This study explored the performance of unbound aggregate materials (UAM). Repeated load tests of single-size, two-size mixed, and three-size mixed gravels were conducted using the precision unbounded material analyzer (PUMA) in single-stage loading mode (SSLM) and multi-stage loading mode (MSLM). The permanent deformation and elastic modulus of the first 400 loading cycles were analyzed under the two loading modes. The modulus of PUMA repeated load tests was compared with modulus models of the repeated CBR test and with constant confining pressure (CCP) and variable confining pressure (VCP) models of the repeated load triaxial test. The results of MSLM showed that the permanent deformation of single-size gravel increased rapidly when the loading strength was lower than 340 kPa and then decreased. The maximum permanent deformation of the mixed gravels appeared as the loading strength was lower than 200 kPa. The increment of permanent deformation tended to single-peak with the large-size aggregate. The loading strength only slightly affected the permanent deformation once it reached a certain extent. The initial-stage permanent deformation of SSLM was the main part of the total, and the proportion increased with the increase in loading strength. A slight difference was observed between the single-size and mixed gravel when the loading strength was under 240 kPa. Then, the permanent deformation of single-size gravel increased rapidly. The permanent deformation of MSLM was smaller than that of SSLM. MSLM can improve the carrying capacity of the unbound materials and reveal the principle of three-stage compaction for UAM. Although the calculated equivalent modulus of the full-friction model was lower than those of the existing studies, it presented the same tendency and was appropriate for the calculation of modulus. The elastic modulus of CCP model was the largest among the four models, and the growth rate of elastic modulus was the highest for VCP model. The effect of confining pressure on the modulus increased with increasing loading strength.

Analysis of the vehicle-pavement couple system was mainly based on the linear elastic model in frequency domain considering pavement roughness. The nonlinear dynamic numerical model for the vehicle-pavement coupled system was established using finite element mothed. Using the model, the deformation characteristics of asphalt concrete pavement were studied under the conditions of different pavement roughness, different vehicle speeds, different vehicle loads and different subgrade strength. The pavement roughness was worse and the vibration deformation of the pavement was larger, the max deformation of the C level pavement roughness was 1.31 times than that of the A level pavement roughness. With the faster of the vehicle speed, the deformation of pavement was smaller, but the trend was not obviously. The deformation of pavement increased obviously for overload, and the ratio of the overload reached by 100%, the ratio of deformation increased by 50%~109%. The deformation of pavement increased obviously for the subgrade strength reduction, the subgrade strength was reduced by 28%, and the deformation of the pavement increased by about 15%.

The viscoelastic constitutive relation for adhesives is described using the modified Maxwell model to study the influences of the viscoelastic constitutive relation of adhesives and of the design parameters of carbon fiber reinforced polymer (CFRP)-strengthened steel beam on CFRP-to-steel interfacial stresses. In view of the fact that the adhesive layer of reinforced beam is mainly shear deformation, the analysis of the viscoelastic constitutive of the adhesive is simplified. The solution to the variables of the modified Maxwell model is given using Laplace transform and inverse Laplace transform. Finite element analysis of a typical simply supported steel beam strengthened by CFRP is conducted using ABAQUS. The variation rule of the interface stress with loading time is analyzed. The effects of CFRP elastic modulus, CFRP thickness, adhesive layer thickness, and distance between the CFRP end and the support on the CFRP-to-steel interfacial stress are discussed in detail. On the basis of the fundamental principle of the sensitivity analysis, the degree of sensitivity of the interfacial stress to the different parameters is investigated through quantitative analysis. Results show that (1) the viscoelasticity of the adhesive causes stress redistribution on the bonding interface, and the peak shear stress and peak normal stress of the interface decrease with time; (2) the thicker the adhesive layer, the thinner the CFRP, and the less the elastic modulus of the CFRP; (3) the closer the CFRP to the bearing, the less the interfacial stress; (4) the parameter that exerts the most influence on the interfacial shear stress at the edge of the CFRP is the distance from the edge of the CFRP to the bearing, with a sensitivity factor of 1.359; and (5) the parameter that exerts the most influence on the interfacial normal stress at the edge of the CFRP is the thickness of the polymer, with a sensitivity factor of 0.956.

