. Moreover, the output power of the arc-bridge transducer with resistance variations is unstable compared with that of the pile transducer. Accelerated pavement testing illustrates that the output power of the half pile array device increases to 1.7 mW with an optimal resistance of 10.0 MΩ; reducing the internal equivalent resistance is a potential way to increase the energy output. The results also show that the load speeds significantly influence the profile of the voltage and have a minor effect on the generated electric energy in the tested conditions. Furthermore, the electrical properties of the piezoelectric device exhibit no statistical degradation after the electrical fatigue test of 100,000 tire loads, indicating a novel electrical fatigue performance. The findings in this paper can further guide the application of such piezoelectric devices in concrete pavement.

This paper presents a method to assess the load transfer efficiency (LTE) of concrete pavement joints using distributed optical vibration sensors. First, a theoretical analysis of concrete pavement vibration was conducted to investigate how to reflect LTE by spectral amplitude. Sec- ond, distributed optical vibration sensor (DOVS) was applied to measure vibration around joints distributedly. Third, the corresponding processing method for DOVS data was proposed to calculate the ratio of spectral amplitude from different slabs through power spectral density (PSD) analysis. Then, field tests were conducted on nine concrete pavement slabs with three different types of joints (dummy joint, rabbet joint, and dowel bars). The deflection-based method as well as the proposed vibration-based method were employed to assess the LTE of eleven joints on two different dates. The comparative analysis results indicate the deflection-based LTE (DLTE) and the ratio of PSD (RPSD) have a strong correlation (0.871) and a slight difference (, Applied Sciences, 12 (18), ISSN:2076-3417

Skid-resistance performance of a runway greatly influences aircraft landing safety. A wet runway significantly increases the incidence rates of aircraft overrun. To study the influence of the skid-...

Accurate monitoring of concrete pavement support condition is critical for pavement maintenance. This paper proposed a novel support condition monitoring method using distributed optical fiber sens...

Prestress force loss is crucial to the structural performance of cross-tensioned concrete pavement (CTCP). Severe loss in prestress force will reduce the constricting-cracking capacity of the CTCP, resulting in damage with load and temperature applied. Vibration-based methods are commonly used in prestress force monitoring, but few relative studies are reported into CTCP and the relationship between prestress force and CTCP vibration is still unclear. The purpose of this paper is to investigate the effect of prestress force on CTCP vibration. The vibration characteristics of CTCP subjected to different prestress forces were studied through field testing and finite element (FE) analysis. Impulse load was applied as excitation at the anchorage zone and dynamic responses were measured in the time domain. A signal processing method was employed to obtain short-time power spectral from original vibration signals, which was utilized to extract vibration characteristics in time and frequency. As shown in both the field testing and the FE analysis, the prestress force has a more significant effect on frequency spectral distribution, rather than the dominant frequency. Integrated frequency is proved to be a reliable index for describing frequency spectral distribution and has a good correlation with prestress force, which suggests it can be used to reflect the change in prestress force. Overall, these findings indicate that vibration testing has potential in prestress force monitoring in CTCP, though the practicality of this method requires further demonstration.

Studying the hydroplaning behaviour is crucial for enhancing the safety of aviation during the landing stage. Due to the special nature of the aviation field, such as high aircraft velocity, wheel ...

Loss of support is a common concrete pavement distress that may affect pavement performance directly. Previous studies have proved that vibration-based methods have the potential for detecting loss of support in a more efficient way but this is limited by loading conditions. This paper presents a further study concerning the effects of moving loads and proposes a novel method for assessing support conditions of concrete pavement under traffic loads using distributed optical vibration sensing technology. First, finite element analysis and laboratory tests were conducted to investigate the impact of loss of support on pavement vibration induced by moving loads with reference to the frequency spectrum. The impact of loading conditions, including loading position and speed, was also studied using the same methods. The results indicate that both loss of support and loading characteristics have a considerable effect on the distribution of the frequency spectrum. It is proved that weighted frequency can be utilized for assessment of support conditions under a specific loading condition. It is suggested the loading position needs to be close to the measurement point (distance < 0.3 m) to obtain stable and reliable data for assessment of support conditions. In addition, the loading speed should be adequately fast and steady (4 to 5 m/s) to ensure the significance of the effect of loss of support. A field test was conducted in an airport, and the novel assessment method was validated by comparing it with a conventional deflection-based method. The novel method proved to be reliable for implementation in practice.