Two kinds of numerical solution of differential equations were first introduced to solve the problem of wind-induced vibration of bridge structures. Fluid-structure interaction (FSI) numerical simulation of a streamlined bridge section was realized using ANSYS Fluent as the computing platform and embedding user-defined function (UDF) in Fluent. Theoretical analysis indicated that the displacement gained by the FSI calculation model, where the grids near the bridge section were driven by conventional Newmark-beta (β) program embedded in UDF, differs from that of grid motion updated in Fluent. A corrected velocity method (i.e., CV Newmark-β) was proposed in this work to eliminate such an error. The corresponding FSI simulation model was then set up through the abovementioned method. For a concrete bridge section, the FSI simulation under low and high wind speeds was obtained by the models set up using conventional Newmark-β and CV Newmark-β programs. Result showed that the displacement time history curves obtained using different calculation models are consistent while the bridge section takes a small amplitude motion. The error from the displacement of conventional Newmark-β program and actual grid motion is small. In addition, the error of the displacement mismatch effect between this algorithm and the real motion of the grid can be ignored under low wind speed. While the bridge section takes a large amplitude flutter motion, the disparities of the displacement time history curves obtained using different calculation models are large. The error of the displacement mismatch effect between the conventional Newmark-β algorithm and the real motion of the grid must be considered under high wind speed. The displacement gained using the FSI calculation model set by the CV Newmark-β program is consistent with the real motion displacement of the grid motion updated in the Fluent program whether under low or high wind speed. Therefore, such a mismatch effect must be considered to establish a reasonable FSI calculation model while taking the numerical simulation of bridge flutter.

This study investigated the influence of material time-dependent performance on a PSC box girder bridge. We prepared 24 sets of standard prismatic concrete specimens in the construction site and synchronous maintenance in the deck for 3, 5, 7, 14, 28, and 60 days of concrete specimen mechanical test. The relationship among early-age concrete axial compressive strength, elastic modulus, and curing time was established, and then the function equation among them was optimized. The state of stress and deflection of the main beam in the maximum cantilever stage of the PSC box girder bridge considering time-dependent performance were analyzed by using the finite element software Midas civil, and the analysis results were compared with the calculation results of the standard value. Data show that the growth of the elastic modulus of early-age concrete lags behind the development of axial compressive strength. In consideration of the material's time-dependent performance, the maximum stress variation on top of the box girder is 2.22%, whereas the variation at the lower edge is 1.02% in the stages. Thus, the effect of material time variation on stress is small. The maximum displacement is 12.3 mm, whereas the current step displacement is 5.1 mm in the maximum cantilever stage. Thus, the displacement is deeply influenced by the material time-dependent performance.

At present, the construction schemes of tunnel enlarging are analogized by creating a new tunnel through a traditional method. However, the traditional excavation method ignores the advantage of long-term support and stability of the original tunnel lining to the surrounding rock, and the construction efficiency is also reduced. The optimized construction plan was theoretically analyzed using the case of the Chongqing Yuzhou tunnel enlarging. The optimization construction schemes of single-sided shallow tunnel enlarging were extracted in accordance with the foundation of the study on the construction mechanics of a shallow tunnel, that is, the way of the rational arch axis enlarging in the crosswise direction and the jump-driving method in the lengthwise direction. The construction analysis was compared with the field monitoring measurement results and ANSYS simulation of the 3D finite element calculation of the entire tunnel enlarging process. By optimizing the construction scheme, the calculation value of the compressive stress of the original tunnel lining was increased by excavation face advancing. The original tunnel lining that had not been dismantled can play the role of the column and bear the surrounding rock pressure caused by the jet-hopping excavation. This lining could effectively improve the safety and stability for tunnel enlarging. The adopted rational arch axis excavation in the transverse direction could reasonably and significantly transfer the surrounding rock pressure. This process could reduce the tensile stress and increase the compressive stress of the initial support structure. Results of the numerical calculation and field monitoring data showed that the excavation scheme of the shallow tunnel is optimized after unilateral expansion. The optimization construction schemes can change the original rock stress path and play a role in the surrounding rock stability. The displacement of the tunnel vault can be reduced by 16%-20%, and the tunnel vault does not appear in the tension zone. The optimization of construction scheme can reduce the arch subsidence and tensile stress of the lining, ensure the safety of construction, and shorten the construction period. These obtained beneficial conclusions can be supplied to the next similar tunnel enlarging projects.

This study aims to obtain satisfactory short-term traffic flow forecasting results in various traffic flow modes. Clustering analysis of traffic flow data is carried out using the Kohonen neural network. Then, different BP neural networks are trained using different classified traffic flow data. Different neural network models are combined with UKF to form multiple traffic estimators to realize the estimation function. Finally, the interactive method is used to fuse the prediction results of each estimator, and comprehensive traffic flow forecasting results are obtained. With the simulation example, a number of single estimators are obtained, and a joint estimator based on this method is constructed. The section flow of one given road is predicted to verify the performance of the estimator. Results show that the joint estimator has a higher prediction accuracy than the single estimator and has adaptive characteristics when traffic flow characteristics change.