The weigh-in-motion (WIM) system is a necessary piece of equipment for an intelligent road. It can provide real-time vehicle weight and lateral distribution data on wheel load to effectively support pavement structure design and service life analysis for autonomous driving. This paper proposed an enhanced weigh-in-motion sensors system using Fabry–Pérot (F-P) cavity fiber optical technology. Laboratory testing was performed to evaluate the feasibility of the proposed system and field application was conducted as well. The laboratory results show that the traffic loads could be obtained by measuring the center wavelength changes in the embedded F-P Cavity tunable filter. The laboratory results also show that the vehicle load and the number of vehicle axles can be estimated based on the system transfer function between the dynamic loading and the wavelength variation. The field application indicates that the weighting accuracy of the proposed system could reach 94.46% for moving vehicles, and the vehicle passing speed is the potentially relevant factor. The proposed system also has the ability to estimate the number of vehicle axles and the loading position, and the precision could reach 97.1% and 300 mm, respectively.

Sustainability 14(2), 863 (2022). doi:10.3390/su14020863 special issue: "Special Issue "Traffic Infrastructure Sustainability in Autonomous Driving and Smart Pavement Environments" / Special Issue Editors: Dr. Young-Ji Byon, Guest Editor; Dr. Feng Chen, Guest Editor; Prof. Meng Guo, Guest Editor", Published by MDPI, Basel

Sensors 21(22), 7708 (2021). doi:10.3390/s21227708 special issue: "Special Issue "Piezoelectric Energy Harvesting Sensors and Their Applications" / Special Issue Editors: Prof. Dr. Linbing Wang, Guest Editor; Dr. Ya Wei, Guest Editor; Dr. Hailu Yang, Guest Editor; Dr. Zhoujing Ye, Guest Editor", Published by MDPI, Basel

This paper presents a new method that uses distributed optical vibration sensing (DOVS) technology and a neural network, which can access the concrete pavement support condition with lower cost and higher efficiency. This method relies on the vibration properties of the concrete pavement slabs, which was captured by an embedded DOVS system and extracted using the wavelet packet transform. Based on the extracted properties, a grading method that using probabilistic neural network (PNN) to assess the support condition was proposed. Through field tests, the accuracy of this method can reach 92.8% for 2-grade assessment and 81.4% for 3-grade assessment, respectively.

This study focuses on the critical responses of airfield composite pavements that are composed of hot-mix asphalt (HMA) overlay and Portland cement concrete (PCC) pavement. Accelerated pavement testing (APT) and a finite element (FE) method were employed to investigate the effects of three influential factors: temperature, interface bonding, and load level. A full-scale test field was constructed for this study and instrumented with 20 strain gauges and 32 temperature sensors. A finite element model was developed based on the parameters derived from laboratory and field tests and the model was then validated through measurements. The results indicate that longitudinal strain is more critical than transverse strain in an HMA overlay when subjected to moving loads. Moreover, the results underscore that temperature significantly affects the responses of HMA overlays and that the relationship between temperature and pavement responses is sigmoidal. Furthermore, a good interface bonding is able to significantly reduce the critical strain in an HMA overlay and the interface bonding strength is very sensitive to the amount of tack coat. The positive strain near to the surface of HMA overlay is due to high compressive stress, which is different from the tensile strain used in fatigue testing.