Smart Transportation is an important part of Smart City. Buses, as one of the most important modes of travel in urban public transport, not only facilitate the work and life of urban residents but also provide effective solutions to urban energy conservation and environmental protection. Improving the accuracy of passenger traffic forecast at bus stations has been a focus of research in smart public transport. To compensate for the limitations of single-station forecasting and short-term memory in traditional time series models (such as ARMA and SVR) and improve the short-term prediction accuracy of urban bus station traffic flow, we propose a long short-term memory (LSTM)-based neural network model than can learn long-term series data at multiple sites and forecast the traffic flow of multiple sites simultaneously. Experimental results show that learning multi-site traffic simultaneously can improve the accuracy of prediction results and minimize mean squared error and mean absolute error to 3.18 and 1.43, respectively. Aside from its long-term memory, the neural network model based on LSTM can also show the potential correlation between multiple sites, suggesting obvious advantages in short-term traffic forecast. This study proves the feasibility of using LSTM for multi-site bus station traffic forecast. In addition, the performance of the proposed model is considerably better than that of single-site traffic forecast. Traffic monitoring data analysis indicates that multi-site bus station traffic flow is correlated. This paper provides a timely and accurate data reference for the rapid decision-making and integrated management of public transport operations.

A bi-level optimization model of synchronous transfer between bus lines and rural passenger lines was established after analysing the transfer mode. The target of upper optimization is minimum travel time on transfer paths, and the target of lower optimization is maximum bus meeting time at valid transfer stations. A heuristic algorithm was applied to solve the model, and the departure times with synchronous transfer were determined. Case analysis was performed by taking the edge and internal synchronous transfer modes as examples. Results show that the model can realize synchronous transfer between bus lines and rural passenger lines and obtain the satisfied departure times.

Health care services are the core elements of the urban public service system. Hospital accessibility network and its decision network system of health care services play a decisive role in the facilitation of medical treatment for urban residents. A distribution map of hospitals in the main city of Dalian is generated using ArcGIS software. The average reach time of medical treatment in each district is calculated using the network analysis module. The average time of arrival is denoted as the evaluation index to discuss the accessibility of public transportation and private cars during peak and non-peak hours, as well as the spatial distribution characteristics and differences of each district and hospital. Moran's I index and LISA local clustering model are used to explore areas of inadequate medical services. The minimum available time of each district is set as a standard, the hinterland of medical service in hospitals at all levels was delimited, and the reasons for its formation were analyzed. Research shows that (1) the overall accessibility of medical care in the downtown district of Dalian is better, and the accessibility of peak and peak hours is in a circle. Relative to private cars, public transport at peak hours has obvious advantages for medical treatment. Peak and non-peak hours are quite different, average peak time average peak area of 10-20 min in a larger proportion of the cell, reaching 68.1%; (2) The hospital accessibility level is generally good, with a coverage area of 96.53% in 30min.. From the core area to the peripheral area, the influence of traffic resistance on reachability gradually increases. (3) The level of equalization of medical services at the street level is obviously different, and the overall spatial autocorrelation is weak. (4) Within each medical hinterland, the number and distance of the hospital's medical services has a decisive influence on the ability hinterland, lack of health areas highly dependent causing residents to a hospital.This article provides some suggestions for the abovementioned problems.

The lack of standards in guide sign layout for freeway major split interchanges in China is imperative to solve considering particular physical form and traffic operation. On the basis of domestic and international standards and specifications, this study designs two types of graphical guide sign in addition to the text-type guide sign in China national standard and forms three placement configurations according to the guide rules. Behavior indicators are obtained through driving simulation experiments, the differences among the indicators of different configurations are studied, the analytic hierarchy of utility evaluation is established on the basis of the three-demarcation analytic hierarchy process, and the utility ranking is acquired through a comprehensive evaluation. Results show that the graphical signs are better than the text-type signs for freeway major split interchanges. This study offers suggestions on the optimal layout for guide signs, which may have certain reference value for improving relevant technical standards in China.

This study aims to optimize the overall mechanism size of trapezoidal steering. A mathematical model is established and optimized in combination with its working characteristics. The objective function is the objective function of the actual momentary position of the vehicle and the error of Ackermann's instantaneous position, so that the actual instantaneous position in the theoretical instantaneous position near the maximum fluctuations in the minimum is close to the ideal Ackermann steering mechanism. Through the numerical experiment method, the instantaneous center position curve is simulated and the length of the trapezoidal pole is taken as the optimization target and the optimal area value. Results show that selecting the length of the steering mechanism in the optimal region is reasonable. The numerical experiment is compared with the theoretical mathematical model, and the optimal region is considered. The method is validated by introducing the existing calculation parameters and drawing the ideal deviation curve of the optimized steering. This study provides a normative guidance and basis for the design of trapezoidal steering mechanism.