The interface bonding between Portland cement concrete (PCC) pavement and hot-mix asphalt (HMA) overlay plays an important role in the performance of the composite pavement. This research conducted a series of comprehensive laboratory studies to investigate the influence factors of the interface bonding strength using a self-designed direct shear test apparatus that can simultaneously apply normal stress and shear stress on a specimen. Four kinds of commonly used tack coat materials were systematically tested and compared under various combinations of normal stress and temperature. Then, coupling effects of the normal stress and temperature on the interface bonding between PCC and HMA were analyzed. The test results show that temperature has a significant impact on the adhesion of the tack coat. Emulsified asphalt was considered the optimal tack coat material because of its simple construction method. In addition, it was found that a damaged interface could still provide considerable bonding strength. Normal stress generated by traffic loads was beneficial to the interface bonding strength, especially at lower temperatures. The temperature had a significant effect on interface bonding and played a leading role in the failure mode of interface bonding.

This paper aims to study the influences of temperature variations on airfield jointed plain concrete pavement (JPCP) deflections. The maximum deflection at the transverse joint ( D 0 j ), the maximum deflection at the corner of a slab ( D 0 c ), and the deflection basin at the centre of a slab were considered. The in-situ deflection measurements at three civil airports were conducted over a 24-hour period and numerical simulations for JPCP at a civil airport were performed as well. The results indicate that the temperature change slightly affects the deflection basin at the centre of a slab unless the positive temperature gradient in the slab increases to exceed a certain critical value. But both D 0 j and D 0 c are significantly affected by temperature variations. The results of in-situ tests show that D 0 j (or D 0 c ) is almost stable from 1 pm and 5 pm in a day. At other times of one day, there is a strong negative liner correlation between D 0 j (or D 0 c ) and the pavement surface temperature during the heating period and the cooling period, respectively. The results of numerical simulations reveal that both D 0 j and D 0 c gradually increase with the increase of the average temperature. The results of numerical simulations also suggest that a critical negative/positive temperature gradient exists at the transverse joint while there is a critical positive temperature gradient at the slab corner. Besides, all the critical temperature gradients are seldom affected by the average temperature. When the temperature gradient exceeds the critical value, D 0 j , D 0 c and all values of the deflection basin have a strong positive linear correlation with the temperature gradient.

The mechanistic-empirical analysis approach assumes a fixed environmental condition in estimating the remaining life of airfield flexible pavements, which may introduce some errors with the real situation. This paper investigated the influences of moisture and frost on resilient modulus of subgrade soil and unbound materials, as well as the influences of temperature on modulus and Poisson’s ratio of asphalt mixture. A time-sharing damage accumulation method, which considered the environmental factors in pavement damage calculation, was provided in this research. Based on the method, this paper proposed a methodology to predict the remaining life of in-service airfield flexible pavements, and a case study was conducted using this methodology. The result shows that environmental factors significantly affect the damage calculation of airfield flexible pavements. Besides, it has been found from the case study that the methodology is applicable for estimating the remaining life of airfield flexible pav...

The deformation of piezoelectric transducer and asphalt pavement differs because of their different stiffness. As the piezoelectric transducer is embedded in asphalt pavement, the differential deformation may cause a non-uniform stress and degrade their performance. In this paper, the synergistic performance of piezoelectric transducer and asphalt pavement is studied through finite element analysis. Results show that the energy conversion efficiency of the transducers decreases with increasing burial depth and modulus of surface course. Under the vehicle loading, the piezoelectric transducer and asphalt pavement are easily separated by shear stress. For the asphalt pavement, the change in the stress of pavement structure and surface deflection is very small, which means that the differential deformation has no effect on fatigue cracking. Furthermore, an energy harvesting system composed of transducers array and asphalt plate is made and evaluated in a laboratory. Results show that the transducers within asphalt pavement have acceptable efficiency and high durability. Keywords: Synergistic performance, Piezoelectric transducer, Asphalt pavement, Energy harvesting, Cymbal, Differential deformation

This paper presents a vibration-based vehicle classification system using distributed optical vibration sensing (DOVS) technology and describes a comprehensive classification method including signal processing and feature extraction. With low maintenance costs, this system can collect vehicle classification data in a larger scale. At first, it utilizes an embedded sensing fiber as a distributed sensor to collect traffic-induced vibration signals, and then extracts several features from the raw signals to estimate axle configurations and identify vehicle categories. At the same time, an empirical mode decomposition (EMD)-based method is applied to reconstruct signals for features extraction, and then several extraction algorithms are proposed to obtain the axle configuration, moving speed, and frequency-domain feature of each vehicle. When all features are extracted, a multi-step classifier is designed to categorize vehicles into different classes. In addition, to evaluate the classification performance of this system, a prototype system was installed on a relief road in Shanghai, China using precast concrete pavement technology. With an overall accuracy of 89%, the test results show a good performance of this classification system.

In this study, a Brillouin Optical Time Domain Analysis (BOTDA)-based compression sensing system is developed to assess the support conditions of concrete pavement slab. The system is implemented b...

This paper proposes a novel method to detect and localize debonding beneath the concrete pavement using transmissibility function (TF) analysis. The layout of the measurement node array, the signal processing approach, and the testing procedures are proposed. Two matrices of transmissibility damage indicator (TDI) are proposed to describe the distribution of debonding. This method is a response-only approach and can offer advantages in easy and low-cost implementation. The theoretical deduction, finite element analysis (FEA), and field tests are conducted to demonstrate and verify detection and localization performance. It is first observed that the arrangement of measurement nodes and the frequency range are crucial to TF analysis. TFs at higher frequencies range are more sensitive to the debonding but may result in higher errors. The density of the measurement node array and the noise’s effect are investigated in the FEA. Using a denser node array and maintaining a lower noise level helps localize the debonding more precisely. Field tests are conducted on a precast concrete pavement plate using a specially designed accelerometer array. The test results demonstrate the feasibility of the TF-based method for debonding detection and localization.

Interface bonding between the cement slab and asphalt overlay is a significant point affecting mechanical behaviour and service life of the pavement. Many factors may influence the interfacial adhesive capacity, including asphalt mixture type, tack coat type and dosage, surface texture on layer below, temperature and moisture conditions. The aim of this study is to determine the most influential factors at the interlayer and evaluate their significant levels. An apparatus is designed to apply the direct shear test with normal load. Specimen is prepared by drilling cores from asphalt overlay over cement concrete pavement, which is constructed in laboratory. Six parameters with three values are examined by orthogonal test. Effects of these factors on interlayer performance are validated by boxplot. The test results conclude that surface texture on cement slab has the most significant influence on interlayer shear strength, and tack coat type, moisture and temperature come next. Rough surface texture like ti...

Asphalt-based composites have the ability to heal themselves. Under certain conditions, strength and stiffness modulus can be restored so that the fatigue life can be extended. However, without the aid of external influences (energy supply or material supplement), the self-healing ability of asphalt mixture is quite limited. In this paper, the efficiency of self-healing of asphalt mixture with Ni-Zn ferrite powders was analyzed based on the concept of microwave heating. The recovery rate of stiffness modulus and the fatigue life extension ratio were adopted to evaluate the self-healing efficiency of asphalt mixture. Different influence factors, such as heating temperature, healing time and damage level, were analyzed in this study. The analysis results proved that Ni-Zn ferrite powders can promote the self-healing ability of asphalt mixture significantly. It is found that when the asphalt mixture is filled with 80% ferrite powders (volume fraction of mineral powders), under the condition of healing for 3 h after heating to 55 °C by microwave, the fatigue life extension ratio of 50% damaged ferrite-filled asphalt mixture can reach 1.33.

The friction force for aircraft landing is mainly provided by the texture of runway surfaces. The mechanism underlying friction force generation is the energy dissipation of tire rubber materials during random excitation induced by asperities. However, the runway surface texture is deteriorated by cyclic loading and environmental effects during the service life of a runway, leading to loss of braking force and extension of landing distance. Additionally, when an aircraft lands on a wet runway at a high velocity, the hydrodynamic force causes the tires to detach from the runway surface, which is risky and may lead to the loss of aircraft control and runway excursion. Worn-out surfaces along with wet conditions increase the risk of poor control during aircraft landing. Accordingly, this study investigated three types of asphalt runways (SMA-13, AC-13, and OGFC-13). Surface texture deterioration was simulated using a surface texture wear algorithm. Kinematic friction models were established based on the viscoelastic property of rubber materials, power spectrum density, and statistics of surface textures. A finite element model was developed by considering a real rough runway surface and different water film depths (3, 7, and 10 mm). A comparison of hydroplaning speed was conducted between numerical simulation and former experiments. The effects of different factors, such as velocity, wear ratio, runway type, water film depth, and slip ratio, on the skid resistance of the runway were analyzed.

Many materials used as phononic crystals (PCs) are viscoelastic one. It is believed that viscosity results in damping to attenuate wave propagation, which may help to tune the defect modes or band gaps of viscoelastic phononic crystals. To investigate above phenomenon, firstly, we have extended the application of boundary element method (BEM) to the study of viscoelastic phononic crystals with and without a point defect. A new developed BEM within the framework of Bloch theory can easily deal with viscoelastic phononic crystals with arbitrary shapes of the scatterers. Experimental methods have been put forward based on the self-made viscoelastic phononic crystals. Verified by the experimental results, systematic comprehensive parametric studies on the band structure of viscoelastic phononic crystals with varying factors (final–initial value ratio, relaxation time, volume fraction of scatterers, shapes of scatterers) have been discussed by the numerical simulation. To further address the possibility to change the defect modes, the band structure of viscoelastic phononic crystals with a point defect has been studied based on the numerical and experimental methods. From present research work, it can be found that by adjusting the two viscous parameters combined with considering the effect of volume fraction and shapes, a wider and lower initial forbidden frequency or lower and higher quality factor resonant frequency can be obtained.

The aim of this paper is to propose a simple empirical prediction model for temperature gradients within concrete slabs of jointed plain concrete pavements (JPCPs) based on data collected b...

This study focused on the rutting characteristics of two typical hot-mix asphalt (HMA) overlays in airfield composite pavement under high tire pressure: asphalt concrete (AC) and stone mast...

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.

Asphalt concrete is a typical self-healing material, and its self-healing rate is influenced by the temperature. Since microwave irradiation is an efficient way of heating, its use could be...

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.

Effective traffic management requires use of monitoring technologies to extract traffic parameters that describe the characteristics of vehicles. This article presents a vibration-based traffic monitoring system to detect traffic parameters comprehensively, including the three major desired characteristics of vehicles: position, speed, and category. Using distributed optical technology, this system can monitor traffic parameters on a large scale. Firstly, distributed optical fiber was embedded into pavement as a series of vibration sensors to collect pavement vibration information. Then, a signal processing method, based on wavelet transform and short-time energy, was applied to reconstruct vibration signals for vibration features extraction. Estimation methods of traffic parameters were proposed based on the vibration characteristics in time, space and frequency domain. To evaluate the performance of this traffic monitoring system, a prototype system was installed on a highway in Shanghai, China. This system shows good accuracy in position locating (± 14.639 cm), category classification (86.98 %), and speed estimation (± 3.046 km/h). Meanwhile, results indicate this system provides a better monitoring performance at high speed.

Water film thickness is of great significance to the skid-resistant performance of an asphalt runway. Obtaining the precise information of water film thickness can help to assess the skid resistance with higher accuracy. This article proposes a wide-area dynamic sensing method of water film thickness on asphalt runway. The model, considering precipitation time-variability, runway geometry, and runway surface characteristics, is established to extract spatial temporal information of water film thickness dynamics on runway during intense rainfall. The model optimization is further conducted to deal with the problems of slope change, singularity issue, and time-spatial evolution of water film, which extends the single-point water film sensing to the large-area sensing. In order to evaluate the developed method, the calculations of water film thickness from the model are compared with the results obtained from a laboratory rainfall simulation experiment. The results show that the method has high accuracy in sensing the water film thickness and can realize a dynamic and whole-area acquisition of runway wet surface condition information. This method can provide data support for intelligent decision making of landing safety under rainfall conditions.

This paper presents a review of harvesting green energy from road. There are three forms of green energy exist in road: light, thermal and mechanical energy. Photovoltaic technology, thermoelectric technology, directly heat transferring and piezoelectric technology are discussed in this paper, as well as the cases studied in Europe, USA, Japan, Israel and China. Solar panels installed along road are current available to harvest light energy from the roadside land. Alternatively, the solar panels can be installed on the road instead of pavement structures, such as the Solar RoadwayTM. This technology is rather conceptual at this moment, and the main challenge is to design and build durable materials and structures that can withstand traffic at a reasonable maintenance and replacement cost. Thermoelectric generators can potentially be embedded in pavements, and generate electric power from the temperature gradient existing in pavements. However, instrument capable of efficiently generate electricity from the relatively small temperature gradient in pavement is still under development. Directly heat transfer solution is to have fluid flow through pavement, and the fluid is heated (in summer) by the pavement. An extra benefit in addition to energy collection is that this method can reduce pavement temperature as well as the associated negative effects on pavement performance and the environment. However how the heated fluid can be utilized was not clear. Electricity can be generated by piezoelectric ceramic generators embedded in pavement, as a result of the compressive stress and deformation induced by moving vehicles. Trials have been reported in Israel and China, and it was estimated that one lane-mile of highway can potentially general electricity of 200 kW.

This paper presents a pavement structure segmentation method based on the results derived from ground-penetrating radar (GPR) data. Surface type, layer thickness, base/sub-base type, shortest segment and outlier point criteria are developed to perform the segmentation. A boundary comparing method using t-tests is developed to perform layer thickness criteria. The value t = 4 is suggested for the HMA (hot mix asphalt) or aggregate layer; and t = 6 is suggested for Portland cement concrete and cement-treated base. During segmentation, segments that are shorter than the minimum length of 100 m are merged into adjacent segments. Furthermore, the flow charts of pavement structure segmentation as well as a procedure for automated segmentation are detailed. Proposed rules for fixing segment boundaries between GPR observations are also presented. Several segmentation examples are calculated by the automated procedure using the data from a pilot project in California. The results show that the method presented in ...

With the current large-scale construction of paved roads, continuous development of science and technology, and higher service requirements. Smart road is becoming the research hotspot in the world. But the most present research concentrate on some single intelligent functions of road or some specific technology such as snow-melting, solar energy harvesting, etc. There is no explicit definition or integrated framework for smart road. In this paper, on the basis of related concepts and researches of smart road at home and abroad, combined with some demonstration programs and technology trials, first, put forward a explicit definition and functions of smart road, then subdivided the functions, analyzed the key technologies and core problems of implementing each sub-function, finally summarized the definition, functions, and technologies, built an integrated framework of smart road, include physical frame and logical frame. The definition and framework construction would define the direction of smart road research and development to some extent.

The objective of this paper is to investigate the characterization of moisture diffusion inside early-age concrete slabs subjected to curing. Time-dependent relative humidity (RH) distributions of three mixture proportions subjected to three different curing methods (i.e., air curing, water curing, and membrane-forming compounds curing) and sealed condition were measured for 28 days. A one-dimensional nonlinear moisture diffusion partial differential equation (PDE) based on Fick’s second law, which incorporates the effect of curing in the Dirichlet boundary condition using a concept of curing factor, is developed to simulate the diffusion process. Model parameters are calibrated by a genetic algorithm (GA). Experimental results show that the RH reducing rate inside concrete under air curing is greater than the rates under membrane-forming compound curing and water curing. It is shown that the effect of water-to-cement (w/c) ratio on self-desiccation is significant. Lower w/c ratio tends to result in larger RH reduction. RH reduction considering both effect of diffusion and self-desiccation in early-age concrete is not sensitive to w/c ratio, but to curing method. Comparison between model simulation and experimental results indicates that the improved model is able to reflect the effect of curing on moisture diffusion in early-age concrete slabs.

The virtual laboratory system played an important role in improving the traditional experimental education. The system for road engineering created A virtual environment to simulate physical labs by using virtual reality and multimedia technology. Its design and implementation are described in the paper. The system design mainly focused on the framework structure, function division and results assessment method. It was shown that the framework took database as core and run over network. Besides, function management was divided into two, which were responsible for the experiment and system, respectively. Moreover, three methods were raised to assess experimental results. As for the implementation, after comparing the commonly used software, Flash was chosen for development. The system consists of virtual programs and websites are successfully established. It indicates that the system will increase the quality of test training.

An online monitoring system was recently built to acquire the inner condition and response of the runway pavement at Shanghai Pudong International Airport. Seven sections were instrumented to detect the responses of pavement when aircrafts were taking off, landing, and taxing. Sensors used in the system include strain gauges, multi-depth deflectometers, temperature sensors, earth pressure cells, moisture sensors and three laser distance sensors for aircraft position. Most of the sensors are fiber bragg grating based sensors, and some are electronic signal based sensors used to improve the reliability and variety of the data. Instruments are divided into dynamic and static parts, which are aimed at measuring pavement responses caused by aircraft load and environmental influence. The instruments are all fiber optic cable connected within the airport area for radio frequency control. This paper presents the (1) layout of sensors; (2) verification tests of the instruments; (3) process of installation; (4) method of data collection; and (5) initial responses test of pavement.

The purpose of this paper is to explore the vibration characteristic of asphalt pavement with various structures for harvesting mechanical energy via finite element analysis (FEA) and analytic model. Part of energies in asphalt pavement caused by mechanical vibration can be harvested by piezoelectric transducers. In order to get more energy from pavement, the sensitivity of structure parameters such as thickness, modulus, mass and stiffness are analyzed by using semi-rigid asphalt pavement as an example. Finite element model and analytic model are established in the analysis, which are calibrated by field measurement and laboratory test. The results show that the vibration frequency of typical semi-rigid asphalt pavement is between 10 Hz and 20 Hz, which is far lower than frequency of typical piezoelectric transducers. The fundamental frequency of asphalt pavement decreases with increasing thickness and mass of surface, base and subbase. However, the fundamental frequency is increase with the modulus and stiffness of subgrade, the increment is about 23 Hz/10 MPa and 0.7 Hz/10⁶ (N/m).

Superposition effects of runway asphalt pavement under multiple aircraft tires load are discussed in this paper. 30 x 20 x 10 m (Full Size Model), 15 x 20 x 10 m (1/2 Model) and 15 x 15 x 10m (1/4 Model) size models are established on ABAQUS 3D numerical analysis platform. Using those models, asphalt pavement responses under single tire, double tires, single tandem, dual tandem, dual triple, and compound landing gear are studied. Results show that multiple superposition effects are apparent. The pavement surface deflection under full landing gear is larger than any other tire groups; the maximum vertical strain on the top of the sub-grade and the horizontal stress at the bottom of the base appear in 6 tires group for A 380 and rear 8 tires group for B-777; the largest strain or stress can reach 1.15 times of the full landing gear’s value. Based on the pavement responses under multiple tires load, the fatigue life of pavement is analyzed. Functions developed by LEDFAA, APSDSR and UC Berkeley are used in the fatigue analysis. The results of flexible and semi-rigid pavements show that the allowed load repetitions of runway asphalt pavement under full landing gear are 20∼30% higher than 6 or 4 tires group. Therefore, the full landing gear is recommended to be used in asphalt pavement structure design